All of BIOLOGY PAPER 1 in 20 mins - GCSE Science Revision Mindmap 9-1 AQA

Summary

This script offers an in-depth GCSE biology review, covering cell structures, mitosis, meiosis, and the roles of organelles. It delves into bioenergetics, explaining respiration and photosynthesis, and explores microscopic techniques. The video also discusses genetic coding, diffusion, osmosis, active transport, and cellular respiration. It addresses infection and response, including the immune system and antibiotics, and concludes with plant diseases, enzyme function, and the human circulatory system, providing a comprehensive guide for students.

Takeaways

• 🌿 Plant and animal cells are both eukaryotic, containing a nucleus, cytoplasm, mitochondria, and ribosomes, but plant cells have additional structures like cell walls, chloroplasts, and vacuoles.
• 🧬 DNA in eukaryotic cells is housed within the nucleus, while in prokaryotic cells, such as bacteria, it is found in a plasmid.
• 🔬 Mitosis is the cell division process that results in two genetically identical daughter cells, whereas meiosis produces gametes with half the genetic material for sexual reproduction.
• 🔬 Stem cells can differentiate into specialized cells, which form tissues and organs, essential for the structure and function of organisms.
• 🔬 Microscopes, particularly electron microscopes, are used to observe cells and their organelles, as they offer higher resolution than light microscopes.
• 🧬 DNA is composed of four bases (A, T, C, G) that code for amino acids, which are the building blocks of proteins.
• 🌀 Diffusion and osmosis are passive processes where particles move from areas of high concentration to low concentration, requiring no energy.
• 🚛 Active transport requires energy to move substances against their concentration gradient, often facilitated by carrier proteins in the cell membrane.
• 🌿 Photosynthesis and respiration are reverse processes; photosynthesis uses sunlight to produce glucose, while respiration breaks down glucose to release energy.
• 💉 Vaccines provide immunity by prompting the body to produce antibodies against specific antigens, preparing the immune system for future encounters with pathogens.
• 🛡️ The human body has several lines of defense against pathogens, including physical barriers like skin, chemical barriers like stomach acid, and immune cells like phagocytes and lymphocytes.

Q & A

What are the two most important types of cells covered in the script and what organelles do they both have?

The two most important types of cells covered are animal and plant cells. Both of them have a nucleus, cytoplasm, mitochondria, ribosomes, and a cell membrane.

What is the main function of the mitochondria in a cell?

The mitochondria are known as the 'power station' of the cell, where respiration takes place, converting energy from nutrients into a form that the cell can use.

What is the difference between eukaryotic and prokaryotic cells in terms of DNA storage?

Eukaryotic cells, like animal and plant cells, have their DNA contained within a nucleus, whereas prokaryotic cells, such as bacteria, have their DNA in a plasmid, which is a loop or ring of DNA outside the nucleus.

What is the process of mitosis and how does it relate to the number of chromosomes in human cells?

Mitosis is the process by which cells divide. The chromosomes, which contain DNA, are copied and then separated into two new cells. Humans have 23 pairs of chromosomes, totaling 46, in every cell except for gametes.

How does meiosis differ from mitosis and what is its purpose?

Meiosis is the process by which gametes (sperm and egg cells) are made. Unlike mitosis, which results in cells with the same number of chromosomes, meiosis results in cells with half the number of chromosomes, preparing them for fertilization to form a new organism with a full set.

What is the role of stem cells and how do they relate to the process of cell specialization?

Stem cells are undifferentiated cells that have the potential to become specialized cells. After fertilization, stem cells can become specialized, taking on specific roles like brain cells or cheek cells, which then contribute to the formation of tissues and organs.

What are the two types of microscopes mentioned in the script and how do they differ from each other?

The two types of microscopes mentioned are the scanning electron microscope and the transmission electron microscope. Both use electrons to image cells but differ in how the electrons interact with the sample; scanning electron microscopes bounce electrons off the surface, while transmission electron microscopes pass electrons through the sample.

What is the significance of the base pairing in DNA and how does it relate to protein synthesis?

In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). This base pairing is crucial for the accurate replication of genetic information. Every three bases in DNA form a codon, which codes for a specific amino acid. The sequence of amino acids determines the structure and function of proteins, which are essential for life processes.

What is diffusion and how does it relate to the concept of osmosis?

Diffusion is the passive movement of particles from an area of high concentration to an area of low concentration, requiring no energy. Osmosis is a specific type of diffusion that involves water molecules moving through a semi-permeable membrane, such as a cell membrane, from an area of lower solute concentration to an area of higher solute concentration.

What is the difference between aerobic and anaerobic respiration?

Aerobic respiration occurs in the presence of oxygen and is the primary way cells generate energy. Anaerobic respiration, on the other hand, occurs when oxygen is scarce, such as during intense exercise. It converts glucose into lactic acid without the need for oxygen, but it is less efficient in terms of energy production.

How do enzymes function in biological processes and what is the 'lock and key' mechanism?

Enzymes are biological catalysts that speed up chemical reactions in the body. They function according to the 'lock and key' mechanism, where the enzyme's active site (the 'lock') binds specifically to the substrate (the 'key'), facilitating the reaction. This specificity ensures that enzymes only catalyze reactions for certain substrates.

Outlines

00:00

🔬 GCSE Biology Overview

This paragraph provides an overview of the key topics for a GCSE Biology paper, focusing on cells, infection and response, organization, and bioenergetics. The narrator introduces the essential organelles found in both animal and plant cells, such as the nucleus, cytoplasm, mitochondria, and ribosomes, and highlights the unique features of plant cells, including vacuoles, cell walls, and chloroplasts. The explanation of eukaryotic and prokaryotic cells is presented, along with a discussion on mitosis and meiosis, the processes of cell division and gamete formation, respectively. The paragraph also touches on the significance of chromosomes and the basics of microscopy, including the use of nanometers and micrometers to measure cellular structures and the types of microscopes available for observing cells and organelles.

05:01

🌿 Plant and Animal Cell Structures and Functions

This section delves deeper into the structures of plant and animal cells, emphasizing the roles of organelles in cellular processes. It explains the concept of eukaryotic cells, where DNA is contained within a nucleus, and contrasts this with prokaryotic cells, like bacteria, which lack a nucleus and have their DNA in a plasmid. The paragraph also covers the process of mitosis, detailing how cells divide and the role of chromosomes in this process. Additionally, it discusses meiosis, the formation of gametes, and the resulting stem cells that differentiate into specialized cells, forming tissues and organs. The importance of cellular microscopy is reiterated, with a focus on the resolution capabilities of different microscopes and the scale of cellular structures measured in nanometers and micrometers.

10:03

🧬 DNA, Protein Synthesis, and Cellular Processes

The paragraph discusses the molecular basis of life, starting with DNA and its role in protein synthesis. It explains how DNA is composed of four bases that pair up to form a code for amino acids, which are the building blocks of proteins. The concept of genes, which are sequences of DNA that determine traits like eye color and height, is introduced. The paragraph then moves on to describe diffusion and osmosis, passive processes where particles move from areas of high concentration to low concentration, with a practical example of osmosis using potato cylinders in sucrose solutions. It also touches on active transport, which requires energy to move substances against a concentration gradient, and introduces carrier proteins in the cell membrane that facilitate this process.

15:04

🌱 Bioenergetics and Cellular Respiration

This section focuses on bioenergetics, particularly cellular respiration, which is the process by which organisms derive energy. It presents the balanced chemical equation for respiration, highlighting the production of water and carbon dioxide from glucose and oxygen, and the release of energy. The paragraph draws a parallel between respiration and a slow combustion reaction, explaining the concept of burning calories. It also covers photosynthesis, the reverse process that requires sunlight and results in the production of glucose. The paragraph further explores factors affecting the rate of photosynthesis, such as light intensity and temperature, and describes practical experiments to measure these rates. The role of different substances in energy storage and the body's metabolic processes are also discussed.

20:06

🛡️ Immune Response and Disease

The paragraph explores the body's immune response to infectious diseases caused by pathogens, such as bacteria, viruses, fungi, and protists. It describes the body's defenses against pathogens, including the skin, blood platelets, cilia, mucus, and white blood cells. The roles of phagocytes and lymphocytes in the immune response are explained, along with the process of antibody production and the development of immunity. The paragraph also touches on vaccination as a way to prime the immune system for future infections. Additionally, it discusses the discovery of antibiotics and the importance of using them responsibly to prevent bacterial resistance. The section concludes with a brief mention of the process of drug development, from discovery to clinical trials and post-market review.

🌿 Plant Diseases and Organization

This section discusses plant diseases, such as those caused by viruses and fungi, and the importance of mineral deficiencies in plant health. It explains how plants have various defenses, including cell walls, a waxy cuticle, and antibacterial chemicals. The paragraph then moves on to describe the organization of plant cells, including root hairs for water absorption and the structure of leaves for photosynthesis. It details the cross-section of a leaf, highlighting the waxy cuticle, epidermis, palisade mesophyll, and spongy metaphyll layers, as well as the role of stomata in gas exchange. The paragraph also covers the structure of a stem, the function of xylem and phloem, and the process of transpiration and its influence on water movement in plants.

🧪 Practical Science and Enzyme Activity

The paragraph describes a practical science experiment involving the use of enzymes, specifically amylase, which breaks down starch. It explains the setup of the experiment, including the use of a water bath and a buffer solution to control the pH. The process of adding iodine to test for the presence of starch and the method of recording the results over time is detailed. The paragraph also discusses the effect of pH on enzyme activity and how the experiment can help determine the optimum pH for the enzyme. Additionally, it touches on the concept of enzymes as biological catalysts and the factors that can affect their activity, such as temperature and pH.

🫀 Human Anatomy and Physiology

This section provides an overview of human anatomy and physiology, focusing on the respiratory and circulatory systems. It describes the structure of the lungs, trachea, bronchi, bronchioles, and alveoli, and explains the process of gas exchange. The paragraph then outlines the structure of the heart and the path of blood flow through the body, highlighting the double circulatory system. It also discusses the function of arteries, veins, and capillaries, and the role of hemoglobin in transporting oxygen and carbon dioxide in the blood. The paragraph concludes with a brief mention of communicable and non-communicable diseases, including atherosclerosis, aneurysms, diabetes, and cancer, and the importance of understanding risk factors and the difference between correlation and causation in disease research.

📚 Study Tips and Conclusion

The final paragraph offers study tips and well-wishes for exams, encouraging students to review the material covered in the script and to seek clarification on any unclear points by leaving comments. It emphasizes the importance of understanding the concepts discussed and the practical applications of the knowledge, such as the use of microscopes and the conduct of scientific experiments. The paragraph concludes with a reminder to engage with the content and a promise to address any additional topics or questions in future sessions.

Keywords

💡Cells

Cells are the fundamental units of life, serving as the building blocks for all living organisms. In the video, both animal and plant cells are discussed, with an emphasis on their organelles and functions. Animal cells and plant cells share common structures like the nucleus, cytoplasm, and mitochondria, but plant cells also have unique features such as cell walls, vacuoles, and chloroplasts. The script explains how these structures contribute to the cell's overall function, which is central to the theme of understanding biological systems.

💡Eukaryotic Cells

Eukaryotic cells are a type of cell that contains a nucleus, where DNA is housed. The video script distinguishes eukaryotic cells from prokaryotic cells, which lack a nucleus and instead have their DNA in a plasmid. Eukaryotic cells are significant in the context of the video as they exemplify the complexity of life forms and are central to the study of biology, including the discussion of mitosis and meiosis, which are processes of cell division in eukaryotic cells.

💡Mitosis

Mitosis is a process of cell division that results in two genetically identical daughter cells, each having the same number of chromosomes as the parent cell. The script describes mitosis as a fundamental process by which cells are made, highlighting the replication and separation of chromosomes. This concept is crucial for understanding growth, development, and the maintenance of organisms.

💡Meiosis

Meiosis is a specialized type of cell division that produces reproductive cells, or gametes, with half the number of chromosomes of the parent cell. The script explains that meiosis is essential for sexual reproduction, as it ensures that when gametes fuse during fertilization, the resulting organism has the correct number of chromosomes. This process is vital for genetic diversity and is a key concept in the video's discussion on genetics and reproduction.

💡Chromosomes

Chromosomes are thread-like structures composed of DNA and protein and carry genetic information. The video script mentions that humans have 23 pairs of chromosomes, totaling 46, which play a crucial role in heredity and cell division. Chromosomes are central to the discussion of genetics and cell biology in the video, particularly in the context of mitosis and meiosis.

💡Microscopy

Microscopy refers to the use of microscopes to observe objects and structures too small to be seen with the naked eye, such as cells and their organelles. The script discusses the importance of microscopy in biological research and education, explaining the difference between light and electron microscopes, and how they are used to study cellular structures. This concept is integral to the theme of exploring the unseen world of biology.

💡DNA

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for the development, functioning, growth, and reproduction of all known living organisms. The video script delves into the structure of DNA, explaining the role of its four chemical bases and how they code for amino acids to form proteins. DNA is a central theme in the video, as it is foundational to the understanding of genetics and heredity.

💡Diffusion

Diffusion is the passive movement of particles from an area of high concentration to an area of low concentration, which does not require energy. The script uses the example of perfume spreading throughout a room to illustrate this concept. In the context of the video, diffusion is a key process in understanding how substances move within and between cells, particularly in relation to osmosis.

💡Osmosis

Osmosis is a specific type of diffusion that involves the movement of water molecules through a semi-permeable membrane, from an area of lower solute concentration to an area of higher solute concentration. The video script describes an experiment involving potato cylinders in sucrose solutions to demonstrate osmosis. This concept is essential for understanding how cells maintain their internal environment and is a key part of the video's exploration of cellular processes.

💡Active Transport

Active transport is the movement of substances across a cell membrane from an area of low concentration to an area of high concentration, which requires energy. The script explains that carrier proteins in the cell membrane facilitate this process, often moving essential nutrients into the cell. Active transport is a critical concept in the video's discussion of how cells maintain their internal conditions and obtain necessary nutrients.

💡Respiration

Respiration is a biological process in which cells convert biochemical energy from nutrients into adenosine triphosphate (ATP), and then release waste products. The script describes the chemical equation for cellular respiration, emphasizing its importance as the primary means by which organisms obtain energy. This concept is central to the video's theme of bioenergetics and the understanding of how life sustains itself.

💡Photosynthesis

Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll pigments. The video script contrasts photosynthesis with respiration, highlighting the role of sunlight and the production of glucose. This process is essential to the video's theme of bioenergetics, illustrating how plants capture and store energy from the environment.

💡Infection and Response

Infection and response encompass the study of how pathogens, such as bacteria, viruses, fungi, or protists, cause diseases and how the body defends against them. The script discusses the body's immune response, including the roles of white blood cells like phagocytes and lymphocytes, and the concept of immunity. This theme is integral to the video's exploration of the body's defenses and the fight against infectious diseases.

💡Antibiotics

Antibiotics are substances that inhibit the growth of or kill bacteria. The script recounts the discovery of penicillin by Alexander Fleming and explains the importance of using antibiotics judiciously to prevent resistance. Antibiotics are a key topic in the video's discussion of treating bacterial infections and the challenges of antimicrobial resistance.

💡Plant Diseases

Plant diseases, as mentioned in the script, can be caused by viruses, fungi, or mineral deficiencies, which can lead to symptoms like stunted growth or chlorosis. The video discusses how plants have various defenses against diseases, including cell walls, waxy cuticles, and antibacterial chemicals. Understanding plant diseases is important for the video's theme of organism health and the strategies that living things use to protect themselves.

💡Enzymes

Enzymes are biological catalysts that speed up chemical reactions in living organisms. The script describes how enzymes work on a 'lock and key' mechanism, with a specific active site that fits a particular substrate. Enzymes are highlighted in the video's practical example involving the enzyme amylase and its role in breaking down starch. This concept is central to the theme of biochemistry and the understanding of how enzymes facilitate life's processes.

💡Non-Communicable Diseases (NCDs)

Non-Communicable Diseases, or NCDs, are conditions that are not transmitted from person to person, such as atherosclerosis, diabetes, and cancer. The script discusses various NCDs and their risk factors, including lifestyle choices and environmental exposures. This theme is important for the video's exploration of health and disease, emphasizing the impact of non-infectious factors on human health.

Highlights

Cells: Animal and plant cells share organelles like the nucleus, cytoplasm, and mitochondria, but plant cells also have a cell wall, vacuole, and chloroplasts.

Eukaryotic vs. Prokaryotic Cells: Eukaryotic cells contain DNA within a nucleus, unlike prokaryotic cells which have DNA in a plasmid.

Mitosis: The process of cell division where chromosomes are copied and separated.

Chromosomes: Humans have 23 pairs, with gametes containing half this number for sexual reproduction.

Meiosis: The process for gamete formation, involving DNA replication and two cell divisions resulting in four cells with half the genetic information.

Differentiation of Stem Cells: Stem cells become specialized for specific functions, forming various tissues and organs.

Microscopy: Magnification is crucial for observing cells and organelles, with electron microscopes providing higher resolution than light microscopes.

DNA Structure: DNA is composed of four bases forming a code for amino acids, which are the building blocks of proteins.

Diffusion and Osmosis: Passive processes where particles move from high to low concentration, including water movement across cell membranes.

Active Transport: The energy-dependent process for moving substances against the concentration gradient, facilitated by carrier proteins.

Respiration: The fundamental biological process where glucose and oxygen are converted into energy, water, and carbon dioxide.

Photosynthesis: The process by which plants convert sunlight, carbon dioxide, and water into glucose and oxygen.

Factors Affecting Photosynthesis: Light intensity, temperature, and carbon dioxide concentration influence the rate of photosynthesis.

Anaerobic Respiration: Occurs when oxygen is scarce, converting glucose into lactic acid with less energy production.

Metabolism: The sum of all chemical reactions in the body, with the liver playing a key role in energy storage and detoxification.

Infection and Response: The body's defense mechanisms against pathogens include skin, white blood cells, and the immune response.

Antibiotics and Drug Development: The discovery of penicillin and the process of developing new drugs, including testing and manufacturing.

Monoclonal Antibodies: The production of antibodies that target specific cells or chemicals in the body for medical treatments.

Plant Diseases and Mineral Deficiencies: Impact on plant growth and health, with defenses including cell walls, cuticles, and antibacterial chemicals.

Organization in Plants: The structure and function of root hairs, leaves, and stems, including the process of transpiration and transport of water and nutrients.

Food Tests for Chemicals: Methods for identifying starch, fats, glucose, and proteins using specific reagents and their color changes.

Enzymes: Biological catalysts that speed up chemical reactions, working on a lock and key mechanism and affected by pH and temperature.

Human Respiratory and Circulatory Systems: The process of gas exchange in the lungs and the double circulatory system of the heart.

Communicable and Non-Communicable Diseases: The differences between diseases caused by pathogens and those like atheroma, diabetes, and cancer.

Risk Factors for Disease: Factors such as diet, smoking, and exercise that can influence the likelihood of developing diseases.

Correlation vs. Causation: The importance of research to establish causation between factors and diseases, rather than just observing correlation.

Transcripts

okay let's try and go through everything

that you need to know for biology paper

one for gcse

specifically we're going to be covering

cells infection and response

organization and bioenergetics you can

download the pdf version of this

from scienceshorts.net link is in the

description here are the two most

important cells animal and plant cells

and these are the organelles that both

of them have they both have a nucleus

cytoplasm that's just the watery goo

that everything swims around in

mitochondria that's where respiration

takes place you might know the cliche

that we say that they're the power

station of the cell

ribosomes are where protein synthesis

takes place

that is where they're made they both

also have a cell membrane i'll put that

on here in a minute

plant cells have a couple of extra

things vacuole is a big hole

in the middle where sap is stored they

also have a cell wall that's made from

cellulose that's what gives it this

rigid shape and then we have

chloroplasts

that's where photosynthesis takes place

so that's where chlorophyll is that's

what gives plants their green color now

these are what we call

eukaryotic cells because dna is inside

the nucleus

however you can have prokaryotic cells

where dna

is not in a nucleus like bacteria their

dna

is in what we call a plasmid that's just

a loop or ring of dna mitosis is the

process by which cells are made

they divide the chromosomes that contain

the dna they're copied and then they all

line up in the middle of the cell

and then they're pulled apart they're

separated speaking of chromosomes humans

have 23

pairs of chromosomes that's 46

altogether

every cell has those apart from gametes

sex cells

you know sperm and egg they have half

they just have

23 each meiosis on the other hand is how

gametes are made

eggs and sperm only have half the

information because then of course

in fertilization they join together to

make a full set diploid cells

in your ovaries or testes they have 23

pairs

what happens is that this dna is all

copied but it

also swaps over the information from one

chromosome swaps over to the other ones

and then when they split we have two

daughter nuclei

and then they divide again to make four

gametes with half of the information

needed to make a person once

fertilization has happened we end up

with

stem cells but then they become

specialized that means they have a

specific job like

brain cells cheek cells etc these go on

to make

tissue like heart tissue lung tissue and

then if we have lots of tissues together

they make an

organ and we can see cells with a

microscope so when it comes to

microscopy

the magnification of your microscope is

equal to the image size divided by the

object size

that is the size of the cell in this

situation but we're dealing with such

small sizes that millimeters are far too

big

so we have nanometers which are a

million times smaller than millimeters

and then micrometers which are a

thousand times smaller than millimeters

so if we want to go from nanometers to

micrometers we divide by a thousand

because we know we want

fewer of them because they're bigger and

then again to go from micro to milli

divided by a thousand again

normal light microscopes can see cells

but they can't really see the individual

organelles inside

the cell so we have electron microscopes

there are two there's the scanning

electron microscope and the transmission

electron microscope they both

involve firing electrons at cells and

the electrons bouncing off or going

through

they have a much better resolution than

light microscopes and so that means they

can see the organelles

dna is made up of four bases that's four

chemicals t

and a always go together and c and g as

well

every three bases in the long line of

dna

are a code for an amino acid that tells

the cell

what order to put amino acids in and if

you put lots of amino acids together

they make a protein it is mind-boggling

if you have lots of these triplets they

make a gene so we have jeans

for eye color hair color height etc

diffusion is when particles move from a

high concentration to a low

concentration

like if you spray perfume it's going to

spread throughout the room

so we say they're moving down the

concentration gradient it's passive

which means that no energy is needed

it'll just happen of its own accord

osmosis is diffusion for water when it

goes through a semi-permeable

membrane like the cell membrane so we

can see this in practice if we do the

osmosis practical what we do is cut same

size cylinders of potato and we weigh

them with

a balance and we put them in different

concentrations of

sucrose solution we leave them to soak

and then we weigh them again afterwards

don't forget to dry first to get the

excess water off

if the potato ends up being heavier than

before water has

osmosed in through the cell membrane

that's because the concentration of

sugar in the cell is greater than

in the solution and it's vice versa for

lighter if there's no change in the mass

of

the cylinder that means no water has

osmosed in or out

so that means the concentration of sugar

is the same in the cell

as it was in that particular solution

but what if you want to move something

up the concentration gradient from a low

concentration to a higher concentration

well we need energy to do that and this

is what we call active transport

like getting minerals into roots that

kind of thing we have carrier proteins

that are

in the cell membrane and they act as a

gate that transports

these chemicals these molecules from

outside the cell

to inside the cell but like we said

energy is needed for that it doesn't

just happen

onto bioenergetics respiration is the

most important

reaction in biology because it's how

things get their energy

and all cells do this animal and plant

glucose plus

oxygen makes water and carbon dioxide

here's the balanced chemical equation

for it i just remember that there's lots

of sixes

and h12 and in this process energy is

released and if you think about it it

looks very similar to the combustion

reaction it's almost like respiration is

a very

slow fire so when we say that you burn

calories

it's not really too far off the mark the

reverse reaction of this

is photosynthesis instead of energy

being released we need sunlight energy

to go in

in order for it to happen it's an

endothermic reaction

when a plant makes its own glucose this

is then used to make starch or cellulose

proteins for growth or lipids which are

used to store energy

the test for starch is to put a drops of

iodine on a leaf or food

and it turns purple we'll do the rest of

the food test later the rate of

photosynthesis is affected by a few

factors and we can test this

by doing a practical we put pond weed in

water in

a test or boiling tube we put a lamp

near the tube

and we collect the oxygen bubbles made

in

an upturned measuring cylinder filled

with water

so the independent variable is the light

intensity and we change this by moving

the lamp further away don't forget to

leave it for a minute or two just to let

the pond weed catch up as it were and

the dependent variable is the volume of

gas collected

other factors that affect the rate are

temperature and carbon dioxide

concentration so you'll want to keep

these as controls in the experiment

here's a graph of the rate that's just

volume of gas divided by

the time that it took against light

intensity we can see that it will

eventually

level out that's because there's a

limiting factor but limiting factor

is never what's on the x-axis because we

can see

that we have lots of light intensity

that's still increasing

but it must be something else that is

preventing the rate of photosynthesis

increasing even more if we repeated it

at 25 degrees celsius then we might see

a curve like this

that means the temperature must be the

limiting factor here

now this respiration up top is aerobic

respiration

that's with oxygen but if there's less

oxygen available

like when you're doing exercise then

eventually anaerobic respiration will

take place

that's when glucose is turned straight

into lactic acid

no oxygen required now it does release

energy but not nearly as much as aerobic

respiration

and technically that's because fewer atp

molecules are being made

this then builds up what we call oxygen

debt and so after exercise

oxygen is needed to break down the acid

afterwards and that's what the recovery

period is that's why you keep panting

for a while after doing exercise and of

course we know during exercise

both heart rate and breathing rate

increase in order to get more oxygen to

the cells

in your muscles for them to respire

metabolism is just the term that we use

to describe

the sum of all chemical reactions in

your body

your liver does a lot of these it

removes lactic acid from the blood

and it turns glucose into glycogen if

not

needed that's one way energy is stored

okay let's go on to infection and

response

infectious diseases are caused by little

things called pathogens

they could be bacteria viruses fungi

or protists an example of a disease

caused by a protest is malaria

thankfully we have lots of defenses

big one being just skin we have

platelets in our blood used to

clot up cuts cilia hairs in your trachea

they move nasties back up your windpipe

instead of them going down into your

lungs

mucus in your nose also in your trachea

as well cilia and mucus work well

together

we have acid as well but the real clever

things are your white blood cells

there are two types phagocytes they

ingest or swallow

pathogens and destroy them they're

non-specific so they just go around

swallowing any nasties they can find

lymphocytes are specific

these are the really clever ones they

make antibodies

that bond to the antigen on the outside

or surface of a virus

these have to be a very specific shape

so it can take time to make the right

one because they just make them

randomly but when it does make the right

one your body then remembers

and so when you have that virus again

the antibodies are ready to be made

straight away that's when you become

immune to a virus

these antibodies make viruses clump

together and then they're ingested

we can get a head start on this process

by doing vaccination

what we do is inject a dead or inert

version of a virus

like the flu virus that's been exposed

to radiation we inject that into the

body and so your body

knows what antibodies to make when the

real

virus arrives it was alexander fleming

who accidentally discovered penicillin

one of the first

antibiotics he was growing bacteria in

petri dishes

and there just happened to be some mold

growing in

one of them and he noticed that where

the mold was growing

there were no bacteria there so that

meant that

the penicillin or what was in the

penicillin

must have been killing or stopping the

bacteria

from growing and now we have all sorts

of antibiotics but they don't kill

viruses

you must make sure that you don't

overuse them because the bacteria can

mutate

and they become resistant that's also

why you have to run the whole course as

well

because let's say you kill 99 of them

that one percent is going to grow and

grow and grow

and it's also going to be a little bit

more resistant because of mutations

when we develop drugs we go through a

process

the first step is discovery we have a

look and see what kind of chemicals

can do the thing that we want the drug

to do maybe in the natural world in

plants

then we go through development we test

on tissue then we go into

trials first animal and then human blind

trials

we have one group that are given the

actual drug but then the other group is

the control group and it's given a

placebo it doesn't do anything and

that's to

avoid the patient being biased then we

have double blind trials that's when we

do a similar thing but not even the

doctors know

which is the control group that

completely eliminates any bias then we

manufacture it

send it out and then we do a review to

see actually

how has the drug performed in the real

world some stuff that's usually just for

triple

testing antibiotics we can do a

practical on this we prepare an

agar plate there's a petri dish with

agor in it we spread bacteria like e

coli

to make a lawn we always do this with a

bunsen flame very

close to the dish and we open it towards

the flame as well

just to make sure that other nasties

other bacteria don't enter the dish and

yes the flame will kill

any bacteria in the immediate vicinity

but more importantly

the convection current from the flame

makes the air rise so it pulls bacteria

upwards

away from the dish this way of making

sure that no other bacteria get in is

what we call

aseptic technique what we do is place

drops or

discs that have been soaked in different

antibiotics on this

lawn of bacteria and we have a control

as well just water and then after a few

days we see how big the areas are

of no bacteria around the drops or discs

and we measured the diameter the one

with the biggest diameter is going to be

the best

antibiotic we can actually manufacture

antibodies

we call them monoclonal antibodies we

make them to target specific cells or

chemicals in the body

we inject a mouse with an antigen from

virus then we extract the white blood

cells

making the right antibody in the mouse

we fuse that with the tumor cell and the

tumor cell will start dividing dividing

divining

and that makes what we call hybridomas

we clone them

and then harvest the antibodies that are

made and then we can inject those

antibodies

into a patient plants can also have

diseases a virus

something like tobacco mosaic virus

fungus like rose black spots

but more importantly we have mineral

deficiencies in plants

they need lots of nitrates for amino

acids to make proteins for growth so if

there's a nitrate deficiency

then there'll be stunted growth

magnesium is needed

for chlorophyll so if there's not a lot

of that this causes chlorosis we have

yellow leaves plants also have defenses

as a result they have cell walls which

means that it's harder for

things to get into the cells we have the

waxy cuticle on top of leaves we have

bargain trees or dead cells

they even have antibacterial chemicals

poisons and other deterrents like

thorns okay going back to stuff for

everyone this is organization

a root hair cell looks generally like

this and it has a large

surface area to make sure water can

osmose in

at as high a rate as possible and other

things you can get into

here's a cross-section of a leaf we have

on top the waxy cuticle that's

waterproof to make sure water doesn't

evaporate

out if that wasn't there then the plant

would just dry out the upper epidermis

just below that

is transparent to make sure that light

can go through to the then

palisade mesophyll layer that's where

most of the photosynthesis happens

that's where your very green cells are

they have lots of chlorophyll

underneath that we have the spongy

metaphyll layer that's where

gas exchange occurs so carbon dioxide

oxygen

and also water vapor so water does

evaporate but the point is is that it

can be controlled

by the guard cells that are around the

holes

called stomata at the bottom of the leaf

these can open or close the holes

depending on how much co2

oxygen or water is needed or needs to be

ejected

here's a cross-section of a stem the

xylem are long tubes made from dead

cells

and they carry water phloem are tubes of

cells they're not just

one continuous tube those lots of cells

they use active transport to move

substances

through the plant how does the water

actually rise up through the xylem then

well this is transpiration water

evaporates from the leaves like we just

saw goes out through the stomata this

causes a low pressure of water in the

plant so that means water osmosis into

the roots and

rises up the xylem the water is getting

sucked up the plant

this is affected by temperature higher

temperature obviously

water evaporates quicker wind or high

air flow will remove

water vapor from the leaves quicker so

that means that it causes a lower

pressure

transpiration will happen quicker

humidity if it's very humid that does

the opposite

lots of water vapor around the plant so

a high pressure of water

transpiration isn't going to happen as

quickly here are your different food

tests like we said starch is tested by

iodine turning purple fats can be tested

for

using ethanol it will turn cloudy the

ethanol does need to be cold

glucose tested by benedict solution it

will go from blue to orange

proteins are tested with bureau reagent

goes from blue to a purpley color

enzymes are special chemicals special

proteins that break down

other molecules specific to the chemical

so amylase is an enzyme that breaks down

starch lipase breaks down lipids

protease breaks down proteins they work

on a lock and key mechanism the enzyme

has

an active site which is the lock and

then the substrate which is the chemical

is going to be broken down

fits into there and then the enzyme is

able to split it apart

so an enzyme is basically a biological

catalyst note that there are some

enzymes that join

molecules together not break them apart

the colder it gets the slower the rate

of reaction

just like with any chemical reaction but

if you have too higher temperature

or too high or low ph the active site on

the enzyme denatures it changes

shape so that stops it from working

because the key will no longer fit

the lock as it were here's the practical

and enzymes we put a few drops of iodine

onto a spotting toilet in all of the

holes

we make a water bath at 30 degrees

celsius and we mix together starch

amylase and a buffer solution let's say

we start off with ph5 that just changes

the ph

that the enzyme amylase is exposed to

the ph is going to be our independent

variable we start the timer as soon as

we add the amylase

to this test tube every 20 seconds we

take a drop and we add it to

one of the spots on the spotting tile

and we see

if it turns purple if it turns purple

then obviously

the starch is still there so the amylase

has not broken down all of the starch

let's say when we get to the 10th spot

it stays orange it doesn't turn purple

that means that there's no starch left

all of the starch has been broken down

by the amylase what we do is draw this

graph of our results we can see that we

have this curve

which means that the optimum the best ph

for the enzyme is somewhere between ph

six

and seven but that's going to be

different for different enzymes your

lungs are where gas exchange occurs

we have the trachea that splits into the

bronchi then we have the bronchioles

and then at the end of these branches we

have the alveoli

which the air sacs where gas that's co2

and o2

goes into and out of your blood they

have a large surface area to make sure

this happens as quickly as possible

around these air sacs we have

capillaries little blood vessels

this is a somewhat sketchy diagram of

the heart don't worry i'll fix it a

little bit in a minute blood comes into

the heart into the right

atrium through the main vein the vena

cava then it goes through the tricuspid

valve into the right

ventricle then that goes out through the

pulmonary artery

to the lungs the blood is deoxygenated

it needs to get oxygen from the lungs

and also get rid of co2 the blood comes

back into the heart from the lungs

through the pulmonary vein into the left

atrium it goes into

the left ventricle and then it gets

pumped out to the body through the

main artery called the aorta so because

it comes in goes out to the lungs comes

back and goes out to the body we call it

a double

circulatory system it's pretty ingenious

arteries always go away

from the heart they have thick walls due

to the high pressure of the blood going

from the heart to the body incidentally

you can see the left hand side of

the heart that is the right hand side as

we're looking at it here but the left

side

has a thicker wall because it has to

pump the blood to the body

not just to the lungs because of these

thick walls the

lumen that's just the hole that the

blood goes through in

the artery is fairly small all arteries

have

oxygenated blood in apart from like we

said the pulmonary artery

veins have thin walls they don't have

the high pressure blood in but they do

have valves to stop

the back flow of blood you don't want

deoxygenated blood

going back into your body capillaries

are the tiny blood vessels like we said

they are what allow oxygen and co2 to

get exchanged into your cells

speaking of oxygen binds to the

hemoglobin

in red blood cells carbon dioxide on the

other hand is just dissolved

in the plasma of your blood that's the

straw colored liquid that the blood

cells are swimming in

okay back up to here communicable

diseases are like your viruses and

infections like we saw above

but we do have non-communicable diseases

ncds as well

atheroma is when fat is deposited in

your blood vessels

and that can restrict the blood flow

that can be very bad for your heart

if this is around your heart then this

is called coronary heart disease or chd

an aneurysm is when you have a

ballooning of an

artery and that can actually burst

you're actually born with those and

quite often people don't know they have

them diabetes is another one that's when

your pancreas is not making insulin or

not making enough insulin

in order to control blood glucose levels

type one you're born with

type two you can develop cancer this is

when mutated cells

start growing out of control benign

cancer that's

okay as it were that's when the mutated

cells are just

restricted to a very specific part of

your body so

they're not really causing much damage

malignant on the other hand

that's when things get bad that's when

the cancerous cells tumor cells start

spreading through your body

and they cause cancer elsewhere risk

factors that can affect your likelihood

of getting these diseases

diet smoking drugs ultraviolet light for

skin cancer

exercise that can drastically affect how

well your heart works

carcinogens any chemical that make you

more susceptible

to contracting cancer and i ran out of

room to put it in that little box there

but

we do have to be careful when finding

out the cause

of diseases sometimes we can see that if

there's an increase in one thing

then there's a greater likelihood of

getting a disease but

even though there's a correlation here

it doesn't necessarily

mean that there's causation there might

be causation the increase in

a might be affecting b if we say that i

don't know a is exposure to carcinogens

b is the likelihood of contracting

cancer but we

must do research in order to prove that

one affects the other

to prove causation so i hope you found

that helpful if you did please leave a

like and if you think i've missed

anything then pop it in a comment down

below

and i'll add it to the mind map for you

good luck for your exams

see you next time