Cellular Respiration Part 1: Introduction & Glycolysis

Summary

This video is the first in a three-part series on cellular respiration, focusing on glycolysis. It encourages active learning with notes, questions, and teaching others. The video explains how cells break down glucose to produce energy in the form of ATP, starting with glycolysis in the cytoplasm. It introduces substrate-level phosphorylation and electron transport phosphorylation, describing how glucose is split into pyruvate, producing a net gain of 2 ATP. The video sets up the next stages—Krebs cycle and electron transport chain—to complete the process of generating approximately 36 ATP.

Takeaways

• 📝 Be an active learner: take notes, pause, rewatch, and explain concepts in your own words to reinforce understanding.
• 📚 The video is part of a three-part series on cellular respiration, focusing on glycolysis, the Krebs cycle, and electron transport phosphorylation.
• 🌱 Cellular respiration is the process of breaking down glucose in the presence of oxygen to produce ATP, carbon dioxide, and water.
• ⚡ Glycolysis is the first stage of cellular respiration, taking place in the cytoplasm, and does not require oxygen (anaerobic).
• 🔬 Glycolysis splits glucose into two molecules of phosphoglyceraldehyde (PGL), consuming 2 ATP in the process (energy investment phase).
• 💡 In the energy return phase, 4 ATP are produced through substrate-level phosphorylation, leading to a net gain of 2 ATP.
• 🚀 NAD+ is reduced to NADH during glycolysis, carrying high-energy electrons to the electron transport chain for later ATP production.
• 🧬 Glycolysis ends with two pyruvate molecules, which will enter the mitochondria for further processing in the Krebs cycle.
• 🔗 ATP can be produced through substrate-level phosphorylation (direct transfer of phosphate) and electron transport phosphorylation (driven by chemiosmosis).
• 🧮 In glycolysis, a net profit of 2 ATP is produced, along with 2 NADH molecules and 2 pyruvate molecules that will fuel the next stages of cellular respiration.

Q & A

What is the main focus of this video series?

The video series focuses on cellular respiration, with part 1 discussing glycolysis, part 2 covering the Krebs cycle, and part 3 explaining electron transport phosphorylation.

What are the three stages of cellular respiration mentioned?

The three stages are glycolysis, the Krebs cycle, and electron transport phosphorylation.

What is the primary function of cellular respiration?

The primary function of cellular respiration is to break down glucose in the presence of oxygen to produce ATP, the cell’s energy currency, along with carbon dioxide and water as byproducts.

Where does glycolysis occur in the cell?

Glycolysis occurs in the cytoplasm of the cell.

What is ATP, and why is it important in cellular respiration?

ATP (adenosine triphosphate) is a molecule that stores and transfers energy within cells, and it is the main energy source produced during cellular respiration.

How many ATP molecules are produced during glycolysis, and what is the net gain?

A total of 4 ATP molecules are produced during glycolysis, but since 2 ATP are used in the process, the net gain is 2 ATP molecules.

What happens to the NADH produced in glycolysis?

The NADH produced in glycolysis carries high-energy electrons that are later used in the electron transport chain to generate more ATP.

What is substrate-level phosphorylation?

Substrate-level phosphorylation is a process where a substrate directly transfers a phosphate group to ADP, forming ATP.

What is the preparatory step before the Krebs cycle, and where does it occur?

Before the Krebs cycle, pyruvate produced from glycolysis is converted in a preparatory step that occurs inside the mitochondria.

Why is the mitochondria referred to as the cell’s power plant?

Mitochondria are referred to as the cell’s power plant because they are the primary site of cellular respiration, where ATP is generated from glucose.

Outlines

00:00

📝 Tips for Active Learning and Series Introduction

The introduction encourages active learning, suggesting viewers use paper and pencil, pause, re-watch, and draw their own pictures. It emphasizes teaching the concepts to others to reinforce understanding. The speaker introduces the video series on cellular respiration, dividing it into three parts: an overview of cellular respiration and glycolysis (Part 1), the Krebs cycle (Part 2), and electron transport phosphorylation (Part 3). The video will cover how energy from glucose is converted into ATP through cellular respiration, starting with glycolysis, a process that occurs in the cytoplasm before entering the mitochondria.

05:02

🔬 Overview of Cellular Respiration and Its Three Stages

Cellular respiration involves breaking down glucose in the presence of oxygen to release energy as ATP. The process occurs in three stages: glycolysis, the Krebs cycle, and electron transport phosphorylation. Glycolysis takes place in the cytoplasm and is anaerobic, while the Krebs cycle and electron transport occur in the mitochondria. The latter stages are aerobic and produce the majority of ATP. The mitochondria, often referred to as the cell’s power plant, is a double membrane-bound organelle where most of the energy extraction happens across the inner membrane.

Keywords

💡Cellular Respiration

Cellular respiration is the process by which cells break down glucose into energy in the form of ATP. It is the main theme of the video, which explains how glucose is converted into usable energy through stages such as glycolysis, the Krebs cycle, and electron transport phosphorylation. This process involves both aerobic and anaerobic pathways and occurs primarily in the mitochondria.

💡Glycolysis

Glycolysis is the first stage of cellular respiration where glucose is broken down into two molecules of pyruvate, yielding a small amount of ATP and NADH. It occurs in the cytoplasm and does not require oxygen, making it an anaerobic process. In the video, glycolysis is described as the 'energy investment stage' where ATP is consumed and then later produced.

💡ATP (Adenosine Triphosphate)

ATP is the main energy currency of the cell, produced during cellular respiration. It stores and transfers energy within cells, powering various biological processes. In the video, ATP is repeatedly emphasized as the ultimate product of respiration, which is synthesized in stages like glycolysis and electron transport phosphorylation.

💡Mitochondria

Mitochondria are organelles often referred to as the 'power plants' of the cell where most stages of cellular respiration take place. The video explains how glycolysis happens in the cytoplasm, but the subsequent stages, including the Krebs cycle and electron transport chain, occur within the mitochondria, particularly across its inner membrane.

💡Krebs Cycle

The Krebs cycle, also known as the citric acid cycle, is the second stage of cellular respiration, which takes place in the mitochondria. It generates electron carriers such as NADH and FADH2 that are used in the electron transport chain to produce ATP. The video highlights how pyruvate from glycolysis enters this cycle and generates energy for the cell.

💡Electron Transport Chain

The electron transport chain is the final stage of cellular respiration, located in the inner mitochondrial membrane. It uses electrons carried by NADH and FADH2 to produce a large amount of ATP through a process called chemiosmosis. The video emphasizes its role as the main ATP producer in respiration, explaining how it is driven by the flow of protons.

💡Substrate-Level Phosphorylation

Substrate-level phosphorylation is a direct way of producing ATP during cellular respiration, occurring when a phosphate group is transferred from a substrate to ADP. The video explains this concept during glycolysis and emphasizes that ATP is created without the need for oxygen in this process, contrasting it with electron transport phosphorylation.

💡Electron Transport Phosphorylation

Electron transport phosphorylation is the process of ATP production driven by the electron transport chain, which creates a chemiosmotic gradient across the mitochondrial membrane. The video explains that this mechanism produces the majority of ATP in cellular respiration and relies on oxygen, distinguishing it from substrate-level phosphorylation.

💡NADH

NADH is a high-energy electron carrier produced during glycolysis and the Krebs cycle. It transports electrons to the electron transport chain where its energy is used to create ATP. The video explains how NADH is formed from NAD+ during glycolysis and carries high-energy electrons that are crucial for the ATP production process.

💡Pyruvate

Pyruvate is the end product of glycolysis, consisting of two three-carbon molecules that are derived from one glucose molecule. The video discusses how pyruvate enters the Krebs cycle after glycolysis, indicating that it still contains energy that will be extracted in later stages of cellular respiration.

Highlights

Introduction to the cellular respiration video series, emphasizing the importance of active learning.

Overview of the three-part series: Part 1 covers glycolysis, Part 2 covers the Krebs cycle, and Part 3 focuses on electron transport phosphorylation.

Explanation of how photosynthesis stores energy in glucose, and how cellular respiration releases this energy to form ATP.

Cellular respiration is broken into three stages: glycolysis, the Krebs cycle, and electron transport phosphorylation.

The first stage, glycolysis, is anaerobic and occurs in the cytoplasm.

Glycolysis starts with glucose, which is broken down into two molecules of phosphoglyceraldehyde (PGL) using ATP.

Glycolysis involves an 'energy investment' stage where 2 ATP are consumed, followed by an 'energy return' stage where 4 ATP are produced.

NAD+ is reduced to NADH during glycolysis, and these molecules will carry high-energy electrons to the electron transport chain.

Substrate-level phosphorylation is explained as the direct transfer of a phosphate group from a substrate to ADP, producing ATP.

In electron transport phosphorylation, ATP is produced by a chemiosmotic gradient involving ATP synthase.

The end products of glycolysis are 2 pyruvate molecules, 2 NADH, and a net gain of 2 ATP.

The pyruvate and NADH produced in glycolysis will be used in subsequent stages of cellular respiration.

Mitochondria are described as the cell's power plants, with the inner membrane being the site of significant respiration activity.

Cellular respiration in its entirety will produce approximately 36 ATP molecules from one glucose molecule.

Recap of glycolysis and a preview of what’s to come in the Krebs cycle and electron transport chain.

Transcripts

welcome to our video series on cellular

respiration before we get started I'm

going to ask you to do a few things

don't be a passive learner have paper

and pencil handy pause the video

frequently rewind and re-watch draw your

own pictures because as you know

pictures are your friends and ask

questions go ahead write them down

research the answers and to really test

your understanding teach it to someone

else in your own words and if you want

you can leave questions in the comment

sections below and only instrument as I

can now let's get started I decided to

make this a three part series in part 1

we'll do an introduction or cell

respiration and the details of

glycolysis that's what you're watching

now then in part 2 we'll take a closer

look at the Krebs cycle and in part 3

we'll look at electron transport

phosphorylation watch these three videos

in sequence I'll have links for these

second two at the end of this video and

after it finished with that series check

out my video on fermentation we'll look

at a different way of getting the energy

out of glucose all right now our last

video series we looked at photosynthesis

how we could take the energy of sunlight

and put into the bonds of glucose to

make our cellular fuel so what we need

to do in this video is figure out how we

get this energy back out we need to turn

photosynthesis around so we can see

respiration we're going to get the

energy back out of glucose in a form

called ATP so when we look at this

overall equation we're taking glucose in

the presence of oxygen and we're going

to break it apart into carbon dioxide

and water to liberate energy in the form

of molecule ATP approximately 36 of them

so the respiration is going to occur in

three stages

the first stage is called glycolysis

it's an inter robic stage that takes

place in the cytoplasm

the products of glycolysis will enter

the mitochondria where the second third

stages of respiration occur the second

stage of respiration is called the Krebs

cycle is preceded by a preparatory step

and it's a series of reactions that

occur in the mitochondria that are often

referred to as a citric acid cycle

because the first intermediate made is

citrate or citric acid in the final

stage of respiration is electron

transport phosphorylation it takes place

deep inside the mitochondria it's a

series of enzymes embedded in the inner

membrane called the electron transport

chain it's this stage of respiration

that's aerobic and that will produce the

majority of our ATP now let's take a

look at where this occurs here we have a

cell you want to zoom in on some

important organelles the mitochondria

whoops there we go the mitochondria

let's take a closer look at these

mitochondria the mitochondria is often

referred to as a cell's power plant it's

the primary site of cellular respiration

where we're going to recapture the

energy from those high energy bonds of

glucose and you'll notice that the

mitochondria is a double membrane-bound

organelle and it's across this inner

membrane where a lot of our action is

going to occur we'll come back to the

mitochondria later because the first

stages of respiration glycolysis occurs

out here in the cytoplasm now let's keep

in mind what it is we're trying to do

we're trying to make ATP

so we need to talk about how ATP is

actually made it turns out there are two

ways to make ATP substrate-level

phosphorylation and electron transport

phosphorylation which is driven by

chemiosmosis now let's look at what

substrate level phosphorylation looks

like in substrate level phosphorylation

is substrate directly hands an adp a

phosphate to become ATP let's watch that

again

we have substrate level phosphorylation

8 DP was phosphorylated into ATP with a

direct transfer of a phosphate group so

we call this substrate level

phosphorylation that substrate donates

the phosphate in electron transport

phosphorylation ATP is driven production

is driven by chemiosmotic gradient the

flow of protons through a special

channel protein that we call ATP

synthase so let's get start with

glycolysis

remember that glycolysis is an aerobic

and it occurs in the cytoplasm and we're

going to start with glucose and in the

first step of glycolysis glucose is

split with the energy from ATP and this

is interesting because we're trying to

make ATP but in the first step we

actually consume 2 ATP to split glucose

into two molecules called pgl or

phosphoglyceraldehyde so in our first

step we take a 6 carbon molecule and

split it into two three carbon PJs and

it's going to cost us two ATP we call

this our energy investment stage we

spend two ATP to make two pjo now these

two pjl molecules are used to reduce nad

plus in the NADH and in doing so the pgl

are converted into B pga or by

phosphoglycerate now these two molecules

of NADH are caring for us high-energy

electrons they're very similar to the

electron carriers NADPH that we saw in

photosynthesis but obviously minus a

phosphate so it's in ADH but these two

molecules have a lot of energy left in

them they're carrying this high energy

electrons that's energy we can tap into

later let's look at again the two pjl we

have a tin of the first step of

glycolysis reduce NAD+ to NADH NADH

which is carrying for us higher energy

electrons and hydrogen that we'll send

to the electron transport chain to get

energy out of later

we can add that to our metabolic pathway

for that next step so now we have B PGA

or by phosphoglycerate let's look what

happens as to those molecules the B PGA

will phosphorylate adp into ATP and B

PGA becomes PGA or phosphoglycerate and

these ATP were made by substrate level

phosphorylation let's add that to our

flow chart here so the B PGA

phosphorylate adp into ATP becoming

phosphoglycerate the 2-phosphoglycerate

then phosphorylate another to adp into

two more ATP again by substrate level

phosphorylation and we end with 2

molecules of pyruvate so let's finish

this out the to be the two PGA is

phosphorylate adp into ATP producing 2

pyruvate so in the second stage we have

made 4 ATP so we call this our energy

return stage we have a net profit of 2

ATP we spend 2 we make 4 we also have

these 2 nadh molecule that are carrying

energy that we've yet to tap into so

let's summarize glycolysis again it's

anaerobic doesn't require action it

takes place in the cytoplasm we have an

energy investment step 2 ATP but energy

return of 4 for a net yield or profit of

2 ATP we also produce 2 NADH molecules

which will go onto the electron

transport chain and we end with 2

pyruvate molecules which will go onto

the Crypt so again we're looking at our

flow chart the products of glycolysis

besides this 4 ATP that we're after act

our profit of 2 the other two products

the NADH and the per rate we're not done

with these per rate still have energy in

them that we're going to get in tap into

in the Krebs cycle and the nadh have

energy in them that will tap into and

the electron transport chain

finally let's finish with a little

accounting let's see here's the overall

reaction for respiration and we've

accomplished so far just glycolysis so

let's take into account what we

have and have not done yet and then grab

a pin here so we use glucose check we're

done with that we've yet to use oxygen

and we've yet to make carbon dioxide and

we've yet to make water but we have made

some ATP but only two so we have

approximately 34 ATP left to make so

where's the energy for those ATP well

hopefully you can see that we've yet to

tap into these molecules and so that's

where we're going to go next we

obviously still have a long way to go to

get through this whole process so that

does it for our first part glycolysis

click on this link right here for the

Krebs cycle as we move through this

series on cellular respiration