Carbohydrates | Biochemistry

Summary

In this video, Dr. Mike discusses carbohydrates, one of the four major macromolecules, alongside proteins, fats, and nucleic acids. He explains that carbohydrates are composed of carbon, hydrogen, and oxygen, and exist in various forms: monosaccharides, disaccharides, and polysaccharides. Glucose, fructose, and galactose are common monosaccharides with the same chemical formula but different structures. The video also covers the digestion and storage of carbohydrates, lactose intolerance, and the difference between plant polysaccharides like cellulose, which humans cannot digest, and glycogen, which the body stores for energy.

Takeaways

• 💡 Carbohydrates are one of the four major macromolecules, along with proteins, fats, and nucleic acids.
• 🧬 Carbohydrates are composed of carbon, hydrogen, and oxygen atoms (carbo = carbon, hydrate = water).
• 🔄 Carbohydrates mainly function as a source of energy in the body and are found in cells and cell membranes.
• 🍬 The three main types of monosaccharides are glucose, fructose, and galactose, all of which have the same chemical formula (C6H12O6) but differ in structure.
• 🏃 Glucose is the primary monosaccharide used for energy production in the body, while fructose and galactose are converted to glucose in the liver.
• 🔗 Disaccharides are formed by joining two monosaccharides through a dehydration reaction (removal of water). Examples include sucrose (glucose + fructose) and lactose (glucose + galactose).
• 🧪 Lactose intolerance occurs when the body lacks the enzyme lactase, preventing the breakdown of lactose into glucose and galactose, which can lead to diarrhea due to osmotic effects.
• 🌾 Polysaccharides, or complex carbohydrates, can be ingested from plants (starch, cellulose) or animals (glycogen).
• 🥬 Humans cannot digest cellulose from plants (e.g., in leafy greens) due to the lack of necessary enzymes, while animals like cows can.
• 🧱 Glucose can be stored in the body as glycogen, a highly branched polysaccharide, for later energy use.

Q & A

What are the four major types of macromolecules mentioned in the script?

The four major types of macromolecules are carbohydrates, proteins, fats, and nucleic acids.

What elements make up carbohydrates?

Carbohydrates are made up of carbon, hydrogen, and oxygen.

What are the three main types of monosaccharides?

The three main types of monosaccharides are glucose, fructose, and galactose.

How do glucose, fructose, and galactose differ chemically?

They have the same chemical formula (C6H12O6) but differ in the arrangement of their atoms, making them isomers.

What happens to galactose and fructose in the liver?

In the liver, galactose and fructose are converted into glucose for energy use or storage as glycogen.

What is a dehydration reaction, and how does it relate to carbohydrates?

A dehydration reaction removes a water molecule to link sugar molecules together, forming disaccharides like sucrose and lactose.

Why do people with lactose intolerance experience digestive issues?

People with lactose intolerance lack the enzyme lactase, which breaks down lactose. Without this enzyme, lactose remains undigested, leading to water retention in the intestines and resulting in diarrhea.

What is the difference between cellulose, starch, and glycogen?

Cellulose is a long linear chain of glucose found in plants, starch is branched glucose from plants, and glycogen is highly branched glucose used by animals for energy storage.

Why can cows digest cellulose but humans cannot?

Cows have the necessary enzymes to break down cellulose into glucose, while humans do not, making cellulose indigestible for us.

What role do polysaccharides play in the human diet?

Polysaccharides like starch and glycogen can be broken down for energy in humans, while cellulose acts as fiber, aiding in digestion by bulking up stool.