Proteins: Composition, Functions, and Structure

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Questions and Answers

What is the meaning of the Greek word 'protein'?

of little importance

macronutrient

of utmost importance (correct)

related to body functions

What is the approximate percentage of protein in the human body?

40%

10%

30%

20% (correct)

How many different proteins exist within the human body?

over 500,000

over 1,000,000

over 100,000 (correct)

over 50,000

What elements are contained in proteins, in addition to carbon, hydrogen, and oxygen?

nitrogen only Signup and view all the answers

What is the main function of proteins in the human body during times of low carbohydrate intake?

to provide energy Signup and view all the answers

Which of the following is a unique component of an amino acid?

all of the above Signup and view all the answers

Why are animal proteins considered better body-building foods than plant proteins?

because they provide all essential amino acids Signup and view all the answers

What is the effect of mixing plant and animal proteins in the diet?

it increases the nutritional value of the proteins Signup and view all the answers

What is the primary function of pepsin in protein digestion?

To dismantle protein chains into smaller fragments Signup and view all the answers

What is the result of eating a high-protein meal on digestion?

Food remains in the stomach longer, making you feel full longer Signup and view all the answers

Where does the majority of protein digestion occur?

Small intestine Signup and view all the answers

What are the two major pancreatic enzymes that digest proteins?

Chymotrypsin and trypsin Signup and view all the answers

What is the role of the stomach contractions in protein digestion?

To churn the partially digested protein into a more uniform mixture Signup and view all the answers

What is required for the movement of individual amino acids from the intestinal lumen to the blood?

Special transport proteins and ATP Signup and view all the answers

What happens to the protein fragments in the small intestine?

They are broken down into amino acids Signup and view all the answers

What is the end product of protein digestion?

Amino acids Signup and view all the answers

What is the reason why amino acids are transported to the liver?

Because they contain nitrogen Signup and view all the answers

What happens to the proteins in a cake when it is baked?

They are denatured Signup and view all the answers

What causes proteins to denature?

Heat, acid, high salt concentrations, and mechanical agitation Signup and view all the answers

What is the function of glutathione in the body?

To act as an antioxidant and combat free radicals Signup and view all the answers

What are the three amino acids that make up glutathione?

Cysteine, glycine, and glutamate Signup and view all the answers

What is the effect of alcohol consumption on vasopressin?

It inhibits vasopressin Signup and view all the answers

What is the role of the liver in the catabolism of amino acids?

To transform ammonia into urea Signup and view all the answers

What is the location where vasopressin is secreted?

Hypothalamus Signup and view all the answers

Study Notes

Proteins

Composition and Functions

Proteins make up approximately 20% of the human body and are present in every single cell.
They are necessary for proper immune system function, digestion, and hair and nail growth, and are involved in numerous other body functions.
There are over 100,000 different proteins exist within the human body.

Definition and Structure

Proteins are macromolecules composed of amino acids, which are their building blocks.
Each amino acid consists of a central carbon atom connected to a side chain, hydrogen, nitrogen-containing amino group, and carboxylic acid.
Proteins contain the elements carbon, hydrogen, oxygen, and nitrogen.

Sources

Main sources of proteins include meats, chicken, eggs, breast milk, beans, ground nuts, lentils, fish, cheese, and milk.
Animal foods contain more protein than plants and are usually better sources of body-building foods.
Plant proteins can become more effective nutritionally when mixed with animal proteins.

Protein Digestion and Absorption

Mechanical Breakdown

The first step in protein digestion involves chewing, which breaks down large pieces of proteins into smaller pieces.
The stomach releases gastric juices containing hydrochloric acid (HCL) and the enzyme pepsin, which initiate the breakdown of the protein.

Chemical Breakdown

Pepsin dismantles protein chains into smaller fragments.
The stomach contractions churn the partially digested protein into a uniform mixture called chyme.
Protein digestion in the stomach takes a longer time than carbohydrate digestion but a shorter time than fat digestion.

Absorption

The chyme enters the small intestine, where the majority of protein digestion occurs.
The pancreas secretes digestive juice containing enzymes that further break down protein fragments.
Amino acids are transported from the intestinal lumen through the intestinal cells to the blood.

Transport and Excretion

Amino acids are transported to the liver, where they are further catabolized and ammonia is released.
The liver transforms ammonia into urea, which is then transported to the kidney and excreted in the urine.

Denaturation of Proteins

Definition

Denaturation refers to the physical changes that take place in a protein exposed to abnormal conditions in the environment.

Causes

Denaturation can be caused by heat, acid, high salt concentrations, alcohol, and mechanical agitation.

Effects

Denaturation causes proteins to vibrate, destroying weak bonds and unravelling protein strands, which then stick together, forming a network.

Important Peptides

Glutathione

Glutathione is a substance made from three amino acids: cysteine, glutamate, and glycine.
It acts as an important antioxidant in the body, combating free radicals and helping to detoxify chemicals.

Vasopressin (Antidiuretic Hormone)

Vasopressin is a peptide hormone secreted in the hypothalamus, responsible for regulating the amount of water present in extracellular fluid.
It causes the kidneys to absorb water and is inhibited by alcohol consumption, leading to increased urination.

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Description

Learn about the importance of proteins in the human body, their composition, and functions. Understand how they are structured and their role in various bodily processes.