Protein Digestion and Nitrogen Balance

Questions and Answers

What is the role of DNA in the synthesis of proteins in the human body?

DNA provides the information for cells to assemble amino acids in specific sequences to make proteins.

Describe the process by which cells assemble amino acids into proteins.

Cells assemble amino acids into proteins by linking them together in specific sequences according to the information provided by DNA.

What is the significance of the 20 amino acids in protein synthesis?

The 20 amino acids are the building blocks of proteins, and their specific sequences determine the structure and function of the protein.

How can the proteins in a sample of blood be used to determine their origin?

The proteins in a sample of blood can be analyzed to determine whether they are from a dog or another animal, such as a human, because every organism synthesizes unique proteins. Signup and view all the answers

What happens to excess amino acids in the body?

Excess amino acids can be broken down and used for energy or converted into other molecules such as glucose or fatty acids. Signup and view all the answers

Describe the concept of nitrogen balance.

Nitrogen balance refers to the balance between the amount of nitrogen taken in through protein consumption and the amount of nitrogen excreted by the body. Signup and view all the answers

How do cells use DNA to synthesize proteins?

Cells use DNA to synthesize proteins by transcribing the DNA code into a molecule of messenger RNA, which then carries the instructions to the ribosome to assemble the amino acids into a protein. Signup and view all the answers

What is the significance of protein synthesis in the human body?

Protein synthesis is essential for the growth, maintenance, and repair of tissues in the human body. Signup and view all the answers

What is the chemical attraction that connects amino acids to form a chain?

peptide bond Signup and view all the answers

What is the minimum number of amino acids required to form a polypeptide?

2 or more Signup and view all the answers

What is the role of mRNA in protein synthesis?

to carry genetic information from DNA to ribosomes Signup and view all the answers

What is the purpose of tRNA in protein synthesis?

to convey specific amino acids to ribosomes Signup and view all the answers

What happens when a diet lacks one or more essential amino acids?

protein synthesis stops Signup and view all the answers

What is the term for small chains of amino acids that usually contain fewer than 15 amino acids?

peptides Signup and view all the answers

What is the primary function of ribosomes in protein synthesis?

to translate mRNA code into a polypeptide chain Signup and view all the answers

What is the term for the process of forming a peptide bond between two amino acids, releasing a molecule of water?

dehydration synthesis Signup and view all the answers

What is the significance of collagen in the human body?

a major structural protein of bones, ligaments, and skin Signup and view all the answers

Why may dietary supplements containing collagen hydrolysates (CHs) not guarantee collagen production in the body?

the body may not use the amino acids derived from CH supplements to produce collagen Signup and view all the answers

Where does the chemical digestion of protein begin?

The stomach Signup and view all the answers

What enzymes break down polypeptides into shorter peptides and amino acids in the small intestine?

Trypsin and chymotrypsin Signup and view all the answers

What is the end product of protein digestion?

Amino acids Signup and view all the answers

Why can cells not distinguish the source of amino acids?

Because cells obtain amino acids from the bloodstream, regardless of their original source Signup and view all the answers

What is protein turnover, and what is its significance?

Protein turnover is the process of breaking down old or unneeded proteins into amino acids and recycling them to make new proteins. Signup and view all the answers

What is the main site of nonessential amino acid production in the human body?

The liver Signup and view all the answers

What are some potential benefits of taking oral collagen supplements, according to scientific studies?

Increased skin elasticity, wound healing, and relief from osteoarthritis pain Signup and view all the answers

What is the purpose of deamination, and what is the resulting product?

Deamination removes the nitrogen-containing group from an unneeded amino acid, resulting in a carbon skeleton. Signup and view all the answers

What determines the three-dimensional shape of a protein?

The polypeptide acid chain coiling and folding Signup and view all the answers

What happens to the nitrogen-containing group removed during deamination?

It is transferred to another substance to make an amino acid during transamination. Signup and view all the answers

What happens when the wrong amino acid is introduced into the amino acid chain during protein synthesis?

Cells usually check for such errors and replace the amino acid with the correct one Signup and view all the answers

What is the end product of transamination, and what is its significance?

An amino acid, such as alanine, is formed, which is then used for protein synthesis. Signup and view all the answers

What is the result of sickle cell anemia, a genetic disorder that affects hemoglobin?

Crescent-shaped red blood cells that cannot transport oxygen efficiently, causing pain, organ damage, and premature death Signup and view all the answers

What is the fate of excess ammonia in the bloodstream?

The liver converts it to urea, a metabolic waste product. Signup and view all the answers

What is protein denaturation, and what causes it?

Denaturation is the alteration of a protein's natural folded and coiled shape, caused by exposure to heat, whipping, acid, or alcohol Signup and view all the answers

What is the purpose of denaturation in cooking and food preparation?

To make protein-rich foods more digestible and safe to eat Signup and view all the answers

What happens to proteins in milk when acidic lemon juice is added?

The proteins in milk become denatured, or 'curdled' Signup and view all the answers

What is the role of hydrochloric acid in the stomach?

It denatures food proteins, making them easier to digest Signup and view all the answers

Why must large proteins in foods be digested before absorption?

To break them down into smaller peptides and amino acids that can be absorbed Signup and view all the answers

What is the relationship between protein shape and function?

The shape of a protein influences its activity in the body Signup and view all the answers

What is the primary function of the kidneys in regards to waste elimination?

The kidneys filter urea, small amounts of ammonia, and creatinine from blood and eliminate the compounds in urine. Signup and view all the answers

What happens to the carbon skeletons of deaminated amino acids in the liver?

The carbon skeletons can be converted to glucose or fat, used to make nonessential amino acids, or metabolized for energy. Signup and view all the answers

What are the primary sources of nitrogen loss in the human body?

Urinary elimination of urea and creatinine, nail and hair growth, and shedding of skin and intestinal cells. Signup and view all the answers

What is the purpose of hormones like insulin, growth hormone, and testosterone in regards to nitrogen balance?

They stimulate positive nitrogen balance, leading to protein synthesis and tissue growth. Signup and view all the answers

What is the Estimated Average Requirement (EAR) for protein in healthy adults?

0.66 g of protein/kg of body weight Signup and view all the answers

How does weight (resistance) training affect nitrogen balance?

It leads to nitrogen retention and positive nitrogen balance. Signup and view all the answers

What is the recommended daily protein intake for a healthy adult?

0.8 g of protein/kg of body weight Signup and view all the answers

What happens to the body when it is in a state of negative nitrogen balance?

The body loses more nitrogen than it retains, and protein intake is less than what the body needs. Signup and view all the answers

What is the purpose of the Recommended Dietary Allowance (RDA) for protein?

To establish the daily protein intake required to maintain nitrogen balance and overall health. Signup and view all the answers

How can you determine your daily protein needs?

By multiplying your weight in kilograms by 0.8 g/kg of body weight. Signup and view all the answers

Study Notes

Protein Synthesis

The body makes proteins by following information coded in DNA
Cells assemble the 20 amino acids in specific sequences according to DNA instructions
Proteins are made up of amino acid "beads" connected by peptide bonds
A polypeptide forms when two or more amino acids join to form a chain
The shape of a protein is important because it influences the compound's activity in the body

Steps of Protein Synthesis

DNA in the cell's nucleus contains the information for making proteins
A section of the DNA double helix unwinds, exposing a gene
Messenger RNA (mRNA) is formed by transcription
mRNA leaves the nucleus and moves to ribosomes in the cytoplasm
Ribosomes translate the gene's coded instructions for adding amino acids to the polypeptide chain
Transfer RNA (tRNA) conveys specific amino acids to the ribosomes
The amino acid from tRNA is added to the last amino acid, causing the peptide chain to grow longer
After the mRNA is read completely, the ribosome releases the polypeptide

Importance of Protein Synthesis

Diets that contain low-quality protein can result in poor growth, slowed recovery from illness, and even death
Protein synthesis in cells cannot proceed when the supply of amino acids does not have one or more of the essential amino acids needed for constructing the polypeptide chain

Protein Denaturation

A protein undergoes denaturation when it is exposed to various conditions that alter its natural folded and coiled shape
Denaturation can occur through heat, acid, or other treatments
Denaturation does not "kill" a protein, but permanently alters its shape and function

Protein Digestion and Absorption

The chemical digestion of protein begins in the stomach, where hydrochloric acid denatures food proteins and pepsin digests proteins into smaller polypeptides
In the small intestine, protein-splitting enzymes, including trypsin and chymotrypsin, break down polypeptides into shorter peptides and amino acids
Enzymes released by the absorptive cells of the small intestine break down most of the shortened peptides into dipeptides, tripeptides, and individual amino acids
Amino acids are absorbed into the bloodstream and transported to the liver
The liver distributes the amino acids to other cells, which use them to make human proteins

Nitrogen Balance

The body conserves nitrogen by recycling amino acids
Nitrogen intake and protein turnover must balance with nitrogen losses
Positive nitrogen balance occurs during periods of rapid growth, recovery from illness or injury, and pregnancy
Negative nitrogen balance occurs during starvation, serious illnesses, and severe injuries

Protein Turnover

Protein turnover is the process of breaking down old or unneeded proteins into their component amino acids and recycling them to make new proteins
The amino acid pool is an endogenous, or internal, source of nitrogen
The body obtains about two-thirds of its amino acid supply from endogenous sources and the remainder from exogenous (dietary) sources

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Description

Test your understanding of protein synthesis, digestion, and absorption in the human body, including nitrogen balance and protein RDA calculations.