CH06: Proteins: Crucial Components of All Body Tissues

Liver

1. Amino acids can be converted into glucose here. 2. Amino acids that enter the bloodstream from the small intestine travel to here.

Taking a bite of a peanut butter sandwich -> Amino acids entering the circulatory system

1. Food containing protein is crushed and moistened with saliva. 2. Proteins are denatured by hydrochloric acid, and pepsinogen is activated. 3. Pepsin breaks down proteins into single amino acids and polypeptides. 4. Proteases from the pancreas are secreted into the small intestine. 5. Proteases break down polypeptides into mostly tripeptides and dipeptides. 6. Tripeptides and dipeptides are broken down into single amino acids.

Stomach

1. Hydrochloric acid denatures protein here. 2. Pepsin is formed from pepsinogen here.

How does your body use the protein once it has been ingested? Consider the following statements and select the correct ones regarding protein use.

1. If calorie intake is inadequate, amino acids can be used for production of energy. 2. The liver uses amino acids to create glucose. 3. Amino acids are used to create new proteins.

mRNA

1. It carries a copy of the DNA instructions that dictate the sequence of amino acids for making a specific protein. 2. The ribosome moves along this and reads the encoded information.

Ribosome

1. It releases the amino acid chain once the chain is complete. 2. It reads the copied genetic information and helps build the corresponding sequence of amino acids.

DNA contains all the genetic information necessary for production of every protein the body makes. Read the statements below and select the correct statements regarding the role of DNA in protein synthesis.

1. Nuclear DNA cannot leave the nucleus. 2. The DNA unwinds in order for a copy to be made of a gene, in the form of an mRNA molecule.

The body can make __________ nonessential amino acids.

11

How much protein should Sarah add to her diet if she gets pregnant? Sarah's protein requirements during pregnancy would be higher.

19 g

The recommended protein intake for a 110-pound (50-kg) adult is __________.

40 g

What is the daily protein requirement for Sarah, a 136-lb, moderately active 32-year-old woman?

49 g

For protein synthesis to continue successfully, adequate amounts of energy and essential amino acids need to be available in the body. Which of the following scenarios describing dietary intake is most likely to result in inadequate protein intake that could interfere with protein synthesis?

Although Dakota enjoys red meat on occasion, he considers himself a semivegetarian. Recently, he put himself on a very-low-energy diet in his efforts to lose 4 lb per week.

The DNA contains all of the instructions for building the hundreds of thousands of proteins that are found in the human body.

DNA

Denaturation occurs when a protein is exposed to heat, acid, bases, or mechanical agitation resulting in unfolding of the protein, though the peptide bonds remain intact.

Denaturation

Dipeptide describes an amino acid chain made up of two amino acids joined together.

Dipeptide

Amino acids are bound together by a chemical bond known as an amino acid bond to form proteins.

False

Deamination occurs mostly in the brain.

False

Mouth

Food containing protein is crushed and moistened here.

Gastrin is a hormone that controls the release of pepsin and the production of hydrochloric acid.

Gastrin

DNA

Instructions on how to build all proteins are stored in this molecule's genetic code.

tRNA

It transfers specific amino acids to the growing amino acid chain.

Pepsin is the active form of the digestive enzyme pepsinogen.

Pepsin

Pancreas

Proteases are produced here and delivered via a duct to the small intestine.

Which of the following is true about the quality of protein?

Proteins from foods of animal origin are generally high-quality proteins.

What would happen if Sarah consistently exceeded her daily protein requirement?

She could gain weight if the extra protein contributed to excess kilocalories over her energy needs.

Small intestine

Single amino acids, dipeptides, and tripeptides are absorbed here.

The body uses two types of amino acids: essential and nonessential. Which of the following statements about essential and nonessential amino acids is correct?

There are 11 nonessential amino acids.

The side chain of an amino acid differentiates one amino acid from another.

True

This is a nutrient of concern in vegetarian diets.

Vitamin D

The 20 different amino acids are the building blocks used for protein synthesis.

amino acids

High-protein diets of predominately animal sources are associated with high __________.

blood cholesterol

A nonessential amino acid is made __________.

by transferring the amino group from one amino acid to a keto acid. A keto acid is an amino acid without the amine group.

Amino acids found in the amino acid pool __________.

can be used for protein synthesis

Which of the following foods would provide the highest quality protein in the smallest portion size?

chicken breast

Which of the following foods provides a moderate amount of protein per serving?

corn

To use amino acids for energy, the nitrogen must first be removed from the amino acid. This process is called __________.

deamination

Which of the following is a protein?

enzyme

Which of the following foods would have the lowest amount of protein per serving?

fruits

A segment of DNA that encodes for the production of a specific protein is called a(n) gene.

gene

The stomach produces hydrochloric acid, which denatures protein.

hydrochloric acid

Nitrogen that has been removed during deamination __________.

is converted to urea and excreted through the urine

Symptoms such as edema, distention of the belly, loss of appetite, skin problems, and retarded growth and development are often associated with __________.

kwashiorkor

Which of the following amino acids are considered essential?

lysine, methionine, and threonine

DNA does not build or synthesize a protein it encodes for; instead, DNA contains information that is copied by an enzyme to make mRNA, which leaves the nucleus and goes to the ribosome where the protein is built.

mRNA

A serious protein-energy malnutrition disease is __________.

marasmus

Unlike lipids and carbohydrates, proteins are __________.

nitrogen containing

The structure in the cell that contains DNA is called the nucleus.

nucleus

When amino acids join together, they form __________.

peptides

Cleavage of proteins by pepsin in the stomach results in formation of shorter polypeptides, which get broken down further in the small intestine.

polypeptides

Single amino acids that are absorbed in the small intestine travel to the liver via the portal vein.

portal vein

Protein is digested in the small intestine by enzymes called proteases.

proteases

To begin the translation stage, mRNA binds to a ribosome with the help of rRNA.

rNA

The ribosome reads the mRNA strand, and with the help of tRNA, builds the corresponding amino acid chain.

ribosome

A type of RNA that plays the important role of transferring specific amino acids to the growing amino acid chain in the ribosomes is called tRNA.

tRNA

Which of the following plant foods have the highest quality of protein?

tofu

An amino acid chain made up of three amino acids joined together is called a tripeptide.

tripeptide