HUN2201- Chapter 6 (Study Guide)

Describe protein synthesis

DNA in the nucleus of each cell serves as a template to make strands of messenger RNA. Each messenger RNA strand carries instructions for some protein the cell needs. The messenger RNA leaves the nucleus, and attaches itself to the protein-making machinery of the cell. Transfer RNA carry amino acids to the messenger RNA which dictates the sequence in which they will snap into place. This lines up the amino acids in sequence. The amino acids are then linked together in sequence, the completed protein strand is released, and later, the messenger RNA is degraded and the transfer RNA are re-used.

What are the health consequences of ingesting inadequate protein and energy? Describe marasmus and kwashiorkor.

Protein-energy malnutrition, poor growth in children, and weight loss and wasting in adults. Marasmus is the disease of starvation and kwashiorkor is the defiance disease caused by inadequate protein in the presence of adequate food energy.

Describe the structure of amino acids and explain how the sequence in proteins affects the proteins' shapes.

Amino acids are linked together to form proteins. The sequence and special characteristics of the side chains determine the protein's shape.

What are the essential amino acids?

The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

What factors are considered in establishing recommended protein intakes?

The quality of the protein eaten, calories and other nutrients consumed, a person's lean body mass, and a person's state of health.

How might protein excess, or type of protein eaten, influence health?

Diets too high in protein offer no benefits. They often contribute fat-rich foods to diets of people who need to lose weight. In the small infant, the accumulation of amino acids stresses the kidneys and liver which have to metabolize and excrete the excess nitrogen. This may cause acidosis, dehydration, diarrhea, elevated blood ammonia, elevated blood urea, and fever. High-protein diets may promote calcium losses and deplete the bones of this mineral. If much animal-derived protein is eaten, this may contribute to the development of heart disease and cancer.

Describe protein digestion and absorption

In the mouth, chewing and crushing moisten protein-rich foods and mix them with saliva to be swallowed. In the stomach, stomach acid uncoils protein strands and activates enzymes. Pepsin and HCl break protein down into smaller polypeptides. In the small intestine, pancreatic and small intestinal enzymes split polypeptides further into dipeptides, and amino acids, then enzymes on the surface of the small intestinal cells hydrolyze these peptides and the cells absorb them.

What factors affect the quality of dietary protein? What is a complete protein?

Its supply of a balance of the essential amino acids and its digestibility. A complete protein is a protein containing all the amino acids essential in human nutrition in amounts adequate for human use.

How does the chemical structure of proteins differ from the structure of carbohydrates and fats?

Like carbohydrates and fats, proteins contain carbon, hydrogen, and oxygen, but proteins also contain nitrogen. Amino acid structures have an amino group, an acid group, a hydrogen, and a side chain which makes each amino acid different from the others.

What are the benefits and risks of taking protein and amino acid supplements?

No benefits, but risks include death, abnormal heart rhythms, severe amino acid imbalances and toxicities. Taking tryptophan supplements can cause eosinophilia myalgia syndrome (EMS).

What are enzymes? What roles do they play in chemical reactions? Describe the differences between enzymes and hormones.

Protein catalysts that facilitate the synthesis of larger compounds from smaller ones and hydrolysis of larger compounds to smaller ones without being affects in the process. Hormones are chemical messengers that are secreted by a variety of endocrine glands in response to altered conditions in the body.

Describe some of the roles proteins play in the human body.

Proteins serve as enzymes, help maintain the body's fluid balance by attracting water, help maintain acid-base balance by acting as buffers, act against disease agents as antibodies, regulate body processes as hormones, transport nutrients and other molecules into and out of cells, help clot blood, help make scar tissue and bones, and serve as light-sensitive visual pigments.

How does the body use amino acids? What is deamination? Define nitrogen balance. What conditions are associated with zero, positive, and negative balance?

The body uses amino acids for proteins or nonessential amino acid, for other compounds such as for synthesis of neurotransmitters norepinephrine and epinephrine and melanin, or for energy. Deamination is removal of the amino group from a compound such as an amino acid. Nitrogen balance: the amount of nitrogen consumed compared with amount of nitrogen excreted. Zero N balance: normal, healthy adult and lactating mothers. Positive N balance: growing children and pregnant women. Negative N balance: people who are sick or in trauma and people with kidney disease.

How can the two conditions be distinguished, and in what ways do they overlap?

The distinction is that someone with kwashiorkor has inadequate energy, while someone with marasmus has both inadequate energy and inadequate protein. Both conditions cause loss of body protein tissue.

How can vegetarians meet their protein needs without eating meat?

Vegetarians can obtain protein from legumes, nuts, vegetables, grains and (in some cases) eggs and milk products.