nutrition ch 5

A comprehensive set of question-and-answer flashcards covering the definition, structure, synthesis, functions, digestion, dietary requirements, health impacts, and vegetarian considerations of proteins.

What element do proteins contain that carbohydrates and lipids generally do not?

Nitrogen

How many different amino acids are used to build human proteins?

Twenty (20)

Which four components surround the central carbon atom of an amino acid?

A hydrogen atom, a carboxyl (acid) group, an amine group, and a unique side chain (R-group)

What are essential amino acids?

Amino acids that cannot be produced by the body and must be obtained from food

What are non-essential amino acids?

Amino acids that can be synthesized by the body

Give three examples of essential amino acids.

Any three of: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine

What type of bond links two amino acids together?

A peptide bond

What determines the specific structure of each protein molecule?

The sequence of DNA in the gene that codes for the protein

Why is a protein’s three-dimensional shape important?

Its shape is critical for the protein’s proper biological function

List two factors that can denature (unfold) proteins.

Examples: heat, strong acids, heavy metals, alcohol, agitation

Define an incomplete protein.

A protein source that lacks one or more of the essential amino acids, making it insufficient for growth and health

Define a complete protein.

A protein source that provides adequate amounts of all nine essential amino acids

What is mutual supplementation?

Combining two incomplete protein sources so together they provide all essential amino acids

What are complementary proteins?

Two food sources whose amino acid profiles together supply all nine essential amino acids (e.g., beans and rice)

Name three major functions of proteins in the body.

Cell growth/repair, enzymes and hormones, fluid & electrolyte balance, pH regulation, immune defense, energy source

Where does digestion of protein begin?

In the stomach

What two roles does hydrochloric acid play in protein digestion?

Denatures protein structure and activates the enzyme pepsin

What does the enzyme pepsin do?

Breaks proteins into shorter polypeptides and amino acids

Where is protein digestion completed?

In the small intestine

What are proteases?

Pancreatic enzymes that break polypeptides into single amino acids in the small intestine

After absorption, to which organ are amino acids first transported?

The liver

What is the protein RDA for a sedentary adult (per kilogram of body weight)?

0.8 g of protein per kilogram

List four population groups that typically require more protein than the RDA.

Children, adolescents, pregnant/lactating women, athletes

What percentage of total daily energy should ideally come from protein?

Approximately 12–20 % of total energy

Recommended protein intake for non-vegetarian endurance athletes is g/kg.

1.2–1.4 g per kilogram body weight

Give two potential health risks associated with very high protein diets.

High cholesterol/heart disease risk, possible bone calcium loss, kidney strain (in those with kidney disease)

Is there evidence that a high-protein diet causes kidney disease in healthy individuals?

No, current evidence does not show causation in healthy people

List five good dietary sources of protein.

Meats, dairy products, soy products, legumes, whole grains, nuts

What is vegetarianism?

A dietary pattern restricting intake to foods of vegetable origin (including fruits, grains, nuts, etc.)

What foods does a lacto-ovo-vegetarian consume?

Plant foods plus dairy products (lacto) and eggs (ovo), but no animal flesh or seafood

Define a vegan diet.

A diet consisting exclusively of plant-based foods with no animal products

Give one common reason people choose a vegetarian diet.

Health, ecological concern, religious belief, ethical reasons, or food-safety concerns

Name two documented health benefits of vegetarianism.

Lower risk of obesity and type 2 diabetes; reduced heart disease and blood pressure; lower risk of certain cancers; decreased kidney stones/gallstones

Which vitamin critical for nerve fiber protection may be low in vegan diets?

Vitamin B12

Which mineral essential for bone health may be insufficient in some vegetarian diets?

Calcium

What eating strategy helps vegetarians obtain all essential amino acids in one day?

Consuming complementary proteins (mutual supplementation)

Which amino acids are typically limiting in legumes?

Methionine and cysteine

Grains are generally limited in which essential amino acid?

Lysine

How can proteins serve as a source of energy?

When carbohydrate and fat intake is insufficient, amino acids are converted to glucose or oxidized for ATP production

What visual tool can help vegetarians plan a balanced diet?

The Vegetarian Food Guide Pyramid