Unit 1,6 Proteins

What elements make up protein?

53% carbon, 7% hydrogen, 23% oxygen, 16% nitrogen.

What is the most abundant nutrient in muscle?

Protein.

What determines a protein's function?

Its structure (primary, secondary, tertiary, quaternary).

What are the building blocks of protein?

Amino acids.

How many amino acids are found in proteins?

22.

What bonds hold amino acids together?

Peptide bonds.

Why must dietary protein be broken down?

To rebuild amino acids into new proteins the body can use.

Do animals require protein or amino acids?

Amino acids.

Name three major functions of protein.

Provides essential AAs, provides nitrogen for nonessential AAs, forms enzymes/hormones.

What structural roles does protein have?

Hair, skin, organs, muscles, tendons, ligaments.

What blood protein carries oxygen?

Hemoglobin.

How does protein support immunity?

Antibodies.

What proteins are involved in muscle contraction?

Actin and myosin.

What are essential amino acids?

Must be fed; cannot be made by the animal.

Name the essential amino acids.

Phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, histidine, arginine, leucine, lysine.

Why do young animals need more essential AAs?

They are forming muscle and tissues.

What are nonessential amino acids?

Can be formed by the animal.

What determines protein quality?

Amount and ratio of amino acids.

Why is corn a poor‑quality protein?

Low in lysine.

Why is soybean meal high‑quality?

Contains more essential amino acids.

What happens when corn and soybean meal are combined?

More balanced ration.

What is a limiting amino acid?

Essential AA present in the lowest quantity.

Examples of limiting amino acids?

Methionine, tryptophan, lysine.

What is protein turnover?

Constant breakdown and replacement of body proteins.

Which tissues have high turnover?

Blood cells, skin, GI lining, pancreas.

What increases protein requirements?

Disease, trauma, lactation, growth.

Can the body store extra protein?

No.

What is deamination?

Removal of nitrogen from excess AAs → converted to urea → excreted.

What happens to the carbon skeleton?

Used for energy, converted to glucose, stored as glycogen, or stored as fat.

What percentage of body protein is in muscle?

50+%.

What percentage of new protein synthesis occurs in muscle?

30%.

What percentage of body protein is in viscera/organs?

10-15%.

What percentage of new protein synthesis occurs in viscera/organs?

50%.

Do cats require more protein than dogs?

Yes — about twice as much per kg.

Why do cats need high protein?

Obligate carnivores; use AAs for primary energy.

Can cats downregulate protein catabolism?

No.

Can dogs slow protein catabolism when dietary protein is low?

Yes.

What happens if cats don't eat enough protein?

Break down muscle; produce excess nitrogenous waste.

What is taurine?

Essential amino acid for cats.

What is taurine required for?

Normal retinal and myocardial function.

What does taurine deficiency cause?

Blindness, retinal degeneration, dilated cardiomyopathy.

Where is taurine found?

Animal tissue only.

Can cats synthesize taurine?

No — must be fed.

Why do plant‑based diets cause taurine deficiency?

Low/no taurine.

Why does canned food have less taurine?

Heat processing destroys taurine.