Animal Nutrition Exam 3

"Conditionally essential amino acids" are best defined as:

Amino acids needed from the diet depending on species, age, or physiological state

Which are essential amino acids for most species?

His, Ile, Leu, Lys, Met, Phe, Thr, Trp, Val

Ruminant diets can include rumen-protected amino acids because:

They resist rumen degradation and supply the small intestine directly with limiting amino acids

Which statement about protein storage is correct?

Protein cannot be stored; excess is catabolized and nitrogen excreted as urea

Which transporter/pathway primarily absorbs di- and tripeptides across the intestinal brush border?

PEPT

Which describes the primary structure of a protein?

Sequence of amino acids linked by peptide bonds

Which digestive enzyme is a gastric enzyme active at low pH?

Pepsin

Which amino acids are strictly ketogenic?

Lysine and leucine

Which statement about amino acid catabolism is TRUE?

The amino group is converted to urea primarily in liver

Which pairing of metabolic fate with definition is CORRECT?

Ketogenesis—formation of ketone bodies from acetyl-CoA

Which molecules directly read codons and bring amino acids during translation?

tRNA (with amino acids attached)

A "codon" is:

A three-base sequence in mRNA specifying an amino acid or stop

"Translation" is the process of:

Converting mRNA codons into an amino acid sequence on ribosomes

"Transcription" in protein synthesis is:

Making RNA from DNA in the nucleus

"Ideal protein" in diet formulation is best defined as:

A dietary amino acid pattern that matches the animal's requirement profile

The "limiting amino acid" concept means:

The amino acid in shortest supply relative to need restricts protein synthesis

At physiological pH, most free amino acids exist as:

Zwitterions (both positive and negative charges)

In typical poultry diets, the first limiting amino acid is often:

Methionine

In typical swine diets (grains + soybean meal), the first limiting amino acid is usually:

Lysine

Why is formulating on digestible (not total) amino acids important?

Digestibility varies by ingredient, species, age, and processing

"Digestible amino acids" in feed formulation refers to:

The fraction of amino acids actually absorbed by the animal

Glutamine has which notable role?

Major energy source for certain immune cells; supports gut and muscle protein metabolism

Arginine can be converted to nitric oxide and:

Creatine and polyamines

Which is a correct example of a functional amino acid conversion?

Tryptophan → serotonin and melatonin

"Functional amino acids" are best described as amino acids that:

Have specific physiological roles beyond protein synthesis/energy (e.g., NO, serotonin)

Which sequence correctly traces the urea cycle steps (simplified)?

Ornithine → Citrulline → Argininosuccinate → Arginine → Urea + Ornithine

The urea cycle primarily occurs in the:

Liver (some in kidney)

The "α-carbon" of an amino acid is directly bonded to which four groups?

Carboxyl, amino, hydrogen, and side chain (R)

For dairy rations, which amino acids are most often limiting and sometimes fed in rumen-protected forms?

Methionine and lysine

"Rumen-undegradable protein" (RUP) is also called:

Escape protein (bypass protein)

Urea recycling in ruminants refers to:

Urea formed in liver returning to rumen via saliva or diffusion for microbial use

Nonprotein nitrogen (NPN) in the rumen is first converted to:

Ammonia, then used to synthesize microbial amino acids

Microbial protein leaving the rumen is valuable because it:

Contains all essential amino acids for the animal

In ruminants, rumen-degradable protein (RDP):

Is hydrolyzed by microbes to peptides and amino acids for microbial protein synthesis

Which statement about colostrum immunoglobulins is correct?

They can be absorbed intact in early life via Fc receptors/pinocytosis

Which statement about amino acid absorption is TRUE?

Most amino acids use carrier-mediated systems (some Na+-dependent, some facilitated)

Approximately what fraction of amino acid absorption occurs via PEPT pathways (di-/tripeptides)?

≥50%

The PEPT transporters in enterocytes mainly absorb:

Dipeptides and tripeptides

What is the bond that links amino acids together in proteins?

Peptide bond

Aminopeptidase and dipeptidase are secreted by:

Small intestinal mucosa

Carboxypeptidase B mainly removes which amino acids from the carboxyl end?

Basic (Arg, Lys)

Carboxypeptidase A mainly removes which amino acids from the carboxyl end?

Aromatic and aliphatic

Elastase (activated by trypsin) preferentially generates peptides ending with:

Aliphatic residues (Ala, Gly, Ile, Leu, Val)

Chymotrypsin is activated by trypsin and preferentially cleaves next to:

Aromatic residues (Phe, Tyr, Trp)

Trypsin preferentially cleaves peptide bonds to yield peptides ending with which residues at the carboxyl end?

Basic residues (Arg, Lys, His)

Trypsin is secreted by the pancreas as trypsinogen and is activated in the small intestine by:

Enterokinase (enteropeptidase)

Which protease is secreted in the stomach and activated at low pH?

Pepsin

Which is an example of a peptide hormone?

Insulin

Which statement best defines an enzyme?

A protein catalyst that speeds biochemical reactions

Protein molecules are primarily composed of which elements?

C, H, O, N (and sometimes S, P)

Grass tetany is:

Hypomagnesemia, often when grazing low-Mg, high-K spring pasture

Milk fever (parturient paresis) is characterized by:

Hypocalcemia in high-producing dairy cows soon after calving

Osteomalacia refers to:

Bone softening in adults due to demineralization

Rickets in young animals is:

Softening/deformation of bones due to failed mineralization

Superoxide dismutase (SOD) is important because it:

Converts superoxide radicals to less reactive species (antioxidant; Cu-containing form)

Glutathione peroxidase is:

A selenium-dependent enzyme that removes peroxides/free radicals

A hemoprotein is best described as:

A protein containing a heme group with iron

Which are typical calcium sources in feeds?

Ground limestone, oyster shell flour, and (di/mono/tri)-calcium phosphates

A central role of selenium (Se) is:

Component of glutathione peroxidase protecting membranes from oxidative damage

Excess dietary zinc can:

Interfere with Cu and Fe absorption and cause anemia

A hallmark of zinc (Zn) deficiency is:

Rough hair coat, poor feathering, and impaired growth

Iodine's primary role is in:

Thyroid hormone synthesis (thyroxine/T₄ and triiodothyronine/T₃)

Cobalt (Co) nutrition is best summarized as:

Rumen microbes use Co to synthesize cobalamin; monogastrics need preformed cobalamin

Copper (Cu) functions include all except:

Major component of thyroid hormones

Newborn pigs commonly receive Fe injections because:

Sow's milk is low in Fe and piglets grow rapidly indoors

Which statement about iron (Fe) is correct?

Fe is a key component of hemoglobin and myoglobin for O₂ transport/storage

Sulfur (S) nutrition is important largely because:

S is a component of Met, Cys, biotin, and thiamin; rumen microbes use S to make S-amino acids

Which statement best defines microminerals?

Minerals required in milligram (trace) amounts compared with macrominerals

Na⁺/K⁺ are required for which of the following?

Sodium-dependent transport of glucose/neutral amino acids and nerve impulses

Regarding fluid distribution, which is correct?

Most Na⁺ and Cl⁻ are extracellular; most K⁺ is intracellular

Magnesium (Mg) deficiency in grazing ruminants commonly presents as:

Grass tetany on low-Mg, high-K pastures

The enzyme phytase is added to some monogastric feeds primarily to:

Hydrolyze phytate and improve phosphorus availability

Which is a major role of phosphorus (P)?

Component of ATP, phospholipids, RNA, and DNA

A classic sign of calcium deficiency in young animals is:

Rickets with bone deformities

Which statement about vitamin D and calcium is correct?

Vitamin D stimulates Ca absorption and incorporation into bone/teeth

The recommended dietary Ca:P ratio to promote bioavailability is approximately:

1.5:1 to 3:1

Which pair most accurately matches mineral and primary location/function?

Ca — 99% in skeleton; blood clotting and muscle contraction

Phytate (phytate-P) in plant feeds is:

A storage form of P largely unavailable to simple-stomached animals without phytase

Which statement best defines macrominerals in animal nutrition?

Minerals needed in gram amounts relative to microminerals

In animals, retinoids (vitamin A forms) include:

Retinol, retinal, retinoic acid

Cleavage of beta-carotene to vitamin A in enterocytes requires:

Dioxygenase and reductase

Niacin (B3) can be synthesized from tryptophan at about:

45-60:1

A core structural role of ascorbic acid is in forming:

Hydroxylysine and hydroxyproline for connective tissues

Thiamin (B1) is typically destroyed by:

Heat and alkaline pH

Cobalamin (B12) is found in which sources and has which key feature?

Animal tissues; produced by bacteria; contains cobalt

Pyridoxine (B6) as PLP primarily supports:

Transamination and amino acid metabolism

Riboflavin (B2) serves as a precursor for which coenzymes in energy metabolism?

FAD and FMN

Which statement best describes vitamins in animal nutrition?

Needed in minute amounts; regulate metabolism/energy transformations

Regarding vitamin K absorption, which is correct?

Phylloquinone needs active transport; menaquinone/menadione diffuse passively

Pantothenic acid is essential because it forms:

Coenzyme A (CoA) for acetyl-CoA and acyl carrier protein

Which species have low efficiency of cutaneous vitamin D synthesis and thus need a dietary source?

Cats and Dogs

Which grouping lists only fat-soluble vitamins?

A, D, E, K

Cholecalciferol is the chemical name for:

Vitamin D3

A hallmark sign of vitamin A deficiency is:

Night blindness

Biotin primarily acts as a coenzyme for:

Carboxylases (e.g., acetyl-CoA carboxylase; pyruvate carboxylase)

A classic deficiency sign of pantothenic acid mentioned in the text is:

Goose stepping

Which situation can precipitate biotin deficiency?

Feeding raw egg whites (avidin)

Tocopherols (vitamin E) primarily function as:

Lipid-phase antioxidants; alpha-tocopherol is most active

Menadione is:

Synthetic vitamin K3

In enzymology, a coenzyme is best defined as a(n):

Non-protein organic molecule that assists enzyme activity