Animal Nutrition Exam 2

Why are rumen microbes not able to oxidize long-chain fatty acids effectively to make ATP?

Rumen is an anaerobic environment

What property of fat is true?

Contain more energy per gram than either carbohydrates or proteins

How many carbons do medium-chain fatty acids contain?

Between 6 and 12

What two molecules are linked to bile acids to form bile salts?

Glycine and taurine

What molecule helps long-chain fatty acids enter the mitochondrial matrix before they can undergo β-oxidation?

Carnitine

What is the main difference in the composition of fatty acids that make up fish oil and beef fat?

Fish oil contains more polyunsaturated fatty acids

What happens to long-chain fatty acids once they are absorbed by enterocytes in the small intestine?

Long-chain fatty acids must be esterified onto a glycerol backbone

What is one way that rumen microbes avoid the negative effects of dietary unsaturated fatty acids in ruminants?

Convert them to saturated fatty acids

What anatomical part of the small intestine villi transports chylomicrons away from the small intestine and toward other parts of the animal?

Lacteal

What is not a product of fat digestion in the small intestine?

bile salt

What is the most important property of bile salts that helps them emulsify fat in the diet?

Bile salts are amphipathic

What lipid is a precursor of bile acids and steroid hormones?

Cholesterol

What happens to short-chain fatty acids once they are absorbed by enterocytes in the small intestine?

Short-chain fatty acids can bypass lymphatic circulation and enter blood directly

Albumin

transports fatty acid from adipose tissue to other tissues

Chylomicron

Transports re-esterified fats from small intestine to other tissues in dogs

Portomicron

Transports re-esterified fats from small intestine to other tissues in poultry

Very-low-density lipoprotein

Transports fats from the liver to other tissues

Mixed micelle

aggregate of bile salts, phospholipids, fatty acids, and other lipids that are absorbed into enterocytes

Carnitine palmitoyltransferase I

transports fatty acetyl-COA from cytosol to the mitochondrial intermembrane space

Carnitine palmitoyltransferase II

transports acetylcarnitine from the mitochondrial intermembrane space to the mitochondrial matrix

Fatty acyl-CoA synthetase

activates fatty acids with coenzyme A

Acyl-CoA dehydrogenase

oxidizes carbon-carbon single bond to carbon-carbon double bond; reduces FAD to FADH2

β-hydroxyacyl-CoA dehydrogenase

oxidizes hydroxyl group to carbonyl group; reduces NAD+ to NADH

β-ketoacyl-CoA thiolase

produces acetyl-coA and a shortened fatty actyl-CoA

What role does the small intestine have in carbohydrate digestion in ruminant animals?

Minimal enzymatic digestion and glucose absorption

Where does most of the acetyl-CoA that enters the citric acid cycle in the ruminant liver come from?

Acetate from rumen fermentation

Which of the three major volatile fatty acids that are produced from carbohydrate fermentation in the rumen is produced in the least amount?

Butyric acid

What is the correct sequence for the enzymatic digestion of cellulose in non-ruminant animals?

Cellulose is not digested by non-ruminant animals

Which of the following sugars is a hexose monosaccharide?

Galactose

What is the major product of structural carbohydrate digestion and fermentation in the hindgut of horses?

Volatile fatty acids

What best describes glucose transport in the small intestine?

ATP-dependent and Na-dependent

What type of glycosidic bond links adjacent D-glucose units in amylose?

α-1,4

Why is cellulose not able to be digested by animals?

Animals do not express an enzyme that targets the β-1,4 glycosidic bond between glucose and glucose

Which of the following sugars is not a hexose monosaccharide?

Ribose

What animal enzyme hydrolyzes the α-1,6 glycosidic bond between two D-glucose molecules?

Isomaltase

What is an important function of the pentose phosphate pathway?

NADPH production

How are amylose, amylopectin, glycogen, and dextrins similar?

All are homoglycans of glucose

Amylose

D-glucose α-1,4 D-glucose

Maltose

D-glucose a-1, 4 D-glucose

Isomaltose

D-glucose a 1, 6 D-glucose

Sucrose

D-glucose a 1, B-2 D-fructose

Cellulose

D- glucose B-1, D-glucose

Lactose

D-galactose B-1, 4 D-glucose

Rank the following carbohydrates according to the rate of digestion and fermentation in the rumen of ruminant animals

Pectin, Amylopectin, Amylose, Hemicellulose, Cellulose

What are carbohydrates?

Neutral and soluble in water; Carbon, hydrogen, and oxygen; General formula= (CH2O)n where n>3; main component of most animal diets; major energy source for most animals

Carbohydrate classification

monosaccharides, disaccharides, oligosaccharides, and polysaccharides

Triose

Glyceraldehyde and Dihydroxyacetone

tetrose

erythose

pentose

arabinose, xylose, xylulose, and ribose

hexose

glucose, galactose, and fructose

Carbonyl oxygen reacts with

hydroxyl group on the chiral 5-carbon to form cyclic structures

Enantiomers

D-glucose and L-glucose

D-glucose Isomers

naturally occurring and biologically active and nutritionally important

D-glucose and D-galactose

epimers

enantiomers

mirror images; not superimposable

epimers

differ around single chiral carbon

α-D-glucose Hydroxyl group oriented

down

β-D-glucose Hydroxyl group oriented

up

Monosaccharide exist in the

cyclic (ring) form in cells (~99%)

α-D-glucose and β-D-glucose are

anomers

anomers

when glucose cyclizes, carbon-1 becomes the chiral center

HEXOSE MONOSACCHARIDES

Six carbons; D-glucose, D-fructose, and D-galactose

D-glucoes

product of sugar and starch digestion; central role in carbohydrate metabolism

D-fructose

fruit sugar; sweeter than all other monosaccharides and disaccharides

D-galactose

monosaccharide componenent of lactose (milk sugar); produced from glucose in the mammary gland

Glycosidic bonds

link sugars together; these sugars form larger carbohydrates

Disaccharide

2 monosaccharides

Oligosaccharides

3 – 10 monosaccharides

Polysaccharides

> 10 monosaccharides

Step one to classify a glycosidic bond

identify the two linked monosaccharides

step two to classify glycosidic bonds

determine the orientation of the anomeric carbon (a or B) (must be cyclized)

step three to classify glycosidic bonds

determine the position of the anomeric carbon on the first monosaccharide (must be cyclized)

step four to classify glycosidic bonds

determine the position of the carbon on the second monosaccharide to which the anomeric carbon on the firs monosaccharide is linked (must be cyclized)

whether or not a glycosidic bonds can be broken down by animal enzymes depends on

the configuration of that bond

Maltose

fundamental repeating unit of glycogen and starch; a-1,4 glycosidic bond between two D-glucose

isomaltose

a-1, 6 glycosidic bond between two D-glucose

Cellobiose

fundamental repeating unit of cellulose; B-1, 4 glycosidic bond between two D-glucose

sucrose

table sugar; a-1, B-2 glycosidic bond between D-glucose and D-fructose

Lactose

milk sugar formed only in the mammary gland; B-1, 4 glycosidic bond between D-galactose and D-glucose

Amylose

Homopolysaccharide formed from a-D-glucose units linked together by a-1, 4-glycosidic bonds (linear); plant starch (15-30%); Packed tightly together

Amylopectin

Homopolysaccharide formed from a-D-glucose units linked together by a-1, 4-glycosidic bonds (linear) and a-1, 6-glycosidic bonds (branches): plant starch (70-85%); packed together loosely

Glycogen

Homopolysaccharide formed from a-D-glucose units linked together by a-1, 4-glycosidic bonds (linear) and a-1, 6-glycosidic bonds (branches); structure is like amylopectin but more highly branched; animal starch; major form of glucose storage in animals in the liver and muscle

Cellulose

homopolysaccharide formed form a-D-glucose units liked together by B-1, 4-glycosidic bonds (linear); most abundant polysaccharide in plants; essential component of cell walls

Homopolysaccharide

contains only one type of monosaccharide; starch; cellulose

Heteropolysaccharide

contain more than one type of monosaccharide; hemicellulose, pectin, arabinoxylans, fructans

non-starch polysaccharide= nsp

cellulose, hemicellulose, pectin, arabinoxylans, fructans

animal enzymes can digest

sugars, amylose, amylopectin: all non-structural carbohydrates

Animal enzymes cannot digest

cellulose, hemicellulose, and pectin: structural carbohydrates

starch and sugars are the

main carbohydrate source in non-ruminant diets

cellulose and hemicellulose are

important carbohydrate sources in ruminant and non-ruminant hindgut fermenter diets

Lignin

not technically a carbohydrate but often with other structural carbohydrates; abundant in wood, mature hays, and straw; highly resistant to degradation; reduces digestion of other nutrients embedded within its structure

shape of cellulose

linear polysaccharide

cellulose role

primary structural scaffold of cell wall

Hemicellulose shape

branched polysaccharide

hemicellulose role

cross-links cellulose microfibrils

pectin shape

branched, acidic polysaccharide

pectin role

cell-to-cell adhesion

lignin shape

aromatic polymer

ligning role

rigid and hydrophobic matrix filling

all structural carbohydrates are resistant to

digestion by animal enzymes