Nutrition Exam 2

What monosaccharide do all three disaccharides have in common?

Glucose

What is the storage form of carbohydrate in animals? What about in plants?

Animals → Glycogen

Plants → Starch

What bonds link sugars together?

Glycosidic bonds

In a “D” isomer, the functional group is oriented to the _____, while it is

oriented to the _____ in an “L” isomer.

Right; Left

List the enzymes involved with carbohydrate digestion in autoenzymatic

digesters.

Maltase, sucrase, and lactase.

What are the end products of carbohydrate digestion in autoenzymatic

digester? Alloenzymatic digesters?

Autoenzymatic: glucose, fructose, galactose

Alloenzymatic: acetate, propionate, butyrate

Name the three VFAs

Acetate, propionate, butyrate

What are the three principal fates of absorbed glucose?

1. Storage as glycogen

2. Oxidation for energy

3. Fat synthesis and storage

Why is glycogen needed?

To store glucose for later energy use.

How is glycogen metabolism regulated?

By insulin, glucagon, and epinephrine.

Where does glycolysis occur & what are its key products?

1. Cytoplasm

2. 2 Pyruvate, 2 ATP, and 2 NADH

Explain the different fates of pyruvate based on aerobic & anaerobic

Aerobic: Pyruvate → acetyl-CoA → citric acid cycle → lots of ATP

Anaerobic: Pyruvate → lactate or ethanol + CO2

How do glucose, pyruvate, and acetyl‑CoA act as central “hub” metabolites that connect carbohydrate metabolism with lipid metabolism in animals?

Glucose → pyruvate → acetyl-CoA forms a metabolic pathway.

Acetyl-CoA links carbohydrate breakdown with fat synthesis and fat breakdown.

What is the general term for carbohydrates with many sugar molecules?

Polysaccharide

What influences the structural and chemical properties of sugars?

Nature of glycosidic bonds

What group reacts with a hydroxyl group on the same sugar during cyclization?

Keto group

What is the name of the carbon atom that becomes a new chiral center when a sugar cyclizes?

Anomeric Carbon

What type of sugar is a ketopentose?

Monosaccharide

What type of sugar is an aldohexose?

Monosaccharide

Both L and D enantiomers can form α and β anomers.

TRUE

Monosaccharides are classified based on which criteria?

Number of carbon atoms and type of carbonyl group.

What are examples of complex carbohydrates?

Starch, amylopectin, glycogen, and cellulose.

What are the functions of carbohydrates?

Provide dietary calories, storage form of energy, cell membrane components, and structural components.

In a β-bond, what is the configuration of the anomeric hydroxyl group?

β configuration

In an α-bond, what is the configuration of the anomeric hydroxyl group?

α configuration

What enzymes form glycosidic bonds?

Glycosyltransferases

What form are monosaccharides predominantly found in when in solution?

Ring form

Most monosaccharides with five or more carbons exist in open-chain form in solution.

FALSE

What special type of isomerism is found in mirror image structures?

Enantiomers

Isomers that differ in configuration around only one specific carbon atom (except for the carbonyl carbon) are known as ____.

Epimers

Compounds that have the same chemical formula but different structures are called ____.

Isomers

Which three elements compose carbohydrates?

Carbon, hydrogen, and oxygen

What are the major products of salivary amylase activity?

Dextrins and maltose

What bonds does pancreatic amylase target?

α−1,4 bonds

Where does pancreatic amylase act?

Small intestine

Where is salivary amylase secreted?

Salivary glands

What is a higher risk due to immature enzyme systems in young animals?

Malabsorption diarrhea

What behavior do rabbits develop as their hindgut capacity grows?

Cecotrophy

What structure shunts milk to the abomasum in calves until the rumen matures?

Esophageal groove

Pancreatic amylase is high at birth in many species.

FALSE

Which enzyme activities rise as the small intestine adapts to starch- and sugar-rich feeds?

Sucrase and maltase

In mammals, lactase activity declines after weaning as ____

Solid feed increases

What type of birds take time to develop carbohydrate digestive enzymes if they consume crop milk?

Altricial birds

Precocial birds have full development of carbohydrate digestive enzymes at birth.

TRUE

How is methane produced during ruminal fermentation released?

Eructation

What are the purposes of processing grains for ruminants?

Decreases particle size, increases surface area.

The process of glucose and galactose absorption creates a higher ____.

Intracellular concentration of glucose.

Which transporter moves glucose and galactose into enterocytes along the brush border?

SGLT1

What monosaccharides are produced when Lactase cleaves lactose?

Galactose and glucose

What monosaccharides are produced when sucrase cleaves sucrose?

Fructose and glucose

What monosaccharide is produced when Maltase cleaves maltose?

Glucose

What bond does Maltase cleave in maltose?

α(1−4) bond

Which enzymes catalyze intestinal carbohydrate digestion?

Disaccharidases and oligosacharidases

Why does salivary amylase activity stop quickly?

Low pH in the stomach

Which enzyme begins starch digestion?

Salivary amylase

What type of bacteria degrade starch in the rumen?

Amylolytic bacteria

What is the role of fungi in rumen fermentation?

Fermentation of cellulose

What does Congenital Sucrase-Isomaltase Deficiency cause an intolerance of?

Ingested sucrose

What type of disorder is Congenital Sucrase-Isomaltase Deficiency?

Autosomal-recessive

What are clinical signs of Exocrine Pancreatic Insufficiency?

Polyphagia, weight loss, and large volume of loose stools.

Besides osmotic diarrhea, what other symptoms can result from bacterial fermentation of undigested carbohydrates in the large intestine?

Cramping, bloating, and flatulence.

Fructose-1 phosphate is released across the basolateral membrane into portal circulation via ____.

GLUT2

Which enzyme phosphorylates fructose to form fructose 1-phosphate inside enterocytes?

Ketohexokinase

Which transporter leaks glucose out of the cell to reduce swelling during absorption?

GLUT2

What is the primary end product of methane production in cattle?

GHG

The final processes of intestinal carbohydrate digestion occur at the mucosal lining of the ____

Duodenum and upper jejunum

What process causes cell swelling during glucose absorption?

Rising glucose concentration

What bond does Lactase cleave in lactose?

β(1-4) bond

Which transporter moves fructose across the apical membrane?

GLUT5

Which enzyme cleaves the a(1-6) bond in isomaltose?

Isomaltase

What is the primary reason for branching in glycogen structure?

Efficient synthesis and degradation

Order the signaling cascade for glycogen breakdown:

1. Hormone binds to receptor

2. PKA activation

3. Phosphorylase kinase activation

4. Glycogen phosphorylase activation

Order the steps of UDP-Glucose synthesis and glycogen initiation:

1. Glucose phosphorylation to G6P

2. Isomerization to G1P

3. Formation of UDP-glucose

4. Glycogenin glucosylates tyrosine

Define anabolic and catabolic.

Anabolic: requires energy

Catabolic: releases energy

Define mechanical and chemical energy.

Mechanical: motion or potential to move

Chemical: stored in chemical bonds

What are characteristics of ATP compared to glucose?

Unstable, used immediately, and seconds of supply.

Metabolism takes place in both the cytoplasm and the mitochondria.

TRUE

Glucose molecules enter liver or muscle cells through ____.

Glucose transporters

Which species is specifically noted for being prone to Type 2 Diabetes?

Cats

Which species is specifically noted for being prone to Type 1 Diabetes?

Dogs

In the liver, which transporter moves G6P into the endoplasmic reticulum?

Glucose 6-phosphate translocase

Which enzyme is missing in muscle cells, preventing them from releasing glucose into the blood?

Glucose 6-phosphatase

Glycogenolysis is a true reversal of the synthesis process.

FALSE

Where are the primary glycogen stores found in the body?

Skeletal muscle and liver

Which protein glucosylates a tyrosine residue to act as a primer for glycogen synthesis?

Glycogenin

What is the byproduct of the reaction catalyzed by UDP-glucose pyrophosphorylase?

Inorganic pyrophosphate

What are the two primary end products of glycogenolysis?

Glucose 1-phosphate and free glucose

Which enzyme relocates fragments from a chain to a branch point during breakdown?

Glucan transferase

Which enzyme is directly activated by Protein Kinase A (PKA) in the glycogenolysis cascade?

Phosphorylase kinase

Which enzyme rearranges 3-phosphoglycerate to 2-phosphoglycerate?

Phosphoglycerate mutase

Which metabolic fate of pyruvate is specific to microbes?

Alcohol fermentation

What are the three main pathways of cellular respiration?

Glycolysis, TCA, Oxidative phosphorylation

A deficiency in which enzyme leads to hemolytic anemia in Beagles and Pugs?

Pyruvate kinase

Which enzyme is responsible for the dehydrogenation of L-malate to oxaloacetate?

Malate dehydrogenase

Order the intermediates of the TCA cycle starting from the condensation step:

1. Citrate

2. Isocitrate

3. a-ketoglutarate

4. Succinyl-CoA

5. Succinate

What are the products of one single turn of the TCA cycle?

3 NADH, 1 FADH2, 1 GTP/ATP, 2 CO2

What molecule does acetyl CoA condense with to start the TCA cycle?

Oxaloacetate

What does citrate synthase do?

Condensation of acetyl CoA

What does aconitase do?

Isomerization of citrate

What does isocitrate dehydrogenase do?

Oxidative decarboxylation