ANIMAL NUTRITION EXAM 2

What is a Carbohydrate?

Broad group of substances which include the sugars, starches, gums and celluloses

What does a carb consist of?

biomolecule that has C, H, & O

What % of carbs do animals have in the body?

• very little

• 1%

Carbohydrates in Plants

• huge component in plant tissues

• plants = 60-70% carbs

What do chloroplasts in plants make?

sugar from sunlight & CO2

-ose (individual sugar molecules)

sugar

-saccharide

sugar compound suffix

Pentose

5 carbon sugar

Hexose

6 carbon sugar

Monosaccharide

1 sugar or simple sugar

Disaccharide

2 sugar

Trisaccharide

3 sugar

Oligosaccharide

3-10 sugar

Polysaccharide

more than 10 sugar

Common Monosaccharides

1. glucose

2. fructose

3. galactose

How are disaccharides formed?

• through condensation - they lose a water molecule (aka dehydration synthesis)

• then share an O molecule

Common Disaccharides

1. sucrose - table sugar

2. maltose - starch breakdown

3. lactose - dairy

Common Polysaccharides

1. starches - plants

2. fiber - indigestible by humans

3. glycogen - animals

Complex carbs

1. monomers - long, complex chains

2. polysaccharides

3. take longer to digest

Starch

1. made up of glucose monomers

2. 1-4 or 1-6 bonds

Amylose

1. starch

2. straight structure

3. 1-4 linkages

Amylopectin

1. starch

2. branched structure

3. 1-4 & 1-6 linkages

What is glycogen?

1. a starch

2. a storage form of glucose in animal body

Cellulose

1. α and β linkages

2. 1-4 bonds

3. Every glucose monomer

   flipped in relation to next one

4. linear, fibrous structure

5. tightly packed

Carbs Functions in animals

1. provide energy (main one)

2. regulates blood glucose

3. decrease use of protein for energy

4. fatty acid breakdown (decreases ketosis)

5. biological recognition processes

6. flavor

7. sweeteners

8. dietary fiber

Carbs function in plants

1. serve as energy

2. energy reserves/storage

Providing energy function

1. glucose - main sugar used by body & brain to provide energy for tissues

2. liver converts mono, di, & polysaccharides to glucose in body

Decrease Use of Protein function

1. Amino acids can be converted to glucose for energy via process of gluconeogenesis

2. Allows AA to be used for enzymes, antibodies, receptors, and most importantly, building up of tissue

Carbohydrates as Sweeteners function

1. mono & disaccharides are sweet

2. increases palatability in feed (agreeable & more tasty)

Carbohydrates as Fiber

1. fiber - structural components of plants that are not easily digestible (by livestock) (broken down by microbes)

2. main source of feed/nutrients for microbes

How is fiber useful when it moves through the digestive system?

It is useful bc it allows the body more time to break down feed which results in more nutrients being absorbed

The mouth is the first site of carbohydrate digestion

True or False?

T

T or F?

The stomach & LI are major sites of monosaccharide absorption

What is the primary site of starch & glycogen digestion in most animals?

SI

The process of forming glycogen from glucose is called:

Glycogenesis

Which animals rely heavily on gluconeogenesis rather than directly absorbing & using large amounts of dietary glucose?

Ruminants

What site of digestion can monosaccharides only be absorbed?

SI

What is ATP?

1. adenosine triphosphate

2. Provides source of energy for

   almost all major biological

   processes

What sections of the SI have the greatest capacity for monosaccharide absorption?

Duodenum & Jejunum

Which digestive system organs absorb little to no monosaccharides?

Stomach & LI

Na+ glucose cotransporters

1. actively sends glucose across apical membrane

2. sent against concentration gradient

3. couples transport to Na+

4. Na+ transported down its gradient

How does glucose absorption get transported?

1. Na+-K+ ATPase continually pumps out Na+

2. Named SGLT1-6

3. Sodium-glucose linked transporter

4. Move glucose from lumen inside cell

5. sends glucose down concentration gradient

6. facilitative

7. moves from inside

   cell to outside basolateral side

How does fructose absorption get transported?

1. Can rely on uniporter (single

   molecule transporter) to cross

   apical membrane

2. turned to glucose in SI cell or leaves cell as is

Glucose Fate in Non-ruminants

1. immediately used for energy (creates ATP)

2. storage for later ATP production (in form of glycogen)

3. used in building other molecules (nucleic, amino, & fatty acids)

How are carbs digested in ruminants?

1. digested to VFAS (volatile fatty acids)

The 3 VFAS

1. acetate

2. propionate

3. butyrate

Microbial Fermentation in Ruminants

microbes hydrolyze β & other tough bonds in plants using diverse microbes for diff parts. This releases VFAS that are absorbed by the host, alongside methane gas that is eructated

What is the fate of acetate?

fatty acids, goes to adipose

What is the fate of propionate?

TCA cycle

What is the fate of butyrate?

ketone bodies

Where is glycogen stored?

the liver & muscle tissue

What is glycogen’s balance regulated by?

insulin & glucagon

Glycogenesis

1. glycogen formation

2. building block = glucose

3. requires 2 molecules of ATP for every glucose added

4. only storage of glucose in body

Glycogenolysis

1. glycogen breakdown

2. adds phosphate group to glucose

3. sends phosphate to ADP to reform ATP

4. Can be rapidly broken down into

   single glucose molecules

Gluconeogenesis

1. Formation of glucose by body

   tissues from non-carbohydrate

   metabolite (lipids & amino acids)

2. enters TCA cycle at many lvls

3. not a main source of energy in non-ruminants

4. 2 net ATP

Pyruvate

1. made from glucose

2. 3 carbon molecule

3. turned into acetyl-CoA (donates carbons, enters TCA cycle)

What is energy?

the capacity to do work

What is the main source of energy in the animal body?

glucose

Glycolysis

1. Series of reactions that split

   one glucose molecule into two

   pyruvate molecules

2. anaerobic (does not need O)

3. found in almost all living organisms

4. 1st step of cellular respiration

2 Stages of Glycolysis

1. Energy-consuming

2. Energy-releasing

How many steps does glycolysis have?

10

Where does glycolysis take place?

cytosol

Energy-Consuming Phase of Glycolysis

Phosphate is added to the 6th carbon of

glucose

• Glucose 6-phosphate

• Traps glucose inside cell because

phosphorylated glucose can’t leave cell

• Glucose is rearranged to fructose with

phosphate attached

• Fructose 6-phosphate

• Phosphate group added to #1 carbon

• Fructose 1,6-bisphosphate

• Very unstable

• “Gate-keeping” step

Fructose 1,6-bisphosphate is

unstable and splits into two pieces

DHAP and glyceraldehyde-3-phosphate

(G3P)

DHAP and G3P are isomers of each

other

Only G3P can move forward in

glycolysis

Eventually all DHAP will be made into

G3P

Energy-Releasing Phase of Glycolysis

Since 2 G3P molecules, this step

happens twice

• Two molecules of NADH and 2 molecules

of ATP created

• NADH is important for ETC

• In first step, G3P is oxidized and NAD+ is

reduced to NADH

• Gives energy to G3P, phosphorylates, and

becomes 1,3-bisphosphoglycerate

• 1,3-bisphosphoglycerate has a lot of

energy

1,3-bisphosphate donates Pi to ADP to make

ATP

First ATP generated

Becomes 3-phosphoglycerate

3-phosphoglycerate isomerized to 2-

phosphoglycerate

2-phosphoglycerate loses a molecule of H2O

and becomes phosphoenolpyruvate (PEP)

Very unstable molecule

PEP donates Pi to ADP

Becomes pyruvate

Generate another ATP

End of Glycolysis

4 ATP generated in second

step (2 from each G3P) – 2

used in beginning to add two

phosphates = 2 net ATP

NAD+/NADH

Two NADH generated

No glucose

2 pyruvate

Tricarboxylic Acid Cycle

1. aka TCA

2. provides precursors of amino acids

3. gives energy & cofactors

4. central driver of cellular respiration

Where does the TCA cycle take place?

mitochondria

How many steps does the TCA cycle have?

8

1st step of TCA cycle

Pyruvate donates carbons to become acetyl-CoA

2nd step of TCA cycle

Acetyl-CoA donates two carbons (acetate group) to oxaloacetate (becomes citrate)

2nd step of TCA Cycle

1. Citrate undergoes reactions and loses 2 carbons

at 2CO2 molecules

2. Generates 2 NADH in the process

3. now has a 4-carbon molecule (succinate) attached to CoA (succinyl-CoA)

3rd step of TCA Cycle

1. phosphate added

2. removes CoA

3. then phosphate donated to GTP/ATP

4th Step of TCA Cycle

1. succinate oxidized to fumarate (donates H₂ to FAD)

5th Step of TCA Cycle

Water added to fumarate to create malate

6th step of TCA Cycle (final)

malate oxidized to oxaloacetate (donate H to NAD+)

TCA Cycle Conclusion

2 molecules of carbon enter

(acetyl-CoA) and two leave (CO2)

3 molecules of NADH generated

1 molecule of FADH2 generated

1 molecule of ATP or GTP

generated

How does propionate (a VFA) from microbial fermentation enter the TCA cycle in ruminants and horses?

• Propionate becomes attached to CoA —→ propionyl-CoA

• Changes through a series of steps to methylmalonyl-CoA

• Eventually becomes succinyl-CoA, which enters the TCA cycle

Electron Transport Chain

1. Completed within the

mitochondrial membrane and

within mitochondria

2. Movements of electrons

along a chain

3. Move from higher to lower

energy

4. Generates significant amount

of ATP

Where do the electrons come from?

1. from NADH & FADH₂, from TCA cycle & glycolysis

What is the role of NADH in redox reactions?

NADH is good at donating electrons in redox reactions (high energy reactions).

How does FADH₂ compare to NADH in electron donation, and where does it donate its electrons?

• FADH₂ is not as good at electron donations as NADH.

• It donates its electrons to intramembrane proteins (specifically within the electron transport chain).

What happens to electrons from Complex I and II in the electron transport chain, and what is the role of ubiquinone (Q)?

• Electrons from Complex I and II are passed to ubiquinone (Q) (so named because it's ubiquitous in mitochondria).

• Q is reduced to QH₂

• $\text{QH}_2$ delivers the electrons to Complex III.

• Throughout this process, $\text{H}^+$ protons are continuously pumped into the intermembrane space.

Complex III (ETC)

passes electrons to cytochrome C

Cytochrome C

1. carries electrons to complex IV

2. final batch of H₂ passed thru complex IV

Complex IV (ETC)

passes hydrogen to oxygen to create H2O

What is the purpose of ETC?

1. Regenerate electron acceptors

2. NADH  NAD+

3. FADH2  FAD

4. Oxidized forms can be used as

electron acceptors in TCA cycle

and glycolysis

5. Create proton gradient

6. Creates a source of energy

7. Have more H+ in intermembrane

space than inside mitochondria

Chemiosmosis

• Electrons moving through the complexes provide energy to pump H⁺ the intermembrane space, creating an electrochemical gradient (the proton-motive force).

• Protons cannot pass directly through the phospholipid membrane.

• $\text{H}^+$ can only get back through via a specific channel: ATP synthase.

ATP Synthase

• Acts like a hydroelectric turbine powered by the flow of $\text{H}^+$ protons.

• The mechanical turning adds a phosphate group to ADP, generating ATP.

• Accounts for 80% of total ATP generation during glucose breakdown in cellular respiration.