Carbohydrates

What produces carbohydrates?

Photosynthesis produces carbohydrates in plants using water and CO2.

What 4 things are carbohydrates composed of?

1. Carbon

2. Hydrogen

3. Oxygen

4. Some contain N, P or S.

What is the ration of carbon, hydrogen and oxygen in carbohydrates?

1:2:1 for example glucose is C6H12O6

Provide three examples of carbohydrates

1. sugars

2. starches

3. fibers

What two carbohydrates make up the cell contents (in dark green)?

1. Sugars

2. Starch

What three carbohydrates make up the cell wall (in fuschia)?

1. cellulose

2. hemicellulose

3. lignin

What two carbohydrates make up the intracellular cement (in blue)?

1. pectin

2. gums

what are the cell wall and intracellular cement composed of (light green)?

Fiber

List the 4 functions of carbohydrates

1. Providing energy.

2. Regulation

3. Structural

4. Production

Describe the 3 ways that carbohydrates provide energy

1. They absorb energy in the form of glucose which is used in glycolysis for ATP production.

2. Through pathways.

3. Excess glucose is stored as glycogen.

What are the 3 pathways that carbohydrates produce energy through?

1. Glycolysis

2. TCA cycle in mitochondria

3. Oxidative phosphorylation.

Where is glycogen stored?

1. muscle

2. liver

What is glycogens purpose in the liver?

It is used to maintain consistent blood glucose levels.

What is glycogen used for in the muscle?

1. So energy is immediately available for use.

2. It is broken down for the ETC to produce energy.

What happens if glycogen content is too high in the muscle?

It is metabolized to lactic acid.

What is the main source of energy for the brain/nervous tissue and why?

Glucose because it can pass the blood brain barrier.

Why do red blood cells rely on glucose?

They lack mitochondria.

What do horses rely on for energy and why?

Horses rely on glycogen for exercise. If they travel long distances they can become depleted of glycogen and cannot continue (it takes 3 days for horses to fill glycogen stores in the muscle).

How do carbohydrates help provide structural support?

1. Excess stored as fat.

2. Cellulose and hemicellulose in plants.

How do carbohydrates contribute to production?

1. Lactose in milk.

2. Glycogen in tissues.

What two things are carbohydrates classified based on?

1. Number of carbons.

2. Number of CHO molecules.

Describe Triose (3C) monosaccharides and provide some examples.

They are intermediates in glucose metabolism. Ex: two molecules that glucose is split into that are later converted into pyruvate. (Glyceraldehyde and Dihydroxyacetone).

True or False, there is a high percentage of Pentose (5C) monosaccharides in plants and animals.

False

Provide 4 examples of pentose 5C monosaccharides?

1. alpha - D - ribose.

2. alpha - D - deoxyribose.

3. Xylose (part of chondroitin SO4).

4. Arabinose.

What is the most abundant monosaccharide in nature?

Hexoses (6C)

What type of monosaccharide is glucose and describe its three primary characteristics:

It is a hexose (6C)

1. Principle CHO in blood.

2. Main end point of CHO digestion.

3. Required energy source for nervous tissue, brain and RBC.

What are 4 examples of 6C monosaccharides?

1. Alpha - D - glucose.

2. Beta - D glucose.

3. Beta - D galactose.

4. Beta - D - fructose.

what are disaccharides?

2 monosaccharides together.

List 5 common disaccharides:

1. Sucrose

2. Lactose

3. Maltose

4. Iso-Maltose

5. Cellobiose

What is sucrose made from and is it easily digested?

Alpha D-glucose + fructose and yes it is rapidly and easily digested.

What is lactose made from and is it easily digested?

Galactose and Beta-D-glucose. It is easily digested.

What is maltose made from?

Alpha-D-glucose + alpha-D-glucose

From the digestion of starch

What is iso-maltose made from?

Maltose with alpha 1-6 linkage.

Where is iso-maltose located?

Located at branch points of amylopectin and glycogen

Where is cellobiose present?

in cellulose.

What is cellobiose made from and is it easily digested?

It is made from Beta-D-glucose + Beta-D-glucose and it must be digested with bacterial enzymes (not mammalian ones).

What are trisaccharides made of?

3 monosaccharides

What is an example of a trisaccharide?

Raffinose

What is raffinose made of and in what foods can it be found?

• Fructose + alpha-D-glucose + galactose.

• Sugar beets and cotton seed and cruciferous vegetables.

What are oligosaccharides made of?

> 2 monosaccharides but < 10

What are oligosaccharides intermediates of?

They are intermediates in the breakdown of polysaccharides.

What do oligosaccharides contain?

Mannose and mannans.

What foods are oligosaccharides found in and what does this help with?

They are found in beans and can help food bacteria in the gut plus the immune system.

What are polysaccharides made of?

1000’s of monosaccharides.

What is the bulk of our dietary CHO?

polysaccharides.

List 4 examples of polysaccharides:

1. Starch

2. Cellulose

3. Hemicellulose

4. Lignin

What is the purpose of starch and what are its properties?

It is used for energy storage

Properties: insoluble in cold water, soluble in hot water, finger print matrix.

List the 3 kinds of starch and what each is found in:

1. Amylose - Plants

2. Amylopectin - Plants

3. Glycogen - Animals

What is amylose made of

1)  α-D-glucose chain

Two glucose molecules together = maltose.

2)  Straight: a1-4 links

What is amylopectin made of?

1)  α-D-glucose chains

2)  Branched:  α 1 → 6 links

What percentage of starch is in the amylose form?

20-30%

What percentage of starch is in the amylopectin form?

70-80%

List the 3 properties of glycogen:

1)  Storage form of CHO in the body.

2)  Found in the muscle and the liver.

3)  Identical to amylopectin, but more highly branched

What is the purpose of cellulose in plants?

Structural CHO in plants.

What is cellulose made of?

Repeating linear units of cellobiose

Can cellulose be digested by mammalian enzymes?

Not it must be digested by bacterial enzymes (cellulase)

What are the 3 characteristics of hemicellulose?

                     1.    Components of the cell wall.

                     2.    Heteroglycan

a.   Xylose, glucose, galactose & arabinose

                     3.     Only digested by microbial enzymes.

As plants mature, how does lignin change? As lignin increases, how does this affect digestibility?

1)   As plants mature, lignin increases.

2)   As lignin increases, digestibility decreases.

Describe the 3 characteristics of lignin:

1.    NOT a CHO (helps with plant structure).

2.    Indigestible by animals & most microbes

3.    Makes plants poorly digestible – Why you have to harvest plants at the right time.

What is the enzymes in saliva and what does it do?

Amylase and it helps to digest starch between teeth by breaking alpha 1 → 4 linkages

List the two parts of digestion in the mouth:

1. mastication

2. saliva

List the 3 parts of digestion in the stomach:

                     1.    Acid disrupts some H bonds.

                     2.    NO CHO-digesting enzymes

                     3.    Some microbial digestion

Where is the primary site for digestion in the pancreas?

Duodenum

What does the pancreas do to help with digestion?

1)  Pancreas secretes sodium bicarbonate to neutralize acids.

2) Amylase hydrolyzes alpha 1 → 4 linkages.

3) Amylase converts amylose into maltose.

4) Amylase converts Amylopectin to maltose and isomaltose.

List the 4 enzymes found in the duodenal mucosal cells at the brush border:

1. Lactase

2. Sucrase

3. Maltase

4. Isomaltase

What does lactase do?

It converts lactose into Galactose and Glucose

What does sucrase do?

It converts sucrose into glucose and fructose

What does maltase do?

It converts maltose into glucose and glucose

What does isomaltase do?

It converts isomaltose into glucose and glucose.

What are the key characteristics of the large intestine?

1. No enzymes.

2. Microbial fermentation.

3. Produce VFA as a byproduct

What 3 carbohydrates enter the large intestine?

1. starch

2. sugar

3. fiber

What enzyme (with microbes) converts starch into VFA + CO2 + CH4?

amylase

What enzyme (with microbes) converts fiber into VFA + CO2 + CH4?

cellulase

List the 3 major VFA and the amount of carbons each has:

1. Acetate (2C).

2. Propionate (3C).

3. Butyrate (4C).

In ruminant digestion are there enzymes in the mouth?

No, there is no salivary amylase.

What is hay mostly comprised of?

cellulose

What is corn mostly comprised of?

Starch

In ruminant digestion, feed like hay and corn are digested by _____ which produces ____

microbes, VFA

If ruminants are predominantly on a forage diet what is their ratio of acetate to propionate? What is their pH?

3.5:1

pH: 6.5-7

If ruminants are predominantly on a grain diet what is their ration of acetate to propionate? What is their pH?

2:1

pH: 5.5-6

If ruminants are on a forage diet what percentage of acetate, propionate and butyrate do they receive?

65% acetate. 20% propionate. 12% butyrate.

If ruminants are on a grain diet what percentage of acetate, propionate and butyrate do they receive?

45% acetate, 35% propionate, 15% butyrate

If ruminants are on a forage diet what are their fluid requirements?

60-80 mmol/ml fluid

If ruminants are on a grain diet what are their fluid requirements?

100-120 mmol/ml fluid

What is the importance of VFA?

1. They can passively diffuse through the rumen wall.

2. They can supply 50-100% of energy requirements.

In digestion in ruminants where do things go?

From the abomasum to the large intestine.

What molecules take part in active transport for absorption in the small intestine?

1. Galactose

2. Glucose

What molecules take part in passive diffusion for absorption in the small intestine?

fructose, mannose, xylose, arabinose

3 characteristics of absorption in the small intestine:

1. Jejunum

2. Active transport

3. Passive diffusion

What molecules take part in absorption in the large intestine?

VFA through passive diffusion.

What is glycogen (simple term)

Stored form of glucose

What is glycogenesis (simple terms)?

Making new glycogen

What is glycogenolysis?

Breakdown of glycogen

What is gluconeogenesis?

Making new sugars from non CHO. Synthesis of glucose by the liver.

What is glycolysis?

Breakdown of glucose

What are blood glucose levels for humans?

90-100 mg/dl

What are blood glucose levels for cattle?

65-75 mg/dl

What are blood glucose levels for horses?

90-100 mg/dl

What are blood glucose levels for poultry?

> 130 mg/dl

Describe the insulin hormone: Where is it produced? What does it cause? How does it cause it?

Produced: Beta cells in the pancreas.

Triggers it: Glucose absorption

Causes: Decrease glycogenolysis and gluconeogenesis and increases glycolysis