Carbohydrate: structure and digestion

How does the content of carbs compare between plants and animals

Plants: energy captured in the form of carbohydrates, makes up majority of their dry matter

Animals: makes up less than 1% of their body weight, broken down to create energy which then creates carbon dioxide and water

What are carbohydrates made up of? How do we remember the proportions of these atoms?

Carbon, Hydrogen, Oxygen

C_nH_2nO_n

How are carbohydrates classified

by the number of sugars (saccharides) within the carbohydrate

What are the different kinds of simple carbs? complex carbs?

Monosacca

What are the different types of monosaccharides commonly seen?

Glucose, Galactose, Fructose

How does Glucose differ from Galactose?

Orientation of the OH at the 4th carbon

How do Glucose and Fructose differ?

Glucose and fructose have the same chemical formula but different arrangement and fructose is commonly represented as a five membered ring

What is the name of the bonds that connect sugar molecules and what kind of bond are the?

Glycosidic Bonds, Covalent Bonds

What kind of reaction occurs to bond sugar molecules

Condensation reaction

Condensation reaction

water molecule release when bond is formed

What are the two types of glycosidic bonds and how do they differ

alpha - down orientation

beta - up orientation

What kind of glycosidic bond can animals digest?

alpha bonds

What monosaccharides make sucrose and how are they bonded

Glucose and Fructose, alpha bond

What monosaccharides make maltose and how are they bonded

2 glucose molecules, alpha bond

What monosaccharides make lactose and how are they bonded

Glucose and Galactose, beta bond

What is special about oligosaccharides

they are non-digestible for mammals

beneficial to microorganisms, support the growth/ activity of desirable microbial populations in GI tract

What kind of polysaccharide is the primary storage for plants?

What kind of polysaccharide is the primary storage for animals?

starch

glycogen

What are the two types of starches

amylose and amylopectin

How do amylose and amylopectin differ

Amylose is only composed of alpha-1,4 glycosidic bond and is coiled shape

Amylopectin has alpha-1,4 glycosidic bonds AND alpha-1,6 glycosidic bonds that create branches.

How do amylopectin and glycogen differ?

They have the same type of bond but glycogen has more branches which allows it to be more compact

What polysaccharide is the primary structural component of plants

Cellulose

What type of glycosidic bond are between the sugars of cellulose

beta-1,4-glycosicidic bonds

How is cellulose digested by animals

Animals cannot digest cellulose, microorganisms in the GIT digest them

What is fiber

broadly used to describe the structural components of the plant cell wall

Rank the parts of the cell wall from most digestible to least/indigestible)

pectic, hemicellulose, cellulose, lignin

What allows fiber composition to vary

species, variety, and maturity of plant

what 2 sources of digestive enzymes break down carbohydrates to monosaccharides before they can be absorbed

Auto-enzymatic = produced by the animal

Alloenzymatic = produced by microorganisms within the GI

Under what conditions does microbial fermentation occur

anaerobic (w/o oxygen)

What are the products of microbial fermentation

gases (methane and carbon dioxide) and volatile fatty acids (acetate, propionate, butyrate)

How are carbohydrates digested by cows

Majority of carbs go through microbial fermentation to produce VFAs (where 80% of energy comes from) in the rumen

Starch that escapes the rumen can be digested in small intestine

How are carbs digested by horses and pigs

autoenzymatic digestion occurs in the small intestine

starch and sugars digested to monosaccharides and absorbed in small intestine

undigested carbs continue to hindgut and microbial fermentation produces VFAs

What is the different in pig and horse digestion of carbs

in horses, rapid or excessive fermentation (large starch intake) it can create problems because the cecum and colon are overwhelmed

horses do not posses as much amylase as pigs to digest carbs in the small intestine

Pigs have minimal energy contribution from VFAs b/c their cecum is smaller than that of horses, horses are hindgut fermenters

Where does carbohydrate absorption primarily occur? In what form are the absorbed?

Small intestine, monosaccharides

Carbs cannot cross cell membrane by simple diffusion. What do they require?

membrane transport proteins

What technique does Sodium-Glucose Linked Transporter 1 (SGLT1)? What monosaccharide(s) does it transport?

Secondary active transport

Glucose and Galactose

Secondary active transport

SGLT1 does not directly use ATP but another protein in the system uses it (Na+/K+ pump)

What technique does GLUT2 use? What monosaccharide(s) does it transport?

Facilitated diffusion

Glucose, galactose, and fructose

What technique does GLUT5 use? What monosaccharide(s) does it transport?

Facilitated diffusion

Fructose

How are VFAs absorbed

simple passive diffusion

What characteristics of feed processing influence the rate and extent of digestion of starches

physical structure and accessibility