Carbohydrate Metabolsim

You will be able to…• Explain how Carbs are digested & absorbed

• Draw the steps involved in Glycolysis

• Compare and contrast aerobic respiration to two different types of fermentation

• Discuss the 3 possible fates of Pyruvate

Mass composition data for the human body

Carbohydrates don’t make

the man or woman

Carbs do run the man or woman:Carbohydrate recommendation is 45 to 65 percent of total calories.

Sugars and starches supply energy to the body as glucose.

Only energy source for red blood cells. Preferred energy source for brain & CNS

Energy sources

Structuralmolecules

Salivary glands secrete saliva which contains mucus, water, ions, and

amylase enzyme.

Food is only briefly in the mouth, so carbohydrate digestion just begins.

Starch polymers are broken down into smaller chains and into some

disaccharides: maltose, sucrose, lactose.

Small intestine > 3 m long, 2 to 3 cm wide. Coils, folding, & villi give surface area of

500-600 m long tube. Upper part (duodenum) most active in digestion:

villi cells produce enzymes which complete digestion of carbohydrates.

Plasma membrane of microvilli use these enzymes to complete digestion:

Disaccharidases: disaccharides converted

into monosaccharide subunits.

Maltase: hydrolyzes maltose into glucose.

Sucrase: hydrolyzes sucrose into glucose & fructose.

Lactase: hydrolyzes lactose into glucose & galactose.

Common Disaccharides:

Milk sugar: galactose and glucose

connectedSucrose: -Glucose and -Fructose

, (12) glycosidic linkage

Maltose: (14) of two D-Glucose molecules

Lactose (14)

Small intestine’s second job: Absorption Uses increased S.A. with folds projecting into lumen (plicae circulares), villi and microvilli.

Sugars into bloodstream: Fructose diffuses into villi, glucose & galactose absorbed by active transport.

Summary of carbohydrate digestion in the human body.

– Aerobic respiration• Requires molecular oxygen• Includes series of redox reactions

-Anaerobic respiration *Fermentation *Does not require oxygen

All are exergonic (occur spontaneously)Use a lot of coupled reactions

What to do with those sugars? Turn them into ATP = Cellular respiration

Reaction Types in Cellular Respiration1. Dehydrogenation - Hydrogens transferred to a coenzyme (an energy carrier molecule).2. Decarboxylations - Carboxyl groups

(COO-) removed from substrates as carbon dioxide (CO2).

3. Preparation reactions - Molecules rearranged in preparation for dehydrogenation or decarboxylation.

4. Phosphorylation – phosphates added to provide energy or transform molecules.

Four stages of aerobic respiration

Note location of each stage & amount of ATP formedProduct of one stage becomes reactant of next stage

Glycolysis:Glyco = sugarLysis = to split

One 6 C glucose split into two 3 C pyruvates (eventually)

Substrate (organic molecule)

Phosphorylationof glucose occurs to make the

reactions exergonicAlso stops glucose from leaving the

cell.

An overview of glycolysis.

6 C stages & 3 C stagesEnergy absorbingEnergy producing

Glycolysis:energy investment

Phase:Phosphorylation

ATP kick start:Glucose turned into

Fructose 1,6 bisphosphate

this turns eventually into 2 glyceraldehyde-3-

phosphate molecules

Structural relationships among glycerol and acetone and the four

C3 intermediates in the process of glycolysis.This

converts intoThat

(isomers)

Glycolysis: E capture phase

The two glyceraldehyde-3-phosphates

eventually turn into two pyruvates

(with what type of rxn?)

The end products of glycolysis include:

•2 molecules of pyruvate •2 molecules of NADH

•2 ATP molecules net gain

(4 made / 2 used)

Glycolysis animation simplistic version

Glycolysis animation details

Glycolysis animation more detailed steps

Enzymes involved in glycolysis

Let’s go through the steps in detail: