Carbohydrate Metabolism

Give the general formula for carboohydrates:

Cx(H2O)n

What is the characteristic functional group of carbohydrates?

carbonyl (C=O)

What value should blood glucose lie around?

5mM

What transporter brings glucose into cells?

GLUT4

Describe how electron movement in aerobic respiration produces energy:

electrons are transferred from C or H to an O atom and as O is more electronegative the electrons lose potential energy, releasing it

Why are carbohydrate and fats so high in energy relative to proteins?

they have a lot of electrons associate with hydrogen

What are the 3 NET products of glycolysis?

1) x2 ATP

2) x2 NADH

3) x2 pyruvate

Describe the Link reaction:

Pyruvate enters the mitochondrial matrix and is decarboxylated and dehydrogenated and bonds with coenzyme A to form acetyl CoA

What are the 2 key products of the Link reaction per molecule of glucose?

1) x2 acetyl CoA

2) x2 NADH

Give the 8 steps of the Krebs cycle:

1) acetyl CoA joins with oxaloacetate to form citrate

2) citrate is isomerised to form isocitrate

3) isocitrate is oxidised to form alpha-ketoglutarate producing NADH

4) alpha-ketoglutarate is oxidised to succinyl-CoA producing NADH

5) succinyl-CoA is converted to succinate producing ATP

6) succinate is oxidised to fumarate producing FADH2

7) fumarate is hydrate and forms malate

8) malate is oxidised to oxaloacetate producing NADH

What are the four products of the Krebs cycle per molecule of gluocse?

1) x6 CO2

2) x6 NADH

3) x2 FADH2

4) x2 ATP

Describe the electron transport chain: (3)

1) NADH and FADH2 are oxidised to produce electrons which move from each protein complex in the inner mitochondrial membrane, releasing energy

2) this energy is used to pump H+ ions against their gradient into the intermembrane space, creating an electrical gradient

3) H+ can pass through ATP synthase via chemiosmosis, producing ATP from ADP

Give the flow chart for anaerobic respiration of gluocse:

glucose -> pyruvate -> ethanol/ lactic acid

What molecule is anaerobic respiration's redox balance linked to?

glyceraldehyde-3-phosphate

What molecule is used to store glucose?

glycogen

What is a glycan?

polysaccharide of a glycoconjugate (glycolipid, glycoprotein etc)

Describe how glycogen is synthesised:

1) glucose-6-phosphate is converted to glucose-1-phosphate and UDP glucose is synthesised

2) glycogenin primers help elongate chains and the intersection of branch points

What are the linkages called in glycogen?

alpha-1,4 linkages

What are the branch points in glycogen called?

alpha-1,6 linkages

What enzyme plays a chief role in glycogen synthesis?

glycogen synthase

Describe glycogen breakdown in the liver and kidneys:

1) glycogen phosphorylase removes glucose units to produce glucose-1-phosphate which is then converted back to glucose-6-phosphate which can enter glycolysis

Describe how fatty acids can be synthesised from sugars:

citrate is used to produce acetyl CoA which goes onto form malonyl CoA using ATP and acetyl CoA carboxylase

How does insulin affect glycolysis?

upregulates glycolysis and downregulates gluconeogenesis

How does glucagon affect glycolysis?

Glucagon inhibits glycolysis in the liver (inhibits glucose breakdown) and increases glycogenolysis (break down of glycogen) to release glucose in the blood