carbohydrates

Question 1

what bonds do carbohydrates contain? why are they important?

Answer 1

• rich in C-H bonds
• important in yielding energy

Question 2

what is breakdown of glucose associated with?

Answer 2

• negative change in Gibbs free energy
• negative enthalpy- huge drop in Gibbs free energy
  -707kcal.mol-1

Question 3

what are the subunits linked together by in disaccharides, oligosaccharides and polysaccharides?

Answer 3

• linked by a (1-4) glycosidic bond

Question 4

what happens as glucose is broken down? what are they passed down to?

Answer 4

• as glucose is broken down electrons in the chemical bonds are passed down to electron carriers which yield energy

Question 5

what are carbs and glycogen in human cells branched with?

Answer 5

• a (1-6) glycosidic bonds

Question 6

how many times do a(1-6) repeat?

Answer 6

• repeat every 20-30 residues for starch
• every 8-12 for glycogen

Question 7

what are the specialised features of carbs and what does this allow

Answer 7

• compact
• hydrophilic
• high surface area
• optimise digestion and energy provision

Question 8

where does digestion of carbohydrates start?

Answer 8

• in the mouth (saliva)

Question 9

what happens in the small intestine?

Answer 9

• pancreatic juices
• enzyme a- amylase hydrolyses hydrolyses a(1-4) glycosidic bonds

Question 10

what does the enzyme a- amylase hydrolyse?

Answer 10

• glycosidic bonds in starch to short chain carbohydrates (oligosaccharides)

Question 11

where are oligosaccharides broken down and what into?

Answer 11

• broken down in villi of small intestine
• into disaccharides

Question 12

what are the specific enzymes that break disaccharides into monosaccharides?

Answer 12

• lactase, maltase and sucrase

Question 13

what does lactase breakdown?

Answer 13

• lactose
• galactose and glucose

Question 14

what does maltase breakdown?

Answer 14

• maltose
• glucose and glucose

Question 15

what does sucrase breakdown?

Answer 15

• sucrose
• fructose and glucose

Question 16

how are monosaccharides absorbed?

Answer 16

• absorbed into cytosol of enterocytes and transported into capillaries that empty into venous blood and portal vein that supplies liver

Question 17

where is glycogen stored?

Answer 17

-liver (3-7%)
-muscle (1-1.5%)

Question 18

where is glycogen optimally located?

Answer 18

• located between thick and thin filaments near the mitochondria

Question 19

how is glycogen stored?

Answer 19

• stored in granules containing enzymes needed for its breakdown and storage

Question 20

how is ATP provision in muscle enhanced?

Answer 20

• enhanced by breakdown of liver glycogen during exercise
• communication between these two tissues

Question 21

describe the synthesis of glycogen

Answer 21

• anabolic condensation reaction> requires energy to build up molecules

Question 22

what does glucose react with to provide energy to build the glycogen chain? how many glucose residues?

Answer 22

• reacts with uridine triphosphate
• 30- 60,000 glucose residues

Question 23

what is the process of glucose synthesis?

Answer 23

1. Glycogenin adds 4 glucose residue cells to it cell
2. Glycogenisnthase uses UT to build the molecule
3. Branching occurs through branching enzyme

Question 24

what reaction is the breakdown of glycogen? what does it involve?

Answer 24

• catabolic hydrolysis reaction
• phosphate group added to glucose to release it from the glycogen chain

Question 25

how does exercise regulate the breakdown of glucose?

Answer 25

• breakdown increases during muscle contraction due to ATP demand

Question 26

what happens when muscle stores decrease? what activity increases?

Answer 26

• signal sent to liver to ^ breakdown
• glycogen phosphorylase activity in muscle ^ due to ^ in Pi, ^ in AMP, ^ in adrenaline, ^Ca2+

Question 27

what happens to synthesis in hard exercise?

Answer 27

• synthesis is inhibited although prolonged periods may activate it to maintain balance

Question 28

what happens to synthesis post exercise?

Answer 28

• rapidly activated

Question 29

describe phosphorylation as a method

Answer 29

• quick and energetically favourable control mechanism
• regulates enzyme function w/ out need to deconstruct a protein