carbohydrates Flashcards
what bonds do carbohydrates contain? why are they important?
- rich in C-H bonds
- important in yielding energy
what is breakdown of glucose associated with?
- negative change in Gibbs free energy
- negative enthalpy- huge drop in Gibbs free energy
-707kcal.mol-1
what are the subunits linked together by in disaccharides, oligosaccharides and polysaccharides?
- linked by a (1-4) glycosidic bond
what happens as glucose is broken down? what are they passed down to?
- as glucose is broken down electrons in the chemical bonds are passed down to electron carriers which yield energy
what are carbs and glycogen in human cells branched with?
- a (1-6) glycosidic bonds
how many times do a(1-6) repeat?
- repeat every 20-30 residues for starch
- every 8-12 for glycogen
what are the specialised features of carbs and what does this allow
- compact
- hydrophilic
- high surface area
- optimise digestion and energy provision
where does digestion of carbohydrates start?
- in the mouth (saliva)
what happens in the small intestine?
- pancreatic juices
- enzyme a- amylase hydrolyses hydrolyses a(1-4) glycosidic bonds
what does the enzyme a- amylase hydrolyse?
- glycosidic bonds in starch to short chain carbohydrates (oligosaccharides)
where are oligosaccharides broken down and what into?
- broken down in villi of small intestine
- into disaccharides
what are the specific enzymes that break disaccharides into monosaccharides?
- lactase, maltase and sucrase
what does lactase breakdown?
- lactose
- galactose and glucose
what does maltase breakdown?
- maltose
- glucose and glucose
what does sucrase breakdown?
- sucrose
- fructose and glucose
how are monosaccharides absorbed?
- absorbed into cytosol of enterocytes and transported into capillaries that empty into venous blood and portal vein that supplies liver
where is glycogen stored?
-liver (3-7%)
-muscle (1-1.5%)
where is glycogen optimally located?
- located between thick and thin filaments near the mitochondria
how is glycogen stored?
- stored in granules containing enzymes needed for its breakdown and storage
how is ATP provision in muscle enhanced?
- enhanced by breakdown of liver glycogen during exercise
- communication between these two tissues
describe the synthesis of glycogen
- anabolic condensation reaction> requires energy to build up molecules
what does glucose react with to provide energy to build the glycogen chain? how many glucose residues?
- reacts with uridine triphosphate
- 30- 60,000 glucose residues
what is the process of glucose synthesis?
- Glycogenin adds 4 glucose residue cells to it cell
- Glycogenisnthase uses UT to build the molecule
- Branching occurs through branching enzyme
what reaction is the breakdown of glycogen? what does it involve?
- catabolic hydrolysis reaction
- phosphate group added to glucose to release it from the glycogen chain
how does exercise regulate the breakdown of glucose?
- breakdown increases during muscle contraction due to ATP demand
what happens when muscle stores decrease? what activity increases?
- signal sent to liver to ^ breakdown
- glycogen phosphorylase activity in muscle ^ due to ^ in Pi, ^ in AMP, ^ in adrenaline, ^Ca2+
what happens to synthesis in hard exercise?
- synthesis is inhibited although prolonged periods may activate it to maintain balance
what happens to synthesis post exercise?
- rapidly activated
describe phosphorylation as a method
- quick and energetically favourable control mechanism
- regulates enzyme function w/ out need to deconstruct a protein
