SfM- Carbohydrates Flashcards
1
Q
name the two types of starch polymers
A
- amylose (glucose joined via a1-4 glycosidic bonds)
- amylopectin (mainly a1-4 glycosidic bonds but a1-6 every 20-30 residues = branching)
2
Q
what is glycogen?
A
- glycogen is a strategy to store glucose in body
- polymer of glucose of a1-4 bonds but a1-6 more frequent
- makes glycogen more extensively branched than starch (more glucose can be stored in a small space)
3
Q
why store glucose as glycogen?
A
- more compact
- has many non-reducing end, means it can be synthesised and degraded easily
- polymers form gels - making it osmotically active but doesn’t disrupt cell balance
4
Q
what are glycoproteins?
A
- proteins that have carbohydrates covalently attached
- can vary from 1-80& carbohydrate mass
5
Q
how can carbohydrates affect protein?
A
- increase proteins solubility
- influence protein confirmation
- increases stability
- act as communication between cells
6
Q
what are glycosaminoglycans (GAGs)?
A
- unbranched polymers of hexuronic acid and an amino-sugar
- very slippery and sticky - also called mucopolysaccharides
- there are groups of genetic disorders meaning the enzymes that breakdown GAGs - can build up in tissues throughout the body (Hurler Syndrome)
7
Q
what are proteoglycans?
A
- more carbohydrate than protein
- formed from GAGs attaching to proteins - when next to each other - can interlink = stronger
8
Q
what are glycoproteins?
A
- more protein than carbohydrates
9
Q
different types of carbohydrates
A
- starch (cereals, potatoes, rice)
- glycogen (meat)
- hemi/cellulose (plant cell walls - don’t digest it)
- oligosaccharides (peas, beans, lentils - a1-6 bonds don’t digest
- lactose/sucrose/maltose - (milk, sugar, beer)
- glucose/fructose (fruit, honey)
10
Q
how are carbohydrates digested?
A
- mouth - amylase breaks starch into glucose
- duodenum - pancreatic amylase (same function as mouth)
- jejunum - digestion by mucosal cell-surface enzymes (isomaltases, glucoamylase, sucrase, lactase)
11
Q
how is glucose absorbed?
A
- Na+-glucose symporter transports both Na and glucose into the cell (relies on high extracellular Na)
- glucose uniporter moves glucose out of cell into blood
12
Q
how are monosaccharides absorbed?
A
- ATP-driven Na+ pump maintains low cellular Na+ to allow glucose to be continually pumped into cell
- galactose also uses gradients to transport
- fructose binds to the channel GLUT5 - moves down conc gradient
13
Q
how is hemi/cellulose absorbed?
A
- these cannot be digested by the gut but increase faecal bulk, increases speed of digestion
- polymers are broken down by gut bacteria - yields CH4 and H2 = FARTS
14
Q
what are the characteristics of a disaccharide deficiency?
A
- abdominal distension (bloat)
- cramps
- diarrhoea
15
Q
what is lactose intolerance?
A
- lactase deficient so lactase can’t be digested
- undigested lactose is broken down by gut bacteria - causes gas build up and irritant acids
- lactose is osmotically active, thus drawing water from the gut into the lumen causing diarrhoea
