Carbohydrates Flashcards
what is the function of carbohydrates?
to store potential energy and yield it from them
cell-cell communication
what is a carbohydrate
organic molecule occurring in food and living tissues etc
sugars
soluble in water
what is a monosaccharide
simplest form of sugar
1 sugar monomer
examples are
glucose, fructose and galactose
disaccharide
2 sugar monomers joined by a glycosidic bond
OH and anomeric carbon usually join
maltose, lactose and sucrose
polysaccharide
a few monomers stitched together (large or small)
glycogen and starch
define anomeric
mirror images of each other
usually carbon number 1
why do we store glucose in polymers
compactness- highly ordered, neatly folded structure takes up less space
polymers aren’t really in solution which is good as free glucose would take in water surrounding it and cause the cell to burst
osmotic lysis
what is a glycoprotein
more protein than carbohydrate (sugar)
increases solubility
influences protein folding/confirmation
protect the protein from degradation
which amino acid contains sulfur atoms?
cysteine, methionine
what geometrical structure does the peptide bond show?
planar
what is not found in the glycogen molecule out of glycogenin and glycogen phosphorylase?
glycogen phosphorylase
what is glycogenin
enzyme involved in converting glucose to glycogen
what is glucose readily converted into once it enters any cell in the body
G-6-P so that it is trapped and can’t leave
don’t want free glucose leaving cells
where is free glucose generated at the end of gluconeogenesis
in the endoplasmic reticulum
why are fatty acid chains said to be energy rich molecules
they have lots of covalent bonds
how many moles of CO2 are produced on each turn of the C.A.C
2
what is amylose
a polymer of glucose- makes up part of starch
what can only liver glycogen do
provide glucose for other tissues
in high levels of ATP what happens to pyruvate dehydrogenase?
it is inactivated
oligomycin blocks proton transport through ATP synthase. What effect does this have on a) ATP synthesis and b) electron transport?
both a and b reduce
hexokinase
enzyme that phosphorylates glucose to make G-6-P
low km due to high affinity for glucose
low Vmax
high prevelance in tissues
glucokinase
high km
high Vmax
high prevelence in liver
which 2 enzymes are important in first rate determining step of glycolysis
hexokinase
glukokinase
when is hexokinase most prevalent?
in state of hypoglycemia (low blood glucose)
because of low km it requires less time to fill active sites- high affinity for substrate
low Vmax means if there is a high amount of glucose then there is a higher chance of saturation and becomes ineffective quickly
so works more effectively in lower concentrations of glucose
when is glucokinase most prevalent?
has high km and high Vmax
this means it has a low affinity for glucose- more time taken for active sites to fill up
but a high Vmax means the capacity is v high- more active sites available for longer
works well in state of hyperglycaemia- more efficient than hexokinase in this state
In vigorously working muscles glucose is converted to lactate. Why?
NAD+ levels in the cell are limited
When O2 is limited the oxidation of NADH to NAD+ (complex 1) by the electron transport chain is insufficient to maintain glycolysis so pyruvate cannot be made
diverted to make lactate
insulin function and structure
a hormone that regulates glucose levels in the body
lack of insulin causes type 1 diabetes
structure stabilised by two disulfide bonds between peptide chains
what is and alpha keto acid
it is simply the carbon skeleton of an α-amino-acid
Structure and characteristics of glycogen
has alpha 1-4 linked subunits
alpha 1-6 branches
HIGHLY BRANCHED
high amounts found in liver and skeletal muscle
many non-reducing ends
what do non-reducing ends mean for a polymer
it can be readily synthesised and degraded to and from monomers
which two carbohydrates have a lot of non-reducing ends
glycogen
amylopectin (makes up starch with amylose)
why are polymers not ‘in solution’
they are osmotically inactive
as if it was just free glucose, the glucose would move out the cell down its concentration gradient
so being in a polymer prevents the movement
GAGs
mucus and synovial fluid
unbranched polymers
genetic disorder involving GAGs= mucopolysaccharidoses
Hurler syndrome
clouding and degradation of cornea
dementia
