Carbohydrats, glucoproteins Flashcards
How many diastereoisomers
does D-glucose have?
Glucose has 4 chiral centers and the number of stereoisomers are 2n=24=16
The number of diastereomers to D-glucose are 14, 16 minus D-glucose and minus the
enantiomer L-glucose.
Why is it more difficult to determine the structure of oligosaccharides compared to
peptide sequences?
Not only the order of the monosaccharides is important –
Type of cyclic sugar (alfa or beta anomer, furanose or pyranose)
Binding – between which carbons eg bindning 1->2 or 1->4 or….
Carbohydrates can be branched
For the analysis of polysaccharides stepwise degradation with enzymes are needed,
and then MS
Protein sequence is linear
What is the benefit for people of having different blood groups?
Antigen on a pathogen similar to the one of the blood group antigens may not be
identified as a pathogen – parasite will flourish. But people with different blood groups
may be protected. Selective pressure on having different blood groups to prevent parasitic mimicry.
Bacteria often have to cope with widely different temperature conditions. The
temperature can be both very high and very low. How does this composition affect
phospholipids in the cell membrane?
Membrane fluiditet affected by chain lenght and number of double bonds. Shorter
chain length and more doubble bonds – less densely packed lipids – less
bonds/interactions = higher fluidity of memebrane
EPO has become an important drug for doping. At the same time, EPO is a natural
protein in the body. What methods do you think the anti-doping agency uses to detect
if an athlete is doped or not with EPO?
Amount of EPO
Glycosylation pattern – can be characterized by isoelectric focusing.
There are several different so-called second messengers, including calcium ions and
cAMP. What are the advantages of secondary messengers and can there be
disadvantages of using these general molecules?
Possible disadvantage is that you stimulate a recation that is not beneficial as a
response to the initial singal. Cross talk gone wrong. Bot it is mostly positive
Stolen on the internet: “A key advantage of second messengers over proteins is that,
unlike proteins, second messenger levels are controlled with rapid kinetics. Thus,
whereas it may take tens of minutes for the levels of a protein to increase significantly,
most second messenger levels increase within microseconds (e.g., ions) to seconds
(e.g., DAG), They are often produced from precursors that are abundant in cells or
released from stores that contain high concentrations of the second messenger; so,
their generation is not rate limiting. Thus, when the appropriate signal is received,
second messengers are rapidly generated, diffuse rapidly, and alter target protein
function highly efficiently.”
What happens if a hormone signal cannot be terminated?
That is very problematic – normal signaling and response cannot occur, and often
leads to disease. Example EGF signaling pathway with mutated RAS that stays in on
position - continues to stimulate cell growth. A common mutation in cancer cells. Dysregulation of the second messenger output in response to a particular agonist can
result in cell/organ dysfunction and disease. For example, chronic exposure to cAMP
in the heart results in an uncontrolled and asynchronous growth of cardiac muscle cells
called pathological hypertrophy.
Why phospholipids do not form micelles?
It is due to the shape of the molecule, its cylindrical and does not favor micelle
formation
Why is glucose phosphorylated in the cytosol?
A) To capture the glucose in the cell
B) To destabilize glucose and facilitate the following metabolic steps
C) To make the glucose more soluble.
D) All options are correct
E) A and B
D)
Carbohydrates are:
A) polyhydroxy aldehydes.
B) polyhydroxy ketones.
C) polyhydroxy acids.
D) polyhydroxy alcohols.
E) a and b.
E)
The simplest carbohydrates are
A) D- and L-glyceraldehyde.
B) dihydroxyacetone and D- or L-glyceraldehyde, respectively.
C) dihydroxyacetone and glycerate.
D) All of these – all are 3 carbons sugars, glycerate has one more OH-group.
E) None of these
D)
Fructose can be cycled into one
A) pyranose ring.
B) furanose ring.
C) both pyranose and furanose rings.
D) None of these.
C)
The storage form for glucose in plants is:
A) glycogen
B) amylose
C) amylopectin
D) b and c
amylose (ogrenad a 1->4) and amylopectin (a1->4 samt grenad a 1->6)
E) All of these
D)
To what amino acids in glycoproteins are carbohydrates usually bound to?
A) Tyrosine and Asparagine
B) Serine, Threonine and Aspargin
C) Serine, Tyrosine and Aspargin
D) Serine and threonine
E) A and D
B)
In what places in the cell are proteins glycosylated?
A) ribosome
B) endoplasmic reticulum
C) Golgi complex
D) b and c
E) a, b, and c
D)
