Carbohydrates Flashcards
What are carbohydrates made of
2+ hydroxyls (OH)
And either aldehyde or ketose
What is the structure of Aldehyde and ketone
Aldehyde - c=O with 1 H and 1 R group
Ketone - c=O with 2 R groups
Why is the C on Aldose numbered 1 but in ketose it is 2
Because ketose usually has a C before the carbonyl C=On
What are the 2 simplest sugars (trioses)
Glyceraldahyde
Dihydroxyacetone
When do carbs/sugars form rings and why do they do that
When they have 4+ carbons
They do it in solution due to them being more energetically favourable than open chain
In aldose sugars such as glucose , what do aldehyde and alcohol when they react form (ring structure)
Hemi acetal
What hydroxyl reacts with the C1 carbon in aldehyde
OH on C5
When glucose/ aldoses form hexose sugar rings. What are they called
Pyranose
What is the projection called when sugars are shown as line form and ring form
Line - Fischer
Ring - haworth projection
In ketose rings, what does ketone reacting with alcohol (C5 OH) produce
A hemi ketal
Why are ketose rings called furanoses
5 sided ring due to C2 (ketone) reacting with C5 OH instead of the C1
Resembles furan
Sugar rings aren’t flat due to carbons tetrahedral geometry. What is the configuration called
Non planar chair configuration (looks like chairs)
What does axial and equatorial mean
When molecules are axial they are up or down from the c plane
Equatorial molecules are in line with the c plane
What is C1 called in aldose anomers
Anomeric carbon
Explain the alpha and beta anomers in a D sugar (eg their position)
Alpha anomers have H OH configuration on C1. OH = axial
Beta have OH. h configuration on C1. OH = equatorial
Beta has same stereochemistry as C5 (OH equatorial in D sugar)
Alpha has opposite stereochemistry to C5 (OH is axial not equatorial)
Which C is anomeric in ketose anomers
C2- this is where the a and b anomers differ
What are D and L sugars called and why
Enantiomers- they are mirrors of each other
Their C5 chirally active carbon differs
How do D and L differ in stereochemistry
In D , the OH is equatorial and H is axial
OH. H
In L, the H is equatorial and OH is axial
H
OH
How is alpha L sugar and beta L sugar different to D anomers
Alpha L has OH equatorial instead of axial (to be opposite to C5)
Beta L has OH axial (to be the same stereochemistry as C5)
What are roomers
Where C 2,3 or 4 differ instead of 5 (D or L)
Give an example of epimers - 2 different sugars due to different C2,3 or 4
Glucose and mannose differ at 2,3
Glucose and galactose differ at C4
What do glycosidic bonds happen between
C1/2 of one sugar and OH of C3,4,5 of next sugar
HOH is lost and O is then shared
Explain Alpha and Beta glycosidic bonds
Alpha bonds are where 1 sugar is an alpha anomer (C1 differs from C5) H OH. H. OH
Beta is where 1 sugar is a beta anomer
OH. H H. OH
What is carb role in energy transport
Transport in disaccharides up into the ileum where they are degraded by enzymes - Maltase, lactase, sucrase
Releases glucose for energy
What are the 2 energy storage polysaccharides
Starch - eg in foods and plants
Glycogen- store of glucose
How is starch/glycogen structure
1-4 alpha bonds in the backbone and 1-6 bonds between chains
What is the advantage of alpha bonds in glycogen and starch energy store
They form spirals which makes it more compact for storage
Why is the end sugar on starch or glycogen called reducing
The C1 is free, unattached
This allows for the ring to form a line again and exposes aldehyde/ketone
They reduce other molecules
What do non reducing ends mean on starch and glycogen
C1 is occupied and so the ring can’t open. Aldehyde or ketone can’t reduce molecules
Why is the fact branches on glycogen and starch are non reducing a good thing
Easier to digest by enzymes. The non reducing ends are attack sites for enzymes
Explain the structure of cellulose (a structural carbohydrate)
1-4 beta glucose chains. They form hydrogen links with other chains due to the beta 1-4 being planar.
This forms microfibrils rigid for the function
Explain the structure of peptidoglycans in cell wall of bacteria (gram - and gram +)
1 N acetyl glucosamine (Glc NAc)
1 N acetyl Muranic acid (sugar and tetrapeptide (chain of amino acids)
Linked by Beta bond
The tetrapeptide on peptidoglycans allows binding of more peptidoglycans. What enzyme is this allowed by
Transpeptidase
Which antibiotic inhibits transpeptidase and therefore breaks down bacteria cell wall (can’t form peptidoglycans)
Penecillin
What enzyme transfers sugars to other molecules from nucleotides eg to make glycolipids
Glycosyltransferase
Glycolipids are receptors on cell membrane example being blood group antigens. How are they different from each other in each blood group
The A antigen has added extra galactose n acetyl (gal NAC)
The B antigen has added extra Galactose (gal)
The sugars were added by different glycosyltransferases
Which glycoprotein/ glycans produces mucins which line epithelial cells for protection from pathogens
N glycans
What is GAG in proteoglycans made from and where is it important
1 amino acid sugar and 1 uronic acid
It is found in joints with high compression such as the knees. It forms a gel cover
How do n glycans allow viruses/ pathogens to enter hosts
The spike proteins are glycosylated which means antibodies can’t keep them away from cell receptors on hosts
Glycosylation also allows the receptor binding domain to be ‘up’ / active
