Carbohydrates Flashcards
4 lectures Pathway's not covered in too much detail. Better to draw them out in notes.
Name the 3 important hexoses.
Glucose
Galactose
Fructose
Name the 3 important Disaccharides in human biochemistry.
Maltose
Sucrose
Lactose
Why is Maltose termed a reducing sugar?
Anomeric C-1 can be oxidised.
Out of Sucrose and Lactose, which is a reducing sugar and why?
Lactose is reducing, because it has a glucose monomer with an anomeric C whereas Sucrose does not.
What monosaccharides make up Lactose?
Galactose
Glucose
What are the monomer units of Sucrose?
Fructose
Glucose
Describe the difference between a Homopolysaccharide and a Heteropolysaccharide.
Homo = One monomeric species
Hetero = more than one “ “
Describe how Amylose differs in structure from Amylopectin.
Amylopectin is branched every 24-30 residues, amylose is straight chained
Yay or Nae, including starch in SFM is fucking pointless
Yay
90% of body glycogen is found in the liver, and what other part of the body?
Skeletal muscle
Why is glycogen’s branched structure beneficial?
More exposed NR ends, so Glucose can be snipped off/added on much more quickly
Highly compact
Insoluble, so is osmotically inactive and is easy to store in the cell
Whats the name for a protein with a covalently attached carbohydrate?
Glycoprotein
List the ways in which Carbohydrates attached to proteins are used.
Increase solubility
Influence conformation/shape
Protect from degradation
Cell-cell communication
Describe what makes Glycosaminoglycans (GAGs) effective lubricants.
Long unbranched polymer chains, so they slide over each other easily
Glycosaminoglycans (GAGs) are made of repeating units of an amino sugar and which acid?
Hexuronic Acid
Proteoglycans differ from glycoproteins in what way?
Proteoglycans - Carbohydrate»_space; protein
Where are proteoglycans found?
On the surface of cells
In between cells in the ECM (connective tissue)
What are proteoglycans made up of?
Protein with long carbohydrate chains covalently bonded
At least one GAG present
Where are glycoproteins found?
On the outer Plasma membrane
+ ECM (similar to ProtGly)
Blood
Within cells in the secretory system (golgi)
Some cytoplasmic proteins are glycoproteins as well
What are Mucopolysaccharidoses?
Genetic disorders causing absence or malfunction of the enzymes that break down Glycosaminoglycans
What effect do Mucopolysaccharidoses have?
Build up of GAGs damages cellular architecture + function
Dementia, heart problems and endothelial structures
Hurler, Scheie, Hunter, Sanflippo syndromes are examples of what?
Mucopolysaccharidoses
List the main effects/symptoms of Hurler syndrome.
Clouding + degradation of cornea
Arterial wall thickening
Dementia (CSF build up + enlarged Ventricular spaces)
Describe the structure of Oligosaccharides and how they are digested.
(α1 - 6) linked galactose monomers
not digested
What 2 types of amylase are used in digestion?
Salivary
Pancreatic
What is the function of Amylase?
Hydrolyses (α1 - 4) bonds of starch
What comes first, Jejunum or Duodenum?
Duodenum
Mucosal cell-surface enzymes are found where in the digestive tract?
Jejunum
Describe the function of Isomaltase.
Hydrolyses (α1-6) bonds
Which enzyme snips of glucose from the end of starch?
Glucoamylase
What are the main products of carbohydrate digestion?
Glucose
Fructose
Galactose
How is glucose absorbed through ‘indirect’ ATP power?
ATP is used to maintain Na+ concentration gradient
Why is Fructose absorption different from the other hexose sugars?
It binds to a channel protein and simply moves down a concentration gradient
Why are cellulose and hemicellulose important?
Increase faecal bulk and decrease transit time
What is transported alongside glucose into the epithelial cells in the gut?
Na+
How is Glc ‘trapped’ in the liver?
Glucokinase phosporylates it - not recognised by transporters
What significance does the portal blood have in Glc transport?
Transport to liver
What role do hepatocytes have in Glc usage?
Site of phosphorylation by glucokinase in the liver
What is glycogen?
Branched polysaccharide of Glc
Describe the structure of a glycogen molecule.
Glycogenin protein attached to primer
Glycogen chains branch out from primer in ‘tiers’
What enzyme is involved in extending glycogen chains?
Glycogen synthase
Describe how glycogen becomes branched.
Glycogen-branching enzyme breaks α1-4 bonds and reattaches α1-6
Which end is broken down during glycogen degradation?
Non-reducing
What is glycolysis?
Sequential breakdown of glucose, glycogen or other carbohydrates
To pyruvate
Not requiring oxygen
How much ATP is gained from each Glycolysis cycle?
2 ATP
Why is the Payoff phase carried out twice?
1 Glc produces 2 G-3-P in preparatory phase
True/False
NADH used to convert pyruvate to lactate must be replaced using stores of NADH.
False
NADH is regenerated in Glycolysis so is not used up
What is gluconeogenesis?
Process that converts lactate (+ other carbohydrates) to glucose
Why is gluconeogenesis not the opposite of glycolysis?
GNG pathway has 4 reactions the bypass the irreversible reactions in glycolysis
Why does the gluconeogenisis process not end with pure Glucose?
G-6-P is trapped in cell
Glc would escape
Why are glycolysis and gluconeogenesis not reverse processes?
Some reactions in glycolysis pathway are irreversible
Bypass reactions take place
Where do the bypass reactions take place in glconeogenesis?
Mitochondria
then Cytosol
In gluconeogenesis, G-6-P is converted to Glc where in the cell?
ER
Enzyme embedded in the membrane
How are Galactose and fructose catabolised?
They do not have their own pathway
They feed into the glycolysis pathway at different points
What does the pentose phosphate pathway do?
Takes G-6-P
Makes NADPH and/or Pentose sugars
Varies depending on cells requirements - energy or replication
Excessive alcohol intake will inhibit gluconeogenesis. How?
Ethanol => Acetate => Acetyle CoA => CAC or stored
Processing ethanol requires NAD+
Uses up NAD+ which is needed for gluconeogenesis
Black water fever arises from a deficiency in what enzyme?
G-6-P dehydrogenase deficiency
Why is a deficiency in G-6-P dehydrogenase a problem?
PPP
Less enzyme - less NADPH produced in RBC
Free radical build up
Damage to membrane
Vulnerable
