Carbohydrates 2: the return Flashcards
Name the 3 important hexoses
Glucose
Galactose
Fructose
Name the 3 important disaccharides
Maltose - Glu&Glu
Sucrose - Glu&Fru
Lactose - Glu&Gal
What feature makes some sugars be called ‘reducing sugars’
Anomeric C1 can be oxidised
The anomeric carbon is the only residue that can be oxidised on these sugars
Which disaccharides are reducing sugars and which aren’t?
Maltose & Lactose are reducing sugars
Sucrose is not a reducing sugar, as it does not have an anomeric C1 that can be oxidised
What is the difference between heteropolysaccharides and homopolysaccharides
Homopolysaccharides have one monomeric species
Heteropolysaccharides have more than one monomeric species
What 2 types of glucose polymers make up starch
Amylose
Amylopectin
What is the difference between amylose and amylopectin
Amylose is straight chained and has a(1-4) linkages
Amylopectin is more abundant, and is branched.
It has a(1-6) bonds every 24 - 30 residues
How is glycogen different from starch?
Glycogen is more extensively branched than starch (amylopectin)
Much higher ‘energy density’ than starch
Glycogen is used in animals, starch is used in plants
Why is glycogen (and starch) an effective energy storage molecule?
1) Compact - lots of glucose can be stored in a small volume
2) Branched - many non-reducing ends means it can be degraded/synthesised quickly to release/store energy
3) Insoluble - osmotically inactive so does not interfere with osmotic activity
What are glycoproteins?
Class of proteins which have carbohydrate groups attached to the polypeptide chain
What effects can adding a carbohydrate to a protein have?
Increase solubility
Influence conformation/shape
Protect it from degradation
Act as communication between cells
What are Glycosaminoglycans?
also called mucopolysaccharides
Un-branched polymers
Repeating units of hexuronic acid and an amino-sugar, which alternate through the chains
Where are glycosaminoglycans mainly found?
What does this indicate about their properties?
Mucus and in synovial joints
Lubricant properties as chains easily slide over each other
What are proteoglycans?
A compound consisting of a protein bonded to mucopolysaccharide groups, present especially in connective tissue
What is the difference between glycoproteins and proteoglycans?
Glycoproteins are proteins with carbohydrates attached
Proteoglycans are GAG’s with proteins bonded to them
What is the group of genetic disorders associated with glycosaminoglycans?
Mucopolysaccharidoses
Absence/malfunction of enzymes required for the breakdown of glycosaminoglycans/mucopolysaccharides
What general health problems are associated with mucopolysaccharidoses
GAG’s build up in connective tissue, blood and other tissues
Can cause:
- dementia
- heart problems
- inflammation to joints
- stunting of bones
- damage to endothelial structures
Where is most glycogen stored?
Liver and skeletal muscle
What is the difference between how glycogen is broken down in the liver and skeletal muscle?
In liver, glycogen is sequentially broken down into Glucose-6-phosphate, which is then dephosphorylated by G-6-phosphotase before entering the blood
In skeletal muscle, there is no G-6-phosphotase, so after glycogen is broken down to G-6-P, it undergoes glycolysis (substrate level phosphorylation) and forms lactate
What disease is characterised by Glucose-6-phosphotase deficiency in the liver, kidney and intestines
This disease shows symptoms such as high liver [glycogen], fasting hypoglycaemia and lacticacidaemia (high blood [lactate])?
Von Gierke’s disease
What disease is characterised by Skeletal muscle phosphorylase deficiency
This disease will show symptoms in early adulthood, with high muscle [glycogen], weakness & cramps and no blood [glucose] increase after exercise?
McArdle’s disease
What is glycolysis?
Sequential, cellular, anaerobic degradation of glucose, to produce pyruvic/lactic acid, yielding a relatively small amount of ATP
What is the net energy product of glycolysis?
2 ATP and 2 NADH per glucose molecule
What is redox balance, and why is it necessary in glycolysis?
NAD+ is necessary in glycolysis, but is limited in cells
Glycolysis uses up NAD+
All fates of pyruvate, produced from glycolysis will produce NAD+, thus regenerating it at the same rate that it is used up
Therefore, there is no net change in the amount of NAD+
What are the two main fates of pyruvate produced from glycogen?
Aerobic conditions = conversion to Acetyl CoA then entry to Citric acid cycle
Anaerobic conditions = entry to Cori cycle = lactate
What process converts Lactate to glucose?
Gluconeogenesis
What is the Cori cycle?
Metabolic pathway in which lactate produced by anaerobic glycolysis in the muscles moves to the liver and is converted to glucose, which then returns to the muscles and is metabolised
In what conditions would the Cori cycle be relied upon?
Intense exercise such as sprinting
The body can’t supply cells with enough oxygen for oxidative phosphorylation
Where does gluconeogenesis take place?
Liver
What is gluconeogensis?
Metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates such as lactate, glycerol, and glucogenic amino acids
What is the purpose of the ‘side step reactions’ in gluconeogenesis?
Avoids the irreversible reactions that take place in glycolysis
What is the basic sequence of molecules in gluconeogenesis
Pyruvate Oxaloacetate PEP G-3-P (DHAP) F-1,6-P G-6-P Glucose
What is the basic sequence of molecule products in glycolysis?
Glucose G-6-P F-1,6-P (DHAP) G-3-P PEP Pyruvate
In gluconeogenesis, where does the first side step reaction, in which Pyruvate is converted to PEP, largely take place?
Mitochondria
In the liver
What is the pentose phosphate pathway?
Metabolic pathway which generates NADPH and pentose sugars, precursors for DNA/RNA synthesis from glucose
What are the two phases of the pentose phosphate pathway?
Oxidative, irreversible phase: generates NADPH
Non-oxidative, reversible phase: generates precursors for nucleotides
The pentose phosphate pathway produces NADPH
What is this used for?
‘Provides energy’ for fatty acid synthesis (anabolism)
Describe how being drunk would inhibit gluconeogenesis
When the body breaks down and processes a lot of ethanol, the amount of NAD+ in your body drops
This leaves very little NAD+ available for gluconeogenesis
This means that gluconeogenesis cant take place, which can lead to hypoglycaemia and lacticacidaemia
What are the 2 anabolic pathways in this brainscape
Gluconeogenesis
Pentose phosphate pathway - although this has some catabolic stages
