Week eight and nine- Carbohydrate metabolism Flashcards
What molecules are carbohydrates made up of?
Carbon, hydrogen and oxygen
What are the classes of carbohydrates?
– Monosaccharides – Disaccharides – Polysaccharides
What group are carbohydrates in?
Carbonyl group
Describe monosaccharides and provide examples.
-Single sugar molecules (e.g. glucose, galactose and fructose)
Describe disaccharides. and provide examples.
Two sugar molecules (e.g. glucose + fructose = sucrose)
Describe Polysaccharides and provide examples.
many sugar molecules (e.g. starch in plant cells and glycogen in animal cells)
Where are carbohydrates stored?
-Blood glucose -Liver glycogen -Muscle glycogen
What is the catalyst for the breakdown of glycogen?
Glycogen phosphorylase
What are the three stages that need to occur for energy to be extracted from CHO?
-Glycolysis -TCA cycle (krebs) -Oxidative phosphorylation
What is glycolysis?
The oxidation of glucose or glycogen.
Where does glycolysis take place?
Cytoplasm
What is produced during aerobic glycolysis vs anaerobic glycolysis?
Pyruvate Lactate
What does glycolysis require?
glucose, enzymes, co-enzymes and ADP
What does glycolysis produce?
Pyruvate, NADH and ATP
What occurs in steps 1-3 in glycolysis and what is the primary regulator of speed?
Energy investment to be recouped later. Atp is required and some ADP is produced Phosphofruktokinase
What occurs in steps 4-5 in glycolysis?
Cleavage of six-carbon sugar to two three-carbon sugars
What occurs in steps 6-10 in glycolysis?
Energy generation
What occurs in step 7 in glycolysis?
First stage where ATP is generated
In stage 6 of glycolysis what happens if the metabolic rate is very high?
NAD+ can become saturated with h+, so there is not enough free NAD+ available, this can cause a ‘bottleneck’ at step 6.
What is produced in step 9 of glycolysis?
Some metabolic water.
What occurs in step 10 of glycolysis?
Second and final ATP generating step. Pyruvate kinase is the catalyst
How much ATP are produced when glucose is used vs glycogen
Glucose- 2 ATP Glycogen- 3ATP
What are the rate limiting steps of glycolysis?
PFK activity drops when acidity increases, causes step 3 to be bottle necked. In step 6 NAD availability can be come limited
Describe in a nut shell what glycolysis is
One glucose molecule is converted via 10 steps to form pyruvate. The energy yield is 2 ATPs
In step one what does hexokinase do?
Helps trap the glucose molecule into the cell by enabling us the attach a phosphate group to it.
In step three what does phosphofruktokinase (PFK) do?
Very sensitive to acidity therefore acidity can become rate limiting.
In step three what does pyruvate kinase do?
Catalyses the formation of pyruvate
What are the ATP generating steps?
7 and 10
What are the three stages when extraction if energy from CHO occurs?
Glycolysis TCA cycle (kerbs) Oxidative phosphorylation
Why do we produce lactate?
The rate of gylcolysis is faster than the subsequent stages of CHO metabolism (TCA and ETC) When metabolic rate is high, NADH availability is low and NAD availability is low.
When do we produce pyruvate?
When metabolic rate is low and O2 availability is high, NAD availability is high
What is pyruvate converted into in the mitochondria?
Acetyl-coenzymeA
Where does glycolysis occur?
Cytosol
Where does the TCA cycle and oxidative phosphorylation occur?
Mitochondria
What does substrate level phosphorylation include?
ATP generated from PCr hydrolysis and glycolysis
Does substrate level phosphorylation require oxygen?
No
What determines the NAD availability?
Metabolic rate
What happens when we have low NAD availability?
Favours lactate production
What happens when we have high NAD availability?
Favours conversion of pyruvate to acetyl-coenzymeA
What does TCA cycle start of with?
acetyl-coenzymeA
Describe the TCA cycle?
A cyclical process of 8 steps
What is the main purpose of the TCA cycle
Oxidise acetyl groups and strip off their electrons of the ETC
What is the end product of one turn of the TCA cycle?
Oxaloacetate
What is the net energy produced in the TCA cycle?
3 NADH 1 FADH2 1 GTP
What occurs in step 1 of the TCA cycle?
Oxaloacetate reacts with acetyl CoA to form 6-carbon molecule citrate
What occurs in step 3 and 4 of the TCA cycle?
Produces CO2 and NADH
What occurs in step 5 of the TCA cycle?
Produces one GTP
What occurs in step 6 of the TCA cycle?
Produces one FADH2
What occurs in step 8 of the TCA cycle?
Produces one NADH and oxaloacetate
How is NAD and FAD regenerated?
ETC
What is the net energy yield from one glucose molecule?
36 ATP
What is the net energy yield from one glycogen molecule?
37 ATP
In the TCA cycle what is a substrate in step 1 and a product in step 8?
Oxaloacetate
What is the capacity of PCr?
Low
How fast can PCr produce energy?
In seconds
What is the capacity of glycolysis?
Intermediate
What is the capacity of oxidative phosphorylation?
High
How fast can glycolysis produce energy?
Intermediate
How fast can oxidative phosphorylation produce energy?
Low rate, mate rate can be achieved in 1-3 mins.
What are the three metabolic pathways?
PCr Glycolysis Oxidative phosphorylation
Do ATP levels within the muscles vary much?
No, even during intense exercise
What does the PCr shuttle allow?
The transfer of phosphate bond energy within the cell
Label the mitochondria
- Inter membrane space
- Matrix
- Inner membrane
