Glycolysis Flashcards
What is Glycolysis?
The breakdown of glucose to smaller molecules, producing ATP
Where does Glycolysis take place?
In the cytoplasm of cells
What are 3 chemical groups and their ends often involved in metabolism?
Aldehydes - C=0-H Carbonyl end (Acetaldehyde)
Ketone- C=O Carbonyl in middle (Acetone)
Carboxyl - C=O-OH end (e.g Acetic acid)
What kind of state can sugars and glucose sit in?
Equilibrium
What does all sugars end in?
-ose
What are the 2 types of glucose and what one is the most naturally occurring?
D and L Glucose - D is the most naturally occurring
What does each sugar have in the centre?
A chiral centre
What happens going from an open chain sugar to a cyclic one?
Water is lost and there are 2 different sugars that can be produced depending on what Hydrogen is lost
How many members does glucose have in its ring?
6 (pyranose ring)
How many members does fructose have in its ring?
5 (furganose ring)
Where is Fructose sugar most commonly found ?
In lots of fruits
Where is the carbonyl group which is attacked to form a cyclic structure positioned?
Carbon 2
What is the basic structure of an amino acid?
NH3+
|
H-C-COO-
|
R1What happens in proteins to form a peptide bond?
The amino group of one amino acid joint to the carboxyl group of its neighbour
What type of acid is common in metabolism?
Keto acids - made from metabolising fats (NOT KETOS IN BODY!)
What does Glycolysis do?
Converts glucose to pyruvate and makes 2 ATP
What are the steps of Glycolysis?
1) . Phosphorylation -(consumes 2 ATP) and traps Glucose in the cell because once it is ionised to Glucose-6-P it is unable to cross the cell membrane
2) . Isomerization - Glucose-6-P covered to Fructose-6-P
3) . Phosphorylation - (consumes 2 ATP) and forms a hexose diphosphate that can be split into two phosphorylated 3-carbon compounds
4) Cleavage and Isomerisation - Forms 2 phosphorylated 3-carbon compounds, then allows dihydroxyacetone-P to be converted to glyceraldehyde-3-P which can be metabolised
5). Oxidative phosphorylation - Glyceraldehyde-3-P is
simultaneously oxidized and
phosphorylated
Hydrogen and electrons from
glyceraldehyde-3-P are
passed to nicotinamide
adenine dinucleotide (NAD+)
6). Transfer of phosphate
- ATP production;
2 molecules of ATP/molecule of glucose consumed
7) . Molecular arrangement
- Phosphate group moved from one position to another (isomerisation)
8) . Dehydration
- Favours transfer of phosphate to ATP
9) . Transfer of Phophate
- ATP production; 2 molecules of ATP/molecule of glucose consumed
What is the full name for NAD?
Nicotinamide Adenine Dinucleotide
How do we get from NAD+ to NADH and vice versa?
NAD+ –Reduce–> NADH
(Oxidative agent)
NADH –Oxidise–> NAD+
(Reducing agent)
Where does the nicotinamide part of NAD+ come from?
Vitamin B3 (Niacin)
How do we get Vitamin B3 and what conditions are cause by a lack of it?
Needs to be provided in our. diets
Lack of Niacin causes. Pellagra - sensitivity to sunlight, dermatitis, alopecia, glossitis, weakness, ataxia
What happens to NAD+ during aerobic conditions?
NAD+ is regenerated because NADH passes the electrons and the hydrogen atoms which is receives from glyceraldehyde-3-P through the Electron Transfer Chain which combines three with molecular oxygen and water
What happens to NAD+ during anaerobic conditions?
Without molecular oxygen NADH builds up and because NAD+ cannot be regenerated glycolysis is halted if this continues
So NADH is re-oxidised by reducing pyruvate to Lactate
What builds up making muscles ache?
Acid from metabolism NOT from Lactate
How does yeast combat anaerobic conditions?
It converts pyruvate to ethanol
What is the function of NAD+?
NAD is an electron and proton acceptor where it receives them from metabolites and uses them in the respiratory chain
Once phosphorylated how does Glucose-6-phosphate get across the membrane?
By GLUT - glucose transporters
and
By SLGT’s (Sodium linked glucose transporters)
What can Glucose-6-phosphate be converted to inside a cell?
Glycogen
What do kinases do?
Phosphorylate
What are the 3 key enzymes involved in Glycolysis and their roles?
1). Hexokinase (Catalyses: glucose –> glucose-6-P)
- Phosphofructokinase (Catalyses: fructose-6-P
- -> fructose-1, 6 - bisphosphate) - Pyruvate kinase
(Catalyses phosphoenolpyruvate –> pyruvate)
What enzyme is the most important in regulating Glycolysis and what are 4 ways it does this?
Phosphofructokinase:
- High [ATP] allosterically inhibits the enzyme (and High ADP stimulates it)
- Low pH inhibits the enzyme
(lactate accumulation) - Due to metabolism - High [citric acid] inhibits
- High [fructose-6-P] stimulates the enzyme (key in regulating Glycolysis)
What happens to ADP when ATP is required?
When energy is required ATP goes down ADP goes up
