Week 12: Glycolysis Flashcards
What cell types require glucose?
erythrocytes, retina, renal, brain
What is the straight chain structure of glucose called?
hexose
What 2 carbons link to make a ring structure?
Carbon 1 (on the aldehyde) & Carbon 5
beta-D-glucose structure?
OH points up on carbon 1
alpha-D-gluose structure?
OH points down on carbon 1
When 2 glucose form a linkage, what is the biproduct?
H2O, Carbon 1 gives the H and the other structure gives the OH.
How to make surcose?
alpha glucose and fructose
How to make maltose?
alpha glucose + beta glucose
How to make cellabiose?
beta and beta glucose
How to make polysaccharides?
many glucose molecules
What do proteins, lipids and carbohydrates breakdown to form?
amino acids, fatty acids, glucose
What needs to happen before the stages of glucose catabolism can occur?
Glucose transport into cells via Na+/glucose symporters
where are the Na+/glucose symporters located?
gut
What is the Na+ concentration outside the cell?
high Na+
What is the Na+ concentration inside the cell?
low Na+
What pump is used to push Na+ out of cell, against its concentration gradient?
Na+/K+ antiport/pump
What substance is needed to drive glucose into cell?
Na+
what tissue is GLUT 1&3 receptors?
brain
Does the brain GLUT receptors operate at low Km
Yes, continue to operate at high affinity even when low glucose. even when energy supply is low
keeps you alive.
What tissue are GLUT 2 receptors located?
Liver & pancreatic beta cells
Do GLUT 2 receptors operate at low Km?
no, really sensitive to changes in glucose conc.
Drop in glucose conc, drop activity of receptor.
What cells produce insulin?
pancreatic beta cells
What receptors/cells do insulin bind to?
GLUT 4 on the muscle and adipose tissue (where it is stored)
what does the GLUT 5 receptor do?
Gut
fructose transport
transports glucose
How does the GLUT 1 receptor work?
glucose binds outside
confo change and binding site moves inside cell
low conc of glucose inside so very little probability of binding to receptor on the inside
receptor is unoccupied, confo change and regenerates binding site to outside
catabolism of glucose to 2Xpyruvate equation?
glucose+2ADP+2Pi+2NAD+–>
2Xpyruvate+ 2ATP + 2H20 +2NADH +2H+
What is the first intermediate product of glucose?
fructose 1,6biphosphate
conversion of 2ATP–>2ADP
What does fructose 1,6 biphosphate change to in the glucose pathway?
2 triose phosphates G3P
what does 2 triose phosphates change to in the glucose pathway?
2X pyruvate
conversion of 4ADP–>4ATP
2NAD+ –> 2NADH + 2H+
What is the first control point in glycolysis?
enzyme hexokinase
glucose to glucose-6-phosphate
not reversible, big energy diff
What is the second control point in glycolysis?
phosphofructokinase
fructose-6-phosphate to fructose-1,6-biphosphate
not reversible, big energy diff
What is the third control point in glycolysis?
pyruvate kinase
phosphoenolpyruvate to pyruvate
not reversible, big energy gap
what are the 2 cellular needs for control points in glycolysis?
- production of ATP
- provision of building blocks for synthetic reactions
>don’t need to breakdown pathway, breakdown precursors if needed
What is stage 1 called in glycolysis?
energy investing reactions
what stage 3 called in glycolysis?
energy harvesting reactions
If you have enough energy do you need to proceed at control points?
don’t need to proceed
no need to source more energy in the body
what are negative modulators of phosphofructokinase?
ATP, H+ & citrate (citric acid)
How does citric acid work as a negative modulator of phosphofructokinase in glycolysis?
early intermediate in the citric acid cycle
biosynthetic precursors are abundant
no need to breakdown glucose
How does H+ work as a negative modulator of phosphofructokinase in glycolysis?
Low pH inside cell
Under anaerobic conditions, breakdown of glucose = lactic acid slowly poisoning itself
doesn’t want to metabolise glucose at the detriment to itself
slow down glycolysis, lactic acid will clear –>
allow glucose metabolism to continue
what are positive modulators of phosphofructokinase?
AMP & fructose-2,6-biphosphate (FBP)
what is the ATP/AMP ratio called?
energy charge
When is a cell fully charged/uncharged?
all adenalate nucleotides are in ATP form = fully charged
cell contains only AMP+P = uncharged
What does energy charge in a cell tell us?
2ADP–>ATP+AMP.
depleted enough ATP, need to start converting
2ADP–>ATP+AMP
