Glycolysis. Flashcards
What is glycolysis?
The process used by the body to break down and obtain energy from glucose.
Which cells will glycolysis primarily occur in?
In almost every cell in the body.
Does glycolysis occur under aerobic or anaerobic conditions?
It can occur under either aerobic or anaerobic conditions.
What part of the cell does glycolysis occur in?
The cytoplasm.
Why are blood glucose levels so tightly controlled?
Because, too much or too little glucose in the bloodstream can lead to debilitating effects for the individual.
What is the condition called, when there is too much glucose in the bloodstream?
Hyperglycaemia.
What is the condition called, when there is too little glucose in the bloodstream?
Hypoglycaemia.
What food group is broken down to give glucose?
Carbohydrates.
What are the 4 pathways that involve the metabolism of glucose?
Glycolysis.
Glycogenolysis.
Gluconeogenesis.
Glycogenesis.
What are the 2 metabolic pathways that consume glucose?
Glycolysis.
Glycogenesis.
What are the 2 metabolic pathways that produce glucose?
Gluconeogenesis.
Glyogenolysis.
What does the glycolysis pathway do?
Glycolysis takes glucose and will break it down to create energy in the form of ATP.
Does glycolysis take place in the fasting state or the well fed state?
Well fed state.
What does the glycogenesis pathway do?
This pathway takes glucose molecules and stores them as glycogen.
Why does glycogenesis convert glucose to glycogen?
Glycogen is made when glucose levels are high so that the energy can be store and then used to produce energy when glucose levels are low.
Does glycogenesis take place in the fasting state or the well fed state?
In the well fed state.
What does the gluconeogenesis pathway do?
This pathway will synthesise glucose from smaller molecules when glucose levels are low.
Why does gluconeogenesis take place in the fasting state or the well fed state?
In the fasting state.
What does the glycogenolysis pathway do?
It releases glucose into the bloodstream by breaking down stored glycogen.
Why does glycogenolysis take place in the fasting state or the well fed state?
In the fasting state.
How is glucose bought into the cell from the bloodstream?
By specific transport proteins.
Can any transport protein carry any organic molecule?
No.
Each class of transport protein can only carry one form of organic molecule.
Where are transport proteins found?
Embedded into the cell membrane.
Where are GLUT-1 transporters found?
In all cells except the kidney and small intestinal cells.
What is the function of GLUT-1 transporters?
They have a high affinity for glucose and will transport it from the bloodstream into the cell.
Is there anything GLUT-1 transporters won’t carry?
Galactose or fructose.
Where are GLUT-2 transporters found?
These are found in red blood cells, pancreatic beta cells and kidney tubules.
What is the function of GLUT-2 transporters?
It can transport glucose in and out of the cell and is said to be bi-directional.
At high blood glucose levels, it will initiate glucose uptake in the liver and serves as a glucose sensor for insulin independent cells.
What is the specificity of GLUT-2 transporters?
It will transport glucose but has a higher affinity for galactose and fructose.
Where are GLUT-3 transporters found?
In the neurons, placenta and testes.
What is the function of GLUT-3 transporters?
It is similar to GLUT-1 as it has a high affinity for glucose and galactose, but not fructose.
Where are GLUT-4 transporters found?
In skeletal and cardiac muscle and also in fat tissue.
What are the characteristics of GLUT-4 transporters?
It is the only insulin sensitive transporter.
Meaning that insulin can activate the cell surface receptor of GLUT-4 which will increase the amount of receptors.
Where are GLUT-5 transporters found?
Small intestine, sperm, brain, kidney, muscle and fat tissue.
What is the function of GLUT-5 transporters?
This is mainly used to transort fructose for which it has a high affinity.
Is there anything GLUT-5 transporters won’t carry?
They do not have a high affinity for glucose or galactose.
Where are GLUT-7 transporters found?
In the ER membranes of the liver and pancreas cells (hepatocytes).
Which type of transporters are not found in the cell membrane?
GLUT-7 transporters.
Where are SGLUT-7 transporters found?
In the epithelial cells of the small intestine and kidneys.
What is the function of GLUT-7 transporters?
It moves glucose from the lumen of the ER to the cytoplasm so that it can be released from the cell by GLUT-2.
What is the function of SGLUT-7 transporters?
It co-transports glucose or galactose with Na+ from the intestinal lumen. This allows it to go against a concentration gradient.
Is there anything SGLUT-7 transporters won’t carry?
Fructose.
Diabetics often have problems with which glucose transporter?
GLUT-4.
Why do diabetics often have a problem with the GLUT-4 transporter?
If GLUT-4 transporters are faulty, then the cells cannot sense rises in insulin and glucose will remain in the bloodstream an not enter the cell.
How many carbons does glucose have?
6.
What is 1 molecule of glucose broken down to at the end of glycolysis?
2, 3 carbon pyruvate molecules.
How many steps are there in glycolysis?
9 in aerobic glycolysis.
10 in anaerobic glycolysis.
Glycolysis produces energy in what forms?
ATP and NADH.
Why is there an extra step in anaerobic glycolysis?
Because, pyruvate is converted to lactate as the electron transport chain cannot occur without oxygen.
Does the conversion of pyruvate to lactate require any energy?
Yes.
1 NADH is used to convert a pyruvate molecule to lactate.
Does aerobic or anaerobic glycolysis produce more energy?
Aerobic glycolysis as anaerobic glycolysis uses up 2 NADH molecules when the 2 pyruvates are converted to lactate.
What are the 2 distinct stages that glycolysis can be broken down to?
The energy investment stage.
The energy pay off stage.
How many ATPs are invested in the energy investment phase?
2.
How many ATPs are generated in the energy pay off phase?
4 ATPs are generated along with 2 NADH molecules.
How many gross ATPs are generated by glycolysis?
4.
How many net ATPs are generated by glycolysis?
2 as 2 ATPs are used up to initiate glycolysis.
How many NADH molecules are generated by glycolysis?
2.
How many pyruvate molecules are generated by glycolysis?
2.
What is generated by anaerobic glycolysis?
2 ATPs and 2 lactate molecules.
How does the brain oxidise glucose?
It will get all of the energy it can out of glucose and will oxidise it all the way to CO2 via the TCA cycle and the electron transport chain.
How does the liver oxidise glucose?
It will oxidise glucose to CO2.
It can form lactate from pyruvate.
It can convert pyruvate to ACoA and then to fat, so that the energy can be stored for later use.
What organ is responsible for releasing glucose into the bloodstream?
The liver.
How does adipose tissue oxidise glucose?
It will convert pyruvate to ACoA and then to fat.
How does muscle oxidise glucose?
It will usually convert pyruvate to CO2.
Except under anaerobic conditions during strenuous exercise, where it will form lactate instead.
How do erythrocytes oxidise glucose?
They are only able to oxidise glucose to lactate.
Why can erythrocytes only form lactate from glycolysis?
Because they have no mitochondria.
To completely oxidise glucose to CO2, mitochondria must be present.
What is the only form of energy for red blood cells?
Glycolysis.
When will glucose be converted to glycogen?
If there is sufficient energy levels in the body, glucose will be stored as glycogen and its energy will be saved for later use.
How many steps of glycolysis make up the energy investment phase?
The 1st 3 steps of glycolysis are the energy investment phase.
In what step of glycolysis are the 2 NADH molecules generated?
In step 5.
In what steps of glycolysis are the ATP molecules generated?
In steps 6 and 9.
What are the irreversible steps of glycolysis?
Steps 1, 3 and 9.
Is step 1 of glycolysis reversible or irreversible?
It is an irreversible, rate limiting step,
What happens in step 1 of glycolysis?
Glucose is bought into the cell by a GLUT-1 transporter.
An ATP molecule is used to phosphorylate glucose at carbon 6 to form glucose 6 phosphate.
What enzyme is used in step 1 of glycolysis?
Hexokinase or glucokinase.
Hexokinase and glucokinase are examples of what kind of family of enzymes?
They are isozymes of each other.
How much energy is used in step 1 of glycolysis?
1 ATP.
Is step 2 of glycolysis reversible or irreversible?
It is reversible.
What happens in step 2 of glycolysis?
An isomerisation reaction takes place and glucose 6 phosphate becomes fructose 6 phosphate.
The carbonyl group is moved from carbon 1 to carbon 2, nothing else changes.
In step 2, the sugar is converted from what form to what form?
An aldose sugar to a ketose sugar.
What enzyme is used in step 2 of glycolysis?
Phosphoglucose isomerase.
Why is glucose phosphorylated in step 1 of glycolysis?
So that it cannot leave the cell.
Is step 3 of glycolysis reversible or irreversible?
Irreversible, rate limiting step.
What happens in step 3 of glycolysis?
Fructose 6 phosphate is phosphorylated at carbon 1 and the molecule becomes fructose 1, 6 bisphosphate.