Energy Production Flashcards
What are the 4 main stages of Catabolism?
- Breakdown to building blocks
- Breakdown to metabolic intermediates (glycolysis)
Release of ‘reducing power’ and ‘energy’ - Tricarboxylic acid (Kreb’s) cycle
- Oxidative phosphorylation
Conversion of ‘reducing power’ into energy currency (ATP)
Lactose intolerance is caused by a deficiency in what?
Lactase enzyme
During stage 1 of catabolism what enzymes are required at each stage? What are they used for?
Salivary amylase in the mouth (convert starch/glycogen to dextrins)
Pancreatic amylase in the duodenum
The brush border of the epithelial cells of the jejunum and duodenum:
Lactase (lactose)
Sucrase (sucrose)
Pancreatic amylase (alpha1-4 bonds)
Isomaltase (alpha1-6 bonds)
What is the cause of primary lactase deficiency?
At what he does this affect individuals?
The absence of lactase persistence allele, when they reach adulthood they no longer express the allele for lactase
Only occurs in adulthood
What is secondary lactase deficiency?
At what age does this occur?
Lactase deficiency caused by injury to the small intestine: -Gastroenteritis -Coeliac disease -Crohn's disease -Ulcerative colitis Any age: infants and adults Generally reversible
What is the cause of congenital lactase deficiency?
At what age does this become apparent?
Autosomal recessive defect in lactase gene
When neonates breast feed- they cannot digest the milk
How are monosaccharides absorbed one they have been produced through the breakdown of larger carbohydrates?
- Through active transport by the sodium dependant glucose transporter 1 (SGLT1) into intestinal epithelial cells
- Then into the blood supply via facilitated diffusion through GLUT transport proteins
GLUT2 transport is found where?
Kidney, liver, pancreatic beta cells, small intestine
GLUT4 transporter is found where?
How is this transporter regulated?
Adipose tissue, striated muscle
Regulated by insulin
Although all tissues can metabolise glucose, which cells have an ABSOLUTE requirement?
In each case, state why.
Red blood cells - no mitochondria
Neutrophils - using mitochondria for oxidative burst to kill bacteria
Innermost cells of the kidney medulla - high oxygen demand and getting blood when most the O2 has been taken- relies on anaerobic respiration
Lens of the eye - needs to be transparent can only derive oxygen through diffusion
Uptake of glucose depends on what?
Concentration of glucose
Which part of the body prefers glucose as its fuel but can use ketone bodies in starvation given time to adapt?
The CNS
Glycolysis overall is the conversion of what to what?
Glucose (6 carbon) into 2 x Pyruvate (3 carbon)
Glycolysis consists of two overall phases, what are they?
The investment phase
The payback phase
How much ATP does the investment phase of glycolysis use and produce?
Uses 2 ATP
Produces: None
How much ATP does the “payback phase” of glycolysis use and produce?
Uses: None
Produces: 4 ATP
What is the overall net production of ATP from glycolysis for every 1 Glucose that enters the process?
Overall Net production: 2 ATP for every 1 Glucose
Besides ATP, what else does the “payback phase” of glycolysis produce?
2 x NADH (reducing power)
Glycolysis is the only pathway that can operate under what conditions?
Anaerobic (without oxygen)
Is glycolysis exergonic or endergonic?
Exergonic
Name the three key enzymes used in glycolysis and at which steps during the process they are required
Hexokinase (Glucokinase in the liver) (Step 1)
Phosphofuctokinase-1 (Step 3)
Pyruvate kinase (Step 10)
Hexokinase (Glucokinase in the liver) is required for the conversion of what to what during glycolysis?
Glucose —> Glucose-6-Phosphate
Phosphofructokinase-1 is an enzyme required to convert what into what during glycolysis?
Fructose-6-Phosphate—>Fructose 1,6-Bis-Phosphate
Pyruvate kinase is the enzyme required to form what from what during glycolysis?
Forms Pyruvate from Phosphienolpyruvate
What is important about steps 1,3 and 10 in glycolysis?
They are irreversible therefore to create glucose from pyruvate, these steps need to be bypassed
Glucose uptake in greater in cells of which disease?
Which imaging can be used to identify this?
Cancerous cells
PET scan
A high NADH signal regulates glycolysis by inhibiting or activating it?
Inhibiting
Phosphofructokinase is an important regulator of glycolysis. What regulation does it use in muscle and in the liver?
Muscle- allosteric regulation
ATP-Inhibits
AMP-Stimulates
Liver- Hormonal regulation
Glucagon-Inhibits
Insulin-Stimulates
What factors are responsible for the regulation of glycolysis?
- Hexokinase
- NADH concentration
- Pyruvate kinase
What is required to regenerate NAD+?
LDH (Lactate dehydrogenase)
What level of lactate is considered hyperlactaemia?
2-5mM
What level of lactate is considered as “lactate acidosis” ?
> 5mM
What three enzymes are required to convert galactose into its products so that it can enter glycolysis?
A deficiency in any of these three enzymes results in what?
Galactokinase
UDP-galactose epimerase
Uridyl transferase
Deficiency results in galactosaemia
Where does the metabolism of fructose occur?
The liver
What condition occurs as a result of a lack of fructokinase enzyme?
Essential fructosuria
We condition is caused by lack of aldolase enzyme?
What damage occurs as a result?
Fructose intolerance
Impaired kidney function
The pentose phosphate pathway produces what 3 main products?
NADPH (reducing power)
Ribose (5C sugar)
CO2
What rate limiting enzyme is required for the pentose phosphate pathway?
Glucose-6-phosphate dehydrogenase
True or false: The pentose phosphate pathway produces ATP?
False
What is the NADPH produced in the pentose phosphate pathway used for?
- Reducing power for biosynthesis
- Maintenance of GSH levels
- Detoxification reactions
What is the significance of the production of 5C Ribose in the pentose phosphate pathway?
Used to go on to make Nucleotides for use in DNA and RNA
What is pyruvate dehydrogenase required for?
To convert Pyruvate into Acetyl Coenzyme A so that it can enter the TCA cycle
What is pyruvate dehydrogenase inhibited by?
Acetyl CoA, NADH, ATP and citrate
Where does the TCA cycle occur?
Mitochondrial matrix
What is pyruvate dehydrogenase activated by?
Pyruvate
NAD+
ADP
Insulin
How many cycles of the TCA cycle are undertaken for every glucose entering glycolysis?
2 cycles
