Energy Production: Carbohydrate 1 Flashcards
(32 cards)
What sources are there of Acetyl CoA?
Keto-Acids from amino acids.
Pyruvate from glucose
Fatty acids
Alcohol
What happens in stage 1 of catabolism?
Protein, carbohydrates and lipids are broken down in to amino acids, monosaccharides, glycerol and fatty acids.
There is no energy release in this stage.
What happens in stage 2 of catabolism?
Amino acids are converted into NH4+, kept-acids and pyruvate.
Monosaccharides such as glucose are converted into pyruvate.
Glycerol is fed into the pathway to form pyruvate.
Some reducing powers are formed such as NAD+ goes to NADH + H+.
Some energy in the form of ATP is produced as well.
Where does stage 1 take place?
Extracellularly in the GI-tract.
Where does stage 2 take place?
Intracellularly in the cytoplasm and mitochondria.
What happens in stage 3 of catabolism?
Keto-acids are fed into the Kreb’s cycle.
Amino acids are converted into acetyl CoA.
Pyruvate is converted into acetyl CoA.
Fatty acids and alcohol are converted into acetyl CoA.
Acetyl CoA starts off the Kreb’s cycle which will then produce some reducing powers and also some ATP. The reducing powers are what’s important here.
Where does stage 3 take place?
In the matrix of the mitochondria.
What happens in stage 4 of catabolism?
Oxidative phosphorylation with the help of the electron transport chain.
The reducing powers that we have stacked up (NADH+H+ and FADH2) are used and re-oxidised in order to form a large amount of ATP.
This step requires oxygen.
What is the general formula of carbohydrates?
(CH2O)n
What groups do carbohydrates contain?
Aldehyde (aldose) or keto (ketose) groups.
Name three main dietary monosaccharides.
Glucose, fructose and galactose
All tissues can metabolise glucose, but which cells have an absolute requirement of glucose? What does this absolute requirement mean?
Red blood cells Neutrophils Innermost cells of kidney medulla Lens of the eye It means they do not use any of the other ways of getting energy, they only use glucose as their source of energy.
What kind of energy source does the brain prefer? Can it use anything else?
It prefers glucose. It can use ketone bodies in times of starvation but then it needs some time to adapt.
Give examples of enzymes used to break down carbohydrates.
Amylase
Sucrase
Lactase
Isomaltase
Why can cellulose not be digested by humans?
Because cellulose contain beta1-4 bonds. This means bonds that face upwards.
Other carbohydrates have alpha1-4 bonds that face downwards.
The alpha glycosidic linkages can be digested.
The beta glycosidic linkages can’t.
What is primary lactase deficiency?
The absence of lactase persistence allele.
Only occurs in adults.
What is secondary lactase deficiency?
Caused by injury to small intestine: Gastroenteritis Coeliac disease Crohn's disease Ulcerative colitis Occurs in both infants and adults This is generally reversible
How does absorption of sugars work?
They are actively transported into intestinal epithelial cells from the GI-tract.
Then passive transport occurs as the sugars are transported from the epithelial cells to the capillary and into blood stream.
SGLT1 is important in active transport.
GLUT1-GLUT5 are used in facilitated transport.
How is glucose taken up by cells from the blood?
Via facilitated diffusion using transport proteins GLUT1-GLUT5.
What can GLUTs be regulated by?
insulin
Where can you find GLUT2s?
Kidney, liver, pancreatic beta cells and small intestine.
Where can you find GLUT4s?
Adipose tissue, striated muscle (insulin regulated)
What is glycolysis?
When glucose is broken down into two pyruvate molecules.
What is phase 1 of glycolysis?
An investment phase where 2 ATP are used to form intermediates.
