Week 3 Biochemistry Flashcards
Gluconeogenesis enzyme activity is activated by ______ and slowed down by _________
Gluconeogenesis is turned on by glucagon and slowed down by insulin.
Where does gluconeogenesis occur?
LIVER (95%) and kidney.
Gluconeogenesis activity is highest when _______
Fasting
What molecules inhibit Complex IV in the ETC? This inhibits the reduction of _____ to _______
Cyanide (CN-) and carbon monoxide (CO) poisoning. It inhibits the reduction of 1/2 O2 to H2O and cell cannot generate ATP.
What do uncoupling agents in the ETC inhibit?
Uncoupling agents inhibit the formation of a proton gradient so H+ does not go through ATP synthase.
Which of the following is NOT a substrate of gluconeogenesis?
- lactate
- glycerol
- acetyl CoA
- alanine
- aspartate
- glutamate
Acetyl coA is NOT a substrate for gluconeogenesis. You cannot use fatty acids (acetyl coA precursors) to form glucose through this pathway.
Signaling from _________ and __________ can increase gene expression for gluconeogenesis enzymes (i.e. PEP carboxykinase) when starving or stressed.
Glucagon when starving, and cortisol when stressed
95% of gluconeogenesis takes place in what organ?
95% in Liver. 5% in kidneys
What molecules are used to form gluconeogenesis?
Lactate, glycerol, and glucogenic amino acids
Can acetylCoA form glucose?
NO! It is part of the TCA/Kreb cycle
Within the liver, what enzyme cleaves what molecule to form glucose?
glucose-6-phosphatase cleaves glucose-6-phosphate to make glucose
What does a deficiency in glucose-6-phosphatase cause?
It prevents the glucose-6-phosphate from being cleaved to make free glucose. This is known as Van Gierke’s disease.
When muscles use glucose to form ATP what is the byproduct and where does it go once it is formed?
The byproduct is lactate and it goes to the liver to become part of gluconeogenesis.
Within the pentose phosphate pathway, glucose-6-phosphate dehydrogenase (G6PDH) is responsible for forming what molecule?
NADPH!
Why is a deficiency in glucose-6-phosphate dehydrogenase in red blood cells bad?
Bc it causes the RBC to be more susceptible to damage by reactive oxygen species due to it’s inability to produce NADPH which reduces GSSG to GSH so it can give up electrons to free radicals (preventing H2O2’s conversion to water).
Transketolase, an enzyme in the PP pathway, requires what special cofactor? And its activity within RBC’s is reflected by the status of what vitamin?
Cofactor: Thiamine pyrophosphate (TPP)
Vitamin: B1
What are the two main functions of pentose phosphate pathway (PPP)?
To produce:
- NADPH (a reducing agent)
- Ribose-5-phosphate (for nucleotide biosynthesis)
Where is glucose stored?
You just fell for the oldest trick in the book! Glucose cannot be stored bc it is so-o-o water soluble, so it must be converted to the insoluble polymer GLYCOGEN. The most important storage spaces for GLYCOGEN are the liver and skeletal muscles.
When do you want glycogen synthase to be active?
After a mean when insulin is high to promote glycogen synthesis.
Glucagon promotes the phosphorylation of what molecule to make glucose?
Glycogen synthase
Where does alpha-amylase hydrolyze glycogen or starch?
In the mouth and small intestine (from the pancreas)
Which enzyme within the human body breaks down cellulose?
Trick question. What do you think we are cows? We can’t break down the beta-1,4 linkages in cellulose!
What will happen if we do not have the enzyme lactase in our bodies?
The gut is unable to break down lactose in the small intestine. Instead it is transported to the large inestine where it will be broken down by bacteria which will cause bloating, diarrhea, and dehydration.
Describe the flow of glucose into the cell.
Glucose is driven against its concentration gradient by coupling to Na+. Once glucose enters, Na+ is driven out of the cell as K+ enters the cell driven by the dephosphorylation of ATP. This allows glucose to also leave the cell and go into the blood stream.
