Week 2 Biochem Flashcards
The Pentose phosphate pathway creates ______ to use for ________ in anabolism.
- NADPH
2. Reducing Power
After becoming G-6-P in the cells, glucose undergoes ________ to yield ______. In anaerobic cells, this is then converted into ______. In aerobic cells, it then enters the _______, is utilized in ________, and yields ______.
- Glycolysis
- TWO Pyruvate
- Lactate
- Mitochondria
- The electron transport chain
- ATP
The GLUT-2 transporter is found in _______, and is characterized as _______.
- The Liver
2. Insulin-Independent
The GLUT-4 transporter is found in _______, and is characterized as _______.
- Skeletal muscle and adipose tissue
2. Insulin-Dependent
_______ is the only metabolic process that is able to produce ATP anaerobically. It is also said to be ________, because regulation of it may be different between species/life forms.
- Glycolysis
2. Ubiquitous
Glucose is structurally considered an ___________, meaning that it has: _______
- Aldo-hexose
2. An aldehyde on the end of its 6-carbon chain
Pyruvate is structurally considered an _______.
Alpha keto acid
Glycolysis inputs: (which is oxidizer/reducer)
Glycolysis outputs:
- Inputs:
- 2 ATP = oxidizer
- 2 NAD+ = reducer
- Outputs:
- 2 NADH (reduced)
- 4 ATP (oxidized)
Glycolysis is broken into 2 Stages:
The first stage involves ________ and is referred to as the ________. The second stage involves ______ and is referred to as the _________.
- Input of 2 ATP
- Priming stage
- Oxidation of ATP to yield a net of 2 ATP
- Payoff Stage
Describe how one might also split glycolysis into 3 phases:
Stage 1: Activation= 2 ATP consumed
Stage 2: Isomerization= Splitting of hexose-bisphos.
Stage 3: Oxidation: Of Glyceral-3-P to form ATP/NADH
What are the 3 types of rxns involved in glycolysis?
- Breakdown of carbon skeleton
- Phos. of ADP
- Formation of reduced coenzyme - NADH
The first step of glycolysis consumes a molecule of ATP and is therefore considered to be _______.
Exergonic
What is the most important regulatory enzyme of glycolysis? Why? Also, What type of enzyme is this?
- Phosphofructokinase-1 (PFK-1)
- After it conducts its catalytic activity, the molecule MUST continue through glycolysis to yield pyruvate.
- Allosteric Enzyme
The glycolytic pathway is OVERALL considered to be ______.
Exergonic
Why is the 4th step of glycolysis driven toward a net breakdown of G-6-P?
Because the products of that reaction are taken away, creating a need for more to be made.
ALL reactions of the glycolytic pathway occur in _______.
The Cytoplasm
What are the 4 major fates of Pyruvate after being formed from glycolysis?
- Acetyl CoA: For mitochondrial ATP production
- Ethanol: In yeasts/bacteria to produce NAD+ and continue glycolysis anaerobically
- Lactate: Same as ethanol, but in eukaryotes
- Oxaloacetate: 1st step of gluconeogenesis
Why must the cell maintain separate pools of NAD+/NADH?
The NADH molecule signals that the cell is in a high energy state and is therefore regulatory in nature. Since reactions are occurring separately in the cytoplasm and mitochondria, they must each have their own pool as a regulator.
Which enzyme catalyzes the conversion of pyruvate to L-Lactate in anaerobic metabolism
Lactate Dehydrogenase
When does the reverse reaction (L-Lactate becomes Pyruvate) occur?
Under Aerobic Conditions
Red blood cells have no ______, and therefore they can only use ______ to generate ______. This means they are constantly undergoing ______.
- Mitochondria
- The Glycolytic Pathway
- ATP
- Lactic Acid Fermentation (Lactate–>Pyruvate)
What is the main point of alcoholic fermentation of pyruvate to ethanol in yeasts?
To produce NAD+ for the glycolytic pathway to continue
In the presence of oxygen, newly formed pyruvate will then ________ in order to ______.
- Enter the mitochondria
2. Complete Oxidation
In order to enter the mitochondria, pyruvate must be ______ to form the ______.
- De-carboxylated (by Pyr. De-H-ase)
2. Pyruvate Dehydrogenase Complex
Pyruvate entering the mitochondria will ultimately form _____ which will go on to be used in ______.
- Acetyl CoA
2. The T.C.A. cycle
What is the function of Insulin?
To move GLUT-4 transporters from the cytoplasm (basal state) to the cell surface to allow uptake of glucose in response to glucose intake
Why is Glucokinase not regulated? How IS Hexokinase regulated?
- Because in the liver, Glucose uptake is constantly possible due to GLUT-2 transporters
- By Glucose-6-Phosphate formation. A buildup will signal these cells that Glycolysis can be inhibited (feedback inhibition).
How is PFK-1 DOWN regulated? (2)
- An abundance of ATP will signal that the cell is in a high energy state and exhibit feedback inhibition on PFK-1
- An abundance of Citrate from the C.A.C.
How is PFK-1 UP regulated? (2)
- Abundant AMP signals a low energy state.
2. Fructose-2,6-Bisphosphate affects substrate affinity
Insulin from Beta Cells ________ glycolysis.
Glucagon from Alpha Cells ______ glycolysis.
Both are able to determine levels of ______ in the ______.
- Stimulates
- Decreases
- Fructose-2,6-Bisphosphate
- Liver
The insulin receptor activates a ________ and almost always ultimately regulates metabolic pathways by activating _______.
- Receptor Tyrosine Kinase
2. Phosphatases
What is the function of PFK-2? What enzyme reverses this action?
- To convert Fructose-6-Phosphate into Fructose-2,6-Bisphosphate.
- Fructose-2,6-Bisphosphatase
What effect does Insulin have by activating phosphatases in liver cells?
Those phosphatases DEphosphorylate PFK-2 in order to INCREASE its sugar KINASE activity of converting Fructose-1,6-BP into Fructose-2,6-BP, but also DECREASE its sugar PHOSPHATASE activity.
*Ultimately= INCREASE Fructose-2,6-BP to be converted into Fructose-1,6-BP
What enzyme converts Fructose-2,6-BP into Fructose 1,6-BP? Under what conditions does this reaction occur?
- PFK-1
- High blood sugar: Since the liver is freely taking up glucose, this is when Insulin can signal the liver to speed up glycolysis (due to an abundance of glucose).
What happens when Glucagon binds its glucagon receptor?
The GPCR pathway activates PKA, which phosphorylates PFK-2. This INHIBITS its sugar kinase and ACTIVATES its sugar phosphatase, REDUCING the amount of Fructose-2,6-BP in the liver cells, and slowing glycolysis.
Why does an increase in Fructose-2,6-BP speed up glycolysis?
It INCREASES the affinity of PFK-1 for its substrate, Fructose-6-Phosphate (lowers its Km).
Pyruvate Kinase is inhibited by ____ and ____. It is activated by _____ and ______.
- ATP (high energy intermediate)
- Acetyl CoA (fuel from FA oxidation)
- AMP abundance (low energy intermediate)
- Fructose-1,6-BP (feed-forward mechanism because it has been committed)
How does Glucagon in the LIVER regulate Pyruvate Kinase activity?
The end result of Glucagon binding its receptor in the liver is activation of a KINASE, which phosphorylates Pyruvate Kinase to deactivate it and inhibit glycolysis.
In the Liver, Fructose can enter Glycolysis at the ______ stage.
3-Carbon (as DHAP and G-3-P)
Fructose is structurally considered a _______.
Keto-Hexose