Bio1 Lesson 3: Cellular Respiration and Metabolism Flashcards
What is glycogenesis?
The storage of carbs in the muscle and liver as glycogen
Where are lipids stored and in what form are they stored?
In adipocytes, as triglycerides
In order, what are the 3 processes used in aerobic cellular respiration?
1) Glycolysis
2) the Kreb’s/Citric Acid Cycle
3) the Electron Transport Chain
What is glycolysis?
The breakdown of glucose into pyruvate; converting a 6-carbon-glucose into TWO 3-carbon pyruvates
Is glycolysis aerobic or anaerobic?
Anaerobic
Where does glycolysis take place?
The cytoplasm
Glycolysis begins the _________ of glucose
Oxidation (loss of electrons)
What is part 1 of glycolysis called and what are its results?
Energy Input Phase:
Glucose is eventually converted to 2 molecules of glyceraldehyde-3-phosphate
What is part 2 of glycolysis called and what are its results?
Energy Output Phase:
2 glyceraldehyde-3-phosphate molecules are eventually converted into 2 pyruvate molecules, yielding 2 ATP, 2 NADH, 2 H+ and 2 H2O
What is the net equation of glycolysis?
1Glucose + 2NAD+ + 2AD + 2Pi — 2Pyruvate + 2NADH + 2H+ + 2ATP + 2H2O
What does a step in glycolysis need to do to be irreversible?
Use ADP/ATP
What steps in glycolysis are irreversible and what happens in these steps? Describe the enzymes used at each step.
Step 1) Hexokinase phosphorylates glucose to glucose 6-phosphate (G6P) by converting ATP to ADP
Step 3) Phosphofructokinase 1 (PFK-1) phosphorylates fructose 6-phosphate (F6P) to fructose 1,6-bisphosphate by converting ATP to ADP
Step 10) Pyruvate kinase transforms phosphoenolpyruvate into pyruvate by converting ADP to ATP
What is the committed step in glycolysis and why is it called this?
Step 3: when PFK-1 phosphorylates fructose 6-phosphate into fructose 1,6-bisphosphate by converting ATP to ADP. This step is the committed step, because once this step is passed, the cell is committed to completing glycolysis
What happens to NAD+ in glycolysis, at which step does it happen, and what are its results used for?
NAD+ is reduced (gains electrons) to NADH during step 6 of glycolysis: Glyceraldehyde 3-phosphate (G3P) dehydrogenase converts G3P into 1,3-bisphosphoglycerate by converting NAD+ and Pi to NADH and H+. NADH is used to carry electrons to the ETC
During which step of glycolysis is a 6 carbon molecule split into two 3 carbon molecules, and what are the 3 carbon molecules?
Steps 4 and 5: adolase eventually splits fructose 1,6-bisphosphate into two molecules of glyceraldehyde 3-phosphate (G3P)
In preparation for the Kreb’s cycle…
1) What happens?
2) What is this stage called?
3) Where does it occur?
4) What are the products per cycle?
1) A Pyruvate molecule is converted into an AcetylCoA molecule
2) Pyruvate oxidation
3) In the mitochondria –> transfering pyruvate from the cytoplasm to mitochondrial matrix
4) 1NADH and 1CO2
What is another name for pyruvate oxidation?
The transition reaction
Which enzyme catalyzes pyruvate oxidation/the transition reaction?
Pyruvate dehydrogenase
What is the most oxidized (lowest energy) form of glucose?
CO2
Is the outer membrane of the mitochondria permeable/impermeable?
Permeable, especially to pyruvate
Is the inner membrane of mitochondria permeable/impermeable?
Impermeable
In regards to the Kreb’s Cycle…
1) What are the products of a single turn of the cycle?
2) How many turns happen from 1 glucose?
3) What are the net products from 1 glucose?
1) 1ATP, 3NADH, 1FADH2
2) 2 turns
3) 2ATP, 6NADH, 2FADH2
The Kreb’s Cycle completes the _______ of glucose and thereby produces _____ as a byproduct
Oxidation, CO2
Where does the Citric Acid Cycle occur?
Mitochondrial matrix
In order, what are the substrates of the Citric Acid Cycle?
Oxaloacetate Citrate Isocitrate A-ketoglutarate Succinyl-CoA Succinate Fumerate Malate
How many CO2 molecules are produced as a by-product of one turn of the Citric Acid Cycle?
2
How many carbons does each substrate of the Kreb’s cycle have?
Oxaloacetate: 4C Citrate: 6C Isocitrate: 6C a-Ketoglutarate: 5C Succinyl-CoA: 4C Succinate: 4C Fumerate: 4C Malate: 4C
How many carbons are in a single molecule of Acetyl CoA?
2C
How does 4 carbon oxaloacetate turn into 6 carbon citrate?
2 carbon Acetyl CoA enters the cycle and together with oxaloacetate, forms citrate
Which steps of the Citric Acid Cycle produce CO2 as a byproduct? Identify the starting and final number of carbons at each step.
1) Isocitrate to a-Ketoglutarate: 6C to 5C
2) a-Ketoglutarate to Succinyl-CoA: 5C to 4C
At which steps of the Kreb’s Cycle are NADH produced?
1) Isocitrate to a-Ketoglutarate
2) a-Ketoglutarate to Succinyl-CoA
3) Malate to Oxaloacetate
At which step of the Kreb’s cycle is ATP produced?
Succinyl-CoA to Succinate
At which step of the Citric Acid Cycle is FADH2 produced?
Succinate to Fumerate
In the Kreb’s cycle, what type of reaction is taking place every time a carbon is lost?
A dehydrogenase reaction
Does the Kreb’s Cycle take place in eukaryotes, prokaryotes, or both?
Eukaryotes
What is the Electron Transport Chain and where is it located?
A series of proteins (cytochromes) embedded within the inner membrane of the mitochondria
The electron transport chain uses _______ reactions to convert energy in ___________ to energy in the form of ______
Redox reactions, electrons, ATP
In the ETC, is NADH oxidized/reduced, losing/gaining electrons?
Oxidized, losing
In the ETC, is FADH2 oxidized/reduced, losing/gaining electrons?
Oxidized, losing
In the ETC, is oxygen oxidized/reduced, losing/gaining electrons?
Reducted, gaining (to form water)
In the ETC, where and how are the proteins arranged?
Embedded in the inner membrane of the mitochondria, in order of increasing electronegativity (increasing strength of electron acceptors)
How does the ETC work?
Proteins pick up electrons from NADH and FADH2 and transfer them to O2, which is reduced to H2O. Energy is released from this transfer of electrons and is used to pump protons into the intermembrane space, establishing an electrochemical proton gradient. When protons diffuse back into the mitochondrial matrix, they travel through ATP synthase which produces ATP molecules
What is the proton-motive force in the ETC?
An electrochemical proton gradient created by pumping protons into the intermembrane space
What is chemiosmotic coupling?
The process of protons diffusing back into the mitochondrial matrix through ATP synthase, forming ATPs
What is the terminal electron accepter (TEA) in the ETC?
Oxygen
In ETC, roughly how many protons are required to diffuse through ATP synthase to form one ATP molecule?
1 ATP for every 3 H+
In the ETC, which complexes are proton pumping sites?
1, 3, 4
I, III, IV
In the ETC, at which complex does FADH2 donate electrons?
2 (II)
In the ETC, at which complex does NADH donate electrons?
1 (I)
In the ETC, what is complex 5 (V)?
ATP Synthase
In the ETC, what type of transport do protons undergo across the mitochondrial inner membrane?
Active transport
What are the net reactants and products of aerobic respiration and what kind of net reaction is this?
Glucose + O2 —> CO2 + H2O
A combustion reaction
Is the ETC aerobic or anaerobic?
Aerobic: oxygen is a key regulator of the ETC since electrons from NADH and FADH2 reduce O2 into H2O
From 1 glucose molecule, how many ATP, NADH, and FADH2 are formed through glycolysis?
2ATP, 2NADH, 0FADH2
For 1 glucose molecule, how many ATP, NADH, and FADH2 are formed through pyruvate oxidation (pre-Kreb’s)?
0ATP, 2NADH, 0FADH2
For 1 glucose molecule, how many ATP, NADH, and FADH2 are formed through the Kreb’s Cycle?
2ATP, 6NADH, 2FADH2
For 1 glucose, how many total ATP, NADH, and FADH2 have been formed by the end of the Kreb’s Cycle?
2ATP (since 2 are used to transport NADH to mitochondria for pyruvate oxidation), 10NADH, 2FADH2
In the ETC, how many ATPs are formed per molecule of NADH?
3ATP for every 1 NADH
In the ETC, how many ATPs are formed per molecule of FADH2?
2ATP for every 1 FADH2
By the end of the ETC, as a result of 1 glucose molecule…
1) How many ATP molecules are formed through NADH and through FADH2?
2) How many ATP molecules are used for transporting glycolysis-produced NADH from the cytosol to the michondriom?
3) How many net ATP molecules are formed?
1) 30ATP from NADH, 4ATP from FADH2
2) 2ATP
3) 36ATP
- +2 ATP from glycolysis
- -2 ATP to transport NADH to mitochondria
- +2 ATP from Kreb’s cycle
- +34 ATP from ETC
Name and describe the two types of fermentation.
1) Lactic acid fermentation:
- 1 step process
- Happens in mammls
- Pyruvate from glycolysis is reduced to lactic acid by using electrons from NADH
- NADH is oxidized to NAD+
- NAD+ is used to start glycolysis again
2) Alcohol fermentation:
- 2 step process
- Happens in yeast
- Pyruvate from glycolysis is reduced to ethanol using electrons from NADH
- NADH is oxidized to NAD+
- NAD+ is used to start glycolysis again
When does fermentation happen?
Under hypoxic conditions
Is fermentation aerobic or anaerobic?
Anaerobic
What is the net ATP yield per 1 glucose molecule in fermentation?
2ATP per 1 glucose molecule
Fermentation recycles _____ for continued ________
NAD+, glycolysis
What is glycogenolysis?
The breakdown of glycogen to form glucose, that is exported into the blood for transport
How is glycogen turned into glucose in glycogenolysis?
Glycogen is broken down into glucose-1-phosphate (G1P) —> then converted to G6P —> G6P dephosphorylated to glucose —> glucose then enters bloodstream
When blood glucose is ___, insulin is used to ___ blood glucose
High, lower
Insulin receptors on cells communicate with ______ transporters to uptake glucose in the cell
GLUT4
Without insulin, only the __________ and _________ continue to absorb glucose.
Nervous system, the liver
What is gluconeogenesis?
A metabolic process that results in the generation of glucose from NON-carbohydrate substrates such as lactate, glycerol, and certain amino acids
Gluconeogenesis results in the generation of glucose from _____ substrates
Non-carbohydrate
Gluconeogenesis is ALMOST identical to the reverse pathway of _______.
Glycolysis
Which steps differ between glycolysis and gluconeogenesis?
The irreversible steps: 1, 3, 10
1: Glucose to G6P
3. F6P to Fructose 1,6-bisphosphate
10. Phosphoenolpyruvate to Pyruvate
Where does gluconeogenesis occur?
In the liver and kidneys
To be a substrate of gluconeogenesis, a molecule must have _______
A 3-carbon backbone
What are some examples of gluconeogenesis substrates?
Glycerol, lactic acid, some amino acids
All of glycolysis, gluconeogenesis, glycogenolysis, and glycogenesis intersect at a common intermediate: _________
Glucose-6-phosphate
Which metabolic processes does insulin promote?
Glycolysis and glycogenesis
Which metabolic pathways does glucagon promote?
Gluconeogenesis and glycogenolysis
How does insulin use glycolysis?
Uses glycolysis to synthesize glycogen, fatty acids, nucleic acids, and steroids
What does glucagon do with broken down molecules?
Used them to power ATP synthesis
Is insulin anabolic or catabolic?
Anabolic
Is glucagon anabolic or catabolic?
Catabolic
What are the two ways fatty acids can be used for energy?
1) Can be broken down into Acetyl CoA by organs they diffuse into. Acetyl CoA then enters Kreb’s
2) Can be converted into ketone bodies
What is beta-oxidation?
The breakdown of fatty acids
When does beta-oxidation occur?
During starvation
In beta-oxidation, fatty acids are released from ______ , travel in blood on _______, and then diffuse into tissues where they are oxidized ___ carbons at a time in the ________
Adipocytes, lipoproteins, 2, mitochondria
What is the first step of beta-oxidation and where does it occur?
Fatty acids are converted into acylCoA at the expense of 1 ATP along the outer mitochondrial membrane
What is the second step of beta-oxidation and where does it occur?
AcylCoA is brought into the mitochondrial matrix and is cleaved 2 carbons at a time to make many molecules of acetylCoA, which then enters the Kreb’s cycle
What products are released during beta-oxidation?
NADH and FADH2 (electron carriers that can be used in the ETC)
Does beta-oxidation work well for fatty acid chains with even or odd numbers of carbons?
Even
What happens in beta-oxidation when the fatty acid chain has an odd number of carbons?
The last 3 carbons are cleaved and can be used as a substrate for gluconeogenesis
What is ketogenesis, when does it happen, and where?
Ketogenesis is the breakdown of fatty acids into acetyl-CoA molecules, some of which are converted into ketone bodies (an alternate source of energy)
- It happens during starvation
- Happens in the mitochondria of liver cells
- Ketone bodies travel to other tissues in the blood to be absorbed, converted back into acetyl-CoA and then fed into the Kreb’s cycle to make ATP
In ketogenesis, what happens to the acetyl-CoA formed?
Some acetylCoA is converted into ketone bodies in the absence of insulin. Some acetylCoA is fed into the Kreb’s cycle to make ATP
What are 3 primary ketone bodies produced in humans?
Acetone, acetoacetic acid, beta-hydroxybutyrate
Are ketone bodies polar/nonpolar?
Polar, they dissolve easily into blood
Protein breakdown begins with the hydrolysis of _________
Amino acid amide bonds
Amino acid breakdown begins wiht the removal of __________
The nitrogen group
Amino acids can be used to make molecules other than proteins such as…
Neurotransmitters, hormones, heme groups
Protein formation happens during the ______ state. Protein breakdown happens during the _______ state.
Fed, fasting
The pentose phosphate pathway is an alternative to _____
Glycolysis
What does the pentose phosphate pathway produce?
NADPH and 5 carbon sugars (for making nucleotides)
What are the two parts of the pentose phosphate pathway and what are their functions?
1) Oxidative phase: generates NADPH
2) Non-oxidative phase: generates 5 carbon sugars (ex: ribulose 5P)
What products are made during the pentose phosphate pathway reactions that can be linked back to glycolysis?
Fructose-6-phosphate, Glyceraldehyde-3-phosphate
Where is the pentose phosphate pathway employed?
In the liver and adipocytes
Instead of continuing through glycolysis, ______ enters the pentose phosphate pathway
glucose-6-phosphate
How many NADPH are generated from 1 glucose-6-phosphate in the oxidative phase of the pentose phosphate pathway?
2
Does the pentose phosphate pathway generate NADH?
NO. It generates NADPH
NADPH is an electron carrier used in ________ reactions
Anabolic
NADH is an electron carrier used in ________ reactions
Catabolic
