EK 3: Metabolism Flashcards Preview

MCAT Biochemistry > EK 3: Metabolism > Flashcards

Flashcards in EK 3: Metabolism Deck (67):
1

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  • Red blood cells do glycolysis, which can also split into the pentose phosphate pathway.
  • The pentose phosphate pathway can merge back into glycolysis.

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Protein Anabolism? Protein Catabolism? In what situations do they occur (fed or fasting state)?

  • Protein anabolism – protein formation
    • Amino acids + Amino acids ⇒ Protein
    • Occurs when you’re fed.
      • Remember: Anabolic steroids work best to make proteins when you’re eating a lot.
  • Protein catabolism – protein degradation
    • Protein ⇒ Amino acids + Amino acids
    • Occurs when fasting.

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Glycogen? Structure? Where is it found in the body? Does glycogenesis use ATP or UTP?

  • Glycogen is highly-branched stored glucose.
    • α-1,4’ + α-1,6’ glucose-glucose glycosidic bonds
  • It is found in the muscles and in the liver.
    • Muscles store their own glycogen.
    • Liver stores glycogen for the entire body.
  • Glycogenesis involves UTP.

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Beta Oxidation? Location in cells? Substrates and products? What happens to odd-numbered fatty acid chains?

Beta oxidation – fatty acid ⇒ acetyl-CoA

  • Occurs in the mitochondria
  • The long carbon chains of fatty acids are oxidized two carbons at a time to form acetyl-CoA (2-carbon molecule).
    • 1 FADH2 + 1 NADH + Acetyl-CoA are produced per 2-carbons of the chain.
  • The leftover glycerol backbone is converted into an intermediate of glycolysis.
  • Beta oxidation of odd-numbered fatty acid chains results in a bunch of acetyl-CoA and a 3-carbon molecule, which can enter glycolysis.

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Catabolism?
Anabolism?

  • Catabolism – breaking down food into building blocks, which can be used to make ATP.
  • Anabolism – taking energy and building blocks to build all the organelles of the cell.

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What metabolic processes does glucagon activate?

  • Glucagon activates:
    • Gluconeogenesis: non-carbs (pyruvate, 3 carbon-molecules, lactic acid, etc.) ⇒ glucose
      • Liver
    • Glycogenolysis: glycogen ⇒ glucose
      • Liver and muscles
    • Lipolysis: triglycerides ⇒ free fatty acids
      • Adipose tissues
    • Beta oxidation: free fatty acids ⇒ acetyl-CoA
      • All tissues

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Which of the following would be expected to cross a cell membrane without the aid of an accessory protein?

A) Glucose
B) Glycine
C) Oxygen
D) Triglycerides
 

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Pentose Phosphate Pathway?
Oxidative branch product? Non-oxidative branch product? Product functions? What inhibits it?

  • It is an alternative pathway to glycolysis that always occurs in cells.
  • It diverges from one substrate of glycolysis and eventually merges back to another substrate of glycolysis.
  • Purpose: To make NADPH + Pentose (5C) sugars
  • Oxidative branch – part of the pathway that creates NADPH
    • NADPH is an antioxidant and used to make cholesterol.
    • High levels of NADPH inhibits the oxidative branch of the pathway.
  • Nonoxidative branch – part of the pathway that creates pentose sugars, such as ribose.
    • Ribose is used to make DNA and RNA

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Can red blood cells use ketone bodies for energy? Why or why not?

  • Red blood cells cannot use ketone bodies for energy.
  • Because they do not have mitochondria to break them down.
  • Red blood cells only do fermentation (anaerobic respiration) with glucose.

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What is oxidative phosphorylation?

  • Oxidative phosphorylation is a series of oxidation reactions that provide the energy for phosphorylating ADP ⇒ ATP.

 

  • In the mitochondria, a series of oxidation reactions creates a proton gradient that powers ATP synthase. This makes ATP

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Citric Acid Cycle? Location? What starts it? What is produced per cycle? What is produced per glucose molecule? Aerobic or anaerobic? Purpose?

  • It is a series of oxidation reactions that occur in the mitochondrial matrix (inner region).
    • Aerobic, because it is linked to the electron transport chain which requires oxygen.
  • Acetyl-CoA (2 carbons) + Oxaloacetate (4 carbons) begin the cycle.
    • The 2 carbons are released as 2 carbon dioxides.
  • 1 glucose ⇒ 2 pyruvate ⇒ 2 acetyl-CoA
    • Thus, 1 glucose results in two citric acid cycle completions.
  • Per cycle: 1 ATP + 2 CO2 + 3 NADH + 1 FADH2
  • Per glucose (2 cycles): 2 ATP + 4 CO2 + 6 NADH + 2 FADH2
  • The purpose of the Citric Acid Cycle is to produce NADH and FADH2 which carry electrons to the electron transport chain for ATP production.

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What body structures bring glucose into our blood stream?

  • The liver and small intestines bring glucose into our blood-stream

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Glycolysis? Substrates and Products? Net Products? Location? Energy input phase? Energy output phase? Aerobic or Anaerobic? Substrate Level phosphorylation?

  • Glycolysis is the breakdown of a glucose molecule ⇒ 2 pyruvate + 2 ATP + 2 NADH
  • Glycolysis can be aerobic or anaerobic (with/without oxygen)
    • Anaerobic glycolysis is called fermentation.
  • Consists of 10 different reactions.
    • Energy input phase – first half of glycolysis when energy (2 ATP) is used to add two phosphates to glucose.
    • Energy output phase – second half of glycolysis when glucose (6-carbons) is split into and converted into 2 pyruvates (3-carbons)
      • 4 ATPs are made in this phase via substrate level phosphorylation.
      • Substrate level phosphorylation – when phosphates are transferred from substrates to ADP, forming ATP.
  • 2 Net ATP
    • -2 ATPs used
    • +4 ATPs made

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Can glucose pass the blood brain barrier?

Yes it can

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When do the brain and red blood cells need glucose?

Can the brain use ketone bodies? What about red blood cells?

  • The brain and red blood cells need glucose all the time.
    • Red blood cells cannot use ketone bodies
    • The brain can use ketone bodies.
  • Red blood cells require glucose because they don’t have mitochondria to break down other molecules.
    • They can only do fermentation (anaerobic respiration) in the cytoplasm.

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What organ is able to do gluconeogenesis? Purpose? What hormone stimulates it? What must molecules have in order to be used in gluconeogenesis?

  • Gluconeogenesis is the opposite of glycolysis, but slightly different.
  • The liver can do gluconeogenesis, to make glucose from non-carb molecules such as proteins, glycerol (triglyceride backbone), and lactic acid.
  • Stimulated when blood glucose levels are low and glucagon is secreted.
  • Used to increase blood glucose levels.
  • Molecules must have a 3-carbon backbone to enter gluconeogenesis.
    • 3-carbon backbone, just like pyruvate.

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How do insulin and glucagon control metabolic enzymes?

  • They control metabolic enzymes by activating/inactivating them via phosphorylation

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What is the intermediate molecule between all 5 glucose pathways

(glycolysis, gluconeogenesis, glycogenesis, glycogenolysis, and pentose phosphate pathway)?

  • Glucose-6-phosphate is the intermediate molecule between all 5 glucose pathways.
  • Glucose + ATP ⇒ Glucose-6-phosphate
  • 2nd step of glycolysis, which can branch to all 5 glucose pathways.​

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Fatty Acid Metabolism pathways (2)? Locations in the cell? Products? What happens to beta oxidation of odd-numbered carbon fatty acid chains?

Beta oxidation + Ketogenesis

  • Beta oxidation – fatty acid ⇒ acetyl-CoA
    • Occurs in the mitochondria of muscle and liver cells.
    • The long carbon chains of fatty acids are oxidized two carbons at a time to form acetyl-CoA (2-carbon molecule).
      • 1 FADH2 + 1 NADH + Acetyl-CoA are produced per 2-carbons of the chain.
    • The leftover glycerol backbone is converted into an intermediate of glycolysis.
    • Beta oxidation of odd-numbered fatty acid chains results in a bunch of acetyl-CoA and a 3-carbon molecule, which can enter glycolysis.
  • Ketogenesis – fatty acid ⇒ ketone body
    • Occurs in the mitochondria of liver cells.
    • Ketone bodies are then sent through the blood to brain for energy when glucose is low.
    • Ketone bodies: acetone + acetoacetic acid + beta-hydroxybutyrate

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Why does a lack of insulin lead to Ketogenesis?

  • Insulin usually moves blood glucose into cells, to be used for glycolysis and glycogenesis.
  • However, a lack of insulin prevents cells from receiving glucose from the blood.
  • Thus, Ketogenesis occurs to make ketone bodies, which are able to enter cells without insulin.
  • This is a problem with diabetes

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What is produced by the pyruvate dehydrogenase complex?

Per Pyruvate?

Per Glucose?

Location?

Pyruvate Dehydrogenase Complex

(Inner Mitochondrial Membrane)

 

•  Pyruvate Dehydrogenase Complex converts  

 1 pyruvate (3C) + 1 NAD⇒​

1 acetyl-CoA (2C) +  1 CO+ NADH

 

•  Per glucose: 1 glucose ⇒ 2 pyruvate

2 pyruvate + 2 NAD+

 2 acetyl-CoA + 2 NADH + 2 CO2

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  • Bond breaking is endergonic, requires energy
  • Bond forming is exergonic, releases energy

 

  • However, ATP is opposite
    • Forming ATP is endergonic, requires energy
    • Breaking ATP is exergonic, releases energy

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Fermentation (Anaerobic Glycolysis)

Fermentation (Anaerobic Glycolysis)

  • Fermentation - metabolism of glucose to form     2 lactic acid and 2 ATP
  • After glycolysis, 2 pyruvate ⇒ 2 lactic acid  
    • 2 NAD+ is remade.
      • The 2 NAD+ is used for glycolysis again, which makes 2 ATP again.
  • Glycolysis is repeatedly done to make 2 ATP.
  • Citric acid cycle and electron transport chain do not occur.

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Does insulin lead to net catabolic or anabolic processes?

 

Does glucagon lead to net catabolic or anabolic processes?

Insulin leads to glycogen and triglyceride formation, thus is net anabolic (build-up)

 

Glucagon leads to glycogen and triglyceride breakdown, thus is net catabolic (breakdown)

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How do red blood cells get their energy?

  • Red blood cells do not have mitochondria, thus they require glucose for energy.
  • They only do fermentation (anaerobic respiration) in their cytoplasm.

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Ketogenesis? Substrates and products? Ketone bodies? Ketoacidosis?
Location in the body and cell? Purpose?

  • Beta-Oxidation: fatty acids ⇒ acetyl-CoA
  • Ketogenesis: acetyl-CoA ⇒ ketone body
    • Occurs in the mitochondria of liver cells.
    • Ketone bodies are then sent through the blood to the brain and red blood cells for energy when glucose is low.
    • Ketone bodies: acetone + acetoacetic acid + beta-hydroxybutyrate
    • Ketone bodies in the blood can reduce blood pH, ketoacidosis

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What is acetyl-CoA?

  • Acetyl-CoA is coenzyme that carries 2 carbons (acetyl) to the 4 carbon oxaloacetate to begin the citric acid cycle

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Where are carbohydrates mainly stored and as what? Names and products of the metabolic pathways for glucose (storage and use)?

  • Carbohydrates are stored as glycogen, mainly in muscles and the liver. 
  • Use pathway: Glycogen ⇒ Glucose ⇒ Pyruvate ⇒ Acetyl-CoA
    • Glycogenolysis: Glycogen ⇒ Glucose
    • Glycolysis: Glucose ⇒ Pyruvate
    • Pyruvate Dehydrogenase: Pyruvate ⇒ Acetyl-CoA
      • Acetyl-CoA can then enter kreb’s and electron transport chain to make ATP.
  • Storage pathway: Pyruvate ⇒ Glucose ⇒ Glycogen
    • Gluconeogenesis: Pyruvate ⇒ Glucose
    • Glycogenesis: Glucose ⇒ Glycogen

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What are lipoproteins and where in the body are they made? What about chylomicrons? What about VLDL, LDL, and HDL?

  • Lipoproteins – a lipid and protein complex that carries fats and cholesterol through the blood.
    • Made in the liver, intestines, and adipose tissues.
  • Chylomicrons – a special type of lipoprotein that carries lipids through the bloodstream.
    • Made in the intestines.
    • Chylomicrons travel to the liver.
    • The liver repackages chylomicrons into VLDL, LDL, and HDL.

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Where does glycolysis occur in the cell?
What about citric acid cycle and electron transport chain?

  • Glycolysis occurs in the cytoplasm
    • Pyruvate enters the mitochondrial matrix, passing through the Pyruvate Dehydrogenase Complex to become   acetyl-CoA.
  • Citric acid cycle and Electron transport chain are located in the mitochondrial matrix.

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Where are lipids mainly stored and as what?
Names and products of the metabolic pathways for fatty acids (storage and use)?

  • Lipids (fatty acids) are stored as triglycerides in adipocytes (fat cells).
    • Lipids are broken down into fatty acids and glycerol.
  • Use pathway: Triglycerides ⇒ Fatty acids ⇒ Acetyl-CoA
    • Lipolysis: Triglycerides ⇒ Fatty acids
    • Beta oxidation: Fatty acids ⇒ Acetyl-CoA
      • Acetyl-CoA can then enter Kreb’s and electron transport chain to make ATP.
  • Storage pathway: Acetyl-CoA ⇒ Fatty acids ⇒ Triglycerides
    • Fatty acid synthesis: Acetyl-CoA ⇒ Fatty acids
    • Lipogenesis: Fatty acids ⇒ Triglycerides

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How much net ATP does each Glucose make?
Fill in the following table: “Fill in ATP”

  • It costs one ATP to transport each glycolysis-produced NADH from the cytoplasm into the mitochondrial matrix.
    • Thus, moving the 2 NADH from glycolysis requires 2 ATPs.
    • That’s why 2 ATPs are removed from the 30 total ATP from NADH.
  • About 36 net ATP produced.

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Amino Acid Breakdown?

  • Amino acids are broken down into ammonia and a carbon chain.
    • Ammonia is released in urine.
    • Carbon chain is used for other cellular purposes.

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Saturated vs Unsaturated fats? Which has more energy? Why?

  • Saturated fats – long-chain fatty acids with only single bonds.
    • Store more energy (calories) because they have more hydride ions (more electrons) to reduce other molecules
      • The movement of electrons releases energy.
    • Very strong reducing agents
  • Unsaturated fats – long-chain fatty acids with single and double bonds.
    • Make less energy (calories) because they have less hydrogens to reduce other molecules due to their double bonds.
    • Somewhat strong reducing agents
    • Thus, are healthier fats

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Which macromolecule can be used to make the most energy? Why?

  • When electrons move, energy is released.
    • Lipids have much more electrons on them due to all the hydride ions attached on the carbon chains.
    • Because of this, lipid are very strong reducing agents and store the most energy.
  • Carbohydrates and proteins have way less hydride ions to reduce other molecules; thus they store less energy (calories)

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Electron Transport Chain (ETC)?

Ubiquinone and Cytochromes?

Energy produced by NADH vs FADH2?

Proton-motive force?

Purpose of O2? What is reduced/oxidized?

Electron Transport Chain (ETC) – series of proteins built into the inner membrane of the mitochondria; they carry electrons from NADH to O2.

  • NADH is oxidized ⇒ NAD 
  • ½ O2 is reduced to ⇒ H2O
  • Ubiquinone and Cytochromes are proteins that carry electrons in the ETC.
  • There are 5 complexes in the ETC
    • Complex 1-4 carry electrons, but only 3 of them each pump a proton out into the intermembrane space.
    • Complex 5 is ATP synthase which allows the protons to re-enter the mitochondrial matrix and power the formation of ATP via a proton-motive force.
  • Electrons from NADH travel through all 3 proton-pumping complexes.
    • Thus NADH causes 3 protons to move out of the matrix, eventually making 3 ATPs.
  • Electrons from FADH2 only travel through 2 proton-pumping complexes.
    • Thus FADH2 causes 2 protons to move out of the matrix, eventually making 2 ATPs.
  • ½ O2 is the last electron acceptor of the electron transport chain; thus ½ O2 is reduced to H2O

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Lipogenesis? Location in the cell and body? When does this occur?

Lipogenesis – acetyl-CoA ⇒ fatty acids

  • Occurs when too many carbs were metabolized into acetyl-CoA via glycolysis and the pyruvate dehydrogenase complex.
  • In the mitochondria of liver cells.
  • The buildup of acetyl-CoA is converted into fatty acids.

 

Opposite of Beta Ox. (fatty acids ⇒ acetyl-CoA)

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Assuming that 2 ATP are consumed in moving NADH from the cytosol to the mitochondrial matrix, and all other conditions are optimal, how many ATP are produced per glucose molecule?

A) 18
B) 34
C) 36
D) 38

Answer is B) 34

 

  • It actually requires 1 ATP to move each glycolysis-produced NADH to the mitochondrial matrix.
  • But, 2 ATP per NADH transport is used for this hypothetical question.

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What metabolic processes does insulin activate?

  • Insulin activates:
    • Glycolysis: glucose ⇒ pyruvate
      • All tissues
    • Glycogenesis: glucose ⇒ glycogen
      • Liver and muscle tissue
    • Fatty acid synthesis: acetyl-CoA ⇒ fatty acids
      • Liver
    • Fatty acid storage: fatty acids ⇒ triglycerides
      • Adipose tissue​

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What happens when ATP ⇒ ADP?
+ or – ΔG? Endergonic/Exergonic?

(-) ΔG: Spontaneous

Energy is released

Exergonic reaction

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What pathways feed into the citric acid cycle?

  • All of the following pathways produce acetyl-CoA (2 carbon), which enters the citric acid cycle.

 

Glycolysis ⇒ Pyruvate Dehydrogenase Complex ⇒ Citric Acid Cycle

 

Beta oxidation of fatty acids ⇒ Citric Acid Cycle

 

Ketone body use ⇒ Citric Acid Cycle

 

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Role of Hormone-sensitive lipase in adipocyte tissues?

 

What hormone activates it?

What hormone inactivates it?

Hormone-Sensitive Lipase

  • In adipocyte tissues, lipase breaks down stored triglyceride fats into free fatty acids and sends them to the bloodstream.
  • The liver can pick the free fatty acids up and convert them into acetyl-CoA (beta oxidation).
    • Acetyl-CoA can then become ketone bodies, which the brain uses for energy when glucose is low.
    • Or Acetyl-CoA can enter the citric acid (krebs) cycle and electron transport chain.
  • Activated by Epinephrine
  • Inactivated by Insulin

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