Chapter 3-Cell Metabolism Flashcards
What is an Anabolic reaction?
An anabolic reaction is the production of larger molecules from smaller reactants. Requires energy.
What is the first and second law of thermodynamics?
The First Law of Thermodynamics states energy cannot be destroyed or created, only transformed.
The Second Law of Thermodynamics states with every transfer or transformation of energy, some useable energy is released as heat.
What is an endergonic reaction?
An Endergonic reaction is a chemical reaction that require an input of energy. Products contain more free energy than the reactants. Energetically uphill.
What is an exergonic reaction?
An Exergonic reactions is a chemical reaction that release energy. Products will have less free energy than the reactants. Energetically downhill.
What the difference between an exergoni and an endergonic reaction?
Exergonic reactions tend to proceed spontaneously
Endergonic reactions do not proceed spontaneously, only when energy is put into them.
How do endergonic reactions in physiology occur?
Energy from the environment (food) is broken down in exergonic reactions to drive the endergonic reactions in our bodies
What is activation energy
Activation energy is the energy required for the reactants to engage in a reaction. Most molecules lack the activation energy needed for a reaction to occur. Activation energy can take the form of heat (molecules colliding together). Activation energy barrier can also be surmounted through catalysts
What are enzymes?
Enzymes are a class of proteins that serve as biological catalysts. Catalysts are chemicals that:
Increase the rate of a reaction
Are not changed by the reaction (so can be used repeatedly)
Have no effect on free energy of reactants or products.
In enzymatic reactions, reactants are called substrates
How are enzymes named
The first enzymes discovered were given arbitrary names. An international committee later decided to end all enzymes with the suffix –ase.
They also decided to make the first part of the name apply to the function of the enzyme.
Phosphatases remove phosphate groups.
Synthetases catalyze dehydration synthesis.
What is enzyme activity?
enzyme activity is measured by the rate at which substrate is converted to product
Influenced by:
Concentration of enzyme and substrate
Enzyme-substrate affinity
Temperature
pH
Regulation by modulators (allosteric regulation)
Covalent regulation (regulation by chemical groups)
Feedback inhibition
Feedforward activation
Who will temperature affect the enzymatic reaction rates?
An increase in temperature will increase the rate of reactions until the temperature reaches a few degrees above body temperature. At this point, the enzyme is denatured. (Can be caused by fever)
How will pH effect the enzymatic reaction rates?
Enzymes exhibit peak activity within a narrow pH range = optimum pH.
Due to changes in enzyme conformation
Optimum pH typically reflects the pH of the fluid the enzyme is found in: Stomach vs. saliva
What is a metabolic pathway?
Most reactions are linked together in a chain (or web) called a metabolic pathway.
These begin with an initial substrate and end with a final product, with many enzymatic steps along the way.
What is cellular respiration?
Cellular respiration AKA Glucose Oxidation is how we get energy to do work. Provides ATP (energy) for cellular processes
Three main stages:
Glycolysis (cytosol)
Krebs Cycle (mitochondrial matrix)
Oxidative Phosphorylation (across inner mitochondrial membrane)
What is glycolysis?
First step in catabolism of glucose
Happens in cytoplasm and does not require oxygen
Occurs in the cytoplasm of the cell. Does NOT require oxygen.
For every molecule of glucose:
2 pyruvate created
2 ATPs consumed, 4 ATPs created, net 2 ATPs
2 NAD+ converted to 2 NADH
(glucose + 2 NAD+ + 2 ADP + 2 Pi —- 2 pyruvate + 2 NADH + 2 H+ + 2 ATP)
What is glycogenesis?
Most body cells can’t store much glucose because it will pull water into the cell via osmosis.
Glucose is stored as a larger molecule called glycogen in the liver and skeletal muscles.
Glycogenesis is the process of combining glucose molecules into glycogen molecules for storage.
When the cell needs glucose, it breaks glycogen down again into glucose. (Glycolysis)
What is the linking step in cellular respiration.
The linking steps requires a pyruvate, CoA, and a NAD+ molecules and reacts to produce Acetyl CoA, CO2, NADH+H+
SO, what happens from glycolysis to the kreb cycles?
Pyruvate leaves the cytoplasm from glycolysis and enters the matrix of the mitochondria.
Carbon dioxide is removed to form acetic acid.
Acetic acid is combined with coenzyme A to form acetyl CoA.
1 glucose makes 2 molecules acetyl CoA
Because, remember, 1 glucose was broken down into 2 pyruvates during glycolysis.
What is the overall reaction of the krebs cycle?
Acetyl CoA + 3NAD+ + FAD + ADP + Pi+ 3H2O —– 2CO2 + 3NADH +3H+ + FADH2 + ATP + CoA
What are the product at the end of the krebs cycle?
For each glucose (2 turns of the Kreb Cycle, glycolysis, and linking step): 10 NADH 2 FADH2 4 ATP 6 CO2
(Remember, 2 NADH and 2 ATP from glycolysis, and 2 NADH from the linking step)
What is oxidative phosphorylation?
Also called the electron transport chain
Occurs across inner mitochondrial membrane. 90% of ATP produced from cellular respiration occurs in this step.
Electron transport molecules pass the electrons down a chain, with each being reduced and then oxidized.
This is an exergonic reaction, and the energy produced is used to make ATP from ADP.
ADP is phosphorylated.
What is chemiosmotic coupling?
Energy released through electron transport chain pumps H+ ions into intermembrane space.
H+ ions flowing back into the matrix down their concentration gradient power ATP synthase to make ATP
What is the overall reaction of oxidative phosphorylation?
10NADH + 10 H+ + 2FADH2 + 34ADP + 34 Pi + 6O2 — 10NAD+ + 2 FAD + 12H2O + 34 ATP
What is the theoretical yield of ATP during cellular respiration?
Glycolysis and the Krebs Cycle yield 4 ATP.
These numbers are constant.
Oxidative phosphorylation in electron transport yields varying amounts of ATP, depending on the cell and conditions.
Theoretically, each NADH yields 3 ATP and each FADH2 yields 2 ATP.
Theoretical ATP yield is 36-38 per glucose.
Glycolysis and the Krebs Cycle yield 4 ATP.
These numbers are constant.
Oxidative phosphorylation in electron transport yields varying amounts of ATP, depending on the cell and conditions.
Theoretically, each NADH yields 3 ATP and each FADH2 yields 2 ATP.
Theoretical ATP yield is 36-38 per glucose.
What happenes when our tissues are low on oxygen?
Saved by the Lactic Acid Fermentation Cycle
No ATP gets made directly by this process.
Does not require O2
Provides NAD+ so that glycolysis can continue to generate 2 ATP for every molecule of glucose that gets broken.
What is a catabolic reaction?
A catabolic reaction breakdowns larger molecules into smaller molecules. Releases energy.
What are the inputs and output and where does everything happen in cellular respiration?
Glycolysis
Cytosol
Input: 1 glucose
Out 2 pyruvates, 2 ATP, 2 NADH
Linking Step In mitochondria; matrix Oxygen required Input: pyruvates Outputs: 2 acetylCoA, 2 NADPH,
Krebs Cycle Mitochondrial matrix Oxygen required In: 2 AcetylcoA Out: 6 NADPH's, 2 FADH2, 2 ATP's
Oxidative phosphorylation Happens along the inner mitochondrial membrane Oxygen required In: Electron carried by NADH and FADH2 Out: H2O, 34-36 ATP
