bio test unit 2 metabolism Flashcards
1
Q
Metabolism
A
the sum of all chemical reactions that occur in the cell
- uses redox
2
Q
Metabolic pathway
A
a sequential series of chemical reactions in living cells; each reaction is catalyzed by an enzyme
- Many metabolic processes involve the breaking down of compounds to release energy
3
Q
Catabolism
A
metabolic pathway
- process of breaking down compounds into smaller molecules to release energy
- Our body works to break down the glycogen polymer into glucose monomers for use (catabolism, or catabolic reaction)
- when eating lots of food, you release energy
- like a polymer to monomer
3
Q
Types of energy released
A
When bonds break or form (a chemical reaction), energy is released as:
- Thermal energy (heat)
- Movement across a membrane (active transport)
- Muscle contraction (microfilaments)
- Emission of light
3
Q
Anabolism
A
metabolic pathway
- the process of using energy to build large molecules from smaller molecules
- condensation is anabolism, but anabolism is not only condensation
3
Q
Kinetic energy
A
- the energy of motion
- EX: Thermal energy
3
Q
Energy
A
- the capacity to do work
- Move matter against an opposing force
- Potential energy is converted to kinetic energy in living cells, this is how molecules are moved into and out of cells in active transport.
- The body will use the energy released from one reaction, to power the next reaction
3
Q
The laws of thermodynamics
A
- govern which reaction is more likely to take place and release energy, and which will require energy to proceed (Spontaneity)
- Thermodynamics studies the transfer and transformation of thermal (heat) energy
3
Q
Potential energy
A
- stored energy
- Chemical energy stored in bonds
- EX: A ball on the table top
3
Q
Primary source of energy
A
- Energy cannot be created or destroyed
- The primary source of energy is the nuclear fusion that occurs in the sun
- H2 + H2 -> He + energy
- Plants take this in, and the food cycle brings it to us
- We store this energy in bonds in macromolecules
4
Q
Endergonic Reactions
A
- (+ΔG)
- Is a chemical reaction that requires energy to proceed
- These reactions do not proceed spontaneously because they require an input of energy
- The reactants do no contain enough energy to form the products, require input from another reaction
- forming bonds, reduced
- ΔG>0
4
Q
open systems
A
- Biological systems are considered to be open systems
- Matter and energy can be exchanged with the surroundings (external environment)
4
Q
System
A
the object being studied
4
Q
Electron Carriers
A
- Redox reactions are coupled reactions that play an important role in energy flow
- Two important carriers are:
- NAD+ (nicotinamide) – oxidized
- FAD (flavin adenine dinucleotide) – oxidized
- Remember, when something is reduced it gains electrons, and it oxidizes when it loses electrons
- These molecules are reduced (gain protons and electrons) in one reaction, and oxidized in another step (give electrons to new molecules) (Like a taxi for electron)
4
Q
Bond Energy
A
- Whenever a chemical bond forms or breaks between two atoms, energy is released
- Hydrolysis of ATP to ADP breaks bonds and releases energy
4
Q
Entropy
A
is the measure of disorder
- highly ordered is organized
- highly disordered is disorganized
4
Q
Exergonic Reactions
A
- (-ΔG)
- These reactions proceed spontaneously and release excess free energy as heat.
- These can be slow reactions
- The reactants contain more energy than is needed to form the products, so the excess is released.
- breaking bonds, oxidized
- ΔG<0
4
Q
First law of Thermodynamics
A
Energy cannot be created or destroyed, but it can be transformed from one type into another and transferred from one object to another
- Chemical reactions release energy
- Some is mechanical energy (contracting a muscle)
- The rest transformed to heat or other forms
- Chemical energy stored in food molecules are converted to kinetic energy to move
4
Q
Surroundings
A
everything in the universe outside of the system
5
Q
Second Law of Thermodynamics
A
- During any process, the universe tends toward disorder
- In order to create order, energy is needed
- Entropy
- This second law only applies to closed systems.
- Organisms are open systems and therefore highly ordered.
- Energy is used to decrease randomness (LOWER ENTROPY)
- disorder happens spontaneously and organization requires energy
5
Q
AEROBIC RESPIRATION
A
- Refers to pathways that require oxygen in order to proceed and can be represented by the net chemical equation:
C6H12O6 (s) + 6O2 (g) -> 6CO2(g) + 6H2O (l) + energy - Aerobic respiration is a catabolic pathway that requires the use of oxygen for reactions to proceed
- Glycolysis is the first pathway, but is not truly aerobic; it produces the starting material for the rest of the metabolic processes, which utilize oxygen.
- It can occur with or without oxygen
- Influences the products produced
5
Q
Glycolysis
A
- Glycolysis: the metabolic pathway that breaks glucose down to 2 pyruvate molecules
- The 2 Pyruvates are passed on to the next cycle for further processing
- There are 10 reactions that occur during glycolysis
- Glycolysis occurs in the cytoplasm and the products proceed into the mitochondria for further breakdown
- ATP (energy) is both used (2) and produced (4)
- NADH and FADH2 (electron carriers) are produced
- Glycolysis occurs within the cytoplasm of cells and the starting material is glucose, a six carbon sugar.
- Glucose molecule is broken down by a series of reactions to release energy, which allows formation of ATP
- The overall process for glycolysis from start to finish uses 2 molecules of ATP and produces 4 molecules of ATP for a net reaction of 2 ATP
- The next step is entirely dependent on the presence of oxygen.
- The role of glycolysis is NOT ATP production, it is the preparation phase for the next pathways
- glucose is broken down to pyruvate, which is then processed for ATP
5
Q
Free Energy
A
- The amount of energy available to do work
- What is left over after all bonds are broken and formed
- A ‘net’ value
- Under constant volume and pressure, as most living systems and cells are, change in free energy is:
ΔG = ΔH -TΔS
G = free energy
H = enthalpy (energy in bonds) (smaller when positive, bigger when negative)
T = temperature
S = entropy(randomness) (bigger when positive, smaller when negative) - smaller H and bigger S (excergonic) is the first to occur, and then bigger H and smaller S (endergonic). This is a coupled reaction
- body has more thermal energy than entropy, so body prefers to be endergonic. We need to provide it with energy, that’s why it’s an open system
5
Q
Pyruvate Oxidation
A
- When oxygen is available, the 2 pyruvates produced in glycolysis in the cytosol are transported into the mitochondrial matrix and oxidized to 2 Acetyl-Coenzyme A’s
- 3-Carbon pyruvate is converted into 2-Carbon Acetyl-Coenzyme A complex (Ac-CoA)
- This releases 1 carbon in the form of CO2
- NAD+ is reduced (gains electrons) to NADH
- This reaction is coupled to the release of carbon dioxide
- The 2 carbon acetyl group associates with CoA
- **this produces 2 NADH and 2 Ac-CoA since two pyruvate molecules enter from glycolysis
5
SUBSTRATE LEVEL PHOSPHORYLATION
- At various steps in the glycolytic pathway, a phosphate group is removed from a substrate molecule and combined with an ADP molecule to form ATP.
- Phosphorylation: the addition of a phosphate group (PO43-)
- Represented by a ‘P’ inside of a circle
- This recycles the hydrolyzed ADP from previous reactions, back into useable ATP
5
Coupled Reactions
- Cells use ATP for endergonic reactions
- If the hydrolysis of ATP releases more energy than the other reaction consumes, the two reactions can be coupled so that the energy released by the hydrolysis of ATP can be used to supply the endergonic reaction to form ADP again
5
Regulating Metabolism
- Cells will regulate the speed of metabolism to ensure a steady concentration of ATP within the cell (not too high, not too low)
- There are 2 main control points for altering the speed of Cellular Respiration
5
Metabolic Rate
the amount of energy consumed by an organism in a given amount of time
6
summary of glycolysis
- starts with a glucose molecule
- The first step is turning ATP to ADP b/c of phosphorylation
- endergonic
- The enzyme used for this is Hexokinase
- step 2 occurs (not important), and then step 3
- step 3 turns ATP to ADP again, making 2 ADP for later. This step also makes Fructose 1,6 bisphosphate. This is very important because since it's symmetrical, it is split in half. That is why everything else in the cycle is doubled, b/c of this step exactly
- endergonic
- step 4 happens (not important) and then step 5 happens, which makes G3P (2 of them since it's doubled)
- step 6 turns G3P to BPG, where two NAD+ on each G3P are turned to NADH, which is an electron carrier. This happens b/c NAD+ takes an electron from the G3P, which means that the NADH is reduced while G3P was oxidized
- In step 7, SLP happens again, where ADP turns to ATP. This is b/c ADP takes away a phosphate group from BPG. This makes 3PG
- In step 8, the molecule reorganizes itself
- In step 9, condensation happens where H2O exits out and this turns 3PG to PEP
- In step 10, SLP happens where ADP borrows a phosphate group from PEP to make ATP. This makes a pyruvate (remember, it's two of them)
- The enzyme that helps step 10 is pyruvate kinase
6
The Krebs Cycle
- The cyclic metabolic pathway that oxidizes acetyl-CoA and breaks it down
- It converts released energy to be stored as ATP, NADH, and FADH2.
- Occurs in the mitochondrial matrix
Reactions 1- 5
- *Acetyl-CoA “delivers” two carbons from glucose to the Krebs cycle by reacting with oxaloacetate to produce a six-carbon molecule called citrate
- Citrate undergoes a series of reactions that break it down to a 4C molecule called succinate.
- Two of these reactions are oxidation reactions that result in the release of two carbons in the form of carbon dioxide molecules.
- Coupled to these oxidation reactions are two reduction reactions, each of which reduces a molecule of NAD+ to produce a molecule of NAD
- In reaction 6 of the cycle, ATP is produced by substrate-level phosphorylation. This is a complex reaction in which a phosphate group replaces the CoA while the substrate succinate, is bound to the enzyme.
- The phosphate group is then added to a molecule of guanosine triphosphate (GTP), and transferred to ATP.
- Although most of the GTP is used to make ATP, a few reactions in the cell use GTP itself for energy.
- Reactions 7-9 are oxidation reactions.
- They give electrons to the carriers
- These reactions are coupled to the reduction of NAD+ to form NADH and the reduction of FAD to form FADH2.
- These electron carriers are used to produce ATP in the oxidative phosphorylation pathway
-
7
How is Krebs a “cycle”?
- The final product of the last three reactions is oxaloacetate. This makes the pathway cyclical as oxaloacetate is regenerated and ready to react with more acetyl-CoA entering the Krebs cycle
- By the end of Krebs Cycle, all six carbon atoms of glucose have been oxidized and released as CO
7
Chemiosmosis
- H+ ions diffuse across the membrane, down the electrochemical gradient
- Just like water built up behind a dam, it is now ready to flow when a specific gate is opened
- This turns a turbine, which drives a generator to convert kinetic energy into electrical energy
- Similarly, to water in a dam, this gradient drives the phosphorylation of ADP to ATP
- The ‘gate’ that allows H+ is an enzyme called ATP Synthase
- The process of phosphorylating ADP to ATP, driven by hydrogen ions moving down the electrochemical gradient through ATP Synthase
- 1 NADH through the ETC Yields 3 ATP
-1 FADH through the ETC Yields 2 ATP
7
Complex 2
Succinate dehydrogenase
7
Complex 3
Cytochrome reductase
8
Other molecules entering Cellular Respiration
Proteins entering
- Broken down into amino acids
- Amino group removed
- Different amino acids can enter as different molecules
Carbohydrates entering
- Most enter during glycolysis, by first being broken down into glucose
Lipids entering
- Glycerol’s can be converted into G3P’s that can enter during glycolysis
- Fatty acids can be broken down into 2-carbon acetyl’s and enter at the end of Pyruvate Oxidation
8
Useful byproducts of Ethanol Fermentation
- Bread making - (CO2) causes bread to rise
- Wine making – grapes are sealed in a container, the sugars in the grapes are converted to ethanol with the help of yeast. Trapped CO2 used to make champagne
- Beer – fermentation of grain (grain + yeast + water)
- Cider – fermentation of apples
- Kombucha – yeast fermentation + bacteria
Fermentation is completed in the bottle, not a barrel, giving it the characteristic carbonation
8
Complex 4
Cytochrome oxidase
8
Complex 1
NADH Reductase
8
Why is it called “Oxidative Phosphorylation”?
- The pumping out of H+ has created a large buildup known as the electrochemical gradient
- large H+ concentration creates a chemical gradient
- large amount of positive charges create an electrical gradient
8
Oxidative Phosphorylation
- Electrons from NADH and FADH2 are transferred through a chain of membrane proteins on the inner mitochondrial membrane
- This occurs in 2 stages:
*The Electron Transport Chain
*Chemiosmosis
- This process drives the phosphorylation of ADP into ATP
- The chain of enzymes and their cofactors in the membrane is called the Electron Transport Chain
- Each component of the ETC is more electronegative than the previous
- This is what drives the electron transfer down the chain
- The Final electron acceptor, O2, is one of the most electronegative substances on earth
9
ATP synthase
- ATP is formed (oxidative phosphorylation)
- As the H+ re-enter the matrix through special protein channels that are coupled with ATP synthase (Fo sub-unit)
- It spins at high speed, creating enough energy to phosphorylate ATP molecules (F1 sub-unit), integral membrane protein
- potential energy gets converted to kinetic energy to make F0 spin. That kinetic energy gets converted back to potential energy in F1. This happens by having proteins come into F0 subunit. After the energy gets converted back to potential in F1, proton goes to matrix. That proton was with the protein, but it went away into the matrix. The energy in F1 makes ADP and Pi form to make ATP, which uses that energy as storage (potential energy)
10
BMR
Basal Metabolic Rate – the minimum amount of energy needed to keep an organism alive
10
VO2 Max
Maximum Oxygen that the cells of the body can remove from the bloodstream in 1 minute / kg of body mass. Typically measured during intense physical activity
11
Anaerobic Cellular Respiration
- The breakdown of glucose that occurs when oxygen is not present
- A molecule other than oxygen is used as the final electron acceptor
- E. coli - nitrate
- Methanogens – H2 + CO2-> CH4 + H2O
11
Ethanol Fermentation
Acetaldehyde + NADH Ethanol
- Some bacteria and yeast function under aerobic and anaerobic conditions
- Facultative aerobes
- 2 step anaerobic process:
- pyruvate converted to acetaldehyde (removal of CO2)
- Acetaldehyde oxidizes NADH to NAD+, forming ethanol (drinking alcohol)
12
lactate fermentation
- Pyruvate is converted to lactate (or lactic acid) in the absence of oxygen
- Reacts with NADH to oxidize to NAD+
- Lactate is acidic and must be transported out of cells to protect the surrounding tissue
- *Lactic Acid contributes to the burning and soreness you feel in your muscles as you work out*
12
Oxygen Debt
- Getting Rid of Lactic Acid Buildup
- The amount of oxygen required to eliminate all lactate
- Method 1 (when oxygen is present):
Lactate is oxidized by NAD+ (loses electrons to NAD+) and becomes Pyruvate again. NAD+ is reduced to NADH.
- Method 2:
Lactate is moved outside the cells and into the bloodstream to be excreted in urine
- ”Foam Rolling”: increases blood flow to muscle cells, allowing lactate to be absorbed into bloodstream
13
Fermentation
Single-celled yeast/bacteria
- Metabolic pathway that transfers electrons from NADH to an organic acceptor
- Lactate (muscle cells) or ethanol (yeast cells)
- ATP is being generated by repeating glycolysis
- Glycolysis will continue to the end, forming the 2 pyruvate molecules
- Pyruvate is then transformed into an organic molecule, depending on the organism
- This allows the NADH to be oxidized back to NAD+, and more ATP to be produced
14
Fermenting Vegetables
The salt solution kills off the harmful bacteria we don’t want, leaving the good fermenting bacteria to do their work
15
Ethanol as a Fuel
- Full break down of Glucose does not occur in ethanol fermentation, leaving much of this stored energy in the form of ethanol
- Ethanol is useful as a specialized fuel, but too expensive to mass produce at the moment
-Corn fermentation is most common in Canada
16
mitochondria
from outer to inner:
- outer mitochondrial membrane
- intermembrane space
- inner mitochondrial membrane
- Matrix
- Prokaryotic cells don't have mitochondria, but they have cytoplasm.
- NADH uses up 2 ATP to get inside to matrix (primary active transport)
