C1.2 Cellular Respiration Flashcards
Function of ATP
- “Energy currency in cells”
- Used in many different contexts
- Constantly recycled
- Temporary storage of energy
- Energy transfer between metabolic processes and parts of the cell
Properties of ATP
- Water soluble: moves freely throughout cell cytoplasm and aqueous solutions
- Cannot simply diffuse across membranes: allows its movement to be controlled via carriers
- Very reactive: takes part in a large variety of metabolic reactions
- ATP + H20 –> ADP + Pi + energy : easily reversible to facilitate use and re-use
- energy released is sufficient for cellular processes with minimal waste
Cellular life processes that require ATP
Anabolic reactions:
- Synthesis or larger more complex macromolecules from smaller simpler monomers: endothermic so requires energy
- Each condensation reaction that links a monomer to polymer is coupled to the conversion of ATP to ADP to provide energy
Active transport:
- Pumping substance across a membrane against concentration gradient is not passive and requires energy
Movement of cell components and of the cell itself to another location require energy
Process of adding a phosphate to a molecule (4)
Phosphorylation.
- Makes molecules more unstable and more likely to react.
- Hydrolysis of ATP –> ADP + Pi releases energy. (endothermic)
- Many reactions in the body are endothermic so need to be coupled with hydrolysis of ATP that releases energy.
Define Cellular respiration
check notes.
Define Cellular Respiration
- Respiration is a complex metabolic process that is carried out by all living organisms.
- Controlled release of energy from carbon compounds in cells to produce ATP
- Purpose is to transfer chemical energy in biomolecules into ATP for easier, later use through a series of reactions in a metabolic pathway.
Aerobic respiration in humans (4)
- Involves complete breakdown of glucose to regenerate a net gain of 36 molecules of ATP.
- Glucose, fats and proteins can be used as substrates.
- Takes place in the presence of oxygen.
- Takes place in cytoplasm or mitochondria.
- Produces water and CO2 as waste products.
Anaerobic respiration in humans (5)
- Involves the partial breakdown of glucose that generates only net 2 ATP.
- Takes place in absence of oxygen.
- Only glucose can be used as respiratory substrate.
- Only takes place in cytoplasm.
- Produces lactic acid or lactate as waste.
Factors that affect the rate of respiration (4)
- Temperature
- pH
- Respiratory substrate concentration.
- Oxygen concentration.
- CO2 concentration: CO2 is produced it can form carbonic acid and lower pH
Define Respirometer (4)
- Simple devices which measure the rate of respiration in organisms which respire aerobically.
- Rate of oxygen consumption is used as an indicator of respiration.
- Alkaline solution is added to absorb CO2.
- There will be a decrease in the volume of gas in tube due to oxygen being used in aerobic respiration.
Calculations needed for C1.2 (3)
Volume of cylinder, rate = volume of gas consumed/time taken, mean rate = add rates together and divide by number of trials.
Structure of Mitochondria (5)
- Intermembrane space.
- Outer membrane.
- Inner membrane.
- Cristae.
- Matrix.
check notes diagram.
Function of the structures of Mitochondria (4)
- Inner and outer membrane aides ability to make ATP.
- Outer membrane is permeable to many small molecules and ions and contains transport proteins (porins).
- The inner membrane is highly folded into cristae which increases surface area.
- Matrix is small space and allows high concentration gradients to form which are necessary for respiration.
Function of NAD in aerobic respiration (3)
- Nicotinamide adenine dinucleotide (NAD).
- functions as a coenzyme.
- Ability to be reduced and oxidised allows it to perform the critical role of a hydrogen carrier.
- Used to transfer and use energy incrementally.
First step of aerobic respiration (6)
Glycolysis.
- Takes place in cytoplasm.
- Complex set of reactions.
- Glucose is converted to 2 pyruvates.
- Net gain of 2 ATP.
- Formation of 2 NADH (reduced NAD).
4 Stages of Glycolysis (4)
- Stage 1: Uses 2 molecules of ATP to phosphorylate glucose (G6P) - less stable, more reactive.
- Stage 2: Phosphorylated glucose splits into two glyceraldehyde 3-phosphate (G3P).
- Stage 3: Each G3P is dehydrogenated to reduce 2NAD into 2NADH.
- Stage 4: generation of net 2 ATP and 2 pyruvate molecules from each G3P by transferring phosphate to ATP.
Second step of aerobic respiration (6)
Links reaction.
- Takes place in matrix of mitochondria.
- The two pyruvates from glycolysis enter this stage. 2 pyruvate –> 2 acetate
- For both pyruvate during process: 2 NADH and 2 CO2 produced.
- 2 acetates bind to Coenzyme A to form acetyl-CoA
- CO2 removed as waste product.
Third step of aerobic respiration (8)
Krebs cycle.
- Takes place in matrix of the mitochondria.
- 1 x Acetyl CoA enters into the Krebs cycle so that there are two cycles.
- Acetyl CoA combines with oxaloacetate to form citrate - CoA released to be reused in link reaction
Per cycle:
- Creates 3 reduced NAD
- Creates 1 reduced FAD.
- Creates 1 ATP.
- Releases 2 molecules of CO2.
- Completes the breakdown of the original glucose.
Factors that determine the amount of ATP that can be generated
How much hydrogen is available from the broken down molecule.
- More hydrogen = More reduced NAD.
- More reduced NAD = more proteins can be transported across the inner mitochondrial membrane.
- More ATP can be generated.
Lipids as respiratory substrates.
- When lipid molecules is set to be respired, it is broken down to glycerol and fatty acids.
- Glycerol can be used in glycolysis.
- Fatty acids can be broken into acetyl groups and through the links reaction, becomes units of acetyl CoA.
- Lipids cannot be used in anaerobic respiration.
For 1 glucose molecule…
- 2 Pyruvates are formed.
- Net of 2 ATP and 2 NADH (reduced NAD) made.
- Each pyruvate makes 1 CO2 and 1 NADH and make Acetyl CoA.
- Then during Krebs cycle, each Acetyl CoA creates 2 CO2, 3 NADH, 1 ATP, and 2 FADH2.
Electron Transfer Chain/ Oxidative Phosphorylation
- Takes place in the inner mitochondrial membrane and intermembrane space.
- creates approx. 34 ATP.
- Produces water which is a waste product excreted from energy.
Components of the Electron Transport Chain
- 4 transmembrane proteins
- 2 electron carriers
Electron Transport Chain process: NADH and FADH
- Reduced NAD (NADH) is delivered to the first protein of the ETC.
- Here it splits: NADH –> NAD+ + H+ + 2e-
- The two electrons are passed along electron carriers
- These electrons power the H+ ions being pumped across the membrane into the intermembrane space
- Reduced FAD (FADH) works in a similar fashion but delivers electrons to the second protein.
Explain Chemiosmosis and role of ATP-synthase
- The pumping of the H+ across the membrane, creates a concentration gradient
- The intermembrane space is very small so the concentration is even greater
- This gradient is key to generating large amounts of ATP.
- The H+ only has one route back across the Inner mitochondrial membrane: through the ATP-synthase (specialized protein channel)
- As the H+ pass through ATP-synthase, it rotates ATP and generates energy to convert ADP to ATP
Explain the role of Oxygen in the ETC
- Once electrons pass along the ETC, they must go somewhere.
- O2 splits and each oxygen molecule joins with 2e- and 2H+ to form two water molecules.
- If no oxygen is present, NAD+ and FAD+ cannot be recycled and used again. In the absence of oxygen, hydrogen carriers cannot transfer energized electrons to the chain and ATP production is halted.
Features of Anaerobic respiration
- Produces a lot less ATP (compared to aerobic)
- When oxygen is lacking or in short supply, anaerobic respiration can provide the cell with a source of ATP
- Takes place in cytoplasm
- Only glycolysis takes place
- Creates 2 ATP and 2 NADH (reduced NAD)
Steps of Anaerobic respiration in animals
- Glucose (6C) will break down into pyruvate (3C)
- In the process, releases net 2 ATP and 2 NADH
- Pyruvate is converted into lactate in animals: this happens in the cytosol (liquid part of cytoplasm)
Steps of Anaerobic respiration (yeast)
- Glucose (6C) will break down into pyruvate (3C)
- In the process, releases 2 ATP
- Pyruvate is converted into ethanal by decarboxylation
- Ethanal –> Ethanol (reduced by NADH): happens in cytosol
- Ethanol and CO2 produced
Carbohydrates as respiratory substrates
- Broken down into monosaccharides
- These enter glycolysis
- Can be respired aerobically and anaerobically
- Compared to lipids, lower energy yield per gram
