Cellular Respiartion- Biology 20IB

What is cellular respiration?

controlled release of energy from organic compounds to form ATP

Where does cellular respiration occur?

cells of all organisms (plants and bacteria too)

What is ATP used for?

\-active transport

\-movement of cilia and flagella

\-muscle contraction

\-synthesizing compounds

How is ATP made?

\-a small amount of ATP can be made by “substrate-level phosphorylation” (ie an exothermic reaction releases enough energy to couple ADP + Pi)

\-most ATP is produced when hydrogen carriers are “reduced” with high energy electrons from glucose: NADH and FADH2. These can be oxidized later to release energy to make ATP

\-most of the ATP ARE PRODUCED THROUGH A RELATED CHAIN OF REACTIONS CALLED OXIDATIVE PHOSPHORYLATION

What os the balanced reaction for aerobic cellular respiration?

C6H12O6 + 36 Pi + 36ADP + 6O2 → 6CO2 + 6H2O + 36 ATP

How is glucose catabolized?

through glycolysis and the Krebs cycle

What are the parts of a mitochondria?

\-two membranes, not connected

\-inner membrane folds to form cristae

\-space between membranes is inter membrane space

\-centre fluid is called the matrix

How many members do mitochondria have?

2 membranes, not connected

What does the inner membrane in mitochondria fold to form?

cristae

What is the space between membranes in mitochondria called?

inter membrane space

What is the centre fluid in mitochondria called?

matrix

What is the structure and function of cristae in mitochondria?

\-highly folded inner membrane so large surface area for many electron transport chains & proton pores

What is the structure and function of inter membrane space in mitochondria?

\-small volume so protons will accumulate here with a high concentration

What is the structure and function of the fluid matrix in mitochondria?

\-contains enzymes and intermediates Krebs cycle

What are the steps of aerobic cellular respiration?

\-glycolysis

\-krebs cycle (including link reaction)

\-oxidative phosphorylation (electron transport chain & chemiosmosis)

What are oxidation/reduction (redox) reactions used for in cellular respiration?

to strop the energy from glucose

What is oxidation?

loss of electrons/hydrogen

What is reduction?

gain of electrons/hydrogen

What is an oxidizing agent?

electron acceptor

What is a reducing agent?

electron donor

What happens when an electron is transferred?

\-some energy is released

\-can be harnessed to do work

What is glycolysis?

first step in aerobic and anaerobic respiration

Where does glycolysis occur?

in cytoplasm

Does glycolysis require O2?

no its anaerobic

What does glycolysis require?

2 ATP to “kick start” cell respiration

What is the net production of glycolysis?

\-2 pyruvic acid (pyruvate)

\-2 ATP (4 made but 2 required)

\-2NADH (+H^+)

What is the first step of glycolysis and what is the process called?

\-glucose (6 carbon) converted to fructose diphosphate by ATP

\-phosphorylation

What is the second step of glycolysis and what is the process called?

\-unstable molecules fall apart in 2 3 carbon triose phosphate (TP) molecules

\-lysis

What is the third step of glycolysis?

\-TP is converted to G3P

\-energy/hydrogen released forms NADH +H^+ (oxidation)

\-NADH(+H^+) formed by oxidation can be used to make 2 ATP later

What is the fourth step of glycolysis?

\-G3P is converted to pyruvate

\-energy released for ATP formation

What happens if oxygen is present in glycolysis?

\-pyruvate is transported by a carrier protein into the mitochondrial matrix for the link reaction and Krebs cycle

What happens if no oxygen is present glycolysis?

\-pyruvate is fermented to make lactate (or ethanol & CO2 in yeast)

What happens when glycolysis is complete?

\-the cell has consumed one glucose molecule

What happens if theres no source of NAD^+ in glycolysis?

\-glycolysis cannot occur

\-cells have a limited supply of NAD^+

\-without a way to convert NADH to NAD^+, glycolysis will grind to a halt

\-ATP no longer will be produced and cell death will occur

Why did anaerobic cellular respiration evolve in organisms?

\-as a way of recycling NAD^+

\-allows glycolyis to continue

What is fermentation?

a method of anaerobic cellular respiration that involves transferring H”s of NADH +H^+ to specific organic molecules

What are the parts of anaerobic respiration?

glycolysis + fermentation

What is lactate fermentation?

\-NADH+H^+ transfers 2H to pyruvate in the cytoplasm

\-regenerates NAD+

\-pyruvate changes into lactic acid/lactate

What does lactate fermentation do in muscle?

\-helps maximize power of muscle contractions (ie. sprinting and power lifting) because these processes require more ATP than can be produced by aerobic cellular respiration

What is alcohol fermentation (yeast)?

\-pyruvate → acetaldehyde (ethanal) + CO2

\-ethanal + NADH + H^+ → ethanol + NAD^+

-same type of alcohol used in alcoholic beverages

\-recycles NAD+ and allows glycolysis to continue

\-the 2 ATP produced are enough to satisfy the organisms energy needs

\-yeast will do some fermentation even when oxygen is available

\-process used for making bread “rise” in baking

What is a respirometer?

simple ones measure volume changes due to oxygen use

What can absorb any CO2 produced in a respirometer?

an alkali (KOH, NaOH, soda lime)

Where does the krebs/citric acid cycle occur?

in mitochondrial matrix

Does the krebs cycle require oxygen?

yes

What does the krebs cycle do to pyruvate and what is it called?

\-completely catabolizes it to form CO2

\-decarboxylation

When are high energy H”s removed in the krebs cycle?

during oxidation steps

What does the krebs cycle and link reaction form for each pyruvate?

\-3CO2

\-4NADH+H^+

\-1FADH2

\-1ATP

What is another name for link reaction?

pyruvate oxidation

What is step 1 of the link reaction?

\-one CO2 is removed from each pyruvate-released as a waste products of decarboxylation

What is step 2 of the link reaction?

\-remaining 2 carbon portions are oxidized by NAD^+

\-Gains 2 H^+ and 2 e- from pyruvate

\-remaining 2-C compounds become an acetic acid

what is step 3 of the link reaction?

\-Coenzyme A (CoA) attaches to acetic acid group-forms acetlyl-CoA

\-this acetyl-CoA can enter the Krebs cycle

What is the Krebs cycle?

\-a series of chemical reactions occurs to break the 6 carbon citric acid molecule back into the 4 carbon oxaloacetate (must recycle the oxaloacetate to keep the cycle going)

\-the carbons removed leave the body as CO2 (decarboxylation)

\-the intermediates are oxidizes. H’s (e^-s) removed from the molecules reduce NAD^+ and FAD (H are transported to the ETC in the form of NADH and FADH2)

How do the carbons removed in the krebs cycle leave the body?

as CO2 (decarboxylation)

How often does the Krebs cycle run?

twice for each glucose (once for each pyruvate)

Where does the electron transport chain occur?

\-in the inner membrane (cristae)

What happens in the electron transport chain?

\-NADH and FADH2 move from matrix to inner mitochondrial membrane

\-electrons are pulled to stronger and stronger electron acceptors in a series of redox reactions (oxygen is final e- acceptor_

\-2 e^-+(H^+)+ 1/2O2 → H2O

\-energy from above reactions pump protons into the inter-membrane space

What is chemiosmosis?

\-how an H^+ gradient is used to make ATP

What happens in chemiosmosis?

\-protons build up in small inter membrane space as a result of ETC

\-diffuse back to matrix through ATP synthase

\-energy from protons moving though ATPase allows for phosphorylation of ADP to produce ATP