8.2 Cell respiration Flashcards
What is oxidation?
the loss of electrons from a substance
What is reduction?
the gain of electrons of a substance
What is an electron carrier?
substances that can accept and give up electrons as required to link oxidations and reductions in cells
What is the main electron carrier in respiration?
NAD
What is used in photosynthesis instead of NAD
NADP
What does glycolysis need?
No oxygen; 2ATPs; 2 ADPs; 2NAD+; 4 electrons; glucose, phosphate
What does glycoslysis produce?
Small net gain of ATP (4 ATPs); NADH; conversion of glucose into pyruvate
Why is phosphorylation needed?
makes organic molecule less stable and more likely to react next stage in metabolic pathway
What are the four main stages of glycolysis?
phosphorylation; lysis; oxidation; ATP formation
What occurs during phosphorylation?
two phosphate groups are added to a molecule of glucose to form hexose biphosphate using 2 ATP molecules; energy is raised, less stable
What occurs during lysis?
hexose biphosphate is split to form two molcules of triose phosphate
How does triose phosphate convert to pyruvate?
two atoms of hydrogen are removed from each triose phosphate molecule. this is oxidation; energy released by oxidation of triose phosphate converts ADP to ATP; end product pyruvate
Summary of glycoslysis
occurs in cytoplasm; ONE glucose is converted into TWO pyruvates; TWO ATP molecules are used and FOUR are produced; small yield of ATP but can be achieved with NO oxygen; two NADs are converted into two reduced NADs
What happens to pyruvate after glycoslysis?
if oxygen available; it can oxidize further; and aerobic respiration; if no oxygen is available it will undergo anarobic respiration
summary of aerobic respiration
pyruvate aborbed by mitochondrion; co2 is removed through decarboxylations; pyruvate is oxidized by removing hydrogen atoms; NAD+ and FAD accept hydrogen atoms; passed onto electron transport chain; oxidative phosphorylation occurs;
What is decarboxylation
removal of carbon and oxygen
What occurs after glycolysis in aerobic respiration?
Link reaction;
What occurs during a link reaction
pyruvate is absorbed by mitochondrion (in mitochondrial matrix); pyruvate is decarboxylated (one carbon removed) and oxidized to form a acetyle group (two carbon compound); 2 electrons are removed from pyruvate (oxidation); NAD+ reacts elctrons to produce reduced NAD
What occurs during krebs cycle?
the acetyle CoA group (a four-carbon compound) forms a six-carbon compound (citrate); co2 is removed in two reactions (decarboxylations); hydrogen is removed in four reactions (oxidations); in 3 oxidation, hydrogen reduces NAD+ (forms NADH); in the other oxidation, FAD accepts the hydrogen (is reduced); oxidation releases energy; ATP is produced through substrate-level phosphorylation
When is NAD reduced during cell respiration?
glycolysis, link reaction, krebs cycle
Where is FADH2 produced?
Krebs cycle
What occurs during oxidative phosphorylation?
final part of aerobic respiration; ADP is phosphorylated to produce ATP; using energy from oxidation; reduced NAD and FADH2 carry energy; to cristae of mitochondria
What is the electron transport chain?
series of electron carriers located in the inner membrane of mitochondrion (including cristae)
How does the electron transport chain work?
electrons released from oxidation reactions; reduced NAD supplies two electron to first carrier; electrons pass along chain; energy is used for protein pumps to pump H+ against concentration gradient; from matrix to intermembrane space; NAD supplies 3 stages reduced FADH2 supplies electrons; but later than NAD; FAd only supplies 2 stages
Outline chemiosmosis
occurs in the inner mitochondria membrane; electrons pass from carrier to carrier; gives energy to protein pumps; H+ moved cross the membrane from matrix to inner membrane space; concentration gradient of protons increased (high concentration of H+ in inner membrane space); H+ pass back from intermembrane space because of osmosis; pass through ATP synthase down concentration gradient; energy produced to phosphorylate ADP into ATP; to keep proton gradient and allow electrons to flow, electrons used to form water from O2 and H+ ions (in matrix)
How can electrons continue to flow in the inner mitochondrial membrane?
must be transferred to a terminal electron acceptor
Where does ATP synthase get its energy for ATP synthesis?
uses energy that protons release as they diffuse down concentration gradient
What is the role of oxygen in oxidative phosphorylation?
electrons given to oxygen at end of electron transport; in matrix; oxygen and free protons form water; use of protons keeps H+ concentration low in matrix; use of oxygen called terminal electron acceptor
What occurs if oxygen is not available as terminal electron acceptor?
electron flow along lectron transport chain stops; NADH cannot be converted to NAD; NAD supply runs out in mitochondrion; link reaction and krebs cannot continue
What is an example of a paradigm shift?
chemiosmotic theory in the field of bioenergetics
Explain how mitochondrion is an example of how structures are adapted to its function
Adaption is a result of evolution by natural selection; if structure varied, organoisms with mitochondria that produced ATP most efficiently would have an advantage; bigger survival chance; more offspring; offspring inherit efficiency; mitochondria evolves as efficient
What is the function of the outer mitochondrial membrane?
separates contents of the mitochondrion from rest of cell, creating a compatment specialized for biochemical reactions of aerobic respiration
What is the function of the inner mitochondrial membrane
site of oxidative phosphorylation; contains electron transport chain and ATP synthase
What are cristae?
tubular projections of inner membrane which increase surface area available for oxidative phosphorylation
What is the function of the intermembrane space?
location where protons build up as a consequence of electron transport chain; space is small so proton built up for ATP synthase is rapid
What is the matrix of mitochondria?
site of krebs cycle and link reaction; matrix fluid contains the enzymes necessary to support these reaction systems
Draw diagram of a mitochondrion
outer mitochondrial membrane; matrix; inner mitochondrial membrane; cristae; ribosome DNA; intermembrane space
What is the electron tomography?
used to develop three dimensional images of active mitochondria
What happens once plastoquinon becomes reduced?
chlorophyll in reaction centre become powerful oxidizing agent; can cause water to split up and give up electrons (photolysis)
What is photolysis?
split of water to generate O2
Why does photolysis occur?
to produce reduced plastoquinone that can carry electrons and energy
