respiration Flashcards
what are the four key stages of aerobic respiration
-glycolysis
-link reaction
-Krebs cycle
-oxidative phosphorylation
what is ATP
nucleotide derivative
-composed of the base adenosine, pentose sugar, 3 phosphate groups
where does glycolysis occur
cytoplasm
glycolysis
first stage of aerobic and anaerobic respiration, however it is an anaerobic process (doesn’t require any energy/oxygen).
glycolysis involves 3 steps:
1. phosphorylating glucose to glucose phosphate, using ATP
2. glucose phosphate forms two molecules of triose phosphate
3. oxidation of triose phosphate to produce pyruvate. this produces two ATP molecules each, as well as reducing NAD into reduced NAD.
what are the products of glycolysis
2x pyruvate
net gain of 2 ATP
2x reduced NAD
where does the link reaction take place and why
mitochondrial matrix
-contains specific enzymes to catalyse steps of the reaction and contains molecules of NAD
link reaction
-the pyruvate made in glycolysis is oxidised to acetate. loses a hydrogen.
-NAD picks up the hydrogen and hence becomes reduced NAD
-acetate then combines with coenzyme A to produce acetylcoenzyme A
what are the products of the link reaction
occurs twice for every glucose molecule, so:
-2x acetyl CoA
-2 carbon dioxide released
-2 reduced NAD
where does the Krebs cycle take place
mitochondrial matrix
krebs cycle
-acetylcoenzyme A (2C) reacts with a 4C molecule, releasing coenzyme A and producing a 6C molecule that enters the krebs cycle
-in a series of redox reactions, the krebs cycle generates reduced coenzymes (reduced NAD and reduced FAD) and ATP by substrate-level phosphorylation, a carbon dioxide is also lost.
what are the products of the krebs cycle
kreb cycle turns two times per molecule of glucose, therefore per molecule of glucose:
-2 ATP molecules
-6 reduced NAD molecules
-2 reduced FAD molecules
-4 carbon dioxide molecules
what happens if there is an absence of oxygen in Krebs and link
all FAD and NAD will be reduced so none will be available to take up the protons produced during Krebs, so enzymes will stop working
where does oxidative phosphorylation take place
inner mitochondrial membrane
oxidative phosphorylation
most ATP is made during this stage
-reduced NAD and reduced FAD deliver their hydrogen atoms to the electron transfer chain, causing these coenzymes to be re-oxidised
-re-oxidised coenzymes return to mitochondrial matrix where they work together with dehydrogenase enzymes and accept any released hydrogen atoms in the link reaction & Krebs cycle
-hydrogen atom splits to produce protons and electrons. protons go into solution in the mitochondrial matrix, electrons are accepted by the first electron carrier protein (cytochrome) in the ECT
-energy released by the electrons flowing down the ECT is used to pump the protons from the matrix, across the inner mitochondrial membrane and into the intermembrane space- creates an electrochemical gradient
-due to reduced permeability of the inner membrane to the hydrogen ions (protons), the protons accumulate in the intermembrane space and a proton gradient forms across the membrane
-protons move down their concentration gradient, through the use of facilitated diffusion through ATP synthase. which then catalyses the addition of Pi to ADP to form ATP
what is the role of oxygen in oxidative phosphorylation
oxygen (final electron acceptor) within the mitochondrial matrix can pick up the electrons at the end of the electron transport chain, it can also pick up protons as they come back through ATP synthase.
-this creates water, which is the final product of respiration
