Flashcards in Biochemistry Deck (556)
Food stuff digested
HCl in stomach
Enzymes - mouth, stomach, small intestine
Enzymes in lysosomes for internal cell digestion
Absorption through cells in SI, enter bloodstream then cells
Starts in cytoplasm
Glucose broken down to 2 pyruvate molecules
2ATP and NADH produced per pyruvate
Pyruvate molecules move to mitochondria where converted to CO2 and 2C acetyl group which attaches to CoA
Describe the structure of CoA
8 trimers of lipoamide reductase-transacetylase
6 dimers of dihydrolipoyl dehydrogenase
12 dimers pyruvate decarboxylase
What are the functions of the three enzymes in CoA?
Pyruvate decarboxylase - removes CO2
Lipoamide reductase transacetylase - transfer acetyl group
Dihydrolipoyl dehydrogenase - reduces NAD
What happens in glycolysis in anaerobic conditions?
Muscle: pyruvate reduced to lactate reforming NAD+
Yeast: pyruvate reduced forming CO2 and acetaldehyde which is reduced to ethanol reforming NAD+
Describe stage 3 of ATP production
Acetyl group enters TCA where it is oxidised to CO2 and large amounts of NADH generated
NADH passed along electron transport chain where energy released produces ATP and consumes O2
What is oxidative phosphorylation?
ATP formation driven by transfer of electrons from food molecules to molecular O2
Electron ends up on O2, with H+ H2O formed
Name the 4 complexes of the electron transport chain
1. NADH dehydrogenase
2. Succinate dehydrogenase
3. Coenzyme Q reductase
4. Cytochrome c reductase
What are the roles of the complexes in electron transport chain?
NADH dehydrogenase, succinate dehydrogenase, coenzyme Q reductase pump protons across membrane into intermebrane space making intermembrane increasing acidic
Cytochrome c reductase give electron to O2 producing H2O
How does the electron transport chain produce ATP?
Due to the high H+ conc. in intermembrane space, protons diffuse down conc. gradient through ATP synthase producing lots of ATP
Name and describe the inhibitors of electron transport chain
Rotenone: blocks NADH from being oxidised by NADH dehydrogenase
Antimycin A: blocks complex 2
CN or CO: prevent O2 being reduced by cytochrome c reductase
What is the role of reactions?
Create order within cells: smaller molecules used to make macromolecules
Define catabolism and anabolism
Catabolism: break down of molecules releasing energy
Anabolism: construction of complex molecules from simple ones, storage of energy
Define free energy
Gibbs free energy (G): measure of energy contained in a molecule due to vibration, rotation, bonds
What is delta G?
Changes/difference in free energy
DG = G(products p) - G(reactants)
Define exergonic and endergonic
Exergonic: releases energy to surroundings -DG
Endergonic: absorbs free energy +DG
Define activation energy
Energy difference between reagents and transition state i.e. energy required for reaction to progress
How do enzymes work in terms of EA?
Lower the EA allowing larger proportion of random collisions with surrounding molecules to push substrate over EA
How do enzymes work?
Bind substrate tightly holding it in a way that facilitates conversion to product
Explain coupled reactions
Favourable (oxidisation of glucose) reactions release energy which is captured in chemical form and used to power unfavourable reactions (forming peptide bond)
Favourable reactions take place spontaneously whereas unfavourable only occur if coupled
What are carrier molecules?
Small proteins that contain 1+ energy-rich covalent bond and diffuse rapidly throughout cell thus carry bind energy from generation to utilisation
How do carrier molecules (coenzymes) store their energy?
In easily transferable groups/high-energy electron (easily oxidised/reduced) - ATP, NADH, NADPH
Describe the synthesis of a polynucleotide
Nucleoside monophosphate activated by sequential transfer of terminal P from 2 ATP
High energy intermediate (nucleoside triphosphate) exists freely until reacts with growing end of R/DNA releasing pyrophosphate
Hydrolysis of pyrophosphate to Pi highly favourable, drives overall reaction
Explain the limits of ATP
DG of ATP is -7.3kcal/M only drive reaction up to that amount
If reaction requires more ATP hydrolysis altered to produce AMP and PPi (pyro) which is hydrolysed producing large amounts of free energy
What is the importance of enzyme inhibitors?
Info about shape of AS and AA residues at AS
Info about chemical mechanism
Info about regulation/control of metabolic pathway
Aide drug design
What are the 2 broad classifications of inhibitors?
Irreversible: usually involves formation or breaking of covalent bonds - enzyme forms covalent bond with AS so cannot be removed
What are the 3 types of reversible inhibitors?
Explain irreversible inhibition
Inhibitor forms covalent bond with AS of enzyme so is permanently attached thus permanently inactivates enzyme
e.g. diisopropylphosphofluoridate prototype for nerve gas sarin, permanently inactivates serine proteases
Explain competitive inhibition
Inhibitor competes with substrate to bind on AS
Inhibitor and substrate have similar structures
ONLY binds to enzyme NOT ES complex