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Flashcards in Biochemistry Deck (556)
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211

Describe digestion

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

212

Describe glycolysis

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

213

Describe the structure of CoA

8 trimers of lipoamide reductase-transacetylase
6 dimers of dihydrolipoyl dehydrogenase
12 dimers pyruvate decarboxylase

214

What are the functions of the three enzymes in CoA?

Pyruvate decarboxylase - removes CO2
Lipoamide reductase transacetylase - transfer acetyl group
Dihydrolipoyl dehydrogenase - reduces NAD

215

What happens in glycolysis in anaerobic conditions?

Fermentation
Muscle: pyruvate reduced to lactate reforming NAD+
Yeast: pyruvate reduced forming CO2 and acetaldehyde which is reduced to ethanol reforming NAD+

216

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

217

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

218

Name the 4 complexes of the electron transport chain

1. NADH dehydrogenase
2. Succinate dehydrogenase
3. Coenzyme Q reductase
4. Cytochrome c reductase

219

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

220

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

221

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

222

What is the role of reactions?

Create order within cells: smaller molecules used to make macromolecules

222

Define catabolism and anabolism

Catabolism: break down of molecules releasing energy
Anabolism: construction of complex molecules from simple ones, storage of energy

223

Define free energy

Gibbs free energy (G): measure of energy contained in a molecule due to vibration, rotation, bonds

224

What is delta G?

Changes/difference in free energy
DG = G(products p) - G(reactants)

225

Define exergonic and endergonic

Exergonic: releases energy to surroundings -DG
Endergonic: absorbs free energy +DG

226

Define activation energy

Energy difference between reagents and transition state i.e. energy required for reaction to progress

227

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

228

How do enzymes work?

Bind substrate tightly holding it in a way that facilitates conversion to product

229

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

230

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

231

How do carrier molecules (coenzymes) store their energy?

In easily transferable groups/high-energy electron (easily oxidised/reduced) - ATP, NADH, NADPH

232

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

233

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

234

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

235

What are the 2 broad classifications of inhibitors?

Reversible
Irreversible: usually involves formation or breaking of covalent bonds - enzyme forms covalent bond with AS so cannot be removed

236

What are the 3 types of reversible inhibitors?

Competitive
Non-competitive
Uncompetitive

237

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

238

Explain competitive inhibition

Inhibitor competes with substrate to bind on AS
Inhibitor and substrate have similar structures
ONLY binds to enzyme NOT ES complex

239

Explain the effect of competitive inhibitors on Vmax and Km

Reduces amount of free enzyme available for substrate binding (forms EI complex) thus Km increased, Vmax unchanged but requires more substrate to reach