Lecture 6 - Metabolism Flashcards
What is metabolism?
Metabolism is the sum of all biochemical reactions inside the cell involving nutrients
Oxidation reduction reactions
Oxidation reduction reactions involve oxidize substances losing electrons and energy and reduced substances gaining electrons or energy
Mnemonic: OILRIG = Oxidation is losing; Reduction is gaining
What are the two important coenzymes in redox reactions?
NAD+ derived from niacin (vitamin B3) can be reduced to NADH + H
FAD is derived from ingested riboflavin (vitamin B2) and can be reduced to FADH2
ATP (what does it do?)
 ATP Is used by all known forms of life to power chemical reactions
- ATP briefly holds chemical energy
- ATP transfers chemical energy to enzyme to power reaction by releasing energy, ATP turns to ADP 
- ADP then gets recharged into ATP to be used again
Substrate level phosphorylation
High energy phosphate groups directly transferred from substrates to ADP
Chemical bonds broken and energy from reactants used to phosphorylate ADP into ATP
Does not require oxygen

Oxidative phosphorylation
Energy from food creates protein gradient (Electron transport chain) that is used to attach phosphates to ADP
Requires oxygen 
carbohydrate metabolism
When glucose enters a cell it is phosphorlated to glucose –6-Phosphate
Can enter Through facilitated diffusion —> once phosphate added, it’s trapped in a cell
This process keeps intracellular glucose concentration low, which continues glucose entry through diffusion
What is Glycolysis?

Anaerobic! Takes place regardless of presents or absence of oxygen
-Glucose molecule is broken into two pyruvic molecules
net gain of 4 but costs 2 to start
If no oxygen NADH returns hydrogen to pyruvic acid forming lactic acid which allows NADH+ To continue excepting electrons
Once enough oxygen lactic acid is oxidized back to pyruvic acid and enters aerobic pathways

Krebs cycle (citric acid cycle)
Pyruvic acid must be actively transported into mitochondria (cannot diffuse across mitochondrial membrane)
In mitochondria it enters transitional phase —> Each pyruvic acid is converted to acetyl CoA if oxygen is available
 Electron transport chain
Energy from NADH and FADH2 move H+ from mitochondrial matrix to the INTER membrane space
H+ diffuse back through enzyme (ATP synthase) which phosphorylates ADP to ATP
WITHOUT OXYGEN SYSTEM BACKS UP AND STOPS WORKING
Glycogenesis
A process that forms glycogen
ATP cannot be used to store energy for long periods so ATP inhibits glycolysis —> Instead glycogen synthase catalyzes the attachment of glucose into a chain of glycogen
Glycogenolysis
A process that breaks down glycogen
When blood glucose levels drop cells can respond by splitting glycogen into glucose molecules
In most body cells glycogen is broken down to glucose-6-phosphate which enters glycolysis
Gluconeogenesis
A process that forms glucose from non-glucose molecules such as glycerol or amino acids —> maintains blood glucose when dietary sources and glucose reserves begin to deplete
Protects the body especially nervous system from the effects of hypoglycemia (low blood sugar)
