Pathway for digestion of food
Energy
>comes from food we eat >ultimately comes from sun >can be conserved/converted
ATP
- Universal energy molecule used by all living cells.
- produced inside the mitochondria (inner membrane)
Metabolic pathways
- Catabolism: breaking molecules apart (energy released)
- Anabolism: refers to making molecules larger (energy used up)
Acetyl-CoenzymeA (acetyl-CoA)
The common intermediate that carries acetyl groups into the citric acid cycle.
- intermediate in the break down of all classes of food
Stages of energy production:
- digestion
- Acetyl-coenzyme A production
- citric acid cycle
- ATP production
ATP & Energy transfer
- Energy of ATP is carried by negative charges on 3 phosphates ⇒high energy/charge repulsion
- ATP>ADP>AMP (energy release @ each step)
Oxidation
- loss of electrons
- loss of hydrogens
- gain of oxygen
NAD+ & FAD
- Electron carrier molecules.
- accept electrons in oxidation
- transport electrons to electron transport chain
- nicotine adenine dinucleotide, NAD+ (from niacin)
- flavin adenine dineucleotide, FAD (from riboflavin)
Whenever FAD or NAD+ appears in a reaction:
- The biomolecule becomes oxidized
Reduction of NAD+:
- Addition of electrons
Reduction of FAD:
- Addition of electrons
Purpose of citric acid cycle:
- harvest energy by oxidation
- provide starting material
- starting materials: acetyl-CoA & oxaloacetate
- products: CO2,GTP,NADH,FADH2
Citric acid cycle
- 1st half oxidizes
- 2nd half regenerates oxacytelate
- Reactions: oxidation & decarboxylation
Electron transport chain
Purpose:
- use energy of moving electrons to pump H+ ions
- recycle NADH & FADH2 back to NAD+ & FAD
Starting materials:
- electrons molecular oxygen
Products:
- recycled NAD+ & FAD for reuse in CAC
- waste water (urine)
ATP synthesis:
ATP is made from ADP and HPO4 2-
>H+ flowing through ATP synthase causes a shape change that fires Pi onto ADP
Lack of oxygen causes:
Electron transport to stop!
Superoxide ion
•O2-
- Oxygen with an extra electron
- free radical
Hydroxyl radical
•OH
- Not a hydroxide ion
- free radical
Hydrogen perioxide
H2O2
- Can split to form a radical
Free radical
- Unpaired electron
- take an electron from any nearby molecule and break covalent bonds in that molecule and creates a new radical
- cause damaged membranes= cell death!
Catalase
- Eliminates H2O2
- fastest know enzyme
Superoxide dimutase
- Eliminates superoxide
Reactive oxygen species (ROS):
- Microbial killers
- ROS that escapes enzymatic destruction are eliminated by Vitamin E (protects membrane), Vitamin C (protects aqueous componets), glutathione (eliminates radical)
