Lecture 4.1: Intro to Metabolism Flashcards
1. Describe the role of ATP within cells (i.e. what is it used for). 2. Compare the absorptive and post-absorptive states in terms of glucose use/storage and nutrient transport. 3. Describe the major metabolic processes noted in this lecture and where they occur (which cells and where inside the cells).
Metabolism
(overview)
Sum of all chemical reactions in the body
Anabolism & Catabolism
Metabolism
- Extract energy from nutrients
- Use energy for work
- Store energy for later work
Anabolism
Smaller molecules -> large molecules
Catabolism
Large molecules -> smaller molecules
Energy Input
Diet
- Hunger/ appetite
- Satiety
- Social and psychological factors
Diet
Goes into the body
Energy Output
Heat
- Unregulated
- Thermoregulation
50% of output
Energy Output
Work
- Transport across membranes
- Mechanical work
– Movement - Chemical work
– Synthesis for growth and maintenance
– Energy storage
» High energry phosphate bonds (ATP, phosphocreatine)
» Chemical bonds (glycogen, fat)
Work
Stages of Metabolism
Overview
Stage 1: GI Tract
Nutrients are:
- Digested into absorbable units.
- Absorbed into the bolld and transported to tissue cells.
Stage 2: Tissue Cells
Anabolism or catabolism:
- Anabolism: nutrients are built into macrobolecules.
- Catabolism: nutrients are broken down to pyruvic acid and acetyl CoA.
- Glycolysis is the major catabolic pathway.
Stage 3: Mitochondria
Oxidative breackdown of stage 2 products:
- CO2 is released.
- The H atoms removed are ultimately delivered to molecular oxygen, forming water.
- Some of the energy released is used to form ATP.
- The citric acid cycle and oxidative phoshorylation are the major pathways.
Adenosine Triphosphate
ATP
Exchange of energy requires ATP to drive cellular processes
- Phosphate bonds allow large change in energy state
- Carries, does not store energy
- Enzymes transpher energy by phosphorylating other molceules -> higher energy molecules
Absorptive State
Metabolic Processes
- Glycogenesis
- Lipogenesis
- Protein Synthesis
Post-Absorptive State
Metabolic Processes
- Gluconeogenesis
- Glycogenolysis
- Lipolysis
Metabolic Processes
List
- Glycolysis
- Krebs Cycle
- Electron Transport Chain
- Glycogenesis
- Glycogenolysis
- Gluconeogenesis
- Lipogenesis
- Lipolysis
- Ketogenessis
- Engergy Storage vs. Mobilization
Glucose Catabolism
Primary source for ATP production
Glycolysis
- Occurs in the cytoplasm
- “Sugar splitting”
- 1 glucose (6 carbon ring) → 2 pyruvate (3carbon molecule) + 2 reduced coenzymes (NADH) + 2 net ATP gained (2 used to start)
Most chemical energy stored in pyruvate molecules
Anaerobic Fermentation
After Glycolysis if no oxygen is available
After Glycolysis if no oxygen is available:
- Pyruvate → lactate
- Only 2 net ATP from glycolysis
- Resets coenzyme NAD+ for necxt time
- Fast but inefficient energy production
Glycolysis: 1 glucose (6 carbon ring) → 2 pyruvate (3carbon molecule) + 2 reduced coenzymes (NADH) + 2 net ATP gained (2 used to start)
Aerobic Respiration
- Occures in the mitochondria
> Citric acid cycle - mitochondrial matrix
> Electron transport chain - mitochondrial membrane - Requires oxygen
- Pyruvate + O2 → CO2 + H2O + 36(ish) ATP
- Efficient but slower way to produce ATP
Glucose Catabolism
Citric acid cycle
- Occures in the mitochondrial matrix
- Pyruvate + lower energy oxidized coenzymes (NAD+ & FAD) → CO2 + 2 ATP + higher energy reduced coenzymes (NADH + FADH2)
- Can also use metabolic products from lipids and amino acids here
Electron transport chain
- Occurs in the inner mitochondrial membrane
- Higher energy coenzymes (NADH & FADH2) + oxygen + chain of membrade enzyme complexes → lower energy coenzymes (NAD+ & FAD) + H2O + H+ pumping → ATP
Glycolysis + Citric acid cycle + electron transport chain
Glycolysis
Table
Principal Reactants: Glucose, 2 ADP, 2 P, 2 NAD+
Principle Products: 2 pyruvate, 2 ATP, 2 NADH, 2 H2O
Purpose: Reorganizes glucose and splits it in two in preparation for further oxidation by the mitochondria; sole source of ATP in anaerobic conditions.
Anaerobic Fermentation
Table
Principal Reactants: 2 pyruvate, 2 NADH
Principle Products: 2 lactate, 2 NAD+
Purpose: Regenerates NAD+ so glycolysis can continue to function (and generate ATP) in the absence of oxygen.
Matrix Reaction
Table
Principal Reactants: 2 pyruvate, 8 NAD+, 2 FAD, 2 ADP, 2 P, 8 H2O
Principle Products: 6 CO2, 8 NADH, 2 FADH, 2 ATP, 2 H2O
Purpose: Remove electrons from pyruvate and transfer them to coenzymes NAD+ and FAD; produce some ATP.
Membrane Reactions
Table
Principal Reactants: 10 NADH, 2 FADH2, 6 O2
Principle Products: Up to 28 ATP, 12 H2O
Purpose: Finish oxidation and produce most of the ATP of cellular respiration.
