Unit 5 - Metabolism - Glycolysis

bioenergetics

the study of the various types of energy transformations that occur in living organisms

thermodynamics

the study of the changes in energy that accompany events in the universe

first law of thermodynamics

enrgy can niether be created or destroyed, only transformed from one form to another. cells are capable of energy trasduction

second law of thermodynamics

the universe always tends toward greater disorder (entropy).

from a higher energy state (ordered) to a lower energy state (disordered)

these changes are spontaneous

Free energy (G)

the amount of energy in a system that can do useful work (not lost as heat)

entropy and free energy are

inversely related

conditions of exergonic reactions

Negative deltaG

releses energy (creates free energy)

spontaneous (thermodynamically favourable)

conditions of endergonic reactions

postive delta G

required energy (uses free energy)

spontaneous (non-thermodynamically favourable)

standard conditions (‘)

products and reactents at concentration 1.0M

1 atm pressure

pH = 7.0

Catabolic Pathways

exergonic

breaks down cellular components

decreses in molecular order

increase entropy

neg deltaGnot’

• release energy for cellualr functions

anabolic pathways

endergonic

synthesize cellular components

increases in molecular order

decreases in entropy

pos deltaGnot’

• store energy in molecular bonds

5 roles of ATP hydrolysis in the cell

1. Maintaining membrane potential

   • Na+/K+ ATPase

2. Concentrate ions inside the cell

   • Concentrate molecules inside the cell

   • Ex) glucose

3. Drive energetically unfavourable reactions

4. Motor proteins

5. Phosphorylation of proteins

   

Reducing agent:

substance that gives up electrons causing another substance to be reduced & is therefore oxidized in the process

aerobic cellular respiration (5 phases)

1. glycolysis

2. pyruvate oxidation

3. citric acid cycle

4. electron transport chain and proton pumping

5. ATP synthesis

glucose oxidation is:

highly exergonic

3 phases of glycolysis

1. preparation and cleavage

2. oxidation and ATP generation

3. pyruvate formation and ATP generation

the main purpose of glycolysis

to generate pyruvate (used in CAC) not ATP

glycolysis phase 1 (preparation and cleavage) summery

energy investment (per glucose)

glucose + 2 ATP —> 2 GA-3-P + 2 ADP

glycolysis phase 2 (oxidation and ATP generation) summery

energy payoff (per glucose)

2 GA-3-P + 2 ADP + 2 Pi + 2 NAD+ —> 2 (3-PG) + 2 ATP + 2 NADH + 2 H+

2 ways to generate ATP in cells

1. cellular respiration

2. direct transfer of high energy phosphates from a molecule to ADP

phosphate transfer potential

more exergonic phophate compounds can give phosphate to make ATP

and ATP can give phophate to less exergonic phophate compounds

glycolsis phase 3 (pyruvate formation and ATP generation) summery

energy payoff (per glucose)

2 (3-PG) + 2 ADP —> 2 pyruvate + 2 ATP + 2 H2O

overall net reaction for Glycolysis

1 glucose + 2 ADP + 2 Pi + 2 NAD+ —> 2 pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O

Allosteric activators

Binding to regulatory site will increase affinity of active site for substrate --> increased amount of product

how is glycolysis regulated by allosteric enzymes

• ATP increase in cell signals that we have enough ATP!

• ATP allosterically inhibits PFK(phosphofructokinase) --> that will inhibit glycolysis

• AMP (adenosine monophosphate) increases in the cell --> we need ATP!

  • AMP is a byproduct of ATP use

• AMP allosterically activates PFK to drive glycolysis forward to increase ATP in the cell

why is it problematic to not have O2 in glycolysis?

If O2 is limited then NADH will not enter the E- transport chain and will accumulate in mitochondria, nothing for it to transfer its electrons to.

• No O2 = no terminal e- acceptor

so NADH then goes to the fermentative pathways

• To regenerate NAD+ so glycolysis can continue

summary of alcoholic fermentation

2 pyruvate + 2 NADH + 2 H+ —> 2 ethanol + 2 CO2 + 2 NAD+ (use in glycolysis)

net reaction of alcoholic fermentaition (glucose to ethanol)

1 glucose + 2 ADP + 2 Pi —> 2 ethanol + 2 ATP + 2 CO2 + 2 H2O

summary of lactate fermentation

2 pyruvate + 2 NADH + 2 H+ —> 2 Lactate + 2 NAD+ (for glycolosis)

net reaction of lactate fermatation (glucose to lactate)

1 glucose + 2 ADP + 2 Pi —> 2 lactate + 2 ATP + 2 H2O

(no net gain of NADH)

products of glycolysis *

2 pyruvate, 2 ATP, 2 NADH, 2 H2O

where does ACR occur

glycolysis is in the cytosol the rest of ACR is in the matrix of the mitocondria