Chapter 9

CELLULAR RESPIRATION

Where do we get our E from?

Food! Food gives us:

Ability to grow/reproduce Raw materials E needed to “use” these materials

9-1 Chemical Pathways

Calorie: amount of E needed to raise 1g of

water 1°C “calorie” on food labels = kilocalorie 1 kilocalorie = 1000 calories

Cells release E stored in food Starts with process called “glycolysis”

“glyco” = sugar “lysis” = split

Chemical E and Food

Releases E by breaking down glucose and

other food molecules in the presence of O2

6O2 + C6H12O6 = 6CO2 + 6H2O + E Look familiar?

Happens in gradual steps Traps E in ATP

Cellular Respiration

1st step of cellular respiration Happens in cytoplasm GOAL: 1 glucose converted to 2 pyruvic acid ATP production NADH production- accepts electrons/E

Starts as NAD+ Just like NADPH in photosynthesis!

Glycolysis

E yield is small but occurs fast so LOTS of ATP

can be made No need for O2

When all NAD+ filled with electrons (making NADH), ATP production pauses When do you think it will start again?

When more NAD+ is available!

Glycolysis

If O2 is present, move on with cell respiration

If no O2 present...FERMENTATION! Fermentation: releases E in food by producing

ATP without O2

Now what?

NADH is converted back to NAD+ If more NAD+, ATP production can continue “anaerobic” process- no O2 needed

Fermentation

Fermentation!

1. Alcoholic fermentation

Pyruvic acid + NADH = alcohol + CO2 + NAD+ ex: yeasts, bread dough

2. Lactic acid fermentation Pyruvic acid + NADH = lactic acid + NAD+ ex: muscle cells, food/beverages

Fermentation(creating more NAD+)

At end of glycolysis, 90% of E is still unused Stored in pyruvic acid MUST have O2 (aerobic!)

O2 = electron acceptor

When O2 present, pyruvic acid moves to Krebs Cycle

9-2 Krebs Cycle and Electron Transport Chain

GOAL: Pyruvic acid CO2 + E Aka: citric acid cycle (1st compound formed) Happens in the mitochondria Occurs in 2 steps

Krebs Cycle

Citric acid production Pyruvic acid acetyl CoA +CO2 +NADH

CO2 = waste product NADH = electron/E acceptor Then Acetyl CoA citric acid

Krebs Cycle Step 1

Energy extraction Citric acid CO2 +NADH + FADH2 + ATP

+ a series of C compounds E totals: 4 NADH, 1 FADH2, 1 ATP

Krebs Cycle Step 2

1. CO2- released as waste 2. ATP- E used for cell activities 3. NADH + FADH2- E carriers

move onto electron transport chain…

Products of Krebs Cycle

ATP

NADH

FADH2

Uses electrons carried from glycolysis and

Krebs cycle NADH and FADH2

Travel down ETC- lose E E picked up and used to bring H+ into

intermembrane space of mitochondria- buildup

Electron Transport Chain (ETC)

O2 is final electron acceptor in chain

O2 + H+ + electrons = water!

H+ buildup in intermembrane space Move thru ATP synthase protein

ADP + P ATP LOTS of ATP!

Electron Transport Chain (ETC)

36 ATP produced by 1 glucose Any E not used is released as heat

Why you feel warm after exercise Waste products = CO2 and water

Totals:

6O2 + C6H12O6 = 6CO2 + 6H2O + E

ATPoxygen glucose carbon dioxide water

3 places to get ATP

1. Stored ATP 2. New ATP from lactic acid fermentation 3. New ATP from cell resp.

At first, you can use all three Over time, stored ATP and lactic acid ferm. run

out Then must rely on cell resp. alone

Energy and Exercise

Used stored ATP (only lasts a few

sec) Then lactic acid ferm. (lasts ~90

sec)

Then you go into O2 debt Must be “repaid” by heavy

breathing

Quick Energy

Must rely on cell resp.

Slower at supplying ATP but lasts longer (15-20 min)

E stored in muscles as glycogen After 20 min. the body will breakdown other

compounds for E (fats, proteins, etc)

Long-term Energy

Opposite E flows Photosynthesis provides the food (for plants) Cell Respiration turns it into E for release

Comparing and Contrasting Photosynthesis and Cell

Respiration

Photosynthesis

Cell Respiration

Function Make food (E source)

Energy release from food

Location chloroplasts mitochondria

Reactants CO2, H2O, light E C6H12O6 and O2

Products C6H12O6 and O2 CO2, H2O and E (ATP)

Equation 6CO2 + 6H2O + light E C6H12O6 + 6O2

C6H12O6 + 6O2 6CO2 + 6H2O + E