CELLULAR RESPIRATION AND FERMENTATION

CELLULAR RESPIRATIONAND

FERMENTATION

DEFINITION

Cellular Respiration – Process of obtaining energy from the chemical bonds of food molecules (glucose), with the use of oxygen.

EXTERNAL VS CELLULAR RESPIRATION

1) External Respiration – Organism takes in oxygen and gives off carbon dioxide

-- breathing

EXTERNAL VS CELLULAR RESPIRATION

2) Cellular Respiration – Every cell in the organism breaks down food (glucose) with the use of oxygen.

Glucose and Oxygen

Glucose and Oxygen

Carbon dioxide and water

IMPORTANCE

It’s how cells get energy from food.

IMPORTANT TERMS

Aerobic – with the use of oxygen

IMPORTANT TERMS

Anaerobic – without the use of oxygen (in the absence of oxygen)

WHERE CELLULAR RESPIRATION TAKES PLACE

1) In the mitochondria of most organisms: animals, plants, single-celled organisms.

NECESSARY THINGS

1) Glucose (other carbohydrates get digested into glucose first).

NECESSARY THINGS

2) Oxygen

WHAT IS PRODUCED

1) ATP – the energy produced is stored in this compound until needed

WHAT IS PRODUCED

2) Carbon dioxide – given off

CO O

WHAT IS PRODUCED

3) Water – given off as water vapor

SIMPLE EQUATION

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP

Glucose + oxygen → carbon dioxide + water + ATP (stored energy)

MORE PRECISE EQUATION (Shows how the ATP is formed)

C6H12O6 + 6 O2 + ADP + P → 6 CO2 + 6 H2O + ATP

STAGES OF CELLULAR RESPIRATION

Cellular respiration takes place in 2 stages:


1) Glycolysis – The break down (lysis) of glucose molecules into two 3-carbon molecules of pyruvic acid.


-- Takes place in the cytoplasm of cells


-- Is anaerobic – oxygen is not needed


-- Produces 2 ATP molecules (stored energy) -- not very efficient in releasing energy from

glucose


2) Aerobic Cellular Respiration -- Starts with pyruvic acid


-- Takes place in the mitochondria of cells


A) Formation of acetyl Co-A -- Pyruvic acid gives off carbon dioxide,

combines with Coenzyme A, and becomes acetyl-CoA


-- Also NADH is made


B) Citric Acid Cycle -- Also called the

Krebs Cycle


-- Is aerobic – oxygen is needed


-- Is a cycle through which several reactions take place:

-- Carbon dioxide is produced

(and given off)


-- NADH is made from NAD and H2

-- FADH2 is made from FAD and H2

-- 2 molecules of ATP are produced


C) Electron Transport Chain -- Takes place in the inner system of membranes

(cristae) in the mitochondria -- Similar to the thylakoid membrane of a chloroplast


-- NADH and FADH2 are called electron carriers (have energized electrons) -- They pass the energized electrons (H+ ions)

from protein to protein


-- Finally, the H+ ions are passed to oxygen and water is made (and given off)


-- Energy is released along the way -- It’s used to add P to ADP to make ATP (stores

the energy) -- Up to 34 molecules of ATP are produced

(under ideal conditions)

BIOCHEMICAL PATHWAY

-- Linked set of chemical reactions – involve many steps

BIOCHEMICAL PATHWAY

Examples:

A) Photosynthesis: Light-dependent reactions (Electron transport chain, splitting water), light-indepenent reactions (Calvin Cycle)

BIOCHEMICAL PATHWAY

B) Cellular respiration – Glycolysis. Citric Acid Cycle (Krebs Cycle), Electron transport chain

COMPARING PHOTOSYNTHESIS AND CELLULAR RESPIRATION

They are opposite reactions


A) Photosynthesis – captures and stores light energy in form of glucose


-- Uses carbon dioxide and water


-- Gives off oxygen as a by product


2) Respiration – Release chemical energy from food (glucose) in form of ATP (stored energy)


-- Uses glucose and oxygen


-- Gives off carbon dioxide and water

FERMENTATION

-- Alternate method to aerobic cellular respiration for releasing energy from food

-- Is anaerobic – no oxygen is needed

FERMENTATION

-- Glycolysis takes place first – just as in cellular respiration

-- Then fermentation occurs instead of aerobic cellular respiration

FERMENTATION

-- Is not very efficient at releasing energy -- Only 2 molecules of ATP (stored energy) are

produced from a molecule of glucose

FERMENTATION

Two Types of Fermentation:

1) Alcoholic Fermentation – Done by yeasts (single-celled organisms)

FERMENTATION

A) Overall equation:

Glucose → ethyl alcohol + carbon dioxide + ATP

FERMENTATION

B) Useful in the production of: -- Bread -- Use Baker’s Yeast -- Produce more carbon dioxide than alcohol

FERMENTATION

-- The carbon dioxide gas bubbles make the dough rise

-- The alcohol evaporates during baking

FERMENTATION

-- Alcoholic Beverages (beer and wine) -- Use Brewer’s Yeast -- produces more alcohol

FERMENTATION

2) Lactic Acid Fermentation – Done by some bacteria and animal cells whenever there is not enough oxygen

FERMENTATION

A) Overall equation:

Glucose → lactic acid + ATP (stored energy)

FERMENTATION

B) Useful in the production of cheese -- Use a certain kind of bacteria -- They feed on the milk and give off lactic acid,

which sours the milk, turning it into curds and whey (cottage cheese).

FERMENTATION

-- The curds can be pressed and aged to make hard cheeses

FERMENTATION

C) Takes place in animal cells whenever there is not enough oxygen

FERMENTATION

-- In humans, occurs in muscle cells during heavy exercise

-- When you’re “out of breath”, cells may not have enough oxygen

FERMENTATION

-- Allows you to still get some energy in the low-oxygen state

FERMENTATION

-- Lactic acid builds up in the muscle tissues -- a little causes a tired feeling -- a lot may cause a muscle cramp

FERMENTATION

-- Eventually, the lactic acid is transported to the liver and turned into pyruvic acid; once it leaves the muscle, the tired feeling goes away.

THE END

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CELLULAR RESPIRATION AND FERMENTATION