Lesson Lesson OverviewOverview

9.1 Cellular Respiration: 9.1 Cellular Respiration: An OverviewAn Overview

THINK ABOUT IT

– You feel weak when you are hungry because food serves as a source of energy. How does the food you eat get converted into a usable form of energy for your cells?

Chemical Energy and Food

– Food provides living things with the chemical building blocks they need to grow and reproduce.

– Food molecules contain chemical energy that is released when its chemical bonds are broken.

http://en.wikipedia.org/wiki/File:Nutrition-label.jpg

Chemical Energy and Food– Energy stored in food are calories.

– A Calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius.

– 1000 calories = 1 kilocalorie, or Calorie.

– Cells use the energy from fats, proteins, and carbohydrates..

– Cells break down food molecules to make ATP

Comparing Photosynthesis and

Cellular Respiration

– What is the relationship between photosynthesis and cellular respiration?

PHOTOSYNTHESIS AND RESPIRATION

Mitochondria Chloroplast

How ATP is Produced: Cellular Respiration

IN Out

Glucose

Oxygen

ADP

Free Phosphate (P)

Carbon Dioxide

Water

Mitochondrion

The ATP can be used directly to power life processes

ATP

Capturing Light Energy: Photosynthesis

Requirements and products of photosynthesis

IN OutCarbon Dioxide

Water

Light Energy

Glucose

Oxygen

Water

Chloroplast

Overview of Cellular Respiration

– What is cellular respiration?– Cellular respiration is the process that releases

energy from food in the presence of oxygen.

– In symbols:

– 6 O2 + C6H12O6 6 CO2 + 6 H2O + Energy

– In words:– Oxygen + Glucose Carbon dioxide + Water +

Energy

What forms of energy?

ATP Adenosine Triphosphate

How ATP provides energy…

ATP links Anabolism (building molecules) and catabolism (breaking down molecules)!!!!!

Stages of Cellular Respiration

– The three main stages of cellular respiration are …

– Glycolysis,

– the Krebs cycle,

– the Electron Transport Chain.

WE START HERE!!

Glycolysis

– Glycolysis produces only a small amount of energy.

– Glycolysis takes place in the cytoplasm of a cell.

– Gylcolysis is an anaerobic process (no O2 needed)

Glycolysis

Cytoplasm

Glycolysis

• During glycolysis, we start with…• 1 molecule of glucose

• We end with…• 2 ATP• 2 NADH• 2 molecules of pyruvic acid

– (these 2 will be used for the Krebs cycle)

Glycolysis

• ATP production– 2 ATP are used to get it started– 4 ATP are produced during Glycolysis

– SO, a total of 2 ATP are produced for each molecule of glucose that enters glycolysis…

NADH Production– 2 NADH molecules are produced for

every molecule of glucose that enters glycolysis.

– During glycolysis, the electron carrier NAD+ (nicotinamide adenine dinucleotide)

accepts a pair of high-energy electrons and becomes NADH.

- Electrons are carried by NADH to the electron transport chain to make more ATP.

The Advantages of Glycolysis

– Glycolysis produces ATP very fast, which is an advantage when the energy demands of the cell suddenly increase.

– Glycolysis does not require oxygen, so it can quickly supply energy to cells when oxygen is unavailable.

NET PRODUCTION OF ATP = 2

Stages of Cellular Respiration

– What molecule is entering the Kreb’s Cycle?

– 2 Pyruvic Acid Molecules

– During the Krebs cycle, a little more energy is generated from pyruvic acid.

Stages of Cellular Respiration

• Glycolysis – takes place in cytoplasm and requires no oxygen

• Krebs Cycle – takes place in mitochondria and requires oxygen

• Electron Transport Chain – takes place in mitochondria, requires oxygen and produces A LOT of energy

Kreb’s CycleKreb’s Cycle

The Process of The Process of Cellular Cellular

RespirationRespiration

The Krebs Cycle

– During the Krebs cycle, pyruvic acid is broken down into CO2

– The Krebs Cycle is also known as the citric acid cycle due to the citric acid that is formed…

Citric Acid Production– pyruvic acid enters the

mitochondria..

– NADH, CO2 and acetyl-CoA form from electrons and carbon atoms.

– Acetyl-CoA combines with a 4-carbon molecule to produce citric acid.

Energy Extraction

– Citric acid breaks down into a 5-carbon compound and a 4-carbon compound.

– The 4-carbon compound can then start the cycle again by combining with acetyl-CoA.

Energy Extraction

– Breaking bonds causes a release of energy.

– ATP, NADH, and FADH2 catch and store this released energy.

Energy Extraction

– Remember!

– Each molecule of glucose results in 2 pyruvic acids..

– 2 pyruvic acids = two complete “turns” of the Krebs cycle.

– 2 pyruvic acids make….

– 6 CO2

– 2 ATP

– 8 NADH

– 2 FADH2

2 pyruvic acids enter the Krebs Cycle, but what would only ONE

pyruvic acid produce?

–3 CO2

–1 ATP–4 NADH

–1 FADH2

Electron Transport and ATP Synthesis

– How does the electron transport chain use high-energy electrons from glycolysis and the Krebs cycle?

– The electron transport chain uses the high-energy electrons from glycolysis and the Krebs cycle to convert ADP into ATP.

Electron Transport

– NADH and FADH2 bring their high-energy electrons to electron carrier proteins in the electron transport chain.

Electron Transport

– At the end of the ETC, electrons combine with H+ ions and oxygen to form water.

Electron Transport– Energy from the ETC moves H+ ions up

the concentration gradient into the intermembrane space.

– H+ ions are building up…

ATP Production– H+ ions pass back quickly across the

mitochondrial membrane through the ATP synthase

– This causes ATP synthase molecule to spin. – With each rotation, the ATP synthase makes 1ATP.

– For every glucose molecule, ATP synthase will spin 34 times and 34 ATP are produced.

FermentationFermentation

Fermentation

– How do organisms generate energy when oxygen is not available?

– In the absence of oxygen, fermentation releases energy from food molecules by producing ATP.

Fermentation

– Fermentation is a process by which energy can be released from food molecules in the absence of oxygen.

– Fermentation occurs in the cytoplasm of cells.

Fermentation

– Under anaerobic conditions, fermentation follows glycolysis.

– During fermentation, cells convert NADH produced by glycolysis, which allows glycolysis to continue producing ATP.

Alcoholic Fermentation– Yeast and a few other microorganisms

use alcoholic fermentation that produces ethyl alcohol and carbon dioxide.

– This process is used to produce alcoholic beverages and causes bread dough to rise.

Alcoholic Fermentation– Chemical equation:

– Pyruvic acid + NADH Alcohol + CO2 + NAD+

Lactic Acid Fermentation– Most organisms, including humans, carry out

fermentation using a chemical reaction that converts pyruvic acid to lactic acid.

– Chemical equation:

– Pyruvic acid + NADH Lactic acid + NAD+

Energy and Exercise

– How does the body produce ATP during different stages of exercise?

– For short, quick bursts of energy, the body uses ATP already in muscles as well as ATP made by lactic acid fermentation.

– For exercise longer than about 90 seconds, cellular respiration is the only way to continue generating a supply of ATP.