Cellular Respiration: Day 04

Process whereby cells breakdown glucose and other food molecules to release energy.

Updates

• We will test on Cellular Respiration before moving onto Photosynthesis

• Test will be next week sometime– When? It depends on if we miss school for the

elections or not – check our WIKI!!

• Lab – Lets talk about that first!

Lets Review the Cellular Respiration Cycle

• Lets begin with a Respiration Tutorial– Take a look at the big picture!

• When you exercise:

– Muscles need energy in order to perform work.

– Enzymes in muscle cells help the cell convert glucose and oxygen into ATP (usable energy).

• Terms we have discussed: – Aerobic Metabolism– Anaerobic Metabolism– Autotrophs– Heterotrophs– Producers– Consumers

• The ingredients for photosynthesis are carbon dioxide and water.

– CO2 is obtained from the air by pores on a plant’s leaves.

– H2O is absorbed from the damp soil by the roots.

– Veins transport the water from roots to leaves.

• Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules (key products = glucose and oxygen).– Oxygen gas is a by-product of photosynthesis

Chemical Cycling Between Photosynthesis and Cellular Respiration

Photosynthesis

Respiration

• Cellular respiration:

CELLULAR RESPIRATION: AEROBIC HARVEST OF FOOD ENERGY

– The main way that chemical energy is harvested from food and converted to ATP

– This is an aerobic process—it requires oxygen

A common fuel molecule for cellular respiration is glucose.

• This is the overall equation for what happens to glucose during cellular respiration.

Glucose Oxygen Carbondioxide

Water Energy

• Cellular respiration can produce up to 38 ATP molecules for each glucose molecule consumed.

• Cellular respiration is an example of a metabolic pathway (a series of chemical reaction in cells).

• All of the reactions involved in cellular respiration can be grouped into three main stages:

1. Glycolysis

2. The Krebs cycle

3. Electron transport

The Metabolic Pathway of Cellular Respiration

• Why does electron transfer to oxygen release energy?

– When electrons move from glucose to oxygen, it is as though they were falling

– This “fall” of electrons releases energy during cellular respiration

Figure 6.5

Releaseof heatenergy

• The path that electrons take on their way down from glucose to oxygen involves many stops

NADH and Electron Transport Chains

Figure 6.6

1/2

(from food via NADH)

2 H 2 e

Energy forsynthesis

of

Electro

n tran

spo

rt chain 2 e

2 H1/2

A Road Map for Cellular RespirationCytosol

Mitochondrion

High-energyelectronscarriedby NADH

High-energyelectrons carriedmainly byNADH

Glycolysis

Glucose2

Pyruvicacid

KrebsCycle

ElectronTransport

I. Glycolysis (click)Process whereby one glucose molecule is broken in half

producing two pyruvate molecules.

• Takes place in cell’s cytoplasm.

• Does not require O2 to take place.

• Occurs very rapidly, however, low energy yield (Net 2 ATP and 2 NADH produced)

Cell with Mitochondria (red spots)

Mitochondria

Site of Krebs cycle and Electron Transport Chain

II. Krebs Cyle (click)Process whereby pyruvate is broken down into CO2 in a

series of energy releasing reactions.

• Only occurs if O2 is present (aerobic respiration).

• Takes place within the mitochondria of the cell.

• Each pyruvate that goes through the cycle produces 1 ATP, 4 NADH, 1 FADH2 and 3 CO2 (2 X that amount for each glucose molecule).

III. Electron Transport Chain (click)Uses the high energy electrons from NADH and FADH2 to

convert ADP into ATP.• Occurs in proteins that are embedded within the inner membrane of the mitochondria.

• As high energy electrons from NADH and FADH2 are passed from protein to protein in the “chain”, H+ ions are pumped across the membrane.

• H+ ions flow back through ATP synthase which converts ADP into ATP.

• Final electron acceptor in the “chain” is O2 forming a H2O molecule.

• 10 NADH and 2 FADH2 make a total of 34 ATPs.

Adding Up the ATP from Cellular Respiration

Figure 6.14

Cytosol

Mitochondrion

Glycolysis

Glucose2

Pyruvicacid

2Acetyl-

CoA

KrebsCycle Electron

Transport

bydirectsynthesis

by directsynthesis

byATPsynthase

Maximumper

glucose:

The Versatility of Cellular Respiration

• Cellular respiration can “burn” other kinds of molecules besides glucose.

– Diverse types of carbohydrates– Fats– Proteins

FERMENTATION: ANAEROBIC HARVEST OF FOOD ENERGY

• Some of your cells can actually work for short periods without oxygen.

– For example, muscle cells can produce ATP under anaerobic conditions.

• Fermentation– The anaerobic harvest of food energy

Without Oxygen!!!

• We cannot enter the Krebs Cycle

• Must use Anaerobic Respiration– Alcohol Fermentation– Lactic Acid Fermentation

In order for Glycolysis to continue NAD+ must be present.

• Without O2 (anaerobic respiration) the NADH can not move onto the Krebs cycle.

• Think of NADH as “full moving trucks” which must be unloaded for the company to survive.

Like our lab!!

2 ways to “unload” the NADH in anaerobic environments

• Alcohol Fermentation NADH passes electron back to pyruvic acid creating alcohol molecules. Occurs in yeast and other microorganisms

• Lactic Acid Fermentation NADH passes electron back to pyruvic acid creating lactic acid molecules. Occurs with our muscle cells and other prokaryotes (helps make yogurt, kimchi and cheese!)

• Human muscle cells can make ATP with and without oxygen

– They have enough ATP to support activities such as quick sprinting for about 5 seconds

– A secondary supply of energy (creatine phosphate) can keep muscle cells going for another 10 seconds

– To keep running, your muscles must generate ATP by the anaerobic process of fermentation

Fermentation in Human Muscle Cells

• Glycolysis is the metabolic pathway that provides ATP during fermentation.

– Pyruvic acid is reduced by NADH, producing NAD+, which keeps glycolysis going

– In human muscle cells, lactic acid is a by-product

2 ADP+ 2

Glycolysis

Glucose

2 NAD

2 Pyruvicacid

+ 2 H

2 NAD

2 Lacticacid

(a) Lactic acid fermentation

• Various types of microorganisms perform fermentation.

– Yeast cells carry out a slightly different type of fermentation pathway

– This pathway produces CO2 and ethyl alcohol

Fermentation in Microorganisms

Figure 6.15b

2 ADP+ 2

2 ATPGlycolysis

Glucose

2 NAD

2 Pyruvicacid

2 CO2 released

+ 2 H

2 NAD

2 Ethylalcohol

(b) Alcoholic fermentation

• The food industry uses yeast to produce various food products

Figure 6.16

• Respiration tutorial– Both high and low oxygen settings– Copy and paste the questions into your

onenote and answer there. – Read the blurb at the beginning of each

section before pressing play.

Images Citedhttp://www.mir.com.my/rb/photography/companies/canon/fdresources/fdlenses/vinpix/swimmer.jpghttp://www.maratonasant-antonio.com/upload/file_ima_8ce13b8605.jpghttp://www.nationalgeographic.com/adventure/images/0609/everest-thomas-pemmba.jpghttp://www.msu.edu/course/isb/202/ebertmay/images/Energy%20Proc%20PNG.pnghttp://www.kidsco.co.uk/Entertainer%20Images/Fire%20Eater.gifhttp://www.chinadaily.com.cn/english/doc/2005-02/04/xin_530202021019679268915.jpghttp://www.topicsites.com/health-fitness/woman-eating-apple.jpghttp://www.nhnr.org/wcheal/images/Ingredients_Healthy_Food.jpghttp://www.stationnight.com/Homer-Sleep1.gifhttp://dept.kent.edu/projects/cell/tly1.jpghttp://www.a3243g.com/a3243g_images/mitochondria.gifhttp://kentsimmons.uwinnipeg.ca/cm1504/Image110.gifhttp://staff.jccc.net/pdecell/bio122/glycolysis.gifhttp://www.biologycorner.com/resources/fermentation.jpghttp://images.jupiterimages.com/common/detail/53/04/23360453.jpghttp://images.jupiterimages.com/common/detail/11/81/23268111.jpghttp://www.trifood.com/image/kimchi_image_final.JPGhttp://www.thefinalsprint.com/images/2007/01/lactic-acid-training.jpghttp://faculty.ircc.edu/faculty/tfischer/images/Krebs%20overview.jpghttp://student.ccbcmd.edu/~gkaiser/biotutorials/energy/images/chemios_il.jpghttp://fig.cox.miami.edu/~cmallery/150/makeatp/c9x6cell-respiration.jpg