Photosynthesis and Cellular Respiration

Outline1I. Photosynthesis

A. IntroductionB. Reactions

II. Cellular RespirationA. IntroductionB. Reactions

Photosynthesis

Method of converting sun energy into chemical energy usable by cells

Word Equation: Carbon dioxide + water + sunlight glucose + oxygen

Chemical Equation:

6CO2 + 6H2O + Energy C6H12O6 + 6O2

Photosynthesis takes place on The thylakoid membrane in a specialized structures

inside plant cells called chloroplasts– Light absorbing pigment molecules e.g. chlorophyll

Chlorophyll absorbs red and blue light from the sunlight that falls on leaves.

Therefore, the light reflected by the leaves is diminished in red and blue and appears green to our eyes. 

How do we explain for these colors?

• In the fall, lower temperature and lack of sun light slows down the production on chlorophyll pigment

• Other pigments in leaves including the carotenoids become dominant.

• They reflect orange and red color; thus, making leaves appear so

Photosynthesis involves 2 reactions:1. Light dependent reaction2. Light independent reaction (Calvin cycle)

1. Light dependent reaction: occurs in the thylakoid membrane inside the chloroplast

1a. Light energy is absorbed by the chlorophyll

1b. Electrons jump out of the chlorophyll atoms

1c. Electrons move down the electron transport chain (series of proteins that pass the electrons along). Electrons are caught by the NADPH compound. ATP is made.

1d. Photolysis: Water is broken down into oxygen (given off by plant) and electrons (replace lost electrons in chlorophyll). These electrons recharge the system so the light reaction can happen again.

2. Dark reaction- Calvin cycle: occurs in the stroma of chloroplast

2a. Electrons and ATP from light reaction get dumped into the Calvin Cycle to run it

2b. Calvin Cycle: Series of steps that build up compounds using carbon dioxide from the air

2c. PGAL compound sometimes leaves the cycle. 2 PGAL compounds added together make 1 glucose.

http://www.youtube.com/watch?v=joZ1EsA5_NY

- Photosynthesis transforms sunlight energy into chemical energy stored in the bonds of glucose molecules

Cellular Respiration Overview A process occurs in the mitochondria where

chemical energy stored in food is converted into ATP

Occurs in both Plants and AnimalsOverall Reaction

Word Equation: glucose + oxygen Carbon dioxide + water + energy

Chemical Equation:

C6H12O6 + 6O2 6CO2 + 6H2O + Energy

Cellular Respiration

Aerobic cellular respiration

Anaerobic cellular respiration (aka fermentation)

requires NO oxygen and carried out by yeast, some bacteria, and sometimes animals

requires oxygen and carried out by plants, animals, and some bacteria

Steps of aerobic respiration1. Glycolysis: First step breaks down glucose into pyruvate(Intermediate step: Change pyruvate to acetyl CoA)

2. Citric Acid Cycle: Second step uses the acetyl CoA to make electrons for the last step

3. Electron transport chain: Third step uses the electrons to make a lot of ATP

•Also called fermentation• 2 types: alcoholic fermentation

and lactic acid fermentation- Both begin with glycolysis- No citric acid cycle or

electron transport chain

Glycolysis (does not require O2)

How many ATP made?

Glucose

How many ATP made?

How many ATP made?

32

ATP tally for aerobic respiration:

Glycolysis : 2 ATPCitric Acid Cycle : 2 ATPElectron Transport Chain : 32 ATP

1 Glucose generates 36 ATP in all for aerobic respiration

Summarizing CR:http://www.sumanasinc.com/webcontent/animations/content/

cellularrespiration.html

Alcoholic fermentation:Pyruvate ethyl alcohol +

carbon dioxide

Lactic acid fermentationPyruvate lactic acid

• Carried out by yeast and some bacteria

• Used in brewing beer, making wine, and baking bread and cakes

• Carried out by your muscles when you’re exercising hard (need ATP) and can’t get oxygen into you fast enough (can’t do aerobic respiration)

• Causes muscle cramps and soreness

Anaerobic Cellular Respiration (or Fermentation)

FERMENTATION

Compare PS and CR

They’re complimentary processes. Why?Because reactants of one are the products of the

otherThe simple story between PS and CR: http://ed.ted.com/on/CySfbPZ9

CO2, water

CO2, water

Glucose (C6H12O6),O2

Glucose (C6H12O6)

yes yes

yesno

no

no

yes

yes

Hands-on clothespin labLactic acid fermentation

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