CHAPTER 8PHOTOSYNTHESIS

ENERGY AND LIFE Living things depend on energy

Sun is source of most energy

2 types of organisms, – AUTOTROPHS make their own food (Ex: plants,

bacteria*, protists*)– HETEROTROPHS get energy from the foods they

consume (animals, fungi)

Research On Photosynthesis

– VAN HELMONT- determined in the 1600’s that plants grew because of water.

– PRIESTLEY- found that plants release oxygen.

– JAN INGENHOUSZ- found aquatic plants produce oxygen bubbles in the light, therefore plants need sunlight to produce oxygen

AN OVERVIEW OF PHOTOSYNTHESIS

Plants use the energy of sunlight to

– convert water & carbon dioxide into high energy carbohydrates (sugar)

– oxygen is a waste product.

light

6H2O + 6CO2 → C6H12O6 + 6O2

Reactants Products

What Else Does The Photosynthesizer Need?

Chlorophyll- a chemical pigment that traps the energy of the sun and converts it to chemical energy

Capturing Light Energy

White light= ROY G BIV Chlorophyll captures (absorbs) energy at the

ends of the spectrum (red/orange & blue/violet) What you see is the wavelengths that are

reflected. (green)

2 Types of Chlorophyll

Chlorophyll a Chlorophyll b

How Chlorophyll Works

Sunlight excites e-s in the chlorophyll molecule.

These excited e-s perform the work of photosynthesis.

Where Photosynthesis Occurs

In the chloroplast

CHLOROPLASTS contain saclike

photosynthetic membranes called THYLAKOIDS

Thylakoids arranged in stacks called GRANA.

Surrounding grana is a gel-like substance-STROMA.

Photosynthesis begins in thylakoid membranes.

The Recipe of Photosynthesis

Photosynthesis Cycle and Teasers

Flow of energy in Photosynthesis

Sunlight energizes the e-s in chlorophyll

Carriers are needed to move these e-s (& their energy) to fuel photosynthesis

Carrier molecules are used!

ANALOGY Fire heats up coals

Carrier is needed to move these coals to another place

A bucket is used!

e- Carriers & the e- Transport Chain

NADP+

(Nicotinamide adenine dinucleotide phosphate)

Accepts & holds a pair of e-s & an H atom to become NADPH

ATP

(adenosine triphosphate)

Holds energy in the bond holding the 3rd phosphate

Photosynthesis is Many Reactions

Light-dependent rxns “"charging the batteries" Location: thylakoid

membranes Reactants:H2O, NADP+

& ADP Products: O2, NADPH &

ATP

Calvin cycle (light- independent rxns)

“Discharging your batteries”

Location: stroma Reactants: CO2,

NADPH, & ATP Products: Sugar, NADP,

& ADP

1. Summarize the light-dependent reactions

2. What reactions make up the Calvin Cycle?

3. How is light energy converted into chemical energy during photosynthesis?

4. What is the function of NADPH?5. Why are the light dependent reactions important to the Calvin Cycle?

Photosynthesis is Many Reactions

Light-dependent rxns Requires sunlight

energy

Calvin cycle (light- independent rxns)

Doesn’t require sunlight energy!

ATP synthase

Is an enzyme (“-ase” ending is a hint)

Is a membrane protein.

It is a protein pump that allows H+ ions to pass thru the cell membrane

This is necessary for the formation of ATP

CHEMICAL ENERGY AND ATP

All living things use chemical energy A chemical compound that cells use to store and

release energy is ATP (ADENOSINE TRIPHOSPHATE).

ATP is like a fully charged battery ready to power the machinery of a cell.

ATP powers many cellular activities Ex: – active transport across cell membranes, – protein synthesis – muscle contraction.

FACTORS THAT AFFECT PHOTOSYNTHESIS

Amount of Water

Amount of CO2

Temperature

Intensity of Light

Wavelength of light

The process of photosynthesis includes the LIGHT-DEPENDENT REACTIONS as well as the CALVIN CYCLE.

LIGHT DEPENDENT REACTIONS – produce oxygen gas and convert ADP and NADP into

the energy carriers ATP and NADPH.

CALVIN CYCLE – uses ATP and NADPH from the light-dependent

reactions to produce high energy sugars.

SUMMARY OF PHOTOSYNTHESIS

CHAPTER 9 CELLULAR RESPIRATION

(In the last chapter, we learned how photosynthe-sizing organisms (such as plants) take energy from sunlight & trap it in sugar (glucose) molecules.)

Now we will learn how living things release this energy to fuel their daily activities.

CHEMICAL ENERGY AND FOOD

The CALORIE is used to measure the amount of energy present in food. .

“calorie” v. “Calorie”-what’s the difference?

calorie- the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius.

Calorie- 1000 calories– More accurately named a “kilocalorie”– The unit used on food packages.

Quick Review of Organic Molecules in Living Things

Carbohydrates (sugars, starches, etc.) Proteins Lipids (mainly fats) Nucleic acids (ATP, NADP, RNA, DNA)

Where’s the Energy?

Energy is trapped in the chemical bonds in organic compounds in food.

Ex: plants convert sunlight energy into chemical energy in glucose (sugar)

When we break down glucose (& other organic compounds), the energy is released again!

Cellular Respiration

the process living things use to releases energy by breaking down glucose and other food molecules in the presence of oxygen

Cellular Respiration

• Cells do not “burn” glucose, instead they slowly release energy from glucose and other food compounds

• They do this in many small steps-WHY?

If all the energy was released once, it would be too much for the cell

and it would be destroyed!

Summary of Cell Respiration

Sugar + oxygen → water + carbon dioxide + energy

C6H12O6 + 6O2 → 6H2O + 6CO2 + energy

Cellular Respiration

ATP is the main molecule that is used to provide direct energy for cell activities. (electron carrier)

Remember, ATP is like a rechargeable battery. Basically, the energy in 1 glucose molecule is

transferred into many ATP molecules to be used little by little. (Kind of like breaking a $100 bill into $1s or $5s to be used little by little for purchases.)

GLYCOLYSIS is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid.

C6H12O6 → (2) 3-Carbon molecules (pyruvic acid)– (see Fig 9-3, p 223 of text)

Releasing Energy From Glucose Step 1: Glycolysis

Glycolysis, cont.

GLYCOLYSIS comes from the Greek word glukus meaning “sweet” and the Latin word lysis which means decomposing.

Thus GLYCOLYSIS means “breaking glucose”.

Glycolysis, cont.

Takes place in the cytoplasm

Releases a small amount of energy – (2 ATP & 2 NADH) & H2O

Is ALWAYS the first step of releasing energy from glucose.

SUMMARY OF GLYCOLYSIS

Reactants: Glucose, ADP, NAD+

Products: 2 ATP, NADH, H2O

WHAT FOLLOWS GLYCOLYSIS?

AFTER glycolysis, living things can release more energy from sugar.

How they do it depends on WHETHER OR NOT O2 IS PRESENT.

Releasing Energy From Glucose: Flow Chart

RED: Fermentation}

{Red + Blue = Cell Respiration

When O2 is not present, GLYCOLYSIS is followed by a process called FERMENTATION.

“No air”=“Anaerobic Pathway”FERMENTATION releases a small

amount of energy from food by producing ATP w/o O2

Releasing Energy From Glucose Step 2A: Fermentation

1. ALCOHOLIC FERMENTATION produces carbon dioxide and alcohol. This type of fermentation causes bread dough to rise.

• Reactants: pyruvic acid, NADH• Products: CO2 , alcohol (ethanol), NAD+

.

2 Types of Fermentation

2 Types of Fermentation, cont.

2. LACTIC ACID FERMENTATION is produced in your muscles during rapid exercise when the body cannot supply enough oxygen to the tissues.

With rapid exercise your muscles run out of oxygen. Your muscle cells rapidly begin to produce ATP by LACTIC ACID FERMENTATION

Fermentation

Also occurs in the CYTOPLASM

Step 2B:KREBS CYCLE

Occurs –when O2 is present (“aerobic”)–In the mitochondria (the powerhouse of the cell)

THE KREBS CYCLE

Pyruvic acid is converted into citric acid (Krebs is also known as “Citric Acid Cycle”)

Citric acid is then broken down, releasing carbon dioxide and many ATPs in a series of small reactions

REACTANTS: O2, pyruvic acid, NAD+, FAD, ADP PRODUCTS: CO2, NADH, FADH, ATP,

about 38% of the total energy of glucose is trapped in ATP & can be used by the cell.

The remaining 62% is released as heat, which is why your body feels warmer after vigorous exercise.

Energy Efficiency of Cell Respiration

QUICK VS. LONG TERM ENERGY

QUICK ENERGY- 1. ATP stored in muscles-only enough ATP

for a few seconds of intense activity2. Lactic Acid Fermentation- when the ATP

is almost gone, the muscles begin producing most of their ATP by this method.– This can last about 90 seconds.

QUICK VS. LONG TERM ENERGY (cont.)

LONG TERM ENERGY- cellular respiration is the only way to generate a continuing supply of ATP.– C.R. produces a lot of energy BUT it does so more slowly

than fermentation

3. You have enough glycogen, (a carb) in your muscles & other tissues) for about 15 or 20 minutes of activity.

QUICK VS. LONG TERM ENERGY (cont.)

LONG TERM ENERGY (CONT.)

4. After that, your body begins to break down other stored molecules including fats for energy. This is why aerobic forms of exercise like running, swimming etc. are beneficial for weight control.