PhotosynthesisChapter 8

In Your Notebook• Suppose you earned extra money by having a part-time job. At

first, you might be tempted to spend all of the money, but then you decide to open a bank account.

• 1. What are the benefits of having a bank account?

• 2. What do you have to do if you need some of this money?

• 3. What might your body do when it has more energy than it needs to carry out its activities?

• 4. What does your body do when it needs energy?

Chapter Mystery• Read the chapter mystery on page 225.• Answer the following in your notebook:

• Predict how the willow tree gained the extra 75 kilograms in Jan van Helmont’s investigation.

• What process occurring at the cellular level in the plant might be connected to its gain in mass?

8.1 Energy and Life• Energy is the ability to do work

• Cars need fuel• Appliances need electricity

• Do living things need energy?• Playing sports• Sleeping?

• Read 3rd paragraph on page 226• “Energy comes in many forms…….”

ATP• Adenosine Triphosphate

• Chemical fuel for our body• We use it to store and release energy

Storing Energy• ADP – Adenosine Diphosphate

• Contains some energy• Like a partially charged

battery• Add more energy

by adding phosphates

Releasing Energy• ATP can release and store energy by

breaking and re-forming the bonds between its phosphate groups.

In Your Notebook• Read “Using Biochemical Energy” on page

227 in your book.

• Answer the following in your notebook:• With respect to energy, how are ATP

and glucose similar?• How are they different?

Heterotrophs and Autotrophs• Where do living things get the energy they

use to produce ATP?• Chemical compounds found in food

• Heterotrophs• Eat plants or eat animals that eat plants • Mushrooms – decompose other

organisms• Autotrophs

• Make their own food• Use energy from sun to produce high

energy carbohydrates - photosynthesis

8.1 Review – In Your Notebook• Create a newspaper-style comic strip that

shows how cells use ATP to get the energy they need to carry out cell activities.• Include how ATP molecules store and

release energy.• Should be at least 3-5 panels long• Draw cartoon figures to the best of your

ability

8.2 Trapping EnergyIn Your Notebook

• Have you ever used a solar-powered calculator? No matter where you go, as long as you have a light source, the calculator works. You never have to put batteries in it.

• 1. A solar-powered calculator uses solar cells that are found in rows along the top of the calculator. Into what kind of energy is the light energy converted so that the calculator works?

• 2. Most plants, no matter what size or shape they are, have some parts that are green. Which parts of a plant are usually green?

• 3. What does the green color have to do with the plant’s ability to convert light energy into the energy found in the food it makes?

Chlorophyll vs. Chloroplast• Chloroplast

• An organelle found in plants• Chlorophyll

• A pigment found in chloroplasts• Used to capture energy from sunlight• Three types

• Chlorophyll A• Chlorophyll B• Carotenoids

Pigments

• Why do leaves look green?• Why do they turn colors in the fall?

Chloroplasts• Double membraned organelle• Has saclike membranes called thylakoids• Stacks of thylakoids are called grana• Fluid portion is stroma

Energy Collection• Chlorophyll is really good at absorbing visible

light• The energy is quickly and efficiently transferred

to electrons• Energy levels of electrons gets raised

• They get excited• These high energy electrons make

photosynthesis work

In Your Notebook• In your own words, explain why most

plants will not grow well if kept under green light.

Photosynthesis Overview• Photosynthesis uses the energy of sunlight to

convert water and carbon dioxide (reactants) into high-energy sugars and oxygen (products).

• In Symbols• 6CO2 + 6H20 light C6H12O6 + 6O2

• In Words• Carbon dioxide plus water in the presence of

light yields sugars and oxygen

Mystery Clue• Answer the following in your notebook:

• Van Helmont concluded that water must have provided the extra mass gained by the tree. Further studies would prove that he had only half of the answer. What reactant involved in the photosynthesis equation was he not accounting for?

Light-Dependent Reactions• Requires direct involvement of light and light absorbing

pigments• Use energy from sun to produce ATP and NADPH• Happens in thylakoid membrane of chloroplast• Requires water

• Provides electrons to get excited• Oxygen is byproduct

Light-Independent Reactions• No light required• Energy from dependent reactions used to

make sugars from carbon dioxide• Happens in stroma• AKA – Calvin Cycle

8.2 ReviewIn Your Notebook

• Choose two of the following elements of photosynthesis:• Sunlight• Chlorophyll molecule• Chloroplast• High-energy electrons• Light-dependent reactions• Light-independent reactions

• Imagine you are the chosen element and offer a first-person explanation of how you are involved in the process of photosynthesis.

8.3 Factors Affecting Photosynthesis• Temperature

• Enzymes work best at 0o-35oC• Too high or too low enzymes break down

• Light Intensity• More light – more photosynthesis• Eventually reaches maximum

• Water• Source of electrons

• No water – no electrons• Also causes tissue damage

Extreme Conditions• When hot, must conserve water• Plants close stomata so water doesn’t escape but that

means carbon dioxide can’t get in so plant can’t make sugars

• C4 Photosynthesis• Don’t use traditional Calvin Cycle• Allows sugars to be made in intense light and high

temperatures• Takes extra energy (ATP)• Corn, sugar cane and sorghum

• CAM Plant• Only open stomata at night to let air in• Pineapple and cacti

Cellular Respiration• How do you feel when you are hungry?• Weakness is your body’s way of telling you that

your energy supplies are low.• How do you restore those energy supplies?

• In Your Notebook• Read “Chemical Energy and Food” on pg 250• Look at the analyzing data box on page 251• Answer the questions in your notebook

Cellular Respiration• Process that releases energy from food in the presence

of oxygen

• In Symbols• 6O2 + C6H12O6 6CO2 + 6H2O + Energy

• In Words• Oxygen plus glucose yields carbon dioxide, water and

energy

• Seems simple, but can’t happen in one big explosion has to be controlled so energy isn’t wasted

Stages of Cellular Respiration• Glycolysis

• Glucose converted to pyruvic acid• 90% of energy still unused• Happens in cytoplasm

• Krebs Cycle• Pyruvic acid is broken down into

carbon dioxide• Also produces very little energy• Happens in mitochondria

• Electron Transport• Uses high-energy electrons from glycolysis and Krebs

cycle to convert ADP into ATP• Requires oxygen as an electron acceptor• Happens in mitochondria

Oxygen and Energy• Respiration = breathing• Cellular respiration = energy releasing pathways in cell• Most of the energy-releasing pathways within cells

require oxygen, and that is the reason we need to breathe, to respire

• Two types of respiration• Aerobic

• Cellular respiration that requires oxygen• Krebs cycle and electron transport chain

• Anaerobic• Doesn’t require oxygen• Glycolysis

Photosynthesis vs. Cellular Respiration• Photosynthesis removes

carbon dioxide from the

atmosphere, and cellular

respiration puts it back.

• Photosynthesis releases

oxygen into the atmosphere,

and cellular respiration uses

that oxygen to release energy

from food

In Your Notebook• Write the equation for photosynthesis.

• Write the equation for cellular respiration.

• Explain how these two equations are related.

• Be sure to identify which equation is which – you may use symbols