Chapter 4

Cell Processes and Energy

Photosynthesis

Respiration

Cell Division

Cell Differentiation

4.1 Photosynthesis

photosynthesis

• The process by which a cell captures energy in sunlight and uses it to make food.

autotroph

•An organism that makes its own food.

heterotroph

• An organism that cannot make its own food.–Many heterotrophs obtain food by

eating other organisms. (lion, zebra, human)–Some absorb their food from other

organisms. (fungi)

pigment•A color chemical

compound that absorbs light and can be used to

color other materials.

chlorophyll

• The main photosynthetic pigment found in the chloroplasts of plants, algae, and some bacteria.

stomata

• Small openings on a leaf through which oxygen and carbon dioxide can move.

Series (SIHR eez)

• Noun• A number of things or events of the

same class coming one after another in a spatial or temporal succession. • Ingesting food is the first step in a

long series of mechanical and chemical steps.

Photosynthesis

• Like baking cupcakes:– Mix ingredients together– Bake in oven– Yields 12 cupcakes

• “Recipe” for photosynthesis:– Combine carbon dioxide and water– Use energy from sunlight– Yields a sugar molecule and 6 oxygen molecules

Photosynthesis and Food Chains

• How do autotrophs get their food?– They make their own food using sunlight and

photosynthesis.• How does the sun supply heterotrophs with

energy?– Heterotrophs get energy by eating plants or other

animals that eat plants. The plants get their energy from sunlight, so heterotrophs get their energy from sunlight indirectly.

What Happens During Photosynthesis?

• What are the two stages of photosynthesis?–Capturing the sun’s energy and producing

sugars• What is the energy captured in the first

stage used for?– To produce sugars in the second stage

What Happens During Photosynthesis?

• What pigment in chloroplasts absorbs light?–Chlorophyll

• How is chlorophyll like a solar cell?–Both chlorophyll and solar cells absorb

light energy and use it to power a process.

What Happens During Photosynthesis?

• What happens in the second stage?– Water and carbon dioxide combine chemically to

form sugars, and oxygen is released.• How are roots and stomata important for

photosynthesis?– Roots take up water, and stomata take in carbon

dioxide, both of which are needed for photosynthesis.

The Photosynthesis Equation

Light energy

CO2

CO2

CO2

CO2

CO2

CO2

H2OH2OH2OH2OH2OH2O

C6H12O6

O2

O2

O2

O2

O2

O2

6 Carbon Dioxide molecules combine with 6 water molecules due to a chemical reaction from light energy and produce one sugar molecule and 6 oxygen molecules!

6 CO2 + 6 H2O C6H12O6 and 6 O2

Section 2

•Respiration

respiration

• The process by which cells obtain energy from glucose.

• During respiration, cells break down simple food molecules such as sugar and release the energy they contain.

fermentation

• The process by which cells break down molecule to release energy without using oxygen.

Constant (KAHN stunt)

• Noun• Something invariable or unchanging.• When birth and death rates are equal, a

closed population will remain at a constant.

Background Knowledge

• What does a fire need to burn?–Fuel and oxygen

• What is released when fuel is burned?–Energy in the form of heat and

light

Respiration

• A similar chemical process, called respiration, “burns” food molecules in cells.

• Like combustion, respiration uses fuel and oxygen to produce energy.

• The fuel comes from food, and the energy is used for cellular functions.

What is Respiration?

• The process by which cells obtain energy from glucose.

• During respiration, cells break down simple food molecules such as sugar and release the energy they contain.

• All cells respire.

Storing and Releasing Energy

• Like money in a bank– Store it until you want to use it

• Store energy– Plants: photosynthesis captures light energy and

then stores it as sugar and carbohydrates.– Animals: eat a meal – add to your energy savings

account.• Withdraw energy when needed

Breathing and Respiration

• Respiration has two meanings.– 1. breathing – moving air into and out of lungs– 2. the process that takes place inside cells –

sometimes called cellular respiration• Connection– Breathing brings oxygen, which is usually

necessary for cellular respiration, into your lungs.

The Two Stages of Respiration

• Stage 1– Takes place in the cytoplasm– Glucose molecules broken into smaller molecules– Small amount of energy released

• Stage 2– Takes place in the mitochondria– The small molecules are broken down even

smaller– Large amount of energy released

The Two Stages of Respiration

• Two products of respiration– Carbon Dioxide– Water

The Respiration Equation

• C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy• Raw materials for Respiration:– Sugar– Oxygen

Comparing Photosynthesis and Respiration

• Equations are opposite.• Opposite processes• These two processes form a cycle that keeps

the levels of oxygen and carbon dioxide fairly constant in Earth’s atmosphere.

Two methods

of producing and using

energy.

These methods

work together to keep

the atmosphere constant.

Events During Respiration

• Reminder:– The food you eat must be broken down to release

energy it contains.• What is the process called that releases

energy from food?– Respiration

• Why is respiration important to cells?– It provides cells with the energy they need to carry

out their functions.

Events During Respiration

• What happens in the first stage of respiration?– Glucose is broken down into smaller molecules

and a small amount of energy is released.• What happens in the second stage of

respiration?– The smaller molecules are broken down into even

smaller molecules and a large amount of energy is released.

Apply It!

• Why do you think muscle cells have many mitochondria?– The second stage of respiration, which produces

lots of energy, takes place in the mitochondria. – The large numbers of mitochondria in muscle cells

supply a great amount of energy for movement.

Fermentation

• Some cells are able o obtain energy from food without using oxygen.– Some single-celled organisms that live deep in the

ocean or in the mud of lakes or swamps.• Through fermentation, an energy-releasing

process that does not require oxygen.

Alcoholic Fermentation

• Occurs when yeast (and some single-celled organisms) break down sugars.

• Products of this process:– Alcohol– Carbon dioxide– Small amounts of energy

• Important to Bakers and Brewers– Bread rises and has air pockets– Creates bubbles in in alcoholic drinks

Lactic Acid Fermentation

• Occurs when muscle use up oxygen faster than it can be replaced

• Fermentation occurs without oxygen to supply energy.

• Lactic Acid is a product of this type of fermentation

• You would have sore and tired muscles.

Obtaining Energy Without Oxygen

• What is the process in which energy is released without using oxygen?– Fermentation

• What are the products of alcoholic fermentation?– Alcohol, carbon dioxide, and energy

Obtaining Energy Without Oxygen

• What is a product of lactic-acid fermentation?– Lactic Acid

• When might your body release energy using fermentation?– If you are exercising so hard or long that your

muscle cells cannot take up oxygen faster than it is being used.

Section 3

Cell Division