A. chloroplast B. photosynthesis C. cellular respiration D. glucose E. fermentation F. chemical energy G. mitochondria ____ 1. To stay alive, a cell must be able to release the ____________ that is stored in a molecule's bonds. ____ 2. ____________ is the process by which plants produce glucose and oxygen. ____ 3. A major energy source for most cells is a sugar molecule called ____________. ____ 4. Cells use oxygen to release the energy in glucose during ____________. ____ 5. Cellular respiration takes place in a cell's ____________. ____ 6. If a muscle cell does not have enough oxygen, it can still release energy through the process of

____________.

1. F. chemical energy 2. B. photosynthesis 3. D. glucose 4. C. cellular respiration 5. G. mitochondria 6. E. fermentation

A. chloroplast B. photosynthesis C. cellular respiration D. glucose E. fermentation F. chemical energy G. mitochondria ____ 1. To stay alive, a cell must be able to release the ____________ that is stored in a molecule's bonds. ____ 2. ____________ is the process by which plants produce glucose and oxygen. ____ 3. A major energy source for most cells is a sugar molecule called ____________. ____ 4. Cells use oxygen to release the energy in glucose during ____________. ____ 5. Cellular respiration takes place in a cell's ____________. ____ 6. If a muscle cell does not have enough oxygen, it can still release energy through the process of

____________.

Time CO2 (ppm)12:00am 9001:00 am 9122:00 am 9303:00 am 9484:00 am 955

Chapter 2: How Cells Function

Have already learned:-the cell is the basic unit of all living things-Plant cells and animal cells have -similarities and differences

2.1: Chemical reactions take place inside cells2.2: Cells capture and release energy2.3: Materials move across the cell’s membranes

Will learn:-why cells need energy-How energy is captured and stored-How plants and animals get energy

All cells need energy

• Animal cells, plant cells, bacteria cells, unicellular organisms: ALL need energy– Animals get it from food– Plants get it from the sun

• Type of energy = chemical energy!– Cells must release the chemical energy stored in

bonds (between atoms) in order to stay alive• Cells release chemical energy from glucose

(sugar molecule)

All cells need energy• Muscle cells – release chemical energy from

glucose to move legs • More running, more glucose

needed

• Energy from?– food!

• For plants:– Sunlight + water + CO2 glucose

+ O2

Some cells capture light energy• Source of ALL energy?

– Ultimately…the SUN!• Photosynthesis – process that plants cells use:

– Energy from sunlight into chemical energy– Takes place in plant cells that have chloroplasts

• Chloroplasts contain chlorophyll• Chlorophyll absorbs light

1. Starting materials: carbon dioxide (air) + water (soil)

2. The process:Materials enter chloroplasts

+ energy (sunlight)

3. The products: Glucose and Oxygen!

Some glucose is linked together to build large carbohydrates: • stored as starch

All cells release energy

• Glucose and other sugars are “cell food”– Glucose is stored as glycogen or starch

• Must be broken down to use as energy• Break the bonds of sugar – release energy!

• Two ways: – Respiration

• Requires oxygen• Release more usable energy than fermentation

– Fermentation• Does not require oxygen

Cellular Respiration

• Think: reverse of photosynthesis…occurs in mitochondria (chloroplasts)1. Starting materials: oxygen and sugar

– USE oxygen to RELEASE energy stored in sugars, such as glucose• Gain oxygen and sugars

2. The process:– Glucose in cytoplasm is broken down into smaller molecules, releasing some energy– Molecules move to mitochondria and oxygen enters cell (and moves to mitochondria)– The smaller molecules are further broken down

• Hydrogen released (combines with oxygen to make water)

3. The products – Energy, carbon dioxide, water (starting products of …)

• Some of this energy is transferred to other molecules, so is released as heat

Fermentation• Cells releasing energy withOUT oxygen• When cells first break glucose into smaller

molecules, a small amount of energy is released– With oxygen…cellular respiration would continue in the

mitochondria– Without oxygen…fermentation continues in the

cytoplasm• Two types: Alcoholic and Lactic Acid Fermentation– Both start with small molecules made from sugars– Next reactions occur producing either alcohol and carbon

dioxide OR lactic acid– In both, a small amount of energy is then released

Fermentation• Examples: – Bread: mix flour, milk, and sugar, with a

microorganism yeast• Without oxygen, yeast converts the sugar into alcohol

and carbon dioxide (CO2) – bubbles of CO2 gas form in the dough causing it to rise…alcohol evaporates, the yeast is killed, and CO2 makes the bread spongy

– Yogurt, cheese, sourdough bread• Lactic acid bacteria convert the sugars found in milk

– Sourdough bread: acidity changes sour flavor– Yogurt and cheese: milk partially solidifies: creamy texture of

yogurt…if fermentation continues cheese

Energy and exercise

• Some cells (and organisms) can release energy using either cellular respiration or fermentation– At rest, muscle cells store both energy and oxygen– During exercise all the energy and oxygen may be used

up• Fermentation is then used to break down the sugars

– Less energy than with cellular respiration– Waste product: lactic acid = burns!

• Breath hard to replace used oxygen• Muscles stop hurting and build back up oxygen and energy

levels

• http://www.cambridgestudents.org.uk/subjectpages/biology/igcsebiology/igcsebiologysimulations

• Grow a plant