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Unit 3: Energy, Photosynthesis, and Cellular Respiration
Standards for Unit 3
4.2.1
Analyze photosynthesis and cellular respiration in terms of how energy is stored, released, and
transferred within and between these systems
Unpacking:
• Analyze overall reactions including reactants and products for photosynthesis and cellular respiration
and factors which affect their rates (amounts of reactants, temperature, pH, light, etc.).
• Compare these processes with regard to efficiency of ATP formation, the types of organisms using
these processes, and the organelles involved. (Anaerobic respiration should include lactic acid and
alcoholic fermentation.)
Note: (1) Instruction should include the comparison of anaerobic and aerobic organisms. (2) Glycolysis,
Kreb’s Cycle, and Electron Transport Chain are not addressed.
Energy is the ability to do work.
Where does energy come from? food
Energy in food comes from? sun
Chemical Energy:
 Living things use chemical energy. ATP is the chemical compound that cells use to store and
release energy. **** All organisms must have ATP in order to function.
 ATP is the universal energy molecule for all cells.
o Adenosine Triphosphate
o Label the parts of this ATP molecule:
How many high energy bonds are
in ATP?
o
o
Energy is released by breaking the bonds. ATP-> ADP +P
Energy Cycle:
o ADP (adenosine diphosphate) consists of adenine, ribose and 2 phosphate groups.
o Energy is continuously cycled in the biochemical pathway as ATP is converted to ADP
and then ADP is converted into ATP
o ADP (adenosine diphosphate) can then gain an extra P to recharge back to ATP.
Energy is stored when the phosphate bonds are formed.
Chemical Reactions
o Reactants: substances that are used during a chemical reaction.
o Products: substances made after a chemical reaction.
o Metabolism is the sum total of all chemical reactions in a cell.
Energy is taken in, stored and used differently by different organisms.
 Light energy from the sun is used by plants to make glucose in a process called photosynthesis.
 Energy from the glucose is used by organisms to make more energy in a process called cellular
respiration.
Plants and some other types of organisms are able to use light energy from sun to produce food,
others cannot use the sun.
Autotrophs: organisms that make their own food (ex. Plants)
Heterotrophs: obtain energy from the food they consume (ex. People)
PHOTOSYNTHESIS AND THE LEAF
Overview: 6CO2 + 6H2O -> C6H12O6 + 6O2 (This is the equation)
Who does photosynthesis? plants
Where in the cell does it occur? Chloroplast
What goes into the
reaction?
What comes out of
the reaction?
Pigments: capture light energy
- Chlorophyll is the main pigment found in most producers (plants)
Inside the chloroplast:
Thylakoids membranes of chloroplast contain chlorophyll and proteins that absorb light
Stroma: liquid portion inside chloroplast
Two steps of photosynthesis:
1. Light Dependent Reactions:
a. Where: in the thylakoid membranes
b. What: sunlight is absorbed by chlorophyll (excites electrons) and water is split by light.
c. Why?: to provide ATP for step 2
d. Purpose: Take sunlight and turn it into chemical energy (ATP)
e. Needs chlorophyll in the chloroplast
f. Light and water in-> ATP and oxygen out
2. Light independent reactions (Dark) Reactions: (Calvin Cycle)
a. Where: stroma
b. What: Takes ATP from step 1 and CO2 and makes glucose
c. Purpose: Takes CO2 and makes glucose
d. CO2 and ATP in -> glucose out
Label the picture below with: water, sunlight, CO2, O2, and glucose
Summary of Photosynthesis
 Who does it? ______________________
 Where does it happen in the cell? ________________________
 What is made? _______________________ and ______________________
 Plants take in ________________, _______________ _______________, ______________
 Plants put out _____________________________, ________________________________
Leaves and leaf parts:
Mesophyll ground tissue leaves, contains chloroplast.
Xylem: carries water
Phloem: carries nutrients
Stomata: tiny openings that allow gas exchange.
Guard Cells: Cells that open and close the stomata
Epidermis: outer layer of leaf cells
Cuticle: waxy covering of leaf
Label the cuticle (used twice), epidermis (used twice) , guard cell, chloroplast, and stomata below.
Factors that affect the rate of photosynthesis:
1. Amount of sunlight
2. Amount of water
3. Amount of carbon dioxide
CHEMOSYNTHESIS
- Process by which some organisms produce energy through a chemical reaction. (ex.
Bacteria) These are also autotrophs.
CELLULAR RESPIRATION
 The process by which food (glucose) is broken down to produce ATP.
 Who does it? ALL living organisms
 C6H12O6 + 6O2 -> 6CO2 + 6 H2O (chemical equation)
 Starts with Glycolysis: (“splitting of sugar”)
a. Breaks down glucose into two molecules of pyruvate
b. Occurs in the cytoplasm of the cell
c. Anaerobic- does not require
Glucose
oxygen
d. Makes 2ATP
e. Not very effective at making
energy
Pyruvate
2 ATP
 After glycolysis two things can happen:
1. If oxygen is present pyruvate enters the mitochondria
a. Citric Acid Cycle (AKA Kreb Cycle)
Series of steps to modify the pyruvate and create ATP… in this process carbon
dioxide is released as waste
2 ATP made
b. The Electron Transport Chain
Electrons fall down a gradient and are used to create ATP
Produces 32 ATP
So: AEROBIC RESPIRATION produces 36-38 ATP (very effective)
By end produces 36 ATP!!!! Lots of energy
2. Anaerobic Respiration
o Occurs when no oxygen is available
o Also called fermentation
o only produces 2-4 ATP
2 types:
1. Alcoholic Fermentation
a. Glucose -> ethanol + CO2 + 2ATP
b. Who??? Yeast -> used in beer brewing, wine making and baking
c. Produces: Ethyl Alcohol and CO2
2. Lactic Acid Fermentation
a. Glucose -> lactic acid + 2 ATP
b. Lactic acid fermentation by some bacteria is used to make yogurt
c. Human muscle cells use lactic acid fermentation to generate ATP when O2 is scare
d. Produces: soreness/ pain in muscles
Cellular Respiration Summary:
o Where in cell: cytoplasm and mitochondria
o Job-> convert food energy into energy for the cell (ATP)
o Equation: C6H12O6 + O2 -> CO2 + H2O + ATP
Use this word bank to plug into the shapes above: autotroph, heterotroph, ATP, glucose, CO2, O2, H20
Fill in the boxes below:
Label the squares:
What organelle is
water, glucose,
oxygen, CO2
this?
1.
What organelle is
Is this an autotroph
2.
or heterotroph
this?
Is this an
autotroph or
heterotroph
3.
4.
5.