9.1.1. Why do cells need energy and how do they use it?
9.1.2. How do your cells get energy?
9.1.3. How does ATP store and release energy?
9.1.4. How do your cells get the energy from ATP?
9.3.5. What is cellular respiration?
9.3.6. Describe Glycolysis.
9.3.7. Describe the Citric Acid Cycle/ Krebs Cycle
9.3.8. Describe the Electron Transport Chain- ETC
9. 3.9 Why is oxygen needed for cellular respiration?
9.3.10. Describe Latic acid fermentation.
9.3.11. Describe Alcoholic fermentation.
9.2.12. What is photosynthesis?
9.2.13. Describe the light- dependent reactions?
9.2.14. Describe the light-independent reactions?
9.2.15. Compare photosynthesis and cellular respiration?
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The Need for Energy
1. Why do cells need energy and how do they use it?
Cells need energy to live. All cell processes require energy including, making new molecules, dividing, build membranes
and cell organelles, and maintain homeostasis (active transport Ch 8.1). The body as a whole uses energy for muscle
contraction (heart beating, digestion, movements) and growing.
2. How do your cells get energy?
The food we eat supplies the energy we need. When we eat the food is broken down and made into energy. We take
sugar (GLUCOSE) and turn it into ATP. ATP (Adenosine Triphosphate) is the energy molecule of our cells like a little
battery.
3. How does ATP store and release energy?
ATP is composed of an adenosine molecule, a ribose sugar, and THREE phosphate groups held together by chemical
bonds. These chemical bonds store energy. When one of these bonds is broken to form ADP (adenosine diphosphate),
energy is released. The bond between each additional phosphate holds more energy.
Little E More e LOTS E
Adenosine – ribose –P1 - - P2- --P3
4. How do your cells get the energy from ATP?
Proteins have a special place where ATP can attach itself. Once ATP is attached, the last bond is broken between the 2nd
and 3rd phosphate group, releasing energy. Now, as ADP, the molecule is released. The ADP will go and have another
phosphate attached so it can be used later. This provides a “renewable” source of energy for your cells.
9.3 Getting Energy to make ATP
5. What is cellular respiration?
Cellular respiration is the process in which the mitochondria (power house organelle- Ch6) break down food (GLUCOSE)
to produce energy as ATP.
Carbon Dioxide
C6H12O6 + 6O2 -> 6CO2 + 6 H2O + ATP
Glucose
There are three stages to cellular respiration:
1. Glycolysis
2. Citric Acid Cyle
Oxygen
Water
Energy
3. Electron Transport Chain
6. Describe Glycolysis. (Include the process and purpose.)
Glycolysis occurs in the cytoplasm of the cell and is anaerobic (no O2 needed). The purpose of glycolysis is to break
down glucose (6C -sugar) into Pyruvid acid (also called pyruvate) (2-3C) and produces 2ATP molecules.
Process
Location in the Cell
Aerobic/Anaerobic
Glycolysis
Cytoplasm
Anaerobic
Starts with
(Reactants)
Glucose (6C)
Ends with (Products)
Pyruvic Acid (2-3C)
2 ATP
7. Describe the Citric Acid Cycle/ Krebs Cycle ((Include the process and purpose.)
After glycolysis the pyruvic acids move to the mitochondria. As the 2-3C molecules move into the mitochondria they are
worked on to turn them into Acetyl- Coenzyme A called acetyle-CoA, now 3-2C. The CAC/KC occurs in the mitochondria
and results in 1 ATP and 2 Carbon Dioxide molecules. This CO2 is what you breath out. The purpose is to supply the
Electron Transport Chain with electrons.
8. Describe the Electron Transport Chain- ETC (Include the process and purpose.)
The electrons taken from the CAC are moved to the inner membrane of the mitochondria. They are then passed down a
“staircase” of proteins. Each electron loses energy at each protein. Some of this energy is used to make ATP.
Some is used to pump in H+. The final electron acceptor at the bottom of the staircase is oxygen. The electrons and
pumped in H+plus the oxygen create water. Pumping in H+ also helps make ATP
Process
Location in the Cell
Aerobic/Anaerobic
Starts with
(Reactants)
Ends with (Products)
Process
Location in the Cell
Aerobic/Anaerobic
Ends with (Products)
CAC
Mitochondria
N/A
Starts with
(Reactants)
Pyruvic acid
ETC
Inner Mitochondrial
memebrane
Aerobic
Electrons (H+)
Electrons (H+)
2ATP
2 CO2
34 ATP
Water
9. Why is oxygen needed for cellular respiration?
The proteins in the ETC can only handle one e- at a time. Without oxygen at the end of the ETC the proteins cannot
pass the electrons along, so the process backs up stopping ATP production. No ATP = No E for cells to do their job.
10. Describe Latic acid fermentation. (Include the process and purpose.)
Sometimes oxygen is not available for a short amount of time, like during exercise. So, following glycolysis your cells
will resort to fermentation. It is a less efficient method of making ATP only meant to make enough energy to get cells
through until oxygen is present again.
Your cells use lactic acid fermentation. The pyruvic acid from glycolysis is turned into lactic acid and ATP is
made. Latic acid builds up in your muscles, that is the “burn” you feel during difficult activities.
Process
Location
Aerobic/Anaerobic
Latic Acid
Fermentation
Muscle Cells
Anaerobic
Starts with
(Reactants)
Pyruvic acid
Ends with (Products)
2 ATP
Latic Acid
11. Describe Alcoholic fermentation. (Include the process and purpose.)
An anaerobic process used by some bacteria and yeast cells (fungi) to convert pyruvic acid into carbon dioxide and ethyl
alcohol. Keeps glycolysis running. Used to make bread rise and for winemaking.
Process
Location
Alcoholic
Fermentation
Aerobic/Anaerobic
Anaerobic
Starts with
(Reactants)
Pyruvic acid
Ends with (Products)
Starts with
(Reactants)
Glucose (6C)
Ends with (Products)
Process
Location in the Cell
Aerobic/Anaerobic
Glycolysis
Cytoplasm
Anaerobic
Citric Acid Cycle
Mitochondria
Aerobic
Pyruvic acid turned
into Acetyl-CoA (2-3C)
Electron Transport
Chain
Latic Acid
Fermentation
Alcoholic
Fermentation
Inner Mitochondrial
memebrane
Muscle Cells
Aerobic
Electrons (H+)
Anaerobic
Pyruvic acid
Anaerobic
Pyruvic acid
Bacteria
Yeast
Ethyl Alcohol
CO2
Pyruvic Acid (2-3C)
2 ATP
Electrons (H+)
2ATP
2 CO2
34 ATP
2 ATP
Latic Acid
Ethyl Alcohol
CO2
9.3 Photosynthesis: Trapping the Sun’s Energy
12. What is photosynthesis?
Photosynthesis is the process plants use to trap and make energy from sunlight. The process takes place in
the cholorplast in plant cells. Chlorophyll is the pigment found in chloroplast that absorbs most wavelengths
of light (except green). Photosynthesis takes place in two different reactions, the Light Dependent reactions
and the Light-Independent reactions.
13. Describe the light- dependent reactions?
The light dependent reactions use light from the sun to energize electrons. These electrons are passed down
an electron transport chain. The end result is production of ATP and splitting water in photolysis that gives us
the oxygen we breath.
14. Describe the light-independent reactions?
The second phase of photosynthesis, taking place in the chloroplast –aka Calvin Cycle. Here, Carbon dioxide
and the ATP and split water from the LDrxn to are used to make glucose.
15. Compare photosynthesis and cellular respiration?
They are almost the exact opposite reactions. However, both make ATP for their respective cells.
Photosynthesis
Glucose made
ATP made
Carbon dioxide and Water used
Oxygen made
Plant cells
Requires Light
Cellular Respiration
Glucose used
ATP made
Carbon dioxide and water made
Oxygen used
Animal cells
Does not require light