Biology
Photosynthesis
Fall 2015
Objective: To understand the process of photosynthesis and how the Sun’s energy is used to build plants and create energy.
Area of Interaction: Approaches to Learning
Criterion C: Knowledge and Understanding of Science
Your Task: To use the information provided to complete the higher-level questions and demonstrate your understanding of
photosynthesis.
Photosynthesis: Goodness from the Sun
Obtaining energy: all living things must acquire and use energy to survive.
Autotrophs: self /feed (make own food, use photosynthesis) get energy from sunlight
Heterotrophs: other/feed feed on the autotrophs (animals) get energy from food)
Chemoautotroph: autotroph that makes energy from chemicals
Overview of photosynthesis
All organisms use energy to carry out the functions of life. Almost all of this energy comes from the sun.
Energy from the sun enters living things as light and is converted by plants, algae, some protists and some
prokaryotes absorb sunlight and use it to make organic compounds.
Capturing light energy (following electrons and making ATP)
Light and pigments: remember that pigments are colored compounds that absorb light.
Chloroplast: Organelles in plants where photosynthesis takes place. Contain and the pigment chlorophyll.
Chlorophyll: pigments that appear green, absorb light, release electrons, and form carbohydrates (where
photosynthesis takes place)(thylakoids)
Converting light energy to chemical energy (sunglight-ATP-sugar) In each chlorophyll
Key Elements of photosynthesis
1. Light reactions: energy is captured from the sun, which excites electrons which turn the energy
into chemical energy (temporarily stored in ATP and NADPH)
2. Calvin cycle: Carbon dioxide and chemical energy (ATP and NADPH) are used to form organic
compounds (sugars)
(3 Things Happen)
A. Energy is captured from sunlight
B. Light Energy is converted to chemical energy (ATP and NADPH)
C. The chemical energy powers the Calvin Cycle, which produces organic compounds from CO 2
The chemical formula:
Light+6CO2+6H2O -> C6H12O6 +4O2
Carbon fixation: using carbon to create organic molecules, like sugar (Calvin Cycle)
Factors that affect photosynthesis
1.
2.
3.
Light intensity (more light=more photosynthesis)
Carbon dioxide levels (more CO2= more photosynthesis)
Temperature (higher temperature=more photosynthesis)
Summary of photosynthesis
This incredibly complex process can be summarized in three easy steps.
a. Energy is captured from sunlight (electrons) Light reactions
b. Light energy is converted to chemical energy (ATP and NADPH)
c. ATP and NADPH are used to make sugar C6H12O6 During the Calvin cycle
Extensions
-Please summarize both photosystem I and photosystem II, electron transport chain
-How are ATP and NADPH formed during light reactions?
-Please describe the two alternative pathways for carbon fixation and tell how they work..
-How are some plants able to continue photosynthesis in the absence of either light or water. Give
examples.
-How does the absence of light inhibit photosynthesis (be specific)
Cell Respiration:
Objective: to understand the process of cellular respiration and to recognize the wonderful products it
creates.
Overview of cell respiration
For now, Think of cell respiration as the opposite of photosynthesis. It’s how animals use the organic substances
made by plants to make energy. In the process they use oxygen and release carbon dioxide.(breathe in, breathe out)
Cell respiration has two main phases: glycolysis-aerobic respiration, or glycolysis-anaerobic respiration.
Cell Respiration: Complex process by which cells make ATP by breaking down organic compounds. (Usually, getting
energy from substances produced by autotrophs).
Aerobic respiration: respiration that occurs in the presence of oxygen.
Anaerobic respiration: respiration that occurs in the absence of oxygen.
Organic substance + oxygen = carbon dioxide + energy (ATP)
Cellular respiration has 2 main parts:
Glycolysis:
Aerobic/anaerobic respiration:
Both autotrophs and heterotrophs use cell respiration to make carbon dioxide and water.
ATP is also produced. So, the three products of cell respiration are: _____, ____ and _________.
There are two steps:
Part 1. Gylcolysis:
Gylcolysis: Organic molecules are broken down into three-carbon molecules of pyruvic acid and small amounts of ATP
and NADH (electron carrier) are also made.
Aerobic respiration=ATP, H20, and CO2
**** This only happens when there is oxygen is present. If not oxygen is present, then fermentation occurs instead:
Part 2: Aerobic/anaerobic respiration:
2A. Aerobic respiration: (with oxygen) Pyruvic acid is converted into CO2 and water and A LOT of ATP is produced.
Extensions:
Please summarize the main events in the Kreb’s cycle ad explain how they help produce large amounts of ATP.\
Please summarize the importance of the electron transport chain to aerobic respiration
2B. Anaerobic Respiration: Fermentation (anaerobic respiration=no oxygen)
Fermentation occurs when no oxygen is present, and pyruvic acid is converted into other substances, such as
lactic acid or ethyl alcohol.
Kreb’s cycle
Lactic acid fermentation (animals)
Occurs when pyruvic acid (CCC) is converted to lactic acid (CCC)
Important for:
Production of dairy products like milk and cheese (microorganisms do the fermenting)
Also happens in your muscle cells during strenuous exercise when your body can’t replace oxygen as quickly as it is used)
aerobic to anaerobic)
Blood doping: is the practice of boosting the number of red blood cells (RBCs) in the bloodstream in order to enhance athletic
performance. Because they carry oxygen from the lungs to the muscles, more RBCs in the blood can improve an athlete’s
aerobic capacity (VO2 max) and endurance.
Do you think this is a fair option for elite athletes?
Alcoholic fermentation (plants, bacteria, yeast)
Some plant cells and yeast use a process called alcoholic fermentation to convert pyruvic acid into ethyl alcohol.
Bread making also depends on alcohol fermentation performed by yeast cells. CO2 forms and makes bubble that force dough
to rise. Relax, the alcohol produced evaporates during baking!
Cell Respiration summary:
1. Know the two main stages and their products.
2.
Determine how those products can be used to demonstrate that something is alive.
Extensions:
Please summarize the main events in the Kreb’s cycle ad explain how they help produce large amounts of ATP (34)
Please summarize the importance of the electron transport chain to aerobic respiration
Please explain lactic acid formation and alcohol formation. Be prepared to argue the effects of each on society.
Is blood doping acceptable practice in order to increase an athlete’s performance?
Question: Now, how can this be demonstrated in a simple lab exercise?
The Yeast Lab:
Background information:
Hypothesis: