Chapter 8 Cellular Energy
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Transcript of Chapter 8 Cellular Energy
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Chapter 8 Cellular Energy
8.1 How Organisms Obtain Energy
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Transformation of Energy
Energy is the ability to do work.
8.1 How Organisms Obtain Energy
Cellular Energy
Thermodynamics is the study of the flow and transformation of energy in the universe.
Chapter 8
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Laws of Thermodynamics
First law—energy can be converted from one form to another, but it cannot be created nor destroyed.
8.1 How Organisms Obtain Energy
Cellular Energy
Second law—energy cannot be converted without the loss of usable energy.
Chapter 8
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Autotrophs and Heterotrophs
Autotrophs are organisms that make their own food.
8.1 How Organisms Obtain Energy
Cellular Energy
Heterotrophs are organisms that need to ingest food to obtain energy.
Chapter 8
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Metabolism
All of the chemical reactions in a cell
8.1 How Organisms Obtain Energy
Cellular Energy
Photosynthesis—light energy from the Sun is converted to chemical energy for use by the cell
Cellular respiration—organic molecules are broken down to release energy for use by the cell
Chapter 8
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Cells need energy for: Making new molecules Maintaining homeostasis Active transport
Endocytosis Exocytosis Going against the concentration gradient
Movement Cilia and flagella Muscle contraction including cardiac muscle
Cell division
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ATP stores energy in chemical bonds
A= adenosine T= tri P= phosphate
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ATP and ADP recycle
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ATP is like currency Cells can only use the ATP for energy even
though they store energy as fats, carbohydrates or proteins
Carbohydrates, fats and proteins must be changed to ATP before they can be used by the cell (process of cellular respiration)
You can only use coins in the soda machine even though you may have a $5 bill in your pocket
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How cells tap into the energy stored in ATP
Many enzymes have a site where ATP fits in like a battery to provide the energy for that enzyme to work
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Chapter 8 Cellular Energy
8.2 Photosynthesis
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Photosynthesis: The Big Picture Plants change solar
energy (sunlight) into ATP then into glucose (chemical energy)
Two step process
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Overall reaction of photosynthesis
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Role of Chloroplasts
Chlorophyll is the pigment found in the chloroplasts of plants and algae
Chloroplast is the location for photosynthesis
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Chloroplast Structure Thylakoid
membrane is the site for photosynthesis
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Chlorophyll Plants have two types of chlorophyll
Chlorophyll a is yellow green Chlorophyll b is blue green
We see plants as green because green is reflected not absorbed by the chlorophyll
Plants also contain red, orange and yellow pigments
When leaves “turn colors” in the fall it is because chlorophyll productions ceases and the other colors are exposed
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Photosynthesis: A Two Step Process
Step One: Light Dependent Reactions Step Two: Light Independent
Reactions (previously called the Dark Reactions or the Calvin Cycle)
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Light Dependent Reactions of Photosynthesis
Light strikes a chlorophyll molecule and excites an electron
Electron gets passed to a series of proteins in an electron transport chain and an ATP gets made
Electron goes to a second electron transport chain and another energy molecule (NADPH) gets made
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Light Dependent Reactions of Photosynthesis
Photolysis must happen to “fill in the hole” left by the electron that was excited
Photolysis is the splitting of water; the hydrogen goes to fill the electron’s place and the oxygen is what we breathe (O2)
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Light Dependent Reactions of Photosynthesis
Start with sunlight and get ATP and NADPH Energy molecules used for Step Two
Start with water and get oxygen
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Light Independent Reactions of Photosynthesis
Light dependent
Light dependent
Light independent
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Light Independent Reactions of Photosynthesis
ATP and NADPH from the light dependent reaction provide the energy to convert CO2 to C6H12O6 (glucose)
Uses many enzymes in a cycle to produce glucose Cycles are important in organisms
because they allow for constant production
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Light Independent Reactions of Photosynthesis
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Light Independent Reactions of Photosynthesis
Each “turn” of the cycle produces ½ of a glucose
ATP and NADPH are used to produce this glucose
No sunlight is needed, reactions happen independent of light
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Alternative Pathways C4 Plants: fix CO2
into four-carbon compoundskeep stomata closed during hot days (less transpiration water loss)Sugar cane and corn
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Alternative Pathways CAM plants: conserve
water by allowing CO2 to enter only at night (stomata closed during day to conserve water)
Examples: pineapple, cacti, orchids and other desert or salt march plants
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Chapter 8 Cellular Energy
8.3 Cellular Respiration
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Cellular Respiration
Process of breaking down food to produce ATP
ALL living things do cellular respiration, even: Plants Bacteria
Eukaryotes in the mitochondria Prokaryotes in the cytoplasm
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Cellular Respiration
Overall reaction
C6H12O6 + O2 CO2 + H2O + energy
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Cellular Respiration
Three Stage Process1. Glycolysis: anaerobic2. Citric Acid Cycle: aerobic3. Electron Transport Chain: aerobic
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Cellular Respiration Overview
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Glycolysis Happens in the
cytoplasm Need to use two
ATP before can get ATP out of the process
One glucose is split and converted into two pyruvate yields four ATP (two net ATP)
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Citric Acid Cycle or Krebs Cycle Happens in the
mitochondrial matrix
CO2 produced Per turn of the
cycle yields: 1 ATP 3 NAPH 1FADH2
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Electron Transport Chain
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Electron Transport Chain Located within the inner
mitochondrial membrane Converts NADH and FADH2 into ATP Energized electrons are passed along
a series of proteins Some energy is converted directly into
ATP Other energy causes H+ ions to be forced
out of the inner mitochondrial matrix
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Electron Transport Chain cont.
The force of H+ ions back into the mitochondrial matrix through the enzyme ATP synthase provides the energy for ATP synthesis
Oxygen is the final electron acceptor Without oxygen the transport chain
would shut down like a traffic jam Traffic (electrons) would back up and
shut down the Krebs Cycle as well
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Electron Transport Chain cont.
For every NADH get 3 ATP For every FADH2 get 2 ATP Overall get a net of 32 ATP from one
molecule of glucose Balanced equation:
C6H12O6 + 6O2 6CO2 + 6H2O + 32 ATP
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Fermentation
Occurs when O2 is not present, no aerobic respiration, no Krebs Cycle, no Electron Transport Chain
Allows the continuation of glycolysis by the removal of pyruvate
Some organisms in anaerobic environments produce energy by fermentation all the time
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Fermentation: Two Types Alcoholic
Yeast Produce CO2, ethyl
alcohol and 2 ATP from pyruvate
Important in bread and alcoholic beverage industries
Lactic Acid Animal muscle cells,
some bacteria and some plants
Produce lactic acid and 2 ATP from pyruvate
Get sore, burning muscles
Liver converts lactic acid back to pyruvate when O2 is present
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Comparing Photosynthesis and Cellular Respiration
Both use electron transport chains Both use cycles of chemical reactions Both use electron carrier proteins Both use concentration gradient of H+
ions
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Comparing Photosynthesis and Cellular Respiration
PhotosynthesisPhotosynthesis Food accumulated Solar energy stored
in glucose CO2 taken in, O2
given off Occurs only in
presence of chlorophyll with sunlight
Cellular RespirationCellular Respiration Food broken down Glucose energy
released O2 taken in, CO2
given off Occurs in all living
things all the time