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.


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.


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.


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


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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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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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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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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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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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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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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Overall reaction

C6H12O6 + O2 CO2 + H2O + energy

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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

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Chapter 8 Cellular Energy