KEY CONCEPT All cells need chemical energy.mrmackrh.weebly.com/uploads/9/1/5/9/9159507/bio_2_ch_4_notes.pdf · KEY CONCEPT All cells need chemical energy. ... •However this shift

Chapter 4: Cellular Metabolism (Sections 1,3,5,6)

KEY CONCEPT All cells need chemical energy.


!  The chemical energy used for most cell processes is carried by ATP.

•  Molecules in food store chemical energy in their bonds.

Starch molecule

Glucose molecule


phosphate removed

•  ATP transfers energy from the breakdown of food molecules to cell functions.

–  Energy is released when a phosphate group is removed.

–  ADP is changed into ATP when a phosphate group is added.


triphosphate adenosine

adenosine diphosphate

tri=3

di=2


!  Organisms break down carbon-based molecules to produce ATP.


•  Fats store the most energy.

–  80 percent of the energy in your body –  about 146 ATP from a triglyceride

•  Proteins are least likely to be broken down to make ATP. –  amino acids not usually needed for energy –  about the same amount of energy as a carbohydrate

•  Carbohydrates are the molecules most commonly broken down to make ATP.

–  not stored in large amounts –  up to 36 ATP from one

glucose molecule

Details


!  A few types of organisms do not need sunlight and photosynthesis as a source of energy.

•  Some organisms live in places that never get sunlight.

•  In chemosynthesis, chemical energy is used to build carbon-based molecules. –  similar to photosynthesis –  uses chemical energy

instead of light energy


KEY CONCEPT Photosynthesis requires a series of chemical reactions.


!  The first stage of photosynthesis captures and transfers energy.

•  The light-dependent reactions include groups of molecules called photosystems.


•  Photosystem II captures and transfers energy.

–  chlorophyll absorbs energy from sunlight

–  energized electrons enter electron transport chain

–  water molecules are split

–  oxygen is released as waste

–  hydrogen ions are transported across thylakoid membrane


•  Photosystem I captures energy and produces energy-carrying molecules.

–  chlorophyll absorbs energy from sunlight

–  energized electrons are used to make NADPH

–  NADPH is transferred to light-independent reactions


•  NADPH and ATP from the photosystems are used in the Calvin Cycle.

•  Light-independent reactions occur in the stroma and use CO2 molecules.

!  The second stage of photosynthesis uses energy from the first stage to make sugars.


•  A molecule of glucose is formed as it stores some of the energy captured from sunlight.

–  carbon dioxide molecules enter the Calvin cycle –  energy is added and carbon molecules are rearranged –  a high-energy three-carbon molecule leaves the cycle


–  two three-carbon molecules bond to form a sugar –  remaining molecules stay in the cycle

•  A molecule of glucose is formed as it stores some of the energy captured from sunlight.


!  Photosynthetic organisms are producers.

•  Producers make their own source of chemical energy.

•  Plants use photosynthesis and are producers.

•  Photosynthesis captures energy from sunlight to make sugars.


•  Chlorophyll is a molecule that absorbs light energy.

chloroplast

leaf cell

leaf

•  In plants, chlorophyll is found in organelles called chloroplasts.


!  Photosynthesis in plants occurs in chloroplasts.

•  Photosynthesis takes place in two parts of chloroplasts. –  grana (thylakoids) –  stroma

chloroplast

stroma

grana (thylakoids)


•  The light-dependent reactions capture energy from sunlight.

–  take place in thylakoids –  water and sunlight are needed –  chlorophyll absorbs energy –  two energy storing molecules (ATP and NADPH) are

produced. –  The solar energy is used to split water molecules which results in the release of oxygen as a waste product.



•  The light-independent reactions make sugars.

–  take place in stroma –  needs carbon dioxide from atmosphere –  use energy to build a sugar in a cycle of chemical

reactions



•  The equation for the overall process is: 6CO2 + 6H2O → C6H12O6 + 6O2

C6H12O6

granum (stack of thylakoids)

thylakoid 1 six-carbon sugar

6H2O

6CO2

6O2

chloroplast 1

2

4 3

energy

stroma (fluid outside the thylakoids)


HW DUE 10/30/03

•  Define the Key Terms (19) for Chapter 4 on p.129

Photosynthesis Quiz on Wednesday!


KEY CONCEPT Cellular respiration is an aerobic process with two main stages.


!  Glycolysis is needed for cellular respiration.

•  The products of glycolysis enter cellular respiration when oxygen is available. –  two ATP molecules are used to split glucose –  four ATP molecules are produced –  two molecules of NADH produced –  two molecules of pyruvate produced


!  The Krebs cycle is the first main part of cellular respiration.

•  Pyruvate is broken down before the Krebs cycle. –  carbon dioxide

released –  NADH produced –  coenzyme A (CoA)

bonds to two-carbon molecule


•  The Krebs cycle produces energy-carrying molecules.


–  NADH and FADH2 are made –  intermediate molecule with

CoA enters Krebs cycle –  citric acid

(six-carbon molecule) is formed

–  citric acid is broken down, carbon dioxide is released, and NADH is made

–  five-carbon molecule is broken down, carbon dioxide is released, NADH and ATP are made

–  four-carbon molecule is rearranged

•  The Krebs cycle produces energy-carrying molecules.


!  The electron transport chain is the second main part of cellular respiration.

•  The electron transport chain uses NADH and FADH2 to make ATP. –  high-energy electrons enter electron transport chain –  energy is used to transport hydrogen ions across the

inner membrane –  hydrogen ions

flow through a channel in the membrane


•  The breakdown of one glucose molecule produces up to 38 molecules of ATP. –  ATP synthase

produces ATP –  oxygen picks up

electrons and hydrogen ions

–  water is released as a waste product

!  The electron transport chain is the second main part of cellular respiration.

•  The electron transport chain uses NADH and FADH2 to make ATP.


KEY CONCEPT Fermentation allows the production of a small amount of ATP without oxygen.


•  If no oxygen is available, cells can obtain energy through the process of anaerobic respiration.

•  A common anaerobic process is fermentation.

•  Fermentation is not an efficient process and results in the formation of far fewer ATP molecules than aerobic respiration.

There are two primary fermentation processes:

1.  Lactic Acid Fermentation 2.  Alcohol Fermentation


Lactic acid fermentation occurs when oxygen is not available.

For example, in muscle tissues during rapid and vigorous exercise, muscle cells may be depleted of oxygen. They then switch from respiration to fermentation.


The pyruvic acid formed during glycolysis is broken down to lactic acid and energy is released (which is used to form ATP).

Glucose → Pyruvic acid → Lactic acid + energy


• The process of lactic acid fermentation replaces the process of aerobic respiration so that the cell can have a continual source of energy, even in the absence of oxygen.

• However this shift is only temporary and cells need oxygen for sustained activity.


• Lactic acid that builds up in the tissue causes a burning, painful sensation.


Alcohol fermentation occurs in yeasts and some bacteria.

Pyruvic acid formed during glycolysis is broken down to produce alcohol and carbon dioxide and is released (which is used to form ATP).


Glucose → Pyruvic acid → alcohol + carbon dioxide + energy


•  Fermentation is used in food production.

–  Yogurt - Soy Sauce

–  Cheese - Vinegar

–  Bread - Olives/Pickles

–  Beer/ Meade - Wine/ Ale

–  Sauerkraut - Malt



HW • Complete Section 4.6 in the Study Guide workbook (p. 41-42)

• Study for Cellular Respiration Quiz on Friday!!

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KEY CONCEPT All cells need chemical energy.mrmackrh.weebly.com/uploads/9/1/5/9/9159507/bio_2_ch_4_notes.pdf · KEY CONCEPT All cells need chemical energy. ... •However this shift