CELLS AND ENERGY

Chapter 4

Preview Vocabulary

Metabolic processes take one of two directions: They synthesize/anabolize (build up material

and store energy). or

They hydrolyze/catabolize (break material down and release energy).

Chemosynthesis and photosynthesis are synthesizing processes that capture the energy needed for life and store it in sugars.

Cellular respiration and fermentation are catabolic processes that break down sugars and deliver energy to sustain life.

AKS Standards8d - explain the role of cell organelles in maintaining homeostasis and cell reproduction for both prokaryotic and eukaryotic cells;

8l - analyze and explain the storage and release of energy through the process of photosynthesis and respiration (GPS);

10a - relate the complexity and organization of organisms to their ability for obtaining, transforming, transporting, releasing and eliminating the matter and energy used to sustain the organism (GPS)

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

Triphosphate ATP is a molecule made up of

adenosine and three negatively charged phosphate groups.

The energy carried by ATP is released when a phosphate group is removed from the molecule.

The bonds holding the 3rd group in ATP is unstable and very easily broken.

When the 3rd phosphate is removed, energy is released and ATP becomes ADP, or adenosine diphosphate.

ADP is a lower-energy molecule.

The ATP Cycle

The breakdown of ATP to ADP and the production of ATP from ATP can be represented by a cycle. ATP ADP releases energy. ADP ATP requires energy.

Types of Phosphorylation

To make ATP, you must PHOSPHORYLATE and ADP molecule.

This means that you must add a PHOSPHATE (P) to ADP to make ATP.

Phosphorylation can occur in THREE WAYS:1. Substrate Level Phosphorylation: directly

transferring a phosphate group to ADP using an enzyme…as seen in glycolysis and the Krebs cycle.

2. Oxidative Phosphorylation: using the power of a concentration gradient where oxygen is the terminal electron acceptor to phosphorylate ADP into ATP...as seen in the electron transport chain of the mitochondria.

3. Photophosphorylation: using the power of sunlight to phosphorylate ADP into ATP….as seen in the photosynthesis light reactions.

Types of Phosphorylation

SUBSTRATE LEVEL PHOSPHORYLATION

OXIDATIVE PHOSPHORYLATION

PHOTOPHOSPHORYLATION

Ways of Obtaining Energy Heterotrophs: obtain energy by breaking down

carbon compounds (food) in the presence or absence of oxygen.

Animals, fungi, and some protistans are heterotrophs. Carbohydrates: 4 energy calories per mg Lipids: 9 energy calories per mg Protein: 4 energy calories per mg

Autotrophs: use chemical energy to build their own food molecules.

Plants and most algae photosynthesize, many bacteria chemosynthesize. Photosynthesis: converts light energy into carbon

compounds. Chemosynthesis: converts chemical energy into carbon

compounds.

AKS Standards8d - explain the role of cell organelles in maintaining homeostasis and cell reproduction for both prokaryotic and eukaryotic cells;

8l - analyze and explain the storage and release of energy through the process of photosynthesis and respiration (GPS);

10a - relate the complexity and organization of organisms to their ability for obtaining, transforming, transporting, releasing and eliminating the matter and energy used to sustain the organism (GPS)

Photosynthetic organisms are producers. Photosynthesis is the process

whereby light energy is converted to chemical energy and carbon is fixed into organic compounds.

In the presence of light, plants transform carbon dioxide and water into carbohydrates and release oxygen. 6 CO2 + 6 H2O + light → C6H12O6 + 6

O2 carbon dioxide + water + light → sugar

+ oxygen Plants then use the sugars to

produce complex carbohydrates such as starches.

COMMON MISCONCEPTIONPlants DO NOT get energy from photosynthesis. Rather, they use light energy to build sugars. They then use the sugars to build ATP via cellular respiration (just like animals).

Photosynthesis in plants occurs in chloroplasts.

Chloroplasts are membrane-bound organelles found in the leaves photosynthetic organisms.

Chlorophyll is the green pigment molecule in chloroplasts that is directly involved in photosynthesis.

Thylakoids: have membranes that contain chlorophyll (where light is absorbed).Grana: stacks of thylakoid.Stroma: fluid surrounding thylakoids where Calvin cycle occurs.

The reactions of photosynthesis occur in two main stages.

http://www.mhhe.com/biosci/bio_animations/02_MH_Photosynthesis_Web

/

1.Light-Dependent Reactions: Capture energy from sunlight and use this energy to

produce ATP and NADPH. ATP and NADPH are the energy required to power the

Calvin cycle. Occur within and across the thylakoid membranes. This is the “photo” phase – uses light.

2.Light-Independent Reactions: Also called the dark reactions or the Calvin cycle. Use the ATP and NADPH produced by the light reactions

to build simple sugars. Occurs in the stroma of the chloroplast. This is the “synthesis” phase – builds sugars.

Light Reactions:

-carried out by molecules in thylakoid membranes

-convert light E to chemical E of ATP and NADPH

-split H2O and release O2 to the atmosphere

Calvin Cycle (Dark) Reactions:

-take place in stroma

-use ATP and NADPH produced in light reactions to convert CO2 into simple sugars

-return ADP, inorganic phosphate, and NADP+ to the light reactions

Overview of Light-Dependent Reactionshttp://www.sumanasinc.com/webcontent/animations/content/harvestinglight.html

Overview of Light-Independent Reactionshttp://highered.mheducation.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.html

AKS Standards8d - explain the role of cell organelles in maintaining homeostasis and cell reproduction for both prokaryotic and eukaryotic cells;

8l - analyze and explain the storage and release of energy through the process of photosynthesis and respiration (GPS);

10a - relate the complexity and organization of organisms to their ability for obtaining, transforming, transporting, releasing and eliminating the matter and energy used to sustain the organism (GPS)

Cellular respiration makes ATP by breaking down sugars.

Animals eat other organisms for food, but food is not a direct source of energy for cells.

Instead, all organisms break down molecules from food to produce ATP.

Because it occurs in the presence of oxygen, cellular respiration is known as aerobic respiration. COMMON MISCONCEPTION

Animals are NOT the only organisms that use cellular respiration. All living organisms use some type of respiration (aerobic or anaerobic) to produce ATP…this includes bacteria, protistans, fungi, plants, and animals!!!

OVERVIEW OF CELLULAR RESPIRATION

The chemical formula for cellular respiration is: 6O2 + C6H12O6 → 6 CO2 + 6 H2O + Energy oxygen + glucose → carbon dioxide + water + ATP

The reactants of cellular respiration are: oxygen (O2) & glucose (C6H12O6)

The products of cellular respiration are: carbon dioxide (CO2) and water (H2O)

The 4 main stages of cellular respiration are:1. Glycolysis2. Intermediate Step3. Krebs Cycle (Citric Acid Cycle)4. Electron Transport / Oxidative Phosphorylation

Cellular respiration occurs in mitochondria.

Mitochondria are membrane-bound organelles found in the cells of organisms that perform cellular respiration.

Mitochondria have a double membrane that serves to compartmentalize the reactions of cellular respiration.

Christae: folds created by convoluted inner membrane, increases the surface area for the electron transport chain.Matrix: aqueous solution in the center of mitochondria where chemical reactions of Krebs cycle occur.Inner-Membrane Space: area where a hydrogen ion gradient is established using energy from electron transport chain – gradient powers the production of ATP from ADP and Pi.

The Players for Cellular Respiration Mitochondria – site of cellular respiration in cells. Glucose – energy source broken down to release

ATP. NADH & FADH2 – coenzymes that shuttle electrons

from Glycolysis & The Krebs Cycle to the Electron Transport Chain.

Glycolysis – begins the breakdown of glucose into two molecules of pyruvate.

Intermediate Step – converts pyruvate from glycolysis into Acetyl CoA for entry into Krebs cycle

Krebs Cycle – completes the breakdown of glucose. CO2 – waste product of cellular respiration. O2 – required for aerobic respiration. Electron Transport Chain – establishes a

concentration gradient of hydrogen across the inner membrane – gradient powers production of ATP.

Cellular respiration occurs in four main stages.http://www.sumanasinc.com/webcontent/animations/content/cellularrespiration.htmlhttp://www.mhhe.com/biosci/bio_animations/MH01_CellularRespiration_Web/index.html

1. Glycolysis Takes place in cytoplasm of cell just outside the mitochondria. Begins the breakdown of glucose into 2 molecules of pyruvate. Produces 2 ATP, 2 NADH, and 2 pyruvate

2. Intermediate Step Takes place just inside the mitochondria. Converts pyruvate from glycolysis into acetyl CoA, which can enter the

Krebs cycle. Produces 2 NADH and 2 acetyl CoA; releases carbon-dioxide waste

3. Krebs (Citric Acid) Cycle Takes place in the matrix of the mitochondria. Completes the breakdown of glucose. Produces 2 ATP, 6 NADH, and 2 FADH2, releases carbon dioxide waste

4. Electron Transport Occurs across the inner membrane of the mitochondria. Uses electrons donated from NADH and FADH2 to establish a hydrogen

ion gradient across the inner membrane which is used to power the production of ATP.

Produces approximately 34 ATP

Glycolysis occurs in the cytoplasm.

Intermediate step occurs just inside the mitochondria.

Krebs cycle occurs in the matrix of the mitochondria.

Electron transport occurs across the inner membrane of the mitochondria – concentration gradient occurs in inner-membrane space.

Overview of Glycolysishttp://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_glycolysis_works.html

Intermediate Step Converts Pyruvate into Acetyl CoA

Overview of Krebs (Citric Acid) Cycle http://highered.mheducation.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html

Overview of Electron Transport Chain http://highered.mheducation.com/sites/0072507470/student_view0/chapter25/animation__electron_transport_system_and_atp_synthesis__quiz_2_.html

Cellular respiration and photosynthesis are like mirror images.

AKS Standards8d - explain the role of cell organelles in maintaining homeostasis and cell reproduction for both prokaryotic and eukaryotic cells;

8l - analyze and explain the storage and release of energy through the process of photosynthesis and respiration (GPS);

10a - relate the complexity and organization of organisms to their ability for obtaining, transforming, transporting, releasing and eliminating the matter and energy used to sustain the organism (GPS)

Respiration in the Absence of Oxygen (Anaerobic Respiration)

When oxygen is NOT present, glycolysis is followed by a different pathway called fermentation. Fermentation releases energy from food

molecules in the absence of oxygen Because fermentation does not require

oxygen, it is said to be anaerobic. The 2 main types of

fermentation are: alcoholic fermentation lactic acid fermentation

Aside from the original 2 ATP’s made during glycolysis, the only energy produced is that which is in the bonds of: ethyl alcohol -- C2H6O lactic acid – C3H5O3

As you can see, the role of fermentation is simply to provide glycolysis with a steady supply of NAD+.

By itself, fermentation does NOT produce ATP.

Instead, it allows glycolysis to continue to produce ATP in the absence of oxygen.

Fermentation and its products are important in several ways.

Fermentation and Aerobic Respiration Compared

Both processes use glycolysis to break down glucose and other organic fuels into pyruvate.

The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O2 in cellular respiration.

Cellular respiration produces 38 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule.