C9- Energy in a Cell

Pp. 220-249

Table of Contents

Section 9.1-The Need for EnergySection 9.2-

Photosynthesis: Trapping the Sun’s Energy

Section 9.3- Getting Energy to Make ATP

9.1-The Need for Energy

Essential for life Active transport, cell division, movement, &

production, transport & storage of proteins require energy.

Energy molecule ATP adenosine triphosphate

Forming & Breaking Down ATP

Phosphate groups are positive so they repel each other.

Bonding them requires an input of energy.AMP adenosine monophosphate 1 groupADP adenosine diphospate 2 groupsATP With 3 groups, breakdown releases even moreenergy.

Forming & Breaking Down ATP

ATP With 3 groups, breakdown releases even more energy.

ADP-ATP cycle is renewable

The cell doesn’t have to store all the energy it needs.

Forming & Breaking Down ATP

When ATP is broken down to ADP, it can be released from the binding site in the protein and be made available to another ATP.

Uses of Cell Energy

Making new molecules

Building cell membranes & organelles

To maintain homeostasis

To eliminate waste Transmit nerve

impulses

9.2 Photosynthesis

Trapping Energy from Sunlight Process of changing sunlight to glucose in 2 steps

Light Dependent RXN converts it to chemical E in form of ATP

Light Independent RXN uses ATP to make glucose

9.2 Photosynthesis

Photosynthesis- light-dependent

Occurs in the chloroplast in the membranes of the thylakoid discs

Pigment chlorophyll absorbs light (reflects green)

Photosynthesis- light-dependent

Energy from light is transferred to electrons

Electron are passed to a series of proteins or electron transport chain

Water is split to release oxygen; H ion joins carrier molecule NADP (photolysis)

Photosynthesis- light-dependent

NADPH transfers energy to stroma

H ions are pumped into thylakoid & provide energy for ATP or chemiosmosis

Second Phase is light independent-

The Calvin Cycle

Photosynthesis- light-independent

o The Calvin Cycleo Series of carbon

dioxide reactions to form sugar.

o C atom from CO2 bonds w/ 5 carbon sugar ribulose. (Carbon fixation)

o 6C sugar divides into 2 3C sugars

Photosynthesis- light-independent

o Calvin Cycleo bonds w/ 5 carbon

sugar ribulose.o 6C sugar divides into

2 3C sugarso Series of rxn convert

3C molecules into higher energy PGAL (phosphoglyceralde-hyde)

Photosynthesis- light-independent

o Calvin Cycleo Series of rxn convert

3C molecules into higher energy PGAL (phosphoglyceralde-hyde)

o 5 PGAL make 3 RuBP to replenish what was used so process can continue

9.3 Getting Energy to Make ATP

Cellular respiration- process that mitochondria use to break down food molecules to ATP.

3 stages of respiration Glycolysis Citric Acid Cycle Electron Transport

Chain

Respiration

Glycolysis series of chemical reactions in cytoplasm to break glucose (6C) to pyruvic acid (3C).

Anaerobic process Takes 2 ATP to start glycolysis but only makes 4 ATP. Not effective

Respiration

Glycolysis uses an electron carrier, NAD+, which forms NADH when it accepts 2 electrons.

After glycolysis, the PGAL moves into the mitochondria where 2 more stages occur.

Respiration

Citric Acid Cycle (Krebs)- another series of chem RxNs changing acetyl-CoA (2C) to form ATP & CO2. NAD+ & FAD pick up energized electrons & pass them to ETC.

Respiration

Electron Transport Chain- inner membrane of the mitochondria- energized electrons are passed from protein to protein releasing energy as they go.

Respiration

Electron Transport Chain- some energy is used to make ATP & some is used to pump H+ into mitochondrion center

Final e acceptor is O which reacts w/ H to form 2 water molecules

Overall, 32 ATP made aerobicly + 4= 36 total

Fermentation

Anaerobic process to produce ATP w/out oxygen during heavy exertion.

Two types: Lactic acid fermentation Alcoholic fermentation

Fermentation

Lactic Acid Fermentation- supplies energy when O is scarce

2 pyruvic acids use NADH to make 2 lactic acid molecules. 2 ATP formed for each glucose and lactic acid goes to the muscle cells & on to the liver to be broken into pyruvic acid.

Lactic acid causes muscle fatigue.

Fermentation

Alcoholic fermentation- used by yeast cells & some bacteria to produce CO2 & ethyl alcohol.

CO2 produced by yeast makes bread rise.

Comparing Photosynthesis & Respiration

Food synthesized Sun’s energy stored CO2 used Oxygen given off Requires light Produces sugars Food broken down Glucose energy released CO2 produced Oxygen used Does not need light Produces CO2 & water