H NOTES

Cell Energy

1) General

A) All cells require energy

B) Cells burn food to get energy- respiration - respiratory enzymes- low temps

C) food- organic molecules like carb, lipids, proteins- glucose is most common food molecule
Most food is burned for energy- some is used for growth and repair

D) Autotrophs- make food
Heterotrophs eat food

E) Most common method to make food - Photosynthesis

F) carbon fixation- using inorganic materials to make organic molecules- making food

G) Ps and Resp are complementary processes- opposite and working together

a) Ps stores energy / resp releases energy

b) Ps makes food / resp burns food

c) Ps produces oxygen / resp uses oxygen

d) Ps uses carbon dioxide and water / resp produces carbon dioxide and water

Note all materials are recycled- only energy must be supplied constantly

H) ATP- used by resp and Ps to store and transfer energy

Sun -----> ATP ------> Glucose ------> ATP ------> Cell activitie

2) ATP- energy storage molecule used to store and transfer energy during Ps and Resp

ATP- adenosine triphosphate

ADP - adenosine diphosphate

Energy can be stored in ATP by attaching a third P to ADP

Energy can be released by removing the third P from ATP

ADP + P + Energy ---------> ATP (the energy is stored in the molecule)

ATP-----------> ADP + P + Energy (this energy is now available to be used by the cell)

ADP + P + Energy <------------> ATP

ATP Synthetase- ATP-ase

Phosphorylation- adding a P

4) PHOTOSYNTHESIS - process by which energy from sunlight is captured and used to make organic molecules where the energy is stored.

A) General Equation

6 CO2 + 6H20 + Energy -----------------> C6H12O6+ 6 O2

B) Pigments

1) Chlorophyll-a: green pigment that captures the energy from light

2) Accessory pigments- Chlorophyll-b, chlorophyll-c yellow( Xanthophyll) yellow-orange (carotene) Others are used when plants live in special environments- phycobilins- deep water algae

3) Chlorophyll is destroyed sooner by cold weather- other pigments more easily seen

C) The Details of Ps-

Chloroplasts have stacks of thylakoid membranes called grana- wherre the light reactions occur

Outside the grana is a colloid called the stroma - where the synthetic phase occurs

Light Reactions-

1) Light is captured by various pigments- the energy is passed to chlorophyll-a

2) electrons in chlorophyll-a become excited (gain energy) and leave the chlorophyll-a molecule.

3) These electrons are passed from molecule to molecule along the Electron Transport Chain

4) Along the way, the energy of these molecules is used to:

a) split water- the oxygen leaves the cell

b) move the hydrogen part of the water to the inside of the thylakoid. This builds a concentration gradient across the membrane.

5) The hydrogen then moves with the gradient and back across the membrane. The energy from the hydrogen as it moves is captured by an enzyme and attaches a third phosphate to ADP to make ATP. This process is called chemiosmosis.

6) The hydrogen is then attached to NADP to form NADPH. This stores and transfers the hydrogen for the next part of Ps. NADP is a form of the vitamin niacin.

Calvin Cycle- Synthetic Phase

This is the part that fixes carbon. It happens in the stroma of the chloroplast.

1) CO2 enters the stroma from the environment

2) It attaches to RuBP

3) The RuBP then breaks into 2 molecules of PGA

4) PGA is changed into PGAL using the energy from ATP and the hydrogen stored on NADPH

5) Most of the PGAL is used to replace the RuBP but some of it is used to make glucose and other organic molecules.

6) Since PGAL is a three carbon molecule, plants that use this are called C-3 plants

In hot dry climates there are variation of the Calvin Cycle

C-4 plants can operate with lower CO2 levels so they can close the openings into the leaf during the hottest part of the day. They lose less water. These use a 4 carbon molecule instead of PGAL

CAM Pathway plants - the openings into their leaves are open only at night. They bring in CO2 at night and temporarily store it. During the day, the openings are closed and the Calvin Cycle occurs. These plants are slow growers but lose much less water

E) Other Things of Interest

1) Calvins Experiments with radioactive tracers- 12 water vs six water

2) Plants require certain minerals to make amino acids etc. Nitrates & phosphates mainly. These are in plant "food" Not really food since these are inorganic materials

3) Venus Fly Trap eats insects to get these minerals- can live in mineral poor soil

4) Some bacteria use chemosynthesis to make food- uses chemical energy- these bacteria are found in hot springs and undersea volcanic vents

5) Chlorophyll absorbs all colors of light except green - green reflects The helper pigments absorb the green

6) When Ps evolved- it changed the earth forever- oxygen was put into the air and the ozone layer formed

7) Ps- provides food, provides oxygen, allows for the ozone layer to protect against UV radiation