Chapter notes

If something is too large to move across a cell membrane the cell uses:

1. Exocytosis-out cell

2. Endocytosis-in cell

Three factors that may affect the ability of an enzyme to work efficiently:

1. Temperature

2. PH

3. Concentration of substrate

An enzyme is NOT used up when catalyzing a reaction.

A cell contains thousands of different kinds of enzymes, each promoting a different chemical reaction

Energy is stored at the cellular level as ATP.

All energy comes from the sun then plants, and then to ammonals, this is obtained through the chloroplast in the stacks of disk-like thylakoid cells.

Possible Essay Questions

List and explain the steps of photosynthesis.1. Capture light energy, 2. Use light energy to make ATP, 3. Building Carbohydrates

List the steps of cellular respiration.

Glycolisis and Oxidative Respiration

During photosynthesis, what is the series of reactions that create the complex carbohydrates needed for energy and growth? Calvin cycle

What is the Calvin cycle used for?

What is the Krebs cycle? Oxidative resiration occurs in two major steps: the Krebs cycle and the electron transport chain

During the Kreb cycle ADP is changed to ATP and NAD+ is changed to NADH.

I. Definitions

A. Energy:  the ability to do work or cause motion

1. potential:  energy of position or condition

2. kinetic:  energy of motion

3. activation:  chemical energy needed to start any reaction

B. Metabolism:  all the chemical reactions occurring within an organism

II. Enzymes

A. Properties

1. globular proteins

2. lower amount of activation energy required

3. act on a substrate

4. most end in –ase

5. many named after their substrate

6. some named after their action

7. not used up in a reaction

8. have an active site to bind to substrate

B. Lock and key hypothesis

1. active site

a. part of enzyme that fits substrate

b. works on shape, composition, or electrical charge of molecule

c. pliable – induced fit

pH, presence of substrate, cofactors can induce fit

C. Different degrees of specificity

1. Absolute specificity – only works on a specific substrate

Ex:  invertase only works on glucose and fructose

2. Relative specificity – works on a group of substrates

Ex:  proteases work on all proteins

D. Enzymes influence speed not direction of reaction

1.  A  +   B à C

2.  high local concentration of substrate molecules at active site would increase speed

3.  hold molecules or atoms in correct position to react so reaction happens easier and quicker

4.  some of the binding energy used to bind substrate to enzyme is used to bind molecules to each other (lowers amount of activation energy needed to start the reaction)

III. Activation Energy

IV. Cells use energy for

A. movement

B. change shape

C. metabolism

D. transport food

E. expel wastes

V. ATP

A. structure

1. adenosine (adenine + ribose)

2. 3 phosphate groups

3. high energy bonds

B. Function

1. break high energy bond to provide energy

2. glucose = $100 bill,  ATP = $1 bill

3. avg. male uses 17 pounds of ATP every hour

C. Energy flow

1. sunlight energy absorbed by plants

2. photosynthesis produces ATP, carbohydrates, organic molecules

3. cellular respiration breaks down carbohydrates and organic molecules into ATP

VI. Photsynthesis

A. Stage I  - capturing light energy

1. Light (electro-magnetic radiation)

a. shorter wavelengths = more energy

b. visible light = intermediate wavelengths

2. Pigments

a. molecules that absorb light

b. retinal – pigment in our eyes

c. chlorophyll – major pigment in plants (inside thylakoids)

d. carotenoids – accessory pigments

3. light strikes chloroplast à light energy changed to ATP à ATP used to split water à  left with H₂ and O₂ à O₂ released into atmosphere

B. Stage II – making ATP and NADPH

1. electrons passed from carrier to carrier in thylakoid membrane

2. energy from electron transfer used to pump protons across membrane in thylakoid

3. excess protons diffuse back across membrane through channels

4. energy used from proton diffusion used to add phosphate to ADP making ATP

5. electrons passed through several carriers and picked up by NADP+ making NADPH (electron carrier)

C. Stage III – making carbohydrates (glucose)

1. energy to “drive” cycle from Stage II ATP and NADPH

2. Carbon dioxide added to Hydrogen (from water splitting in Stage I) to make glucose

VII. Cellular Respiration

A. Glycolysis – splitting glucose

1. takes place in cytoplasm

2. no oxygen in required

3. makes 2 pyruvic acid and 2 ATP

B. Fermentation

1. incomplete breakdown of organic compounds in the absence of oxygen

2. pyruvic acid from glycolysis broken down into CO₂ and alcohol in plant cells or lactic acid in animal cells

C. Oxidative Respiration

1. takes place in mitochondria

2. step 1

a. pyruvic acid split into a 2 carbon compound  +  CO₂  +  electrons picked up by NAD⁺ making NADH

3. step 2

a. two carbon compound put into Krebs cycle producing ATP  +  CO₂  +  NADH

4. step 3

a. NADH passes electrons it was carrying through electron transport chain producing energy in the form of ATP

b. Electrons eventually join oxygen and protons to make water

D. Feedback inhibition

1. slowing or stopping a reaction early by using the end product of the reaction to inhibit the first enzyme used in the reaction

2. keeps cells from “wasting” energy by producing something not needed