Bio 107 topic 4

Question 1

What type of energy do organisms absorb?

Answer 1

light or chemical

Question 2

What type of energy do organisms release?

Answer 2

thermal and metabolic wastes

Question 3

Laws of thermodynamics in terms of organisms transformation of energy

Answer 3

• energy is neither created nor destroyed, only transferred and transformed
• every energy transfer or transformation increases the entropy of the surroundings

Question 4

Entropy

Answer 4

randomness/disorder
- inversely related to free energy

Question 5

What is the most disorganized form of energy?

Answer 5

heat
release of heat=increase entropy

Question 6

What happens to a chemical reaction if they result in an increase in entropy?

Answer 6

the reaction will proceed spontaneously-not necessarily fast

Question 7

The 2nd law of thermodynamics states that energy transformations increase entropy, but living things are very ordered and non-random. Explain how living things can exist without violating the second law of thermodynamics.

Answer 7

­- Cells are open systems
­- Take in energy and matter in low entropy forms → used to create localized order in the cell
­- Energy and matter are returned to surroundings in a less ordered form →Organisms decrease order of their surroundings

Question 8

What has to happen in order for a non spontaneous reaction to occur in the cell?

Answer 8

energy has to be added

Question 9

Exergonic reaction

Answer 9

• releases free energy
• (ΔG <0)
• occurs spontaneously
  ex. breaking polymers into monomers

Question 10

Endergonic reaction

Answer 10

• absorbs free energy from the surrounds to power the reaction
• (ΔG>0)
• non spontaneous
  ex. making a polymer from monomers

Question 11

Metabolism

Answer 11

all of an organism’s chemical reactions organized into pathways

Question 12

Metabolic pathway

Answer 12

the chemical reactions from a starting material to an ending material
- each step catalyzed by a different enzyme

Question 13

Catabolic pathway

Answer 13

type of metabolic pathway that break down complex molecules into simpler molecules
- releases energy (exergonic)
- requires enzymes
ex. breakdown of starch to glucose

Question 14

Anabolic pathway

Answer 14

type of metabolic pathway that build complex molecules from simpler molecules
- requires energy (endergonic)
- requires enzymes
ex. photosynthesis

Question 15

Energy coupling

Answer 15

energy released from one set of reactions is used to power another set of reactions that require energy
- energy release from catabolic used to power anabolic

Question 16

Cellular work that relies on ATP

Answer 16

1. Movement
   - transport vesicles around cell
   - flagella and cilia
2. Transport
   - moves substances across membrane against concentration gradient
3. Chemical
   - driving endergonic chemical reactions

Question 17

ATP

Answer 17

adenosine triphosphate
- three phosphate groups
- ribose sugar
-adenine nitrogenous base
-nucleotide

Question 18

Why is ATP hydrolysis exergonic?

Answer 18

repulsive forces between negatively charged phosphate groups make ATP less stable than ADP

Question 19

Phosphorylation

Answer 19

phosphate from ATP hydrolysis is added to another molecule
- makes molecules more reactive causing endergonic reactions to occur

Question 20

What can cause a protein to change shape?

Answer 20

-phosphorylation
- binding and hydrolyzing ATP

Question 21

ATP cycle

Answer 21

cell constantly makes ATP by re-phosphorylation

Question 22

Electrons going from a less electronegative atom to a more electronegative atom release or absorb energy?

Answer 22

release. Sometimes it is not all used so it is stored in electron shuttle molecules

Question 23

Which type of covalent bonds have a high and low potential energy of electrons?

Answer 23

C-H: high
C-C: high
O-O: Very high
C-O: low
O-H: low

Non polar=high
Polar=low

Question 24

Redox reaction

Answer 24

reaction where there is a transfer of electrons from one reactant to another

Question 25

Oxidation

Answer 25

loss of electrons

Question 26

Reduction

Answer 26

gains electrons

Question 27

Electron shuttle molecules

Answer 27

temporary storage site for high energy elections. Uses dehydrogenase ex. NAD+

Question 28

Dehydrogenase

Answer 28

enzyme that removes 2 hydrogen atoms from high energy substrates and transfers them into shuttle molecules

Question 29

Oxidized form NAD+

Answer 29

-low energy - can accept electrons

Question 30

Reduced form (NADH)

Answer 30

- high energy - stores electrons

Question 31

Electron transport chains

Answer 31

a series of electron-carrying membrane proteins that transfer electrons and release energy - receive high energy electrons (from electron shuttles) - release energy in small steps by redox reactions

Question 32

Enzyme

Answer 32

catalytic protein that speeds up a reaction without being consumed itself

Question 33

Enzyme properties

Answer 33

- increases reaction rate - does not change the reaction - does not provide energy to the reaction - used in both exergonic and endergonic reactions - activity can be regulated - lowers Ea needed for a reaction to occur without changing G

Question 34

Substrate

Answer 34

reactant that an enzyme acts upon

Question 35

Product

Answer 35

molecules produced at the end of the reaction

Question 36

Active site

Answer 36

Pocket on the surface of the enzyme where the substrate binds and where the reaction happens - enzyme specific to its substrate due to shape of active site which is caused by amino acid sequence

Question 37

How does an enzyme work?

Answer 37

1. Substrate enters the active site and enzymes change shape to interact with the substrate 2. Substrate is held in place in the active site of the enzyme -H-bonds, hydrophobic interactions, charge interactions form between active site amino acids and substrate 3. Activation energy is lowered by the active site (3 ways this can be done) a) Enzyme lines up the substrates correctly for new bonds to form b) Bonds in the substrate are stressed making them easier to break c) Creates a charge environment that favours the reaction 4. Substrate is converted into products that are released from active site o Products have a different shape than substrates, and don’t fit in active site 5. Cycle repeats

Question 38

Induced fit

Answer 38

enzyme changes shape to interact with substrate

Question 39

What factors affect enzyme activity ?

Answer 39

- concentration of substrate - concentration of enzyme - temperature - pH - cofactors and coenzymes - enzyme inhibitors

Question 40

Concentration of substrate (enzyme activity)

Answer 40

- more substrate=faster reaction rate - rate increases until all active sits in all enzymes are full (maximum)

Question 41

Concentration of enzyme (enzyme activity)

Answer 41

- more enzyme= faster reaction rate as long as there is substrate for all enzymes at max

Question 42

Temperature (enzyme activity)

Answer 42

- ↑ temperature = ↑ enzyme/substrate interactions = increases reaction rate - Too much heat = enzymes denature = lower reaction rate - Optimal temperature produces fastest rate:

Question 43

pH (enzyme activity)

Answer 43

- affects charges on amino acid side chains - changes in pH = changes protein shape and ability of substrate to bind in active site= decreased reaction rate - optimal pH produces

Question 44

Cofactors

Answer 44

metal ions or inorganic minerals

Question 45

Coenzymes

Answer 45

organic molecules (vitamins)

Question 46

Cofactors and Coenzymes

Answer 46

non protein helpers that are required for catalytic activity of enzymes

Question 47

Enzyme inhibitors

Answer 47

chemicals that selectively decrease activity of an enzyme ex. chemicals, drugs, poisons, normal molecules in the cell

Question 48

Irreversible inhibitors

Answer 48

Type of enzyme inhibitor - bind to enzyme using covalent bonds - permanent inactivation

Question 49

Reversible inhibitors

Answer 49

Type of inhibitory enzyme - bind to enzyme using hydrogen bonds - temporary inactivation (enzyme will return to normal when inhibitor removed

Question 50

Competitive inhibitor

Answer 50

Type of reversible inhibitor - mimics the normal enzyme substrate - competes with substrate for binding to active site - blocks the active site and prevents formation of enzyme-substrate complex=decreased reaction rate - can be overcome by increasing substrate concentration

Question 51

Non-competitive inhibitor

Answer 51

Type of reversible inhibitor - bind to region of enzyme other than the active site - changes the shape of the enzyme to make it less able to bind substrate - does not compete with substrate for active site - cannot be overcome by adding more substrate