Unit 3: Cell Energetics #1

Question 1

What is metabolism?

Answer 1

All of the chemical reactions in an organism.

Question 2

What are metabolic pathways?

Answer 2

A series of chemical reactions that either build complex molecules or break down complex molecules.

Question 3

What are the two types of metabolic pathways?

Answer 3

Catabolic pathways and anabolic pathways.

Question 4

What are catabolic pathways?

Answer 4

Pathways that release energy by breaking down complex molecules into simpler compounds =.W

Question 5

What are anabolic pathways?

Answer 5

Pathways that consume energy to build complicated molecules from simpler compounds.

Question 6

What is energy?

Answer 6

The ability to do work.

Question 7

What are the two types of energy?

Answer 7

Kinetic energy and potential energy.

Question 8

What is kinetic energy?

Answer 8

Energy associated with motion, ex. thermal energy: energy associated with the movement of atoms or molecules.

Question 9

What is potential energy?

Answer 9

Stored energy, ex. chemical energy: potential energy available for release in a chemical reaction.

Question 10

What is thermodynamics?

Answer 10

The study of energy transformations.

Question 11

What is the 1st Law of thermodynamics?

Answer 11

Energy cannot be created or destroyed, energy can be transferred or transformed.

Question 12

What is entropy?

Answer 12

The randomness of the universe.

Question 13

What is the 2nd law of thermodynamics?

Answer 13

That energy transformation increases the entropy of the universe, because during energy transformations some energy is unusable and often lost as heat.

Question 14

Compared to early life, organisms are highly organized today. How does this not violate the 2nd law?

Answer 14

The entropy of a particular system may decrease, but he total entropy of the universe increases.

Question 15

What is free energy?

Answer 15

Since thermodynamics laws apply to the whole universe, scientists use free energy to determine the likelihood of reactions in organisms. Free energy is used to determine how much work a system can improve, or if reactions are energetically favorable.

Question 16

What is the formula for free energy?

Answer 16

∆G (change in free energy) = ∆H (change in total energy) - T (absolute temp (k)) * ∆S (change in entropy)

Question 17

What does the free energy change of reactions determine?

Answer 17

The free energy change (∆G) of a chemical reaction is the amount of energy released in the conversion of reactants to products, so it determines whether the reaction was spontaneous (no outside energy) and if it is classified as exergonic or endergonic.

Question 18

What are exergonic reactions?

Answer 18

Reactions that release energy like cellular respiration where ∆G < 0 and the reaction is spontaneous.

Question 19

What are endergonic reactions?

Answer 19

Reactions that absorb energy like photosynthesis where ∆G > 0 and the reaction is not spontaneous and absorbs free energy.

Question 20

Are cells at equilibrium?

Answer 20

No, they are not because living cells have a constant flow of materials in and out of the membrane.

Question 21

What are the three kinds of work cells perform?

Answer 21

Mechanical (movement of cilia, chromosomes, muscle cell contractions), transport (pumping substances across membrane against spontaneous movement) or chemical (synthesis of molecules)

Question 22

What is ATP?

Answer 22

Adenosine triphosphate which is a molecule that organisms use as a source of energy to perform work.

Question 23

How does ATP work?

Answer 23

ATP uses energy from the exergonic reactions (it breaking apart) to drive endergonic reactions (cellular work or putting ADP + Pi into ATP). Organisms obtain energy by breaking the bond between the 2nd and 3rd phosphate in an hydrolysis reaction.

Question 24

What is phosphorylation?

Answer 24

When the released 3rd phosphate moves to another molecule to give it energy.

Question 25

How do cells make slow spontaneous reactions faster?

Answer 25

Enzymes!!!!!!

Question 26

What are enzymes?

Answer 26

Proteins that catalyse reactions by lowering the activation energy, and can perform multiple reactions (are not affected) and their names end in -ase.

Question 27

What does an enzyme act on?

Answer 27

A substrate.

Question 28

Where does an enzyme act on a substrate?

Answer 28

In the active site, an area for a substrate to bind.

Question 29

What is induced fit?

Answer 29

When enzymes change the shape of their active site to allow the substrate to bind better (tighter grip).

Question 30

What is enzyme catabolism?

Answer 30

When enzymes help break down complex molecules into parts.

Question 31

What is enzyme anabolism?

Answer 31

Enzymes that help build complex molecules.

Question 32

How can the efficiency of enzymes be affected?

Answer 32

By temperature, pH, and chemicals (concentration of substrate and enzymes).

Question 33

How does temperature affect enzymes?

Answer 33

The rate of enzyme activity increases with temperature and decreases as temperature does up to a certain point in high temperature where enzymes will denature from the heat.

Question 34

How does pH affect enzymes?

Answer 34

Enzymes function best at a specific pH, being outside that range can cause hydrogen bonds in the enzyme to break, denaturing the enzyme/changing its shape.

Question 35

What are cofactors?

Answer 35

Non-protein molecules that assist in enzyme function, can be bound loosely or tightly. Can have Holoenzymes which are enzymes with the cofactor attached.

Question 36

What are the two types of cofactors?

Answer 36

Inorganic cofactors which are metals (no carbon) and organic cofactors (coenzymes) which are vitamins (yes carbon).

Question 37

What are enzyme inhibitors, and what are the two types?

Answer 37

Enzyme inhibitors reduce the activity of specific enzymes by binding to it. Inhibition can be permanent, inhibitor binds with covalent bonds (ex. poison) or reversible, inhibitor binds with weak interactions.

Question 38

What are competitive inhibitors?

Answer 38

They reduce enzyme activity by blocking substrates from binding to the active site, and this can be reversed with increased substrate concentrations that can outcompete the inhibitors.

Question 39

What are noncompetitive inhibitors?

Answer 39

Inhibitors that bind to the allosteric site which changes the shape of the active site, preventing substrates from binding. (TYPE OF ALLOSTERIC INHIBITOR OTHER ONE IS NONCOMPETITIVE)

Question 40

What is the allosteric site?

Answer 40

Another site on an enzyme which, if binded to, could change the shape of the enzyme and therefore the active site.

Question 41

How can a cell regulate its metabolic pathways?

Answer 41

By controlling where and when enzymes are active and switching the genes that code for an enzyme on and off.

Question 42

What are allosteric enzymes?

Answer 42

Enzymes that have two binding sites, 1 active site, and 1 allosteric site (regulatory site).

Question 43

What is a multi-subunit enzyme?

Answer 43

An enzyme that have multiple subunits so multiple binding sites and allosteric sites.

Question 44

What is allosteric regulation?

Answer 44

When molecules bind (noncovalent) to an allosteric site which changes the shape and function of the active site (results in inhibition by inhibitor or stimulation by an activator).

Question 45

What is an allosteric activator?

Answer 45

When a substrate binds to an allosteric sites and stabilizes the enzyme so the site remains open (before binding, it oscillates between open and closed).

Question 46

What is an allosteric inhibitor?

Answer 46

When a substrate binds to an allosteric sites and stabilizes the enzyme so the site remains closed (inactive). (before binding, it oscillates between open and closed).

Question 47

What is cooperativity?

Answer 47

When a substrate binds to one active site (on an enzyme with more than one) which stabilities to the open or active form, considered allosteric regulation even though it is not an allosteric site. It is because one site changes the shape of other sites.

Question 48

What is feedback inhibition?

Answer 48

When the end product of a metabolic pathway can act as an inhibitor to an early enzyme in the same pathway.