Cell Biology Exam 2

Unlike animals, plants make most of their ATP during photosynthesis

FALSE

Glycolysis occurs in the ______ of a cell. Citric acid cycle occurs in the _______. Oxidative phosphorylation occurs in the ________.

cytoplasm, mitochondrial matrix, inner mitochondrial membrane

your skeletal muscle cells can use _____ as a backup when oxygen is in short supply.

oxygen

In the third stage of aerobic respiration, _____ is the final acceptor of electrons from glucose.

O2/oxygen

How is ATP generated during oxidative phosphorylation?

H+ flow through ATP synthase

What do enzymes do?

catalyze chemical reactions within cells

How do enzymes do their job?

lowering activation energy by properly orienting, destabilizing, and shielding substrates

Type of enzyme regulation where an inhibitor binds to the active site

competitive inhibition

type of enzyme regulation where the product in a pathway inhibits the first enzyme in the pathway

feedback inhibition

This is how allosteric activators work

allosteric activators bind to allosteric site on enzyme changing the active site to a high-affinity state

release energy by breaking down

catabolic pathways

consume energy by building up

anabolic pathways

___________ Energy can be associated with the relative motion of objects.

kinetic

_________ energy is associated with the random movement of atoms or molecules. (heat related)

thermal

________ is a type of energy that can be harnessed to perform work, such as powering photosynthesis in green plants.

light

Energy that is not kinetic is called (energy that matter possesses because of its location or structure):

potential energy

__________ is the potential energy available for release in a chemical reaction.

chemical energy

1st Law of thermodynamics

The principle of conservation of energy. Energy can be transferred and transformed, but it cannot be created or destroyed.

2nd law of thermodynamics

Every energy transfer or transformation increases the entropy of the universe.

entropy

measure of disorder in the universe

spontaneous process

a process that can occur without an input of energy

nonspontaneous process

change cannot occur without input of energy (+G)

________ is the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell.

free energy

change in free energy is called

delta G

equation for change in free energy

delta G = delta H - T delta S

energy outward

exergonic

energy inward

endergonic

The greater the _______ in free energy, the greater the amount of work that can be done.

decrease

An _________ reaction proceeds with a net release of free energy. Because the chemical mixture loses free energy (G decreases), ΔG is negative for an exergonic reaction. Using ΔG as a standard for spontaneity, ________ reactions are those that occur spontaneously.

exergonic

downhill

exergonic

uphill

endergonic

An ________ reaction is one that absorbs free energy from its surroundings. Because this kind of reaction essentially stores free energy in molecules (G increases), ΔG is positive. Such reactions are non-spontaneous, and the magnitude of ΔG is the quantity of energy required to drive the reaction.

endergonic

Is cellular respiration spontaneous or not?

It is spontaneous

Is cellular respiration exergonic or endergonic?

exergonic because it releases energy

3 main kinds of work cells do

chemical, transport, mechanical

energy coupling

The use of an exergonic process to drive an endergonic one.

What is the immediate source of energy that powers cellular work?

ATP

ATP

contains the sugar ribose, with the nitrogenous base adenine and a chain of three phosphate groups (the triphosphate group) bonded to it

hydrolysis

ATP+H2O--->ADP+Ⓟi

metabolism

the totality of an organism's chemical reactions

protein synthesis

anabolic pathways

Delta G

change in free energy

Delta H

change in enthalpy (total energy)

Delta S

change in entropy

True or False: living cells can reach equilibrium.

False

ATP cycle

energy from catabolism--->ATP+H2O--->energy for cellular work

catalyst

speeds up chemical reaction without being consumed

enzymes speed up metabolic reactions by __________ energy barriers

lowering

provides a barrier that determines the rate of spontaneous reactions

activation energy

Enzymes catalyze reactions by:

lowering the activation energy

The reactant that an enzyme acts on

enzyme's substrate

most enzymes names end in

-ase

region of the enzyme that binds to the substrate

active site

when the substrate enters the active site:

the enzyme changes shape slightly, tightening around the substrate like a handshake

what type of bonds hold the substrate in an enzyme's active site?

weak, hydrogen bonds

What happens when you increase substrate concentration?

the enzyme-catalyzed reaction is sped up

When is an enzyme saturated?

when all enzyme molecules have their active sites engaged

If the enzyme is saturated:

the reaction rate can only be sped up by adding more enzyme

organic cofactors are called

coenzymes

cofactors are:

nonprotein enzyme helpers

Inhibitor with a covalent bond:

irreversible

Inhibitor with a weak interaction

reversible inhibition

Where do noncompetitive inhibitors bind?

At a site other than the active site (where the substrate binds)

allosteric regulation

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.

feedback inhibition

process in which the product or result stops or limits the process

enzyme activation can be achieved by:

optimal conditions, allosteric activation

enzyme inhibition can be achieved by:

sub-optimal conditions, competitive inhibition, allosteric inhibition, feedback inhibition.

catabolic pathways release stored energy by:

breaking down complex molecules

The breakdown of organic molecules is

exergonic

a partial degradation of molecules that occurs without oxygen:

fermentation

consumes organic molecules and O2 and yields ATP

aerobic respiration

similar to aerobic respiration but consumes compounds other than O2

anaerobic respiration

cellular respiration

C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy

true or false: cells must constantly regenerate their supply of ATP from ADP and phosphate

true

the transfer of electrons during chemical reactions release energy stored in organic molecules:

redox reaction

True or False: the energy used to synthesize ATP is from redox reactions

true

a _______ consists of a series of molecules built into the inner membrane of the mitochondria

electron transport chain

O2 is always ______

the final electron acceptor

energy yielded from the electron transport chain:

regenerates ATP

Cellular respiration is:

aerobic

fermentation is:

anaerobic

steps of cellular respiration

1. Glycolysis (cytoplasm)

glucose + 2ATP = 2 pyruvate + 4ATP + 2NADH

2A. Pyruvate Oxidations/Krebs cycle (mitochondrial matrix)

Pyruvate + CoA = CO2 + NADH + Acetyl CoA x2

2B. Citric Acid Cycle (mitochondrial matrix)

Acetyl-CoA--->---->----> 2CO2 + 3NADH + FAOH2 + ATP x2

3. Oxidative Phosphorylation (inner mitochondrial membrane)

NADH/FADH2 passes e- to ECT-----> ATP (x28)

electrons land on O2 to form H2O

oxidative phosphorylation

powered by the redox reactions of the electron transport chain

substrate-level phosphorylation

The formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism.

for every molecule degraded to CO2 and H2O via cellular respiration:

up to 32 molecules of ATP are produced

Chemeiosmosis

synthesis of ATP

proton-motive force

H+ gradient

Energy Flow in Cellular Respiration

glucose -> NADH -> electron transport chain -> proton-motive force -> ATP

Steps of Fermentation (Lactate)

2NADH+ +glucose + 2 ATP = 2 pyruvate +4ATP + 2NADH

(pyruvate + NADH = lactate + NAD+)x2

NAD+ reused in glycolysis=continued ATP synthesis

Steps of Fermentation (alcoholic)

2NADH+ +glucose + 2 ATP = 2 pyruvate +4ATP + 2NADH

(pyruvate + NADH = ethyl alcohol + NAD+ +CO2+)x2

NAD+ reused in glycolysis=continued ATP synthesis

Where does the light dependent reaction in photosynthesis take place?

thylakoid membrane

Where does the light independent reaction in photosynthesis take place?

Stroma (AKA Calvin Cycle)

steps of photosynthesis (light dependent)

1. Sunlight excites electrons on chlorophyll in PS2.

2. Energy from the excited electrons is transferred to P680.

3. P680 donates excited electrons to Primary Acceptor.

4. Water is split to replenish electrons on P680, O2 released.

5. Excited electron is passed from the primary acceptor to the electron transport chain.

6. Energy from the electron used to pump H+ into thylakoid lumen.

7. H+ concentration gradient drives ATP synthaseàATP.

8. Electron passed from ETC to P700 in PS1.

9. Sunlight excites electrons on chlorophyll in PS1.

10. Energy from the excited electrons is transferred to P700.

11. P700 donates excited electrons to Primary Acceptor.

12. Excited electrons passed down short electron transport chain to NADP+àNADPH

steps of photosynthesis (light independent)

1. Carbon Fixation: CO2 + RuBPà 2 (3-PGA)

2. Reduction: ATP + NAPDH + 3-PGAà2 (G3P) (building blocks of sugar)

3. Regeneration: 5G3P used to regenerate RuBP; 1G3P leftover goes towards making glucose (6G3P to make 1 glucose)

Photosystem

light-collecting units of the chloroplast

reaction-center complex

organized association of proteins holding a special pair of chlorophyll a molecules and a primary electron acceptor

photosystem II (PSII)

P680

photosystem I (PSI)

P700

type of transport used to move molecules from low to high concentration

active transport

when molecules move from an area of higher concentration to lower concentration through a transport protein

facilitated diffusion