Question 1

What is the First Law of Thermodynamics?

Accepted Answer

Energy cannot be created or destroyed

(the sum of energy in the universe is constant)

Question 2

What is the Second Law of Thermodynamics?

Accepted Answer

Entropy/disorder will always increase in a closed system

(an ice cube will melt into a drink, but a drink will never randomly create an ice cube)

Question 3

What is entropy?

Accepted Answer

Disorder/chaos in a system

Question 4

How does the First Law of Thermodynamics relate to cells?

Accepted Answer

Cells cannot create energy from thin air, so they must get it from something

Question 5

How does the Second Law of Thermodynamics relate to cells?

Accepted Answer

If cells do not use energy to repair themselves, they eventually die because of increasing entropy

Question 6

What are exergonic reactions?

Accepted Answer

Chemical reactions where the products have less energy than the reactants

(energy is lost during the reaction)

Question 7

What are endergonic reactions?

Accepted Answer

Reactions that require an input of energy, causing the products to have more energy than the reactants

(photosynthesis uses energy from the sun to create sugars that have more energy than carbon dioxide and water)

Question 8

What is the difference between exergonic and endergonic reactions?

Accepted Answer

Exergonic: loses energy during the reaction (products have less energy than reactants)

Endergonic: requires energy to react (products have more energy than reactants)

Question 9

What is an energy diagram?

Accepted Answer

A diagram that represents the course of a chemical reaction

(energy is y-axis; time is x-axis)

Question 10

What is a transition state?

Accepted Answer

A temporary state of atoms in a reaction that contains a lot of energy

(reactants must enter the transition state before turning into products)

Question 11

What is activation energy?

Accepted Answer

The energy required to reach the transition state

(provides the boost to get over the "hump" and start the reaction)

Question 12

Why do reactions require activation energy to "get them going"?

Accepted Answer

It is difficult to reach the transition state, so they need activation energy to help

Question 13

What are catalysts?

Accepted Answer

A substance that speeds up the rate of a chemical reaction

(without being changed itself)

Question 14

What are enzymes?

Accepted Answer

Biological catalysts that speed up reactions

Question 15

How do enzymes speed up reactions?

Accepted Answer

They lower the activation energy required, making it easier to reach the transition state

Question 16

What is enzyme specificity?

Accepted Answer

The tendency of enzymes to only catalyze a single type of reaction

Question 17

What are substrates?

Accepted Answer

The substances enzymes target

Question 18

What is an active site?

Accepted Answer

A special region on each enzyme that binds to a protein/substance during a reaction

Question 19

What is an enzyme-substrate complex?

Accepted Answer

The temporary form where a substrate is bound to an enzyme's active site

Question 20

What is induced-fit?

Accepted Answer

Enzymes changing their shape a tiny bit to accommodate the shape of the substrate

(enzymes and substrates don't actually fit perfectly)

Question 21

What are cofactors?

Accepted Answer

A substance that helps an enzyme catalyze a reaction

(NOT a substrate itself)

Question 22

What are coenzymes?

Accepted Answer

A type of non-protein organic compound that is essential for enzymes to properly function

Question 23

How does temperature affect enzymes?

Accepted Answer

Higher temperatures make enzymes work faster, but too much heat will damage an enzyme

(max temperature is around 40℃ or 104℉)

Question 24

What are denatured enzymes?

Accepted Answer

Enzymes that have been broken and no longer work

(excessive heat will denature enzymes)

Question 25

What is the  temperature coefficient?

Accepted Answer

A measure of temperature sensitivity for enzyme reaction rate

Question 26

How does pH affect enzymes?

Accepted Answer

Enzymes operate best a specific pH (usually 7)

(some enzymes, like pepsin (digestive enzyme in stomach) operate at much more acidic like 2)

Question 27

What are allosteric sites?

Accepted Answer

A site on enzymes that allow other molecules to activate/deactivate them

Question 28

What is competitive inhibition?

Accepted Answer

A type of enzyme inhibition where the substance directly blocks the active site

Question 29

What is allosteric inhibition?

Accepted Answer

A type of enzyme inhibition where the substance binds to an allosteric site

Question 30

What is noncompetitive inhibition?

Accepted Answer

A type of allosteric inhibition that doesn't directly block the active site

(usually distorts the enzyme shape so it can't function)

Question 31

What is enzyme inhibition?

Accepted Answer

The process of temporarily disabling/inhibiting an enzyme from functioning

(three types: competitive, allosteric, noncompetitive)

Question 32

Why is enzyme inhibition important?

Accepted Answer

Allows enzymes to temporarily be disabled

Variety of purposes, including medicine, drugs for metabolic imbalance, and pesticides

Question 33

How do cells get energy from ATP?

Accepted Answer

It splits off one of the energy-packed phosphates, forming ADP and a loose phosphate, releasing energy in the process

Question 34

What is photosynthesis?

Accepted Answer

Process of green plants using sunlight to synthesize energy

Question 35

What are photons?

Accepted Answer

Basic units of light

(in photosynthesis, photons activate chlorophyll)

Question 36

How does sunlight cause photosynthesis?

Accepted Answer

Photons of sunlight strike a leaf, activating chlorophyll, and exciting electrons

The electrons are passed down through a series of carriers, eventually creating ATP (and NADPH)

Question 37

What is the stroma, in chloroplasts?

Accepted Answer

A fluid-filled region in chloroplasts that is essential for photosynthesis

Question 38

What are grana, in chloroplasts?

Accepted Answer

Structures inside stroma that look like stacks of coins

Question 39

What are thylakoids, in chloroplasts?

Accepted Answer

The individual disk-like structures that make up grana

Contain chlorophyll, and enzymes essential to photosynthesis

Question 40

What does a chloroplast look like?

Accepted Answer

(sorry if it takes a second to load)

Question 41

What are chlorophyll a, chlorophyll b, and carotenoids?

Accepted Answer

Light absorbing pigments in thylakoid membranes, that participate in photosynthesis

Question 42

What is the reaction center, in chloroplasts?

Accepted Answer

A special place in chloroplasts that contains a molecule capable of transforming light energy to chemical energy

Question 43

What are antenna pigments?

Accepted Answer

Pigments in the chloroplast that gather and bounce light to the reaction center

(don't create chemical energy themselves)

Question 44

What are photosystem I (PS I) and photosystem II (PS II)?

Accepted Answer

Two types of reaction centers in chloroplasts, each of which has a specific type of chlorophyll

Question 45

What is P680, in chloroplasts?

Accepted Answer

The reaction center of photosystem II, which has a maximum absorption at a wavelength of 680 nanometers

Question 46

What is P700, in chloroplasts?

Accepted Answer

The reaction center for photosystem I, which best absorbs light with a wavelength of 700 nanometers

Question 47

What is photophosphorylation?

Accepted Answer

The process of using sunlight energy to convert ADP to ATP

(photo=light; phosphorylation=ADP + phosphates)

Question 48

What is an absorption spectrum?

Accepted Answer

A graph that shows how well a certain pigment absorbs different wavelengths of light

Question 49

What is an emission spectrum?

Accepted Answer

The opposite of an absorption spectrum, instead giving information on which wavelengths a pigment emits

Question 50

What does the absorption spectrum look like for chlorophyll a, chlorophyll b, and carotenoids?

Accepted Answer

Chl a and b absorb blue and red light well; carotenoids also absorb blue light, but do not absorb red light

(all the green gets reflected, which is why plants look green)

Question 51

Why do plants look green?

Accepted Answer

Chlorophyll a, b, and carotenoids reflect green light

Question 52

What is photolysis?

Accepted Answer

The process of splitting water into oxygen, hydrogen, and electrons to replenish the electrons in the thykaloid

(powered by light from the Sun)

Question 53

How are electrons in the thylakoid replaced?

Accepted Answer

Via photolysis: electrons are taken from water to replace the missing electrons in PS II

Question 54

What is the thylakoid lumen?

Accepted Answer

The inner part of the thylakoid

Question 55

How does the ATP synthase produce ATP, in photosynthesis?

Accepted Answer

Hydrogen ions flow from the thylakoid through the ATP synthase via a concentration gradient, producing ATP as they move

(the hydrogen ions come from photolysis)

Question 56

What happens after electrons leave photosystem II?

Accepted Answer

They go to photosystem I, are passed through a second electron transport chain, and finally create NADPH

Question 57

What is NADPH?

Accepted Answer

An energy carrying molecule produced in the first stage of photosynthesis

It provides energy to fuel the Calvin cycle in the second stage

Question 58

Where are the light-absorbing pigments and enzymes for light-dependent reactions?

Accepted Answer

In the chloroplast's thylakoids

Question 59

What is carbon fixation (a.k.a. carbon assimilation)?

Accepted Answer

The process of  being converted into carbohydrates inside the stroma using RuBisCO

(during the Calvin cycle)

Question 60

What is the Calvin-Benson cycle (a.k.a. Calvin cycle)?

Accepted Answer

Chemical reactions in photosynthesis that convert CO2 and other compounds into glucose

(occurs in the stroma, and requires ATP and NADPH)

Question 61

What is the difference between light-dependent and light-independent reactions?

Accepted Answer

Light-dependent reactions use light to create the energy molecules light-independent reactions (the Calvin cycle) need

Question 62

What are stomata?

Accepted Answer

Pores on the leaf surface that allow  to enter the leaf, and  and water to exit

Question 63

What is photorespiration?

Accepted Answer

An inefficient process in plants, where RuBisCO accidentally uses O2 instead of CO2, causing it to be much less efficient

(most likely to happen in hot, dry conditions)

Question 64

Why do plants sometimes need photorespiration instead of photosynthesis?

Accepted Answer

When it is hot outside, most plants close their stomata to prevent water loss

Closed stomata leads to less  available and an accumulation of , so the plant must perform photorespiration

Unit 3: Cellular Energetics, AP Biology Flashcards