Metabolic processes

Question 1

Eukaryotic cells

Answer 1

ound in organisms that contain a nucleus surrounded by a membrane and specialized organelles not present in prokaryotic cells
Linear DNA
Mitosis and meiosis

Question 2

prokaryotic cells

Answer 2

unicellular microorganisms that do not have a distinct nucleus or membrane bound organelles. Bacteria

Circular DNA

Question 3

Type 2, diabetes usually results from

Answer 3

The pancreas’s gradual inability to produce insulin
Cells becoming resistant to absorbing glucose, a type of sugar, from the blood
Individuals with the lack of ability to control blood sugar levels

Question 4

What is energy?

Answer 4

Energy is defined as the ability to do work

Kinetic energy is the energy that causes objects to move. This is the energy that is being used up
Potential energy is energy that is stored for later use.

Question 5

First law of thermodynamics

Answer 5

The first law of thermodynamics states that energy can be changed from one form to another, but it cannot be created or destroyed. The amount of energy in the universe is always conserved.

Question 6

Second law of thermodynamics

Answer 6

disorder (called “entropy”) in the universe is always increasing. Each time energy is used, some will be converted (“lost”) to heat (random motion).

Question 7

Diffusion of sugar in a cup of tea

Answer 7

Entropy Increase
It takes more work to keep the sugar molecules in one place in a cup of tea. During diffusion, molecules naturally move from an area of higher concentration to an area of lower concentration, leading to an increase of randomness and entropy when sugar diffuses in a cup of tea.

Question 8

Salt crystals breaking into ions

Answer 8

Entropy Increase
Chemical Breakdown: It takes more energy to keep the molecules bound together, as well as to combine those molecules together to create such a compound. Thus if left to nature the compound would naturally decompose and the amount of entropy would increase.

Question 9

Endergonic reactions

Answer 9

reactants have less energy than their products require energy
require continual inputs of energy until the reaction is completed.

Question 10

Exergonic reactions

Answer 10

reactants have more energy stored in their bonds than their products release energy,
do not require any energy inputs
catabolic reactions are exergonic - fat is hydrolyzed so its exergonic

Question 11

nad

Answer 11

NAD+ is and electron-deficient molecule and is in an oxidized state.
An enzyme binds NAD+ and a hydrogen atom in the presence of two electrons
NAD+ accepts hydrogen atoms and two electrons and becomes reduced to NADH
Question 2NADH is an energy rich molecule that is ready transfer electrons and energy to reactions that require them.

Question 12

APT cycle

Answer 12

provide the energy to drive endergonic reactions involving enzymes, such as the synthesis of polypeptides, DNA, and complex polysaccharides.
the energy required to make ATP is from the exergonic reactions of metabolizing (breaking down) carbohydrates, proteins or lipids.

Question 13

Aerobic cellular respiration is

Answer 13

catabolic, exothermic
process of capturing the energy of the electrons that are shared in the covalent bonds (C-H) of glucose, using oxygen as a final electron acceptor.
(both aerobic and anaerobic) begins in the cytoplasm.
The process results in the release of energy and the formation of water and carbon dioxide as products:
C6H12O6 + 6O2→ 6CO2+ 6H2O + energy in the form of ATP

Question 14

Stage of glycolysis

Answer 14

Two ATP molecules are consumed to prepare the 6-carbon glucose molecule to be broken down into 3-carbon molecules.

After the fourth reaction in the glycolysis pathway, the glucose is separated into two 3-carbon molecules called glyceraldehyde-3-phosphate (G3P).

From this point on, the metabolic reactions occur twice (once for each 3-carbon half of the original glucose molecule).

In the next series of reactions, glyceraldehyde-3-phosphate (G3P) is converted to two, 3-carbon pyruvate molecules. The energy harvested during the exothermic and enzyme catalyzed formation of pyruvate produces 2 NADH and 4 ATP molecules

NET tally of the products of one molecule of glucose by the end of glycolysis:
Two (3-C) Pyruvate molecules

2 NADH

2 ATP
the glycolytic pathway does not require oxygen and thus, is an anaerobic reaction. In fact, it is the key stage, initiating both aerobic and anaerobic respiration
most energy is retained in the pyruvate

enzymes of glycolysis are located in the cytosol of the cell

Question 15

Pyruvate oxidation

Answer 15

occurs in the mitochondrial matrix
Also known as the oxidative decarboxylation of pyruvate

A CO2 molecule is removed from one pyruvate.
Each pyruvate is also quickly oxidized by the energy carrier, NAD+, which gains two electrons and two protons, to become NADH and H+. Acetic acid is formed as the remaining product
A vitamin B5 derivative called coenzyme A (CoA) bonds with the acetic acid and forms a complex called acetyl-CoA. This complex is the final product in the oxidation of pyruvate.
2 CO2

2 Acetyl-CoA

2 NADH

2 H+
no ATP produced in pyruvate oxidation
reduction of the coenzyme NAD+ to NADH is an energy-storing endergonic reaction

Question 16

Krebs cycle

Answer 16

occurs in the mitochondrial matrix
known as the citric acid cycle
dehydrogenation, decarboxylation, and phosphorylation - involves 8 enzymes
Oxaloacetate, which begins the cycle as a reactant, is regenerated as a product, during the last reactions in the cycle.
4	CO2
6	NADH
2	FADH2
2	ATP

releases the most co2 from catabolism

Question 17

Explain why the Krebs cycle needs to occur twice for each glucose molecule undergoing cellular respiration.

Answer 17

Each glucose molecule leads to the production 2 acetyl-CoA molecules at the end of pyruvate oxidation and each “turn” of the Krebs cycle uses one acetyl-CoA molecule. Thus the Krebs cycle has to occur twice for each glucose molecule.

Question 18

Name the energy carriers in the Krebs cycle.

Answer 18

ATP, NADH, FADH2

Question 19

Electron transport chain (ETC) and chemiosmosis

Answer 19

Stage 4 occurs in the cristae of the matrix, the inner membrane, and the intermembrane space.
ETC is made up of a sequence of molecules called cytochrome complexes release some energy from the electrons at each step in the chain.
The energy released is used to power three proton pumps that push H+ ions out across the mitochondrial matrix membrane into the intermembrane space. The resulting transmembrane proton gradient is used to make ATP by chemiosmosis.
The NADH and FADH2 produced in the Krebs cycle have their high-energy electrons and associated protons removed in the ETC.

chemiosmosis is the coupling of atp synthesis to the electron transport and proton movement

Question 20

ETC steps

Answer 20

-NADH dehydrogenase removes the high-energy electrons from NADH. H+ is free
The NAD+ produced goes back into the Krebs cycle, where it gets turned again into NADH-

The FADH2 has its high-energy electrons removed by the next molecule in the chain, ubiquinone then FAD also returns to krebs cycle

The electron carrier, cytochrome C, carries electrons to the third proton pump, called cytochrome C oxidase. pumps H into intermembrane space (3rd proton pump)

All of the electrons that were stripped from glucose in the Krebs cycle have had their energy used to pump protons (H+) out of the matrix and are now at a very low energy level. formation for h2o

O2 is the last electron acceptor

Question 21

What is the original source of the carbon in the carbon dioxide that is produced?

Answer 21

Glucose

Question 22

β-oxidation of fats

Answer 22

the aerobic breakdown (catabolism) of fats is accomplished

Proteins can also provide a source of energy through a process called deamination.

Question 23

Explain how other sources of carbon are oxidized for energy.

Answer 23

Lipids

are broken down to glycerol and fatty acid chains
fatty acids chains enter the krebs cycle as acetyl- CoA by having enzymes in the adding CoA to the end of the fatty acid chains
glycerol enters glycolysis as G3P

Proteins

Due to varying functional groups, amino acids that are formed after deamination can enter the pathway as pyruvate, acetyl-CoA or into the Krebs cycle

Question 24

Anaerobic cellular respiration

Answer 24

Pyruvate is decarboxylated (CO2 is removed), resulting in the formation of the intermediate compound, acetaldehyde.
Acetaldehyde is then reduced as NADH dumps its electrons onto it to form ethanol (alcohol).

Aerobic cellular respiration is 16x more efficient than anaerobic respiration because 32 ATP are produced in the former and 2 ATP in the latter process.

Question 25

How does the second law of thermodynamics affect the efficiency of cellular respiration?

Answer 25

The second law states that the disorder of the universe increases, entropy increases, and energy that is lost is lost in the form of heat to the surrounding environment.

Question 26

“photosynthesis” literally means

Answer 26

making with light

Question 27

glucose is made from in photosynthesis

Answer 27

carbon dioxide, water and light energy.

6CO2 + 6H2O + light energy → C6H12O6 + 6O2

Question 28

bacteria that do not need light energy at all

Answer 28

chemosynthetic

Question 29

chloroplast

Answer 29

organelle that is responsible for carrying out photosynthesis in plants. Its appearance is like that of a miniature cell with an outer membrane.
The chloroplast contains stacks of membranous disks called thylakoids internal environment is lumen. The thylakoid membrane is embedded with many proteins bound to the membrane is chlorophyll
Thylakoids are grouped into columns, each called a granum (plural: grana, from Greek, meaning “stack of coins”) connected by lamellae
everything suspended in an aqueous medium called the stroma.

Question 30

Chlorophyll comes in two main forms

Answer 30

methyl (-CH3) in chlorophyll a, and carbonyl (-CHO) in chlorophyll b.
Plants’ pigments absorb light mostly within the visible spectrum

Question 31

Why are plants green

Answer 31

Chlorophylls a and b absorb light at the blue-violet and red wavelengths (400–500 nm and 600–700 nm respectively), and generally do not absorb, but instead reflect, the green light wavelengths from 500–600 nm.
Only chlorophyll a can absorb the energy and transfer the electrons required for photosynthesis. However, chlorophyll b, and various other accessory pigments, can absorb energy and pass electrons to chlorophyll a
Their combined effect is called the action spectrum.

Question 32

Role of chlorophyll a

Answer 32

To absorb energy of the red and blue wavelengths from light photons and transfer the electrons required for photosynthesis.

Question 33

Role of chlorophyll b

Answer 33

Question 1To absorb energy of the red and blue wavelengths from light photons and pass them on through the antenna complex to chlorophyll a

Question 34

Role of other pigments

Answer 34

Xanthophylls and carotenoids absorb light wavelengths that chlorophylls a and b do not, and pass the energy they absorb onto chlorophyll a via the antenna complex.

Question 35

The Calvin Cycle, which is responsible for

Answer 35

combining carbon into sugar molecules, is powered by the energy harvested during the light reactions. The process of combining the carbon atoms from carbon dioxide into a glucose molecule is called “fixing” the carbon.

Question 36

three stages of the light dependent reactions

Answer 36

Capture of light energy
Transfer of light energy by intermediate energy carriers
Transformation of light energy into chemical potential energy (ATP and NADPH)

Question 37

3 stage of Light-independent reactions, or Calvin cycle

Answer 37

Carbon fixation
Reduction of PGA
Regeneration of RuBP

uses the ATP and H+ protons from the light-dependent reactions to reduce carbon from CO2 to form carbohydrate molecules like glucose
do not depend on photons for energy

Calvin cycle must run six times for every glucose molecule

Question 38

capture of light energy

Answer 38

When a photon of light energy hits a chlorophyll molecule that is bound to the thylakoid membrane, an electron absorbs much of this energy.
The electron becomes excited to a higher energy level and leaves the chlorophyll a in order to move to neighbouring pigments.
excited electron is captured by a primary electron acceptor which oxidizes the reaction centre to gain the electron.

photosystem II (or photosystem 680)

b. photosystem I (or photosystem 700)

Question 39

transfer of light energy

Answer 39

Photolysis-energy passed through photosystem 680 is used to remove electrons from water and release protons (H+ ions).The oxygen that is released diffuses out of the chloroplast (which explains how oxygen is a product of photosynthesis).
The protons are pumped into the lumen (interior) of the thylakoids and create a chemiosmotic gradient. Photosystem II feeds the same electrons to photosystem I

transfer of electrons from photosystem II to photosystem is called the ETC. Another intermediate energy carrier called ferrodoxin (Fd) transfers the excited electron from photosystem I to the enzyme, NADP reductase
ATP is produced after photosystem II.

NADPH is produced after photosystem I

Question 40

Non-cyclic photophosphorylation

Answer 40

green plants predominantly use
electrons that are donated by chlorophyll a are never returned to it. Instead, the electrons are accepted by NADP, at the end of the process, to form NADPH

This gradient (proton motive force) is used by ATP synthase to generate ATP, whose energy is used later to help make glucose.

Question 41

Cyclic photophosphorylation

Answer 41

photosynthetic bacteria
electrons that are donated by chlorophyll a are returned to it via the ETC.
The path of the electrons is a loop that cycles between photosystem I and the ETC.

Question 42

Compare the roles of photosystems I and II in photosynthesis.

Answer 42

Photosystem II functions to harvest photon energy and donate high-energy excited electrons to the first of the electron carriers of the ETC. Photosystem I accepts the electrons passed along from photosystem II and, using more light energy from photons, re-excites those electrons to an even higher energy level, before passing them on to the rest of the electron carriers of the ETC.

Question 43

What is the result of light energy absorbed by photosystem I?

Answer 43

It energizes an electron that transfers to ferredoxin, which then forms NADPH.

Question 44

In photosynthesis, where does the oxygen that is released come from

Answer 44

water

Question 45

The Krebs cycle and the Calvin cycle are arguably very different from each other, yet they have some similarities. One such similarity is:

Answer 45

they both regenerate a starting compound or “reactant”

Question 46

what moves into the intermembrane space

Answer 46

protons

Question 47

the protein where protons re-enter the mitochondrial matrix

Answer 47

ATP synthase

Question 48

what is the first protein complex of the chain

Answer 48

NADH dehydrogenase

Question 49

the molecules are electron donors at the beginning of the chain

Answer 49

NADH/FADH2

Question 50

In the light-independent reactions, carbon dioxide is fixed in the Calvin cycle by the enzyme

Answer 50

_RuBisCO__

Question 51

In the chloroplast, electron transport takes place on membranes of the

Answer 51

thylakoid

Question 52

carbon fixation of the Calvin cycle,

Answer 52

CO2 molecule is added to a five-carbon compound called RuBP -present in the stroma.
yielding two molecules of the 3-carbon compound, PGA (3-phosphoglycerate).
cycle must be repeated three times to produce one molecule of G3P (3C) with 6 PGA

Question 3Three RuBP molecules are joined with three CO2 molecules by the enzyme rubisco, to make six molecules of PGA.

Question 53

Phase 2: Reduction of PGA in calvin cycle

Answer 53

each of the six PGA molecules created from carbon fixation is raised to a higher energy level by the addition of a phosphate group. The phosphate comes from the ATP generated during the light-dependent reactions.
One of the six G3P leaves the cycle to make glucose and fructose which can then be synthesized into sucrose or starch., while the other five remain behind to replenish the supply of RuBP to keep the cycle going

Six ATP molecules are used and six NADPH molecules are oxidized by PGA kinase and G3P dehydrogenase, to form six G3P molecules. One of the G3P molecules leaves the cycle as a product, becoming further processed into a sugar.

Question 54

Phase 3: Regeneration of RuBP

Answer 54

In the third and final phase of the Calvin cycle, the remaining five G3P molecules, in combination with three phosphates and three ATP, synthesize three energy-rich RuBP molecules.
RuBP is required to fix each CO2
regeneration is key

Three ATP molecules are used to form three RuBP molecules from the five G3P molecules that remained.

Question 55

Summarize the events of the light-independent reactions by referring to the reactants, products, and cellular components involved.

Answer 55

CO2 molecules enter into a three-step metabolic pathway called the Calvin cycle. ATP provides energy for enzymes to add the carbon from the CO2 to intermediate carbon- and phosphate-rich molecules, eventually yielding the energy-rich G3P molecule, which leaves the Calvin cycle. NADPH is then used with more ATP to regenerate the carbon-rich intermediate RuBP, so that the cycle can begin again with the entry of more CO2.

Question 56

What is the relationship between the light reactions and the Calvin Cycle?

Answer 56

The light reactions use light energy and water to provide the energy (in the form of ATP and NADPH) for the Calvin Cycle, which fix carbon from gaseous carbon dioxide into energy-rich sugar molecules.

Question 57

How many ATP and NADPH molecules are required to form one glucose molecule during photosynthesis?

Answer 57

18 ATP, 12 NADPH

Question 58

Photorespiration

Answer 58

process that reduces the efficiency of photosynthesis, thus preventing photosynthesis when unfavourable temperatures are present.
Rubisco, the enzyme that catalyzes the first step in the Calvin cycle, is required to fix carbon dioxide. However, Rubisco can also react with oxygen instead of carbon dioxide. If this occurs, it would lead to a less efficient photosynthetic rate. Photorespiration results when plants try to conserve water loss when the temperature rises above the optimal temperature for photosynthesis as seen in the image below.

Question 59

C3 and C4 plants differ how?

Answer 59

higher the plant’s rate of photorespiration, the less efficient it is at converting sunlight into food. C4 plants have important adaptations that make them more efficient at higher temperatures than C3 plants, but less efficient at lower temperatures.

Question 60

c3 plants

Answer 60

Plants that fix carbon into molecules containing three carbon atoms
trees, wheat, barley, potatoes, cotton, and sugar beets
cannot grow well in hot, dry areas because these conditions produce higher rates of photorespiration for them, which limit their growth.

Question 61

C4 Plants

Answer 61

Plants that fix carbon into molecules containing four carbon atoms are called C4 plants.
corn, sugar cane, sorghum, and crabgrass. C4 plants are more efficient at photosynthesis under hot, dry conditions
more efficient at higher temperatures than C3 plants, but less efficient at lower temperatures..

Question 62

Crassulacean acid metabolism, or CAM

Answer 62

way that some water-storing succulent plants like pineapples, cacti, aloe vera, and orchids cope, especially in hot and dry climates.
carrying out the C4 pathway at night and switching to the Calvin cycle during the day.

Question 63

why is photorespiration a problem for plants?

Answer 63

Photorespiration occurs when plants try to conserve water by closing their stomata and consequently, the carbon dioxide concentration drops and oxygen binds to RuBP in the Calvin Cycle and glucose production is halted.

Question 64

The electron comes from the enzyme breakdown of ______. The electron _____ energy twice in the process: once in photosystem ____, where the energy from a photon of ____ is transferred to the electron, and once again in photosystem ______.

Answer 64

Water – Gains – 680 – Light – 700

Question 65

Similarities between chloroplasts and mitochondria

Answer 65

Both have a double membrane.
A cyclic process occurs in both organelles - Krebs cycle in mitochondria and Calvin cycle in the stroma of the chloroplast.
An electron transport chain (ETC) occurs in both thylakoid and inner mitochondrial membranes, and it contains some proteins and cytochromes that are identical or very similar.
ATP synthase uses proton motive force to power chemiosmosis during the main ATP generation phase (oxidative phosphorylation), both in the final stage of the light reactions (in the chloroplast) and in the final stage of respiration (in the mitochondria).

Question 66

increased CO2 levels cause

Answer 66

changing precipitation patterns
changing weather patterns
shifting climate zones which result in species extinction rates
increased melting of glacial and polar ice caps
water levels rising and coastal flooding
extreme weather events to occur more often and more severely