Nucleus, mitochondria, plastids

Question 1

what are the functions of the nucleus

Answer 1

• storage and maintenance of a cells genetic information
• control of gene expression through transcription
• regulation of protein synthesis machinery through ribosomal RNA and assembly of ribosomes in the nucleus

Question 2

how does the nucleus maintain its shape

Answer 2

usually spherical or oval

inner side of nuclear envelope lined by the nuclear lamina - anchor interphase chromatin at nuclear periphery

Question 3

what is the structure of DNA

Answer 3

a twisted ladder made by a double helix and it is highly packaged into chromatin

Question 4

why are mitochondria the powerhouse of the cell

Answer 4

convert energy contained in food into energy forms that the cell can use (ATP) through a process that uses oxygen

Question 5

what are the three stages of cellular respiration

Answer 5

1. glycolysis
2. citric acid cycle (Krebs cycle)
3. oxidative phosphorylation

Question 6

cellular respiration
describe what happens during glycolysis

Answer 6

glucose (C6) broken down into two molecules of pyruvate (C3)

aerobic = respiration
anaerobic = fermentation

Question 7

cellular respiration
describe what happens during the citric acid cycle

Answer 7

• completes the breakdown of glucose to carbon dioxide
• catalysed by pyruvate dehydrogenase
• oxidation of pyruvate carboxyl group produces first CO2
• NAD+ reduced to NADH
• remaining 2C fragments combine with coenzyme A to form acetyl CoA
• because 2 pyruvate are produced per glucose, the cycle runs twice per glucose molecule consumed

Question 8

cellular respiration
describe what happens during oxidative phosphorylation

Answer 8

the electron transfer chain and chemiosmosis facilitate the synthesis of most of the cell’s ATP
- NADH and FADH2 donate electrons to ETC, powers the ATP synthesis via oxidative phosphorylation
- electron carriers alternate between reduced and oxidised states as they accept and donate electrons
- ETC does not directly make ATP, it breaks a large free-energy drop into a series of smaller steps that release energy in smaller amounts

Question 9

what is an example of a plastid

Answer 9

chloroplasts

Question 10

what is the endosymbiotic theory

Answer 10

plastids & mitochondria represent formerly free living bacteria which had invaded ancestral host cells

Question 11

what are thylakoids

Answer 11

flattened and interconnected sacs found in inner membrane system of chloroplasts
can be stacked in columns called grana

Question 12

where in the chloroplast is chlorophyll found

Answer 12

thylakoid membranes

Question 13

where in the chloroplast does the light stage take place

Answer 13

the thylakoids

Question 14

describe what happens in the light stage

Answer 14

• water is split, giving electrons and protons
• oxygen released as a byproduct
• the ETC NADP+ to NADPH
• ATP generated from ADP by photophosphorylation

Question 15

see diagrams for Respiration & Photosynthesis

Answer 15

in notes !!

Question 15

where in the chloroplast does the Calvin cycle take place

Answer 15

the stroma

Question 16

describe what happens in the dark stage

Answer 16

• sugar made from carbon dioxide using the ATP and NADPH generated during the light reactions
• carbon fixation occurs, incorporating carbon dioxide into organic moleucles
• fixed carbon is then reduced to carbohydrate by transferring electrons from NADPH

Question 17

what are the different types of pigment in chloroplasts and their function

Answer 17

chlorophyll a - key light-capturing pigment that participates directly in light reactions
chlorophyll b - an accessory pigment
carotenoids - a separate group of accessory pigments (photoprotective)

Question 18

what makes up the photosystem

Answer 18

the reaction-centre complex and the light-harvesting complexes

Question 19

what is the role of the photosystem

Answer 19

converts light energy to chemical energy which will ultimately be used for the synthesis of sugar

Question 20

what is PSI

Answer 20

photosystem I - contains a chlorophyll a dimer (donor of electrons)
absorption peak at 700nm (far red)

Question 21

what is PSII

Answer 21

photosystem II - contains chlorophyll a but in a different protein environment to PSI
absorption peak at 680nm (red)

Question 22

If nuclear lamina fall into disarray, what would you expect to be
the most likely direct consequence?
A. a change in the shape of the nucleus
B. failure of chromosomes to carry genetic information
C. the inability of the cell to withstand enzymatic digestion
D. inability of the nucleus to keep out destructive chemicals
E. the loss of all nuclear function

Answer 22

A - nuclear lamina provide structural support

Question 23

Which of the following is a component of the nuclear
envelope?
A. Actin filaments
B. Myosin bundles
C. Mitotic spindle
D. Intermediate filaments called lamins
E. Ribosomes

Answer 23

D - lamins provide structural support and help organise chromatin

Question 24

A typical eukaryotic cell has enough available ATP to meet its needs for about 30 seconds. What is likely to happen to an individual when they exhaust their ATP supply? A) The athlete will have to sit down and rest. B) Catabolic processes will be activated to generate additional ATP. C) ATP will be transported into the cells from the circulatory system. D) Anabolic processes will be activated to produce new mitochondria

Answer 24

B - when a cell starts to run low on ATP it activates catabolic pathways to break down molecules and produce more

Question 25

Glycolysis results in the net production of which of the following sets of molecules per glucose molecule? A) 2 NAD+, 2 pyruvate, and 2 ATP B) 2 NADH, 2 pyruvate, and 2 ATP C) 4 NADH, 2 pyruvate, and 4 ATP D) 6 CO2, 2 pyruvate, and 2 ATP

Answer 25

B NAD+ is consumed not produced, CO2 is not released during glycolysis, that occurs during citric acid cycle

Question 26

Inhibition of which of the following metabolic pathways would result in decreased rates of CO2 production? A) glycolysis and the oxidation of pyruvate to acetyl CoA B) oxidation of pyruvate to acetyl CoA and the citric acid cycle C) oxidative phosphorylation and fermentation D) fermentation and glycolysis

Answer 26

B

Question 27

If glucose is the sole energy source for cellular respiration in an animal, what proportion of the carbon dioxide exhaled is derived from oxidation of pyruvate to acetyl CoA? A) 1/6 B) 1/3 C) 2/3 D) 100%

Answer 27

B - 1 molecule of glucose produces 6CO2 in total - " from oxidation of pyruvate and 4 from citric acid cycle

Question 28

For each mole of glucose (C₆H₁₂O₆) oxidized by cellular respiration, how many moles of CO2 are released in the citric acid cycle? A) 2 B) 4 C) 6 D) 32

Answer 28

B - Glycolysis → 0 CO₂ Pyruvate oxidation → 2 CO₂ Citric acid cycle → 4 CO₂ Total CO₂ per glucose = 6 (but 4 specifically from the citric acid cycle)

Question 29

Which of the following statements best describes the relationship between photosynthesis and cellular respiration? A) Cellular respiration runs the biochemical pathways of photosynthesis in reverse. B) Photosynthesis stores energy in complex organic molecules; cellular respiration releases energy from complex organic molecules. C) Photosynthesis occurs only in plants; cellular respiration occurs only in animals. D) Photosynthesis is catabolic; cellular respiration is anabolic

Answer 29

B plants and animals perform cellular respiration; photosynthesis mainly occurs in plants, algae and some bacteria

Question 30

Which of the following observations would be the best indicator that an organism lacks photosystem II? A) It produces glucose in the light and dark. B) It does not produce CO2 in the dark. C) It does not produce O2 in the light. D) It produces CO2 in the light

Answer 30

C - light causes water split to give O2 in PII