Chapter 7- cell cycle

Question 1

cells exist from…

Answer 1

pre-existing cells through the process of cell division

Question 2

cell growth and division is important for…

Answer 2

• Increasing population size (single-celled organisms)
• Growing new tissues (e.g. new leaves during plant development)
• Asexual reproduction (bacteria, fungi, corals, many others)
• Replacement of lost cells (lining of gut) and/or damaged cells (wound repair)

Question 3

The Bacterial Cell Cycle

Answer 3

• It begins at a single site called the origin of replication (ori) through reactions catalyzed by enzymes located in the middle of the cell
• Once the ori is duplicated, the two origins actively migrate to either end of the cell
• Division of the cytoplasm then occurs to separate into two daughter cells:
• Inward growth of plasma membrane and cell wall
• Involves cytoskeletal proteins

Question 4

Cell cycle

Answer 4

A period of growth followed by nuclear division and cytokinesis

Question 5

mitosis

Answer 5

divides replicated DNA equally and precisely
* Ensures the two cells resulting from a cell division have the same genetic information as the parent cell entering division

Question 6

Mitosis is the basis for:

Answer 6

• Growth and maintenance of body mass in multicellular Eukaryotes
• The reproduction of many single-celled eukaryotes

Question 7

Ploidy of a cell or species

Answer 7

the number of chromosomes in each set

Question 8

Haploid (n)

Answer 8

a cell with one complete set of chromosomes

Question 9

Diploid (2n)

Answer 9

a cell with two complete sets of chromosomes

Question 10

Sister Chromatids

Answer 10

Replication of DNA of each individual chromosome creates two identical molecules

Question 11

Chromosome segregation:

Answer 11

Equal distribution of daughter chromosomes to each of two cells resulting from cell division

Question 12

Interphase

Answer 12

the first stages of the cell cycle; it begins immediately after mitosis (& cytokinesis) and continues until the beginning of the next mitosis

Question 13

what are the three phases of interphase

Answer 13

G1, S, G2

Question 14

G1 phase

Answer 14

The cell carries out its function(s), and in some cases grows, during this initial “gap” phase

Question 15

S phase

Answer 15

DNA replication and chromosome duplication occur

Question 16

G2 Phase

Answer 16

A second “gap” in the cell cycle when cell growth continues and the cell prepares for mitosis and cytokinesis

Question 17

Mitosis steps

Answer 17

prophase, prometaphase, metaphase, anaphase, telophase

Question 18

Stage 1: Prophase

Answer 18

• Chromosomes condense into a compact, rod-like structures
• Spindle forms in the cytoplasm

Question 19

Stage 2: Prometaphase

Answer 19

• Nuclear envelope breaks down
• Spindle enters former nuclear area
• Microtubules from opposite spindle poles attach to two kinetochores of each chromosome

Question 20

Stage 3: Metaphase

Answer 20

• Spindle is fully formed
• Chromosomes align at spindle midpoint
• Moved by spindle microtubule

Question 21

Stage 4: Anaphase

Answer 21

• Spindle separates sister chromatids and moves them to opposite spindle poles
• Chromosome segregation is complete

Question 22

Stage 5: Telophase

Answer 22

• Chromosomes decondense
• Return to extended state typical of interphase
• New nuclear envelope forms around chromosomes

Question 23

Cytokinesis

Answer 23

completes cell division by dividing the cytoplasm between daughter cells

Question 24

Plant Cytokinesis

Answer 24

• Cell wall material is deposited along the plane of the former spindle midpoint
• Deposition continues until a continuous new wall (cell plate) separates daughter cells

Question 25

Spindle Formation In animal cells

Answer 25

- Centrosomes contain a pair of centrioles that divide and move apart - Microtubules radiate outwards from centrosomes to form the spindle

Question 26

spindle formation in plant cells

Answer 26

- Plant cells do not contain centrosomes - Spindles still form and are composed of microtubules - Self-assembly

Question 27

Different cyclin

Answer 27

CDK combinations regulate cell cycle transitions at different “checkpoints”

Question 28

Cell Cycle Control

Answer 28

Specific molecules (proteins, enzymes) in the cytoplasm regulate the progression of cells from G1 to S, from G2 into M, and progression through Mitosis * Important internal controls create checkpoints

Question 29

CDK's

Answer 29

Protein kinases, which phosphorylate, and regulate activity of, target proteins Activated when bound to cyclins

Question 30

what are external controls based on

Answer 30

surface receptors that receive external signals * Examples: Hormones, including plant hormones Growth and death factors Extra-cellular matrix molecules (including neighbouring cells)

Question 31

what are the internal controls

Answer 31

Cyclins + cyclin-dependent kinase complexes are the internal controls that directly regulate progression through the cell cycle

Question 32

what do external control coordinate

Answer 32

the miotic cell cycle of individual cells with the overall activities of the organism

Question 33

Asymmetric Cell Division

Answer 33

- not all cells divisions are symmetrical

Question 34

can cells divide indefinetly

Answer 34

no

Question 35

Cellular senescence

Answer 35

Loss of proliferative ability over time

Question 36

what is responsible for cellular senescence

Answer 36

DNA damage and Telomere shortening

Question 37

Apoptosis

Answer 37

Programmed cell death

Question 38

Initiation of cell death results from

Answer 38

internal or external signals

Question 39

Why do Some plants have evolved the C4 pathway

Answer 39

to increase the concentration of CO2 relative to O2 near Rubisco so that photorespiration is minimized

Question 40

what happens in the C4 cycle

Answer 40

* CO2 is combined with a 3-carbon molecule, phosphoenolpyruvate (PEP), to produce a 4- carbon intermediate * The enzyme PEP carboxylase that binds CO2 does not have any oxygenase activity * Later, when O2 concentrations are low, the 4-carbon molecule is oxidized to release CO2 * CO2 then enters the Calvin cycle by binding to Rubisco

Question 41

what does CAM stand for

Answer 41

Crassulacean Acid Metabolism

Question 42

CAM

Answer 42

* Some C4 plants run the C4 and Calvin cycles at different times (instead of in different cells) to avoid photorespiration: temporal separation * In crassulacean acid metabolism (CAM), certain cacti and succulent desert plants capture CO2 at night with the C4 cycle, but run the Calvin cycle during the day when sunlight is available (and therefore more ATP & NADPH are being generated)

Question 43

how do CAM plants capture CO2 at night

Answer 43

CAM plants open their leaf stomata during the night to capture CO2 using the C4 cycle