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BI101 > Chapter 7- cell cycle > Flashcards

Chapter 7- cell cycle Flashcards

1
Q

cells exist from…

A

pre-existing cells through the process of cell division

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2
Q

cell growth and division is important for…

A
  • 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)
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3
Q

The Bacterial Cell Cycle

A
  • 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
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4
Q

Cell cycle

A

A period of growth followed by nuclear division and cytokinesis

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5
Q

mitosis

A

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

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6
Q

Mitosis is the basis for:

A
  • Growth and maintenance of body mass in multicellular Eukaryotes
  • The reproduction of many single-celled eukaryotes
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7
Q

Ploidy of a cell or species

A

the number of chromosomes in each set

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8
Q

Haploid (n)

A

a cell with one complete set of chromosomes

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9
Q

Diploid (2n)

A

a cell with two complete sets of chromosomes

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10
Q

Sister Chromatids

A

Replication of DNA of each individual chromosome creates two identical molecules

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11
Q

Chromosome segregation:

A

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

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12
Q

Interphase

A

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

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13
Q

what are the three phases of interphase

A

G1, S, G2

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14
Q

G1 phase

A

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

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15
Q

S phase

A

DNA replication and chromosome duplication occur

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16
Q

G2 Phase

A

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

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17
Q

Mitosis steps

A

prophase, prometaphase, metaphase, anaphase, telophase

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18
Q

Stage 1: Prophase

A
  • Chromosomes condense into a compact, rod-like structures
  • Spindle forms in the cytoplasm
19
Q

Stage 2: Prometaphase

A
  • Nuclear envelope breaks down
  • Spindle enters former nuclear area
  • Microtubules from opposite spindle poles attach to two kinetochores of each chromosome
20
Q

Stage 3: Metaphase

A
  • Spindle is fully formed
  • Chromosomes align at spindle midpoint
  • Moved by spindle microtubule
21
Q

Stage 4: Anaphase

A
  • Spindle separates sister chromatids and moves them to opposite spindle poles
  • Chromosome segregation is complete
22
Q

Stage 5: Telophase

A
  • Chromosomes decondense
  • Return to extended state typical of interphase
  • New nuclear envelope forms around chromosomes
23
Q

Cytokinesis

A

completes cell division by dividing the cytoplasm between daughter cells

24
Q

Plant Cytokinesis

A
  • 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
25
Q

Spindle Formation In animal cells

A
  • Centrosomes contain a pair of centrioles that divide and move apart
  • Microtubules radiate outwards from centrosomes to form the spindle
26
Q

spindle formation in plant cells

A
  • Plant cells do not contain centrosomes
  • Spindles still form and are composed of microtubules
  • Self-assembly
27
Q

Different cyclin

A

CDK combinations regulate cell cycle transitions at different “checkpoints”

28
Q

Cell Cycle Control

A

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

29
Q

CDK’s

A

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

30
Q

what are external controls based on

A

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

31
Q

what are the internal controls

A

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

32
Q

what do external control coordinate

A

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

33
Q

Asymmetric Cell Division

A
  • not all cells divisions are symmetrical
34
Q

can cells divide indefinetly

A

no

35
Q

Cellular senescence

A

Loss of proliferative ability over time

36
Q

what is responsible for cellular senescence

A

DNA damage and Telomere shortening

37
Q

Apoptosis

A

Programmed cell death

38
Q

Initiation of cell death results from

A

internal or external signals

39
Q

Why do Some plants have evolved the C4 pathway

A

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

40
Q

what happens in the C4 cycle

A
  • 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
41
Q

what does CAM stand for

A

Crassulacean Acid Metabolism

42
Q

CAM

A
  • 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)
43
Q

how do CAM plants capture CO2 at night

A

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

BI101 (6 decks)

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