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Biology HL > Cell Biology CHAP 1 > Flashcards

Cell Biology CHAP 1 Flashcards

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1
Q

What 3 statements make up CELL Theory

A

1) All living things are composed of cells
2) The cell is the smallest unit of life
3) cells only arise from pre-existing cells

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2
Q

1) All living things are composed of cells
2) The cell is the smallest unit of life
3) cells only arise from pre-existing cells

A

Cell theory

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3
Q

What types of cells are an exception to cell theory?

A

1) striated (striped or streaked) muscle fibres
2) giant algae
3) Aseptate fungal hyphae

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4
Q

Why are striated muscle fibres an exception to typical cells?

A

Muscle cells fuse together to form fibres, therefore each fibre has multiple nuclei

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5
Q

Why are giant algae an exception to typical cells?

A

Some species of algae grow to large sizes therefore cells may not always be microscopic.
(e.g, ACETABULARIA may exceed 7cm)

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6
Q

Why are Aseptate fungal cells an exception to typical cells ?

A

Hyphae (branch of fungus) are separated into cells by internal walls called septa. Some hyphae lack separation and therefore have a continuous cytoplasm.

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7
Q

What are the 7 basic characteristics that all living things share? “MR SHENG”

A

M metabolism , R reproduction, S sensitivity, H homostasis, E excretion, N nutrition, G grow/move

MR SHENG

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8
Q

What does MR SHENG stand for? than list them.

A

metabolism, reproduction, sensitivity, homostasis, excretion, nutrition, growth/movement

7 characteristics of life

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9
Q

Unicellular organisms must carry out all the functions of life. How does a paramecium do this? give an example for each of the 7 characteristics.

A

Paramecium:
M: Heterotrophic, R: asexual reproduction via mitosis,
S: Towards food, H: Regulate gas and water levels, E: Via anal pore, N: Food vacuoles, G: move via cilia.

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10
Q

Unicellular organisms must carry out all the functions of life. How does a Chlorella (single celled algae) do this? give an example for each of the 7 characteristics.

A

Chlorella:
M: Autotrophic, R: asexual reproduction via mitosis,
S: Towards light, H: Regulate gas and water levels, E: Via diffusion, N: photosynthesis , G: non-motile

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11
Q

Cells produce energy to survive and this requires material exchange. Metabolic rate is a function of its ______

A

Volume

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12
Q

What is metabolic rate?

A

The rate in which metabolism occurs in living organisms

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13
Q

Cells produce energy to survive and this requires material exchange. Rate of material exchange is a function of its ________

A

Surface area

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14
Q

As a cell grows, its volume ________ faster than its surface area

A

Increases

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15
Q

What causes a decreased SA: Vol ratio?

A

As a cells grows its volume increases faster than its surface area

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16
Q

What happens if material exchange is insufficient to maintain metabolism? How to cells prevent this?

A

The cell dies

Cells remain small by dividing

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17
Q

Name a specialised cell for material exchange that will increase their surface area?

A

Microvilli

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18
Q

What system of measurement is used to measure size and dimensions of biological materials ?

A

Metric system (metre, milimetre, micrometres, nanometre, picometre)

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19
Q

Sort these measurements in order from largest to smallest mentioning the division difference between them
(pm,um,mm,m,nm)

A

m , mm , um , nm , pm

To get from one to another in decreasing order you divide by 1000

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20
Q

What is the approximate size of a eukaryotic cell?

A

100 um

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21
Q

What is the approximate size of an organelle (e.g, nucleus)

A

> 10um

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22
Q

What is the approximate size of a bacteria ?

A

1-5 um

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23
Q

What is the approximate size of a virus ?

A

100nm

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24
Q

What is the approximate size of a ribosome ?

A

30nm

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25
Q

What is the approximate width of a cell membrane ?

A

7.5nm

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26
Q

What is the approximate size of a molecule ?

A

1nm

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27
Q

What is the equation for linear magnification?

A

Magnification = Image size (with ruler) / Actual size (scale bar)
M I A

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28
Q

Define “emergent properties” and say how they’re useful

A

When different cells interact together creating new functions. Useful because multicellular organisms are capable of completing functions that individual cells could not undertake

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29
Q

Give an example of emergent properties

A

Cell -> Tissue -> Organ -> System

Muscle -> Cardiac -> Heart -> Vascular

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30
Q

Define Differentiation

A

The process in which new cells become more specialised and distinct from one another

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31
Q

All cells of an organism share an identical ______

A

Genome

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32
Q

Define Genome

A

The complete set of genes or genetic material present in a cell or organism. The haploid set of chromosomes in a gamete or microorganisms.

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33
Q

What causes a cell to differentiate?

A

The activation of some genes but not others

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34
Q

What causes some genes to activate ?

A

Chemical signals (e.g hormones, transcription factors)

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35
Q

What are stem cells?

A

Unspecialised cells

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36
Q

What 2 qualities do stem cells have ?

A

Self renewal: Can divide and replicate

Potency: Capable of differentiation

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37
Q

What are the 4 levels of potency regarding stem cells?

A

Totipotent
Pluripotent
Multipotent
Unipotent

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38
Q

What are Totipotent cells?

A

Cells that can form new organisms

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39
Q

What are Pluripotent cells?

A

Cells that can for most cell types

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40
Q

What are Multipotent cells ?

A

Cells than can form limited cell types

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41
Q

What are Unipotent cells?

A

Cells that cannot differentiate

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42
Q

What potency level are Embryonic stem cells?

A

Totipotent / Pluripotent

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43
Q

What potency level are Fetal stem cells?

A

Pluripotent / Multipotent

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44
Q

What potency level are Adult stem cells?

A

Multipotent / Unipotent

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45
Q

Where can you get stem cells from? Live examples

A

Embryos, the placenta, umbilical cord, certain adult tissues (e.g. bone marrow)

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46
Q

What can you use stem cells for?

A

Used to replace damaged or diseased tissue with healthy tissue

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47
Q

Describe the process of replacing damaged tissue with healthy tissue

A
  • Chemicals to trigger differentiation
  • Surgical implantation into patient’s tissue
  • Suppression of immune system to prevent rejection
  • Monitoring new cells to ensure they don’t become cancerous.
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48
Q

Give specific examples of Therapeutic stem cells

A
  • Replacing dead retinal cells to treat macula dystrophy (Stargardt’s disease)
  • Grafting new skin cells in burns victim
  • Replacing nerve cells in spinal injuries
  • Bone marrow transplants for patients on Chemotherapy
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49
Q

Name some ethics (both positive and negative) associated with therapeutic use of stem cells from EMBRYONIC CELLS

A

Embryonic cells
Good: Have almost unlimited growth potential
Can be generated artificially by SCNT

Bad: Involves destruction of an embryo
Higher risk of cancer development

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50
Q

Name some ethics (both positive and negative) associated with therapeutic use of stem cells from UMBILICAL CORD BLOOD OF A NEWBORN

A

Umbilical cord blood of newborn
Good: Easy to extract from umbilical cord

Bad: Cells must be stored from birth at cost

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51
Q

Name some ethics (both positive and negative) associated with therapeutic use of stem cells from ADULT TISSUES (e.g. Bone marrow)

A

Adult stem cells
Good: Can be obtained at any stage of life

Bad: Cells may be difficult / painful to extract
Lowest growth potential (multipotent)

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52
Q

Name an alternative technology that may be used to generate stem cells

A

Nuclear programming

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53
Q

List one positive and one negative regarding light microscopes

A

Good: Can view living things in natural colour
Bad: Have lower magnification / resolution

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54
Q

List one positive and one negative regarding Electron Microscopes

A

Good: Have higher magnification / resolution
Bad: Can view dead things in monochrome (Black and white)

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55
Q

How can Electron microscopy prepare images ?

A

As cross-sections (transmission EM)

As surface renderings (scanning EM)

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56
Q

What 2 categories can cells be sorted into?

A

Prokaryotes

Eukaryotes

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57
Q

What category of cell consists of cells that lack a nucleus and are bacteria

A

Prokaryotes

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58
Q

What category of cell consists of cells that have nucleus and show compartmentalisation (divided into sections)

A

Eukaryotes

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59
Q

Compare Prokaryote and Eukaryote DNA

A

Prokaryote DNA: Is Naked, Is Circular, No Introns

Eukaryote DNA: Protein bound, Is linear, Has Introns

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60
Q

Compare Prokaryote and Eukaryote Organelles

A

Prokaryote Organelles: No nucleus, 70S ribosomes, No organelles are membrane-bound

Eukaryote Organelles: Have a nucleus, 80S ribosomes, Membrane-bound organelles present

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61
Q

Compare Prokaryote and Eukaryote Reproduction

A

Prokaryote reproduction: Via Binary Fission

Eukaryote reproduction: Mitosis + meiosis

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62
Q

Compare Prokaryote and Eukaryote Average sizes

A

Prokaryote Size: Smaller (1-5 um)

Eukaryote Size: Larger (>10 um)

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63
Q

Who do Prokaryotic cells reproduce?

A

Binary Fission

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64
Q

Describe the Process of Binary Fission

A

1) The circular DNA is first copied
2) Both DNA loops attach to the membrane
3) The cells elongates, drawing loops apart
4) Cytokinesis occurs, forming 2 cells

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65
Q

Name what 10 organelles are in an animal cell

A

Lysosome, Rough ER, Nucleolus, Nucleus, Golgi apparatus, Mitochondrion, Smooth ER, Cell membrane, 80S ribosomes, Cytosol

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66
Q

Name what 11 organelles are in an plant cell

A

Golgi apparatus, Smooth ER, Nucleus, Rough ER, Cytosol, Ribosomes 80s, Cell membrane, Cell wall, Chloroplast, Vacuole, Mitochondrion

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67
Q

What are 6 key features of animal and plant cells

A
  • Cells have a nucleus and compartments
  • Nucleus has a double membrane and pores
  • Animal cells possess lysosomes
  • Plant cells have chloroplasts and large vacuole
  • Plant cell wall is made up of cellulose
  • Eukaryotic ribosomes are 80S
68
Q

Define organelles

A

Specialised sub-structures within a cell that serve a specific function

69
Q

What is the function of a RIBOSOME ?

A

The site of protein synthesis : Both in prokaryote and eukaryote

70
Q

What is the function of a CYTOSKELETON ?

A

Internal scaffolding (a microscopic network of protein filaments and tubules found in the cytoplasm in organisms giving shape) : Both in prokaryote and eukaryote

71
Q

What is the function of a NUCLEUS ?

A

Stores genetic material (DNA)

NUCLEOLUS - is the site of ribosome assembly

72
Q

What is the function of the ER ? Distinguish between ROUGH and SMOOTH

A

Internal transport network
ROUGH = PROTEINS
SMOOTH = LIPIDS

73
Q

What is the function of a GOLGI APPARATUS

EUKARYOTIC : both animal and plant

A

Export secretory products

74
Q

What is the function of the MITOCHONDRIA

EUKARYOTIC : both animal and plant

A

ATP production (aerobic respiration)

75
Q

What is the function of PEROXISOME

EUKARYOTIC : both animal and plant

A

Digests toxic Metabolites

76
Q

What is the function of CENTROSOME

EUKARYOTIC : both animal and plant

A

Involved in cell division

77
Q

What is the function of a CHLOROPLAST

PLANT ONLY

A

Site of photosynthesis

78
Q

What is the function of the CELL WALL

PLANT ONLY

A

Provides mechanical support

79
Q

What is the function of a VACUOLE

PLANT ONLY

A

Stores fluid (for internal pressure) (Animal cells may have temporary vacuoles)

80
Q

What is the function of the LYSOSOME

ANIMAL ONLY

A

Digests macromolecules

presence in plants is subject to debate

81
Q

Name the key differences between ANIMAL AND PLANT cells

A

PLASTIDS:
PLANT CELLS have chloroplasts
ANIMALS cells do not have plastids

CELL WALL:
PLANT CELLS have a cellulose cell wall
ANIMAL CELLS do not have a cell wall

VACUOLE:
PLANT CELLS: Have a large central vacuole
ANIMAL CELLS: Have temporary vacuoles

GLUCOSE STORAG:
PLANT CELLS: Store excess glucose as starch
ANIMAL CELLS: Store excess glucose as glycogen

OTHER:

  • Only plant cells have plasmodesmata
  • Plant cells do not possess centrioles
  • No cholesterol in plant cell membranes
82
Q

Name the 2 key properties of Cell Membranes

A

SEMI- PERMEABILITY : (only some materials can cross unaided) Small molecules can cross, large cannot

SELECTIVITY: (the passage of materials is regulated) membrane proteins assist material movement

83
Q

What are the two main components in a cells plasma membrane

A
  • Phospholipids (arranged in a bilayer)

- Membrane Proteins

84
Q

What are the 2 models used to describe MEMBRANE STRUCTURE?

A

Davson-Danielli Model

Singer- Nicolson model

85
Q

Distinguish between the Davson- Danieli and Singer-Nicolson model

A

Davson = Two outer layers of protien flank an inner phospholipid bilayer (Lipo-protein sandwich)

Singer = Proteins embedded within phospholipid bilayer instead of existing as separate layers

86
Q

Which Membrane structure is correct, and which has been rejected ?

A 
Singer = Correct 
Davson = wrong and rejected
87
Q

Describe how BIOCHEMICAL EVIDENCE helps reject the DAVSON-DANIELLI model

A

1) Not all membranes have a constant ratio of lipid:protein (no to sandwich model)
2) Membrane proteins vary in size and are insoluble in water (can’t form an outer layer)

88
Q

Describe how FLUORESCENT ANTIBODY TAGGING helps reject the DAVSON-DANIELLI model

A

1) Membrane proteins are mobile and are not fixed in place (do not form a static layer)

89
Q

Describe how FREEZE FRACTURING helps reject the DAVSON-DANIELLI model

A

1) Fracturing the membrane reveals a rough and irregular internal surface
2) These irregularities are interpreted as transmembrane proteins

90
Q

The Fluid-Mosaic model is based on whose model?

A

Singer-Nicolson
Integral protein (the channel between)
Phospholipid (the heads of the “sperm”)
Peripheral protein (the big lump attached)
Cholesterol (The hexagonal small in comparison bits)

91
Q

Explain the structure of Phospholipids

A
  • Polar head (hydrophilic) consisting of phosphate and glycerol
  • Non-polar tail (hydrophobic) consisting of 2 fatty acid chains
92
Q

Explain the arrangement of the phospholipid membrane

A
  • Phospholipids arrange into bilayer
  • Hydrophobic tail regions face inwards (shielded from fluid)
  • Hydrophilic head regions face outwards towards the surrounding fluids
93
Q

Explain the structural properties of the phospholipid membrane

A
  • Bilayer held together by hydrophobic interactions (weak associations)
  • Weak associations allow for membrane fluidity and flexibility
  • Fluidity allows membrane to break and reform (exocytosis / endocytosis)
  • Hydrophilic / hydrophobic layers restrict entry of certain substances
94
Q

What are the 2 types of membrane proteins?

A

1) Integral proteins (Transmembrane = existing or occurring across a cell membrane)
2) Peripheral proteins (localised to one side)

95
Q

Describe INTEGRAL PROTEINS and their 2 structural forms

A

Integral proteins are permanently attached to a membrane and span into the bilayer (may move via fluidity)

1) Helical bundles (Gated transporters / pumps)
2) Beta barrels (channel proteins

96
Q

Describe PERIPHERAL PROTEINS

A

Peripheral proteins are temporarily attached via weak bonds and associate with ONE membrane surface (may attach to the inner or outer surface

97
Q

What 6 functions do membrane proteins serve

A

Junctions, Enzymatic, Transport, Receptors, Anchorage, Transduction.
JETRAT

98
Q

Cholesterol interacts with PHOSPHOLIPIDS to moderate membrane properties, What are the 3 interactions

A

1) Reduces fluidity (immobilises phospholipids)
2) Reduces permeability (to hydrophilic ions)
3) Prevents crystallisation (increase flexibility)

99
Q

Plant cell membranes have a DIFFERENT sterol compound. Why?

A

Plants have a cell wall

100
Q

All transport across a plasma membrane involve one of two processes. What are they?

A

PASSIVE TRANSPORT

ACTIVE TRANSPORT

101
Q

Describe PASSIVE TRANSPORT

A

Movement ALONG concentration gradient (from region of high concentration to low)
-Does NOT require the use of ATP

102
Q

Describe ACTIVE TRANSPORT

A

Movement AGAINST the concentration gradient (from region of a low concentration to high)
-Does REQUIRE ATP

103
Q

What type of transport mechanism is SIMPLE DIFFUSION

A

Passive Transport

104
Q

Describe SIMPLE DIFFUSION

A

A passive transport mechanism for materials that can FREELY cross the plasma membrane. SMALL molecules may freely move via the gaps between phospholipid molecules (e.g. Water, Urea, Oxygen, Carbon Dioxide)

105
Q

What are LIPOPHILIC molecules?

A

molecules that can combine or dissolve with lipids/fats

106
Q

LIPOPHILIC molecules are ________ soluble and hence can dissolve across the membrane. Fill the word and name some examples

A

LIPID

e.g. Alcohol, chloroform, steroids

107
Q

Simple diffusion continues until ______

A

Equilibrium

108
Q

Describe FACILITAED Diffusion.

A

Facilitated diffusion is a passive transport mechanism for materials that CANNOT freely cross the plasma membrane. LARGE and CHARGED substances cannot freely cross the hydrophobic bilayer (E.g. Ions, macromolecules)

Membrane proteins facilitate (make it easier) the transport of these materials across the membrane.

  • Channel proteins form a hydrophilic pore
  • Carrier proteins translocate substances
109
Q

Give an example of a channel protein

A

Example: Channel protein - the voltage-gated potassium channel in axons.

110
Q

Define OSMOSIS

A

Passive transport for free water molecules. Osmosis is the movement of water across a permeable membrane from a concentration of low solute to high solute

111
Q

Define OSMOLARITY

A

The measure of the level of solutes in a solution (units: osmol/L)

112
Q

Solutions may be categorised as either: HYPERTONIC, HYPOTONIC, ISOTONIC. Explain the difference between them.

A 
Hypertonic = High solutes -> gains water
Hypotonic = Low solutes -> Loses water 
Isotonic = equal solutes -> not net flow
113
Q

What happens to an animal and plant cell in a HYPERTONIC solution ?

A 
Animals = Cells will shrivel from water loss 
Plants = Membrane retracts from cell wall
114
Q

What happens to an animal and plant cell in a HYPOTONIC solution?

A 
Animals = Cell expands until it ruptures 
Plant = Cell wall prevents rupturing
115
Q

Define ACTIVE TRANSPORT

A

The movement of materials against a concentration gradient (regions of a low -> high concentration)

116
Q

Give an example of ACTIVE TRANSPORT

A

Sodium-Potassium pump in axons

117
Q

Explain ACTIVE TRANSPORT

A

1) Protein pumps use energy from ATP to translocate molecules against a gradient
2) The hydrolysis of ATP causes a change in the conformation of the protein pump, resulting in forced substance movement
3) Protein pumps are specific for a given molecule, mediating regulated transport

118
Q

What is CO-TRANSPORT and what does it involve

A

Co-transport is a simultaneous movement of two substance by one transport protein. This can involve either:
SYMPORT (same directional movement)
ANTIPORT (opposite directional movement)

119
Q

Describe SECONDARY active transport

A

Substance moving along a gradient provides driving energy for substance moving against a gradient. NO ATP hydrolysis is required.

120
Q

Give an example for both ANTIPORT AND SYMPORT

A 
ANTIPORT = K+ in and Na+ out 
SYMPORT = NA+ in GLUCOSE in
121
Q

Outline the sequence of VESICULAR TRANSPORT

A

1) Polypeptides destined for secretion are synthesised by ribosomes on rough ER
2) They are transported to the Golgi body via vesicles (formed from the ER membrane)
3) The Golgi body will potentially sort, store and modify these secretory products
4) The proteins are then transported by another vesicle to the cell membrane for secretion via the process of exocytosis
5) External materials can be internalised into cellular vesicles via endocytosis
Nucleus - Rough ER -V esicle-golgi -vesicle - Outerfluid

122
Q

The phospholipid bilayer of membranes is held together by _________.
(This means they can break and reform)

A

Hydrophobic associations

123
Q

Describe ENDOCYTOSIS (material entry)

A 
An invagination (folding back on itself/being turned inside out) of the membrane creates a depression which envelopes material.
Phagocytosis = the engulfment of solids
Pinocytosis = the engulfment of fluids
124
Q

What is PHAGOCYTOSIS

A

Engulfment of solids

125
Q

What is PINOCYTOSIS

A

Engulfment of fluids

126
Q

Describe EXOCYTOSIS (material exit)

A

Vesicles from the golgi body fuse with the cell membrane, expelling contents
- Proteins attached to the vesicle bilayer will become membrane proteins upon fusion

127
Q

What is the theory of ABIOGENESIS

A

The theory that life spontaneously arose from non-living matter

128
Q

What are the 4 stages of ABIOGENESIS

A

1) Abiotic synthesis of organic molecules
2) Assembly of molecules into polymers
3) Formation of self-replicating polymers
4) Packaging molecules into membranes
= a cell with stable internal chemistry

129
Q

What did Miller and Urey recreate

A

The conditions of a pre-biotic earth within a closed system.

  • These conditions included reducing atmosphere, high temperatures and electrical discharges.
  • Water was boiled to form vapour before mixing with other gases
  • The mixture was then allowed to cool and after one week was analysed
  • Some simple amino acids and complex oily hydrocarbons had formed
130
Q

The conditions required for the non-living synthesis of life are distinct and unusual. Where did these conditions exist

A 
HYDROTHERMAL vents and volcanoes 
EXTRACELLULAR locations (panspermia)
131
Q

What is the law of BIOGENESIS ?

A

cells only arise from pre-existing cells

132
Q

Briefly outline Pasteur’s experiment demonstrating biogenesis

A
  • Broths were stored in vessels with ducts that did not allow external dust to pass
  • Broths were heated to kill any living cells
  • Growth occurred if ducts were broken, exposing broth to external contaminants
  • lack of growth in broken vessels proved that spontaneous generation won’t occur
133
Q

What is an ENDOSYMBIONT

A

a cell which lives inside another cell with mutual benefit

134
Q

Mitochondria and chloroplasts are likely to have originated via_______

A

Endosymbiosis

135
Q

What is evidence for endosymbiosis ?

MAD DR

A 
Membrane, Antibiotics, Division, DNA, Ribosomes 
M: Double membrane 
A: has susceptibility 
D: Fission-like
D: Naked and circular 
R: 70S Ribosomes 
MAD DR
136
Q

What does MAD DR stand for?

A 
Evidence for Endosymbiosis. 
Membrane, Antibiotics, Division, DNA, Ribosomes 
M: Double membrane 
A: has susceptibility 
D: Fission-like
D: Naked and circular 
R: 70S Ribosomes 
MAD DR
137
Q

How do Prokaryotes reproduce ?

A

Binary fission

138
Q

How do Eukaryotes Reproduce ?

A 
Somatic (body) cells divide by mitosis 
Sex cells (gametes) divide by meiosis 
Some eukaryotes don't reproduce sexually and use mitosis for asexual reproduction
139
Q

What is the cell cycle?

A

Describes the events that occur over the typical life cycle of the cell

140
Q

Very briefly explain Interphase and its stages

A

G1:Cell grows and duplicates organelles
S: DNA replication occurs
G2: Cell prepares for division
(Replicated DNA proofread for errors in G2)

141
Q

What is M phase ?

A

Mitosis: Division of the nucleus
Cytokinesis: Cytoplasmic division
(if a cell is not actively dividing, it will enter a quiescent phase (G0) following division).

142
Q

Interphase in an active period in the cell cycle. What events occur ? DOCTOR

A

DNA replication, Organelle cloning, Cell growth, Translation, Obtain nutrients, Respiration
DOCTOR

143
Q

In eukaryotic cells, DNA is usually loosely packed within the nucleus as _______

A

Chromatin

144
Q

When a cell undergoes mitosis, this DNA supercoils to a condensed ____________

A

Chromosome

145
Q

When is DNA replicated ?

A

In Interphase
Because DNA is replicated in interphase chromosomes have duplicate chromatids.
(these chromatids separate during division, so daughter cells have identical chromosomes)

146
Q

Define MITOSIS

A

The division of nucleus to produce two genetically identical nuclei

147
Q

What stages occur in Mitosis

A

Prophase, Metahase, Anaphase, Telophase

148
Q

What happens before mitosis in INTERPHASE ?

A
  • cell grows in size, - Organelles are duplicated, - DNA is replicated (s phase) to form identical chromatids
149
Q

What happens in PROPHASE ?

A
  • DNA Supercoils and condenses, - Nuclear membrane dissolves, - Centrosomes move to poles and begin to form spindle fibres
150
Q

What happens in METAPHASE ?

A
  • Centrosome spindle fibres attach to chromosome centromere, - Spindle fibres contract and move chromosomes to centre of cell
151
Q

What happens in ANAPHASE ?

A
  • Sister chromatids separate and move to opposite sides of cell, - Sister chromatids now regarded as two identical chromosomes
152
Q

What happens in TELOPHASE ?

A
  • Chromosomes deconense, - Nuclear membranes reform, - Cytokinesis occurs concurrently (cells divide in 2)
153
Q

What happens after MITOSIS?

A
  • Two daughter cells are formed, - Each cell contains one of the duplicated chromatid pair, - Cells are genetically identical
154
Q

Define CYTOKINESIS

A

The process of cytoplasmic division, whereby a cell splits into two
(occurs concurrently with telophase)

155
Q

Outline cytokinesis in animals

A
  • Microtubule filaments form a concentric ring around the middle of the cell
  • Filament contraction creates a cleavage furrow, which pinches off to form 2 cells
  • Separation is centripetal because it starts at the outside and then moves in
156
Q

Outline Cytokinesis in plants

A
  • Carbohydrate- rich vesicles form in a row at the centre of the cell (equatorial plane)
  • Vesicles fuse to form an end plate, which extends out to separate the cell in two
  • Separation is centrifugal because it starts in the centre and then moves out
157
Q

Mitosis is involved in 4 key processes. What are they?

TOAD

A

Tissue repair, Organism growth, Asexual reproduction, Development of embryo
TOAD

158
Q

How can you identify cells are undergoing mitosis?

A
  • The lack of clearly identifiable nucleus

- The presence of visible chromosomes

159
Q

The mitotic index is a measure of the proliferation status of a cell population. Whats the calculation equation?

A

Mitotic Index = cells in Mitosis/Total number of cells

160
Q

What are Cyclins ?

A

A family of regulatory proteins that control progression of the cell cycle

161
Q

Explain Cyclins

A
  • Cyclins bind cyclin dependent kinases (CDKs) and form an activated complex
  • This complex phosphorylates proteins involved in specific cell cycle events
  • After the events has occurred, the cyclin is degraded and CDK rendered inactive
  • Cyclin concentrations must be tightly regulated to ensure proper progression.
162
Q

What are the 2 methods of cell death?

A

Necrosis (uncontrolled cell death)

Apoptosis (programmed cell death)

163
Q

What is Necrosis ?

A

-The premature death of a cell
-There is destabilisation of the membrane that leads to swelling and eventual lysis
(Released contents may cause inflammation)

164
Q

What is Apoptosis ?

A
  • The controlled destruction of a cell in response to molecular signals
  • The membrane bulges and contents are repackaged for removal
    (Released content is recycled by other cells
165
Q

What is a carcinogen ?

A

Something that gives you cancer

166
Q

There is a strong positive correlation between ______ and cancer

A

Smoking

Biology HL (2 decks)

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