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OCR Biology A Level > 2.1.6 Cell Division, Cell Diversity and Cellular Organisation > Flashcards

2.1.6 Cell Division, Cell Diversity and Cellular Organisation Flashcards

1
Q

Compare cell division via mitosis and meiosis

A

Mitosis
- makes clones
- no variation
- 2 cells made
- 1 division
- genetically identical
- maintained chromosome number
Meiosis
- genetic variation from parent
- daughter cells have 1/2 number of chromosomes as parent cell
- 4 cells made
- 2 divisions
- chromosome number halves

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2
Q

What is the difference between diploid and haploid cells?

A

Diploid - chromosomes in the cell are part of a pair (2n)
Haploid - chromosomes in the cell are not part of a pair (n)

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3
Q

Uses of mitosis

A
  1. growth of tissues
  2. replacement of cells + repair of tissues
  3. asexual reproduction
  4. development of body plans
  5. proliferation of white blood cells
  6. producing gametes from haploid cells
  7. making NEW stem cells
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3
Q

Name the different phases in the cell cycle

A

Interphase
- first growth phase
- synthesis phase
- second growth phase
Mitotic phase
- prophase
- metaphase
- anaphase
- telophase

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4
Q

What is G0 phase and why does it occur?

A
  • the cell leaves the cell cycle (temporarily or permanently)
  • differentiation
  • DNA may be damaged
  • cells eventually becomes senescent
  • mutations
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5
Q

What does the cell need to have done before it divides?

A
  • grown to the right size
  • make sure the replciated DNA is error free
  • ensuer the chromosones are in the correct positions during mitosis
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6
Q

What do cell cycle checkpoints do?

A

Monitor and verify whether the processes at each phase of the cell cycle have been accuratley completed

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7
Q

Where does checkpoint G1 occur and what does it check for?

A

Where
- at the end of G1, before S phase
Checks
- cell size
- nutrients
- growth factors
- DNA damage

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8
Q

Where does S phase checkpoint occur and what does it check for?

A

Where
- at the end of S phase
Checks
- DNA replicated correctly
- DNA damge

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9
Q

Where does checkpoint G2 occur and what does it check for?

A

Where
- at the end of G2 phase, befpre mitotic phase
Checks
- cell size
- DNA replicated correctly
- DNA damage

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10
Q

Where does spindle assembley/metaphase checkpoint occur and what does it check for?

A

Where
- metaphase of mitosis
Checks
- chromosone attachment to spindle

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11
Q

What are the consequences if genetic information is not checked?

A
  • mutations
  • daughter cells may not recieve identical genetic information
  • proteins may not function or be made
  • new cells may not function or be made
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12
Q

What is a homologous chromosome?

A
  • has one maternal and one paternal chromosome
  • carry the same genes at the same loci
  • have their centromere in the same position
  • usually the same length
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13
Q

How to observe mitosis

A
  • must use cells from growing part of plant (root or shoot tip)
  • must squash to provide a thin layer of cells
  • mus stain to see the crhomosones - provides contrast
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14
Q

Describe key aspects of Interphase

A
  • not part of mitosis
  • amount of DNA in nucles doubles
  • no visible chromosomes
  • new organelles made
  • protein synthesis
  • cell growth
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15
Q

Describe key aspects of Prophase

A
  • chromosomes supercoil - become visible - two chromatids held together by centromere
  • centrioles divide - move to opposiute ends of cell
  • spidle fibres come out from centrioles
  • spindle fibres attach to centromere - start to mvoe chromosones
  • end of prophase - nucleolus dissapears + nuclear envelope disintegrates
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16
Q

Key apects of Metaphase

A
  • chromosones allign at equator - spindle fibres help
  • chromosomes attached to spindle fibres via centromere
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17
Q

Key aspects of Anaphase

A
  • spindle fibres shorten - pull chromatids apart
  • centromeres divide
  • chromosomes move to opposite ends of the cell
  • chormosome number doubles
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18
Q

Key aspects of Telophase

A
  • nucllear envelopes form around each group ofchromoso,mes
  • chromosones uncoil - return to chromatin
  • nucleolus is formed
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19
Q

Key aspects of Cytokinesis

A
  • when cell cytoplasm divides
  • happenes between telophase + interphase
  • occurs when nucleus has divide, before DNA replication
20
Q

How does cytokinesis occur in animal cells?

A
  • invovles 2 protein filaments: actin + myosin
  • filamnts form a constricting belt - slide past each other tightening belt
  • pinches cell + creates cleave furrow - cell membrane pulled inwards
  • furrow deepens before cell splits
21
Q

How does cytokinesis occur in plant cells?

A
  • ce;ll wall inhibits cleave furrow
  • vesicles assemble in middle of cell
    -vesicles fuse to form 2 plasma membranes - cellulose deposited to form new cell walls
22
Q

Asexual preoduction in yeast cells

A
  • budding
  • nucelus divides by mitosis
  • fungi
23
Q

Explain the process of budding

A
  1. a bulge forms in membrane of th cell
  2. mitosis occurs
  3. nucleus, organelles, cytoplasm move into bulge
  4. new bud pinches off - 2 new cells
24
Q

Asexual preoduction in bacteria

A
  • binary fision
  • do not divide genetic material - no chromosomes + nucleus
25
Q

Key aspects of stem cells

A
  • unspecialised/undifferentiated
  • capable of mitosis
  • can differentiate into other cell types
  • lose ability to divide after specialisation (enter G0)
26
Q

Explain the differences between totipotent, pluripotent and multipotent stem cells

A
  • totipotent = can form all types of cell
  • multipotent = can form tissue but not whole organisms
  • multipotent = can only form cells within a certain type of tissuer
27
Q

Where can stem cells be found?

A
  • umbilical cord
  • bone marow
  • embryo
  • other tissue
28
Q

Uses of stem cells

A
  • spinal injuries
  • treatemnt of diseases
  • treatment of burns
  • drug trials
  • develoipmental biology
29
Q

Advantages + disadvantages of using embryonic stem cells

A

Advantages
- can lead to treatment of ‘incurable’ dioseases
- imrpvoed QOL of patientsa
- techniques being developed that will not damage embryo while being extracted

Disadvantages
- religous objections
- embryonic stem cell removal destroys embryo
- moral obections
- embryo can’t give consent
- embryos embryos left over are discarded

30
Q

Where are plant stem cells found?

A
  • apex of shoots and root (meristematic tissue)
  • cambium - meristematic tissue found in xylem + phloem
31
Q

Define differentiation

A

When a stem cell becomes specialised to perform a particular function

32
Q

Key aspects of erythocryte cells (RBC)

A
  • small size + biconcave shape = large SA:V ratio
  • small (7.5nm) + flexible = squeeze through narrow capillaries
  • no organeles/nucleus = more space for haemoglobin
33
Q

Key aspects of nutrophil cells (type of WBC)

A
  • defend against diseases
  • flexible shape
  • many lysosomes = hydrolise pathogens
  • many ribsomes + rough ER = to create enzymes
  • many mitochondira for ATP = movement of cytoskeleton
  • many golgi bodies = lysosome production
34
Q

Key aspects of sperm cells

A
  • acrosome which contains digestive enxymes = penetrate protective layer around egg
  • flagellum = allows swimming to egg
  • many mitochondria for ATP - flagellum movement
35
Q

Key aspects of epithelial cells (line surfaces)

A
  • linked together with a basement membrane
    may be ciliated = move substances
  • may be squamous = short diffusion pathway
  • may have microvilli - increased surface area
36
Q

Key aspects of palisade mesophyll cell

A
  • long + thin = forms continous layer at leaf surface
  • movable mitochondira = captures most light
  • large vacule = pushes chloroplasts to edge of the cell
  • thin cell wall = increased rate of diffusion for photosynthesis
37
Q

Key aspects of root hair cells

A
  • root hairs = increased SA - absorb water by ososis + minerals by AT
  • thin cell walls = short diffusion pathway
  • many mitochondira for ATP = AT of minerals
38
Q

Key aspects of guard cells

A
  • opens in light + closes in dark
  • thicker inner cell walls + thinner outer cell walls - makes them bend open
39
Q

Definitions of a tissue, organ and system

A
  • tissue = collection of cells that are specialised to work together for a particualr function
  • organ = collection of different tissues working together for a common cuntion
  • system - a group of organs working together for as particular function
40
Q

Types of tissue

A
  • nervous tisue
  • epitherial tissue - covers surfaces internally + externally
  • muscle tissue
  • connective tissue - holds other tissues together
41
Q

Key aspects of squamous epitherial tissue

A
  • one cell thick - short diffusion pathway
  • large SA
  • lines tubes (blood vessels)
  • forms walls of alveoli
42
Q

Key aspects of ciliated epithelial tissue

A
  • columnar cells
  • have cilia
  • line trachea/ wind pipes
  • produce mucus
43
Q

Key aspects of cartilage

A
  • connective tissue
  • found in ear,nose + end of bones
  • consists of chondrocyte cells
  • stops bones rubbing
44
Q

Key aspects of muscle

A
  • shortens in lengths as it contracts
  • highly specialised - contain multiple nucleus
  • different types = skeletal (voluntary), smooth (involuntary), cardiac (in heart)
45
Q

Key aspects of xylem tissue

A
  • dead hollow cells with lignified cell wals + no organelles
  • multiple cells form one continous tubes
  • transport water + minerals
    strengthened + thgrickened by lignin + waterproofs wal
  • walls contain pits so water can move through vessells - bypass a blockage + suply other parts of a plant
  • can flow against gravity
46
Q

Key aspects of phloem tissue

A
  • living elongated cells, little cytoplasm
  • joined end to end, forming a vessel
  • sieve plates so solutes can pass between cells
  • few organelles + no nucleus = more space for solutes to move
  • has companion cells - contain more organelles + provides ATP for AT
47
Q

Compare xylem + phloem tissue

A
  • lignified cell walls? X = Yes P = No
  • end walls? X = no P = sieve plates
  • companion cells? X = no P = yes
  • vessels? X = Y P = no
  • bordered pits? X = yes P = no
  • cytoplasm? X = no P = yes
48
Q

Examples of organ systems

A
  • the digestive system
  • the cardiovascular saystem
  • the respiratory system

OCR Biology A Level (11 decks)

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