2.1.6 Cell Division, Cell Diversity and Cellular Organisation Flashcards
Compare cell division via mitosis and meiosis
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
What is the difference between diploid and haploid cells?
Diploid - chromosomes in the cell are part of a pair (2n)
Haploid - chromosomes in the cell are not part of a pair (n)
Uses of mitosis
- growth of tissues
- replacement of cells + repair of tissues
- asexual reproduction
- development of body plans
- proliferation of white blood cells
- producing gametes from haploid cells
- making NEW stem cells
Name the different phases in the cell cycle
Interphase
- first growth phase
- synthesis phase
- second growth phase
Mitotic phase
- prophase
- metaphase
- anaphase
- telophase
What is G0 phase and why does it occur?
- the cell leaves the cell cycle (temporarily or permanently)
- differentiation
- DNA may be damaged
- cells eventually becomes senescent
- mutations
What does the cell need to have done before it divides?
- grown to the right size
- make sure the replciated DNA is error free
- ensuer the chromosones are in the correct positions during mitosis
What do cell cycle checkpoints do?
Monitor and verify whether the processes at each phase of the cell cycle have been accuratley completed
Where does checkpoint G1 occur and what does it check for?
Where
- at the end of G1, before S phase
Checks
- cell size
- nutrients
- growth factors
- DNA damage
Where does S phase checkpoint occur and what does it check for?
Where
- at the end of S phase
Checks
- DNA replicated correctly
- DNA damge
Where does checkpoint G2 occur and what does it check for?
Where
- at the end of G2 phase, befpre mitotic phase
Checks
- cell size
- DNA replicated correctly
- DNA damage
Where does spindle assembley/metaphase checkpoint occur and what does it check for?
Where
- metaphase of mitosis
Checks
- chromosone attachment to spindle
What are the consequences if genetic information is not checked?
- mutations
- daughter cells may not recieve identical genetic information
- proteins may not function or be made
- new cells may not function or be made
What is a homologous chromosome?
- 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
How to observe mitosis
- 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
Describe key aspects of Interphase
- not part of mitosis
- amount of DNA in nucles doubles
- no visible chromosomes
- new organelles made
- protein synthesis
- cell growth
Describe key aspects of Prophase
- 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
Key apects of Metaphase
- chromosones allign at equator - spindle fibres help
- chromosomes attached to spindle fibres via centromere
Key aspects of Anaphase
- spindle fibres shorten - pull chromatids apart
- centromeres divide
- chromosomes move to opposite ends of the cell
- chormosome number doubles
Key aspects of Telophase
- nucllear envelopes form around each group ofchromoso,mes
- chromosones uncoil - return to chromatin
- nucleolus is formed
Key aspects of Cytokinesis
- when cell cytoplasm divides
- happenes between telophase + interphase
- occurs when nucleus has divide, before DNA replication
How does cytokinesis occur in animal cells?
- 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
How does cytokinesis occur in plant cells?
- 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
Asexual preoduction in yeast cells
- budding
- nucelus divides by mitosis
- fungi
Explain the process of budding
- a bulge forms in membrane of th cell
- mitosis occurs
- nucleus, organelles, cytoplasm move into bulge
- new bud pinches off - 2 new cells
Asexual preoduction in bacteria
- binary fision
- do not divide genetic material - no chromosomes + nucleus
Key aspects of stem cells
- unspecialised/undifferentiated
- capable of mitosis
- can differentiate into other cell types
- lose ability to divide after specialisation (enter G0)
Explain the differences between totipotent, pluripotent and multipotent stem cells
- 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
Where can stem cells be found?
- umbilical cord
- bone marow
- embryo
- other tissue
Uses of stem cells
- spinal injuries
- treatemnt of diseases
- treatment of burns
- drug trials
- develoipmental biology
Advantages + disadvantages of using embryonic stem cells
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
Where are plant stem cells found?
- apex of shoots and root (meristematic tissue)
- cambium - meristematic tissue found in xylem + phloem
Define differentiation
When a stem cell becomes specialised to perform a particular function
Key aspects of erythocryte cells (RBC)
- small size + biconcave shape = large SA:V ratio
- small (7.5nm) + flexible = squeeze through narrow capillaries
- no organeles/nucleus = more space for haemoglobin
Key aspects of nutrophil cells (type of WBC)
- 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
Key aspects of sperm cells
- acrosome which contains digestive enxymes = penetrate protective layer around egg
- flagellum = allows swimming to egg
- many mitochondria for ATP - flagellum movement
Key aspects of epithelial cells (line surfaces)
- linked together with a basement membrane
may be ciliated = move substances - may be squamous = short diffusion pathway
- may have microvilli - increased surface area
Key aspects of palisade mesophyll cell
- 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
Key aspects of root hair cells
- root hairs = increased SA - absorb water by ososis + minerals by AT
- thin cell walls = short diffusion pathway
- many mitochondira for ATP = AT of minerals
Key aspects of guard cells
- opens in light + closes in dark
- thicker inner cell walls + thinner outer cell walls - makes them bend open
Definitions of a tissue, organ and system
- 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
Types of tissue
- nervous tisue
- epitherial tissue - covers surfaces internally + externally
- muscle tissue
- connective tissue - holds other tissues together
Key aspects of squamous epitherial tissue
- one cell thick - short diffusion pathway
- large SA
- lines tubes (blood vessels)
- forms walls of alveoli
Key aspects of ciliated epithelial tissue
- columnar cells
- have cilia
- line trachea/ wind pipes
- produce mucus
Key aspects of cartilage
- connective tissue
- found in ear,nose + end of bones
- consists of chondrocyte cells
- stops bones rubbing
Key aspects of muscle
- shortens in lengths as it contracts
- highly specialised - contain multiple nucleus
- different types = skeletal (voluntary), smooth (involuntary), cardiac (in heart)
Key aspects of xylem tissue
- 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
Key aspects of phloem tissue
- 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
Compare xylem + phloem tissue
- 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
Examples of organ systems
- the digestive system
- the cardiovascular saystem
- the respiratory system
