2.6 Cell Division, Cell Diversity And Cell Differentiation Flashcards
What happens at prophase?
- chromosomes condense (DNA SUPERCOILING)
- centriole divides and new centrioles move to poles
- spindle forms
- nuclear envelope breaks down
What happens at metaphase?
-chromosomes line up and get attached to spindle by centromere
What happens at anaphase?
chromatids separate, pulled by centromeres first
motor proteins pull
What happens at telophase?
- reach the opposite poles on the spindle
- uncoil
- nuclear envelope forms
- Cell has 2 nuclei
What is cytokinesis?
When the cytoplasm divides.
What happens at G0 phase?
Cells undergo apoptosis, differentiation or senescence
What happens in the G1 phase?
- cell grows and organelles duplicate
- transcription of genes to make RNA
What happens at the S phase?
-every molecule of DNA is replicated
What happens at G2 phase?
- special chemicals ensure the cell is ready for mitosis
- cells grow
What is apoptosis?
Programmed cell death
What is senescence?
Where cells can no longer divide.
Where are the two main checkpoints?
G1/S
G2/M
Which checkpoint is called the restriction point?
G1/S checkpoint.
What are the purposes of checkpoints?
- prevent uncontrolled divisions
- repair damaged DNA
What do the molecular evens that control the cell cycle ensure?
- the cycle cannot be reversed
- the DNA is only duplicated once during each cell cycle
Why is the p53 gene important?
It triggers the two main checkpoints in the regulation of the cycle.
Define interphase
Phase of cell cycle where the cell is not dividing; it is subdivided into growth and synthesis phases.
Define mitosis
Type of nuclear division that produces daughter cells genetically identical to each other and the parent cell.
How to protoctists multiply?
Asexual reproduction.
Why is mitosis important?
- asexual reproduction
- growth
- tissue repair
What is the mnemonic for mitosis?
PMAT
How does cytokinesis happen in plants?
- End plate forms where equator of the spindle was
- a new plasma membrane and cell wall are laid down
How does cytokinesis happen in animals?
Plasma membrane folds and nips in
Define chromatids.
Replicates of chromosomes.
Define haploid.
Having only one set of chromosomes; represented by the symbol n.
Define homologous chromosomes.
Matching chromosomes, containing the same genes in the same places (loci) but might contain different alleles of the same gene.
Define meiosis.
Type of nuclear division that results in the formation of cells containing half the number of chromosomes from the parent cell.
How does meiosis produce genetic variation?
-crossing over during prophase 1 shuffles alleles.
Define differentiation.
Process by which stem cells become specialised into different types of cell.
What are epithelial cells?
Cells that constitute lining tissue.
What is another name for a red blood cell?
Erythrocyte
Another name for a phagocytic white blood cell?
Neutrophil
Define stem cell
Unspecialised cell able to express all of its genes and divide by mitosis.
How are erythrocytes specialised?
Very small, 7.5 micrometers, so large SA/V ratio for oxygen diffusion
Biconcave shape
Flexible
No nucleus
How are neutrophils specialised?
- twice the size of erythrocytes and have a multilobed nucleus.
- travel by chemotaxis
- phagocytosis
- flexible shape
- many lysosomes
How are spermatozoa specialised?
- many mitochondria
- long and thin
- releases enzymes from acrosome digests outer protective covering
- flagellum so they can swim
What are guard cells and how are they specialised?
Found in pairs with a gap to form stoma
- In the light, they take up water and become turgid
- they have thin outer walls and thick inner walls that make them bend outwards and open stomata
What are root hair cells and how are they specialised?
Epidermal cells of roots with long projections
- large SA
- thin, permeable cell wall
- extra mitochondria
How are palisade cells specialised?
Pack together closely with space between for air to circulate
Large vacuole
Chloroplasts
Cytoskeleton threads and motor proteins to move chloroplasts
Thin walls
Define tissue.
A group of cells that work together to perform a specific function/set of functions.
What are the five main types of animal tissue?
- Squamous epithelium
- Ciliated epithelium
- Muscle
- Cartilage
- Nervous
Difference between microvilli and cilia?
- microvilli are extensions of the plasma membrane from surface area
- cilia of organelles for receptions and moving
What is connective tissue made from?
Proteins (collagen and elastin) and polysaccharides (such as hyaluronic acid) and cells
What are immature cells in cartilage called?
Chrondoblasts
What are mature cells in cartilage called?
Chondrocytes
What are the three types of cartilage?
Hyaline
Fibrous
Elastic
What does vascularised mean?
Has many blood vessels.
What allows muscle tissue to contract?
Muscles cells are called fibres and contain special organs called myofilaments made of the proteins actin and myosin.
What are the three types of muscle tissue?
- skeletal muscles cause bones to move
- cardiac muscle for heart
- smooth muscle in intestine, blood vessels, uterus, etc
Define meristem.
Area of unspecialised cells within a plant that can divide and differentiate into other cell types
Define organ.
Collection of tissues working together to perform a function / set of functions.
Define phloem
Tissue that carries products of photosynthesis in solution within plants.
Define xylem
Tissue that carries water and mineral ions from the roots to all other parts of plant.
What type of tissue are the xylem and phloem?
Vascular tissue
How are stems in meristems specialised?
Thin walls with little cellulose
No chloroplasts
No large vacuole
Can differentiate by mitosis
How do cambium cells differentiate into xylem vessles?
Lignin is deposited in cell walls to reinforce but this kills cells
Ends of the cells break down so that the xylem forms continuous columns with wide lumens
What organ system contains the skin hair and nails?
Integumentary system for waterproofing, protection and temperature regulation.
What organ system makes hormones?
endocrine system
What organ system contains lymph nodes and vessels?
Lymph system.
What are four sources of stem cells?
- embryonic
- umbilical cord blood
- adult stem cells
- induced pluripotent stem cells (iPS)
What happens in prophase 1 of meiosis?
Nuclear envelope breaks down
Chromosomes condense
Chromosomes come together in homologous pairs
Crossing over alleles shuffled
What happens at interphase?
DNA replicated
Organelles replicated
ATP content increased
When does cytokinesis begin and end?
Begins in anaphase
Ends in telophase
Significance of mitosis in life cycles
- growth
- tissue repair
- asexual reproduction in plants, animals and fungi
Significance of meiosis in life cycles
- production of haploid cells
- genetic variation by independent assortment and crossing over
When are chromatids crossed over?
Prophase 1
How are different epithelial cells specialised?
- Ciliated epithelial cells have cilia to move particles
- Squamous epithelial cells are very thin to allow efficient diffusion of gasses
What type of cells does xylem have?
hollow, dead xylem vessel cells and living parenchyma cells
Where are erythrocytes and neutrophils derived from?
stem cells in bone marrow
Potential uses of stem cells in research and medicine?
- repair of damaged tissues
- treatment of neurological conditions such as Alzheimers and Parkinsons
- research into developmental biology
Why does the genetic material get copied?
- so cells are genetically identical
- so both daughter cells have a full copy of DNA
Features of homologous chromosomes
- one maternal one paternal
- same genes usually
- same/different alleles
- centromere in same position
- same banding pattern
- pair up in meiosis
Function of squamous epithelium
acts as a surface
short diffusion pathway
Example of squamous epithelium
alveoli
cheek lining
blood vessels
Function of ciliated epithelium
Move mucus
Example of ciliated epithelium
bronchioles
bronchi
trachea
Where can meristem tissue be found?
apex of root
apex of shoot
cambium
bud
How is cell division different in plant cells than animal cells?
- cell wall forms
- cytokinesis starts from middle of cell
- only occurs in meristem
- no centrioles
What happens at G2/M checkpoint?
- chemicals stimulate spindle formation
- trigger condensation of chromatin
What happens at G1/S checkpoint?
restriction point
ensures cell is ready to enter S phase
some cell enter G0
What is a centrosome?
The system set up in cell division by the centrioles
Order of cells in plants
cuticle upper epidermis palisade mesophyll spongy mesophyll lower epidermis cuticle
Main plant organs
flowers-reproduction
leaves - photosynthesis
stem - support + transport
roots - anchor + storage + absorption
Do sperm have flagellum or undulipodium?
undulipodium
What does epithelial tissue do?
-lines surfaces
-cells close in contact (desmosomes)
-short cell cycles
secretion
absorption
filtration
protection
excretion
Function of connective tissue
separates living cells within tissues and enables them to withstand forces
- blood
- cartilage
- ligaments bones tendons skin
What do chondroblasts do?
mitosis and secrete extracellular matrix
What do chondrocytes do?
maintain extra cellular matrix
What does hyaline cartilage do?
embryonic skeleton
ends long adult bones
ribs to sternum, nose etc
What does fibrous cartilage do?
-discs in spine and knee
What does elastic cartilage do?
outer ear
epiglottis windpipe flap
Which cells are totipotent?
zygote (any cell)
Which cells are pluripotent?
embryo (almost any cell or any cell of the organism)
Which cells are multipotent?
adults (go to limited number of specialised cells)
Which cells are unipotent?
adults (can only diff. into one type of cell)
Uses of stem cells
- Bone marrow transplants (blood diseases, cancer, immune system diseases)
- Drug research
- Developmental biology
- Repair of damaged tissues or replace host tissues
- Regenerative medicine
