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cell cycle in eukaryotes
-2 phases:
-interphase(G1,S,G2)
-mitosis
G1
-cell grow
-trascription=mRNA from DNA
-trasnaltion
-organelles duplicate
S
-DNA replication occurs
G2
-cell grows
-energy stores increases
G1/S checkpoint
-cell size
-DNA damage
G2/M checkpint
-cell size
-dna replication
sindle fibres assembly
-chromosomes attached to spindle
Go phase
-specialised cells that no longer divide
-the cell leaves the cell cycle as the DNA damaged (resting phase)
cancer
uncontrolled cell divines due to mutations in DNA
benign tumor
-stops growing,does not spread, less harmful
malignant tumor
-continues growing, spreads,harmful
increase of mutations
-UV rays
-X rays
-tar
-nitrous acid
Mitosis=PROPHASE
-nucleur envelope breaks down
-the 2 chromatids shorten and thicken as the DNA condenses into visible chromosomes
-the centriole divides and moves to opposite poles of the cell
METAPHASE
-the pairs of chromatids attach to spindle threads at the equator region
-they attach by their centromeres
ANAPHASE
-the centromere of each chromatid splits
-the motor proteins pull each sister chromatid in opposite directions towards opposite poles
TELOPHASE
-the separated chromosomes reach the poles
-a new nucleus envelope forms around each set of chromosomes
-the cell now contains two nuclei genetically identical
-chromosomes decondense and uncoil
CYTOKINESIS
-the cytoplasm divides
-cell membranes fuses to separate the 2 daughter cells
plant cell
-no centriole
-occurs in plant meristem
-cell plate develops into he cell wall
products
2 genetically diploid daughter cells
cell differentiation
-cells become specialised to perform a particular function
-stem cells are undifferentiated cells that divide by mitosis and can develop into any type of body cells
specialised animal cells:RBC
-RBC(erythrocyte)
-biconcave shape
-transports oxygen to respiratory cells,tissues using hb
Adaptations of RBC
-biconcave shape,small in size,so large SA:V
-flexible so can twist/turn around body capillaries
- a lot of organelles have been removed to create space for hb which binds to oxygen
neutrophil
-multilabeled nucleus
-to ingest bacteria and fungi by phagocytosis
Adaptations of neutrophil
-twice the side of erythrocyte and contains a multilabeled nucleus which enables them to be flexible so they can leave the blood capillaries
-they are attracted to and travel towards infections by chemotaxis
sperm cell
carry genetic material toward the egg during fertilisation
adaptations of sperm cell
-many mitochondria,the ATP proved is energy for the tail to move and propel the egg towards ovum
-small long and thin so they can move easily
-acrosome which releases enzymes to penetrate the egg
-tail propels the egg
-nucleus gas half of the genetic material
epithelial cells (squamous)
-flat+thin,so allow short diffusion distance
-found lining the alveoli and cheek
-the ones lining the blood vessels are called endothelium
epithelial cells(ciliated)
-found lining the trachea
-have goblet cells that secret mucus to trap the bacteria
-have cilia to waft the mucus outwards
-in oviduct help to move the egg cells from the ovary to he uterus
specialised plant cell:palisade cells in leaf
-waxy cuticule
-epidermal cells
-palisade cells that have chloroplast so can carry out photosynthesis
-spongy mesophyll tissue have air spaces
-xylem,phloem
-guard cells have chloroplast to provide ATP and its inner wall is thick
root hair cells
-many root hair extensions which provide large surface area for diffusion
-thin =short diffusion distance
-absorb water by osmosis and mineral ions by active transport
tissues
similar cells specialised to perform a particular function
organ
collections of different tissues that work together to perform a specialised function
stem cells
-pluripotent
-can divide by mitosis to provide more cells and then differentiate into specialised cells for growth and tissue repair
embryonic stem cells
-from early embryos
-induced pluripotent stem cells
adult stem cells
found in developed tissues of children and adults were they repaired damaged tissues e.g brain
total potent stem cells
are able to differentiate into all cell types and conform the whole organism
pluripotent stem cells
can differentiate into many cell types that cannot form the whole organism e.g placenta
Multipotent stem cells
can differentiate into few types of cell e.g bone marrow stem cells can only form blood cells such as neutrophil or erythrocytes
ethical issues of using ESC in research
-embryonic stem cells have not developed a nervous system
-risk of rejection
-risk of forming tumours
-religious reasons
-killing potential human lives
meiosis
-4 haploid daughter gameres are produced
-homologous pair:a pair of chromosomes (one mother,one father)
prophase 1
-Chromosomes condense and become visible.
• Homologous chromosomes pair up (synapsis) to form bivalents.
• Crossing over occurs at chiasmata, increasing genetic variation.
• Nuclear envelope breaks down, and spindle fibers begin to form.
metaphase 1
-Homologous chromosomes line up at the equator in random orientation.
• Independent assortment occurs, generating genetic variation, as different combinations of genes are separating into daughter cells
anaphase 1
• Homologous chromosomes are pulled apart (not sister chromatids).
• Chromosome number is halved.
telophase 1+ cytokinesis
• Nuclear envelope reforms (in some species).
• Cytokinesis occurs, forming two haploid daughter cells.
meiosis 2
-prophase 2:chromosomes recondense
-metaphase 2:chromosomes line up at the equator
-anaphase 2:the chromatids are pulled apart by spindle fibres breaking the centromere
-telophase 2:chromosomes de condense and forms 4 haploid daughter cells
xylem
-vascular tissue
-transports water+mineral ions from roots to other parts of the plant
-vessel
-non living
adaptations of xylem
-lignified walls for structural support
-spiral lining gives plant flexibility
-hollow Centre so water can be transported freely
-pits so water can move from one xylem vessel to one another or other parts of the cell
phloem
-vascular tissue
-transport sucrose and amino acids around the plant from the leaf
adaptations of phloem
-sieve plates, give support to the tube and keep the lumen open
-The companion cell has numerous mitochondria to produce ATP for the active processes
-The sieve plates have pores so sucrose can be transported through it
-The sieve tube has no nucleus so there is plenty of room to transport Sucrose
-Plasmodesmata:gaps that allow exchange of materials between the companion cell and sieve tube
