2.1.6 Cell division, cell diversity and cellular organisation Flashcards
list 3 ways mitosis is used
growth
repair
asexual reproduction
what is produced by mitosis
2 genetically identical diploid cells
what is a haploid cell
a cell that contains a single set of chromosomes, e.g gametes
what are the 4 stages of the cell cycle
G1, synthesis, G2 (interphase) and mitosis
describe the events that take place in G1
cell grows bigger
replicates organelles
high volume of protein synthesis
describe the events that take place in synthesis phase
DNA replication
describe the events that take place in G2
cell continues to grow
organelles and proteins needed for mitosis are produced
when are the two checkpoints
before and after S phase
what do the checkpoints do
check for DNA damage/errors
check DNA replication was succesfull
checks if the cell has enough nutrients, and the proteins and organelles for mitosis
why would a cell enter G0 phase
conditions are not suitable for DNA replication
specialised cells that do not need to divide
senescent cells (old cells)
what is formed after DNA replication
two sister chromatids
(92 in total in humans)
where are sister chromatids joined together by
centromere
stages of mitosis in order
prophase
metophase
anaphase
telophase
describe events in prophase
chromomes condense
nuclear envelope disintegrates
centrioles move to opposite poles and form spindle fibres
describe events in metaphase
chromosomes align at the equator
spindle fibres attach to the centromere
(sister chromatid on either side of equator)
describe events in anaphase
centromere splits
chromatids are pulled to opposite poles of the cell
describe events in telophase
two groups of chromosomes decondense
nuclear envelope reforms around them
(two new nuclei)
what happens in cytokinesis
the cytoplasm divides and plasma membrane pinches off
2 genteically identical daughter cells formed
what are gametes
sex cells
hapolid cells contain…
half the number of chromosomes of somatic cells
what is the fusion of nuclei between sperm and egg cells called
fertilisation
what causes genetic variation in meiosis and what stage are they done at
crossing over (Prophase I)
independent assortment (Metaphase I & Metaphase II)
describe events in
Prophase I
chromatids condense and arrange themselves into homologous pairs called bivalent (4 chromatids)
crossing over occurs at the chiasmata, exchange of genetic material occurs
nuclear envelope disintegrates
centrioles move to opposite poles spindle fibres form
describe events in
Metaphase I
bivalents align at the equator
spindle fibres attach to centromere
independent assortment occurs
describe events in
Anaphase I
homologous chromosomes are pulled to oppsoite poles
describe events in
Telophase I & cytokinesis
chromosomes decondense
nuclear envelope reforms
cytoplasm divides
2 genetically different hapoid cells formed
describe events in
Prophase II
chromsomes condense
nuclear envelope disintegrates
centrioles move to opposite poles, spindle fibres form
describe events in
Metaphase II
chromosomes align at the equator (not in pairs)
spindle fibres attach to centromere
independent assortment happens again
describe events in
Anaphase II
Sister chromatids separate and are pulled to opposite poles.
describe events in
Telophase II & cytokinesis
chromsomes decondense
nuclear enevelope reforms
cytoplasm divides
what is produced at the end of meiosis
4 genetically unique daughter cells
what happens during crossing over
homologous chromosomes connect through the chiasmata
genetic material is exchanged
resulting in new combinations of alleles on each chromosome
what happens during independent assortment
random arrangment of homologous pairs along the equator
What are Stem cells?
Unspecialised cells that can divide by mitosis and differentiate into specialised cells.
What is Stem cell Potency?
The ability of stem cells to undergo differentiation
What are totipotent stem cells?
Have the ability to divide into any type of cell, including extraembryonic cells
What are pluripotent stem cells?
Have the ability to divide into any type of cell except the extraembryonic cells.
What are multipotent stem cells?
Can divide into a handful of different cell type
An example are stem cells found in bone marrow
What are unipotent stem cells?
Can only divide into one type of cell
What are 2 uses of Stem cells in medicine?
- Leukemia Treatment - replace destroyed bone marrow stem cells.
- Organ Regeneration - growing whole organs from stem cells.
Define a tissue.
A group of cells working together to perform a particular function
Define an organ
A collection of tissues all performing a specific function
What is the term for a group of organs that work together to perform a specific function?
An organ system
Name 2 examples of organs in animals and plants
Heart, lungs, leaves and roots
Describe the 6 tissues that make up the leaf
Upper epidermis - covered in waxy cuticle to prevent transpiration
Palisade mesophyll - tighly packed cells, located towards top of leaf, lots of mitochondria & chloroplasts
Spongy mesophyll - loosely arranged, air spaces for gas exchange
Phloem - translocation
Xylem - transpiration
Lower epidermis - stomata & guard cells for gas exchange
Describe the 3 tissue that make up the lungs
Endothelium - forms capillary walls, supplying alveoli with O₂
Squamous Epithelium - line walls of alveoli
Fibrous connective tissue - helps push air out of lungs.
Describe the function and adaptations of Erythrocytes (red blood cells).
F - transports O₂ around the body and CO₂ to the lungs
A - bioconcave=increase SA, cytoplasm contains high volume of haemoglobin=binds to O₂,
no nucleus=more space for haemoglobin, max. O₂-capacity, Elastic membrane=flexible cell & changes shape, to fit through narrow capillaries.
Describe the function and adaptations of Neutrophils
F - destroy pathogens by phagocytosis and secrete enzymes
A- Flexible shape=squeeze through cell junctions in capillary walls
Large no. of Lysosomes=
digestive enzymes help to digest and destroy invading cells
Lobed nucleus
Describe the function and adaptations of Sperm cells
F - reproduction, fuse with egg
A - Head contains a nucleus with half the no. of normal chromosomes (hapolid)
Acrosome in head contains digestive enzymes=breaks down outer layer of egg cell
Mid-piece packed with mitochondria=tail movement
Describe the function and adaptations of Root hair cells
F: absorption of H₂O & mineral ions from soil
A: Root hair=increase SA, rate of water uptake by osmosis is greater
Thinner walls than other cells=short diffusion distance
Permanent vacuole contains more concentrated cell sap than soil water=maintaing water potential gradient
Mitochondria=active transport ions
No chlorplasts
Describe the function and adaptations of Ciliated Epithelium.
F: Moving (brushing) substances away from surface of tissue.
A: Have cilia (hair-like structures)=beat to shift materials along the surfaces
Goblet cells secrete mucus=traps dust, dirt and microogranisms, preventing them from entering vital organs.
Describe the function and adaptations of Squamous Epithelium.
F: provide an outer layer, found on variety of organs and structures (e.g. alveoli)
A: Single layer of flattened cells on a basement membrane
Thin cross-section=short diffusion distance
Permeable=easy diffusion of gases.
Describe the function and adaptations Palisade cells.
F: Carry out photosynthesis
A: Large no. of chloroplasts in cytoplasm to maximisde absorption of light for photosynthesis
Tall & thin shape=allows light to penetrate deeper before encountering another cell wall.
Describe the function and adaptations Guard cells.
F: control the opeing of stomata
A: Inner cell wall are thicker while outer walls are thinner= difference in thickness allows cell to bend when turgid (filled with water), opening stomata.
High density of chloroplasts and mitochondria
