2.1.6 Cell division, cell diversity and cellular organisation Flashcards
what is the cell cycle
- the cell cycle is when cells divide in order to make new cells
what are parts of the cell cycle
- Interphase (G1 phase, S phase, G2 phase)
- mitosis
- cytokinesis
what occurs during G1 phase
- the cell is growing and carrying out its normal functions ( eg producing energy)
what is the main goal in G1 phase
- to increase the size of the cell and make sure it has all the resources needed for DNA replication
What does the cell check before entering S phase
- the cell checks whether the cell is large enough, has enough nutrients and is in good condition to replicate DNA
what occurs in S phase
- cell makes an exact copy of its DNA every chromosome is replicated, so the cell now has two sets of chromosomes
( one for each daughter cell)
what is the main goal of S phase
- the DNA is synthesised to ensure that when the cell divides the daughter cell will have identical genetic material
What occurs during G2 phase
- the cell continues growing and and the new DNA which was synthesised ( during s phase) is checked for any errors.
- other preparations are made for cell division such as production of tubulin protein.
what are the 4 stages of mitosis
- prophase
- metaphase
- anaphase
- telophase
what is the centromere
a region of a chromosome where the spindle fibres attach during cell division
what does each chromosome consist of
- two sister chromatids joined at the centromere
what is a chromatid
one of the two identical halves of a chromosome that have been replicated for cell division
what occurs during prophase
- chromosomes condenses (visible when stained)
- the nuclear envelope break down
- nucleolus disappears
- the centrioles go to opposite side of the cell and proteins form spindle fibres attached to the centromeres of each chromosome
- the spindle fibres move the chromosomes to the equator (center) of the cell
what occurs during metaphase
- the spindle fibre is fully formed
- the chromosomes are now lined up at the equator of the cell
what occurs during anaphase
- chromatids are pulled to opposite sides of the cell
- the centromeres divide into two and the spindle fibres shorten
- this pulls the sister chromatids towards opposite poles of the cell.
what occurs during telophase
- the chromatids( now called chromosomes) have reached the poles of the cell.
- the spindle apparatus breaks down and the nuclear membrane reforms
- the chromosomes uncoil back to a chromatid
- the nucleolus reappears in each cell.
- the nuclear membrane surrounds the chromatids to form a nucleus
what occurs during cytokinese
- the central cell membrane is pulled inwards by the cytoskeleton.
- this creates a groove which deepens.
- eventually the membranes fuse to form two independent cells
the significance of mitosis in life cycles
- important for growth
- tissue repair
- asexual reproduction in plants, animals and fungi
what is meiosis
a type of cell division to produce gametes that produce four genetically different haploid daughter cells from one parent cell.
what is the significance of meiosis in life cycles
- it produces 4 haploid gametes.
- there cells are genetical different by independent assortment and crossing over
what are the mainstages of meiosis
- interphase
- prophase 1
- metaphase 1
- anaphase 1
- telophase 1
- prophase 2
- metaphase 2
- anaphase 2
- telophase 2
define homologous chromosomes
two chromosomes with similar genes but different alleles, one inherited from each parent
what occurs during prophase 1
- chromatin condenses
- nuclear envelope breaks down and spindle fibres made from centrioles
- chromosomes pair in homologous pairs
- crossing over between non-sister chromatids occur where alleles are exchanges
what occurs during metaphase 1
- homologous chromosomes line at chromosomes line at equator to spindle the centromeres at the sides of the cell
- pairs are arranged randomly
what occurs during anaphase 1
- Homologous chromosomes pulls apart by motor proteins
(independent assortment) - each chromosome still has two chromatids
what occurs during telophase 1
- nuclear envelop forms around chromosomes and cytokinesis may occur
- cells go into short interphase
what occurs during prophase 2
- chromatin condenses
- nuclear envelope breaks down and spindle fibres made from centrioles
- chromatids are different due to crossing over in prophase 1
what occurs during metaphase 2
- chromosomes line at equator to spindle by centromeres
- chromatids randomly arranged
what occurs during anaphase 2
- centromere divides and chromatids pulled apart by motor proteins
- chromatids randomly segregated ( independent assortment)
what occurs during telophase 2
- nuclear envelope forms around chromosomes and cytokinesis occurs
- 4 cells made in total as each cell from meiosis 1 divides.
when is genetic variation achieved in meiosis
- crossing over of chromatids ( pairs of chromosomes line up and exchange some of there genetic material)
occurs in prophase 1
how are erythrocytes specialised for its function
- red blood cells - used to carry oxygen around the body
specialised - no nucleus, mitochondria or golgi, for more space
function - allows for more space for oxygen
specialised - packed with lots of haemoglobin
function - to store more oxygen
specialised - bioconcave shape
function - increases surface area to volume ratio, which makes gas exchange more efficient
how are neutrophils specialised for its function
white blood cells - specialised to engulf and destroy pathogens
specialised - contains lots of lysosome which is a digestive enzyme
function - the digestive enzyme is able to break down the engulfed particle
specialised - flexible
function - easier to engulf larger particles
how are squamous epithelial cells specialised for its function
a cell which is specialised for rapid diffusion
specialised - thin, flat smooth surface
function - this increases the rate of diffusion due to a short diffusion distance
how are ciliated epithelial cells specialised for its function
a cell used to sweep dirt and debris out of the body
specialised - has a lot of cilia
function - lots of cilia make it easier to sweep the dirt and debris out of the body
How are sperm cells specialised for its function
specialised - contains lots of mitochondria
function - to provide energy/ATP for movement
specialised - specialised lysosome in the acrosome of the sperm
function - the digestive enzyme is able to break down/digest the protective jelly coat of the egg cell.
specialised - stream lined body and flagellum
function - to move more quickly towards the egg cells
how are palisade cells specialised for its function
a cell used to carry out photosynthesis
specialised - contains lots of chloroplast
function - chloroplast contains chlorophyll which changes light into energy
how are root hairs cell specialised for its function
a cell which is used for the uptake of ions and water from the soil.
specialised - a large surface area
function - to increase the rate of absorption
How are guard cells specialised for its function
used for the control of opening and closing of the stomata
specialised - it uses pressure to open and close the stomata
function - the guard cell is able to control the amount of water and solutes within them
