cell divison

Question 1

how do eukaryotic cells divide

Answer 1

entering the cell cycle and dividing by mitosis

Question 2

how do prokaryotic cells and viruses divide

Answer 2

binary fission and viruses do not do cell division as they are non living

Question 3

the cell cycle stages

Answer 3

1. interphase
2. nuclear division ( mitosis or meiosis )
3. cytockinesis

Question 4

interphase

Answer 4

G1
protein synthesis
organelles replicate
cell is checked if its the right size
S phase
dna is replicated
G2
cell grows, newly replicated dna is checked for errrors

Question 5

mitosis

Answer 5

mitosis creates indentical diploid cells and is used for growth, tissue repair and asexual reproduction in plants and production new stem cells

Question 6

prophase

Answer 6

the chromosomes condense and become visible
in animal cells the centrioles separate and move to opposite poles of the cell
the centrioles create spindle fibres

Question 7

metaphase

Answer 7

the chromosomes align and meet along the equator of the cell

Question 8

anaphase

Answer 8

chromatids are separating and are being pulled to opposite sides of the cell

Question 9

telophase

Answer 9

a new cell membrane is visible down the centre of the cell
chromatids have been pulled to opposite sides of the cell

Question 10

cytokinesis

Answer 10

the cytoplasm splits into two gentically identical cells
in animals - the membrane constricts around the middle of the cell
in plant cells- a cell plate forms around the middle of the cell and forms the new cell wall

Question 11

observing mitosis

Answer 11

mitosis are visible under a light microscope in onion and garlic root tips
an iodine stain is added to make the chromosomes visible and the cover slip is pushed down

Question 12

mitosis index

Answer 12

mitotic index = the number of cells in mitosis divided my the total number of cells
x 100

Question 13

meiosis

Answer 13

two nuclear divisions resulting in four producing gentically diffrent haploid daughter cells
haploid = one copy of each chromosome
diploid = two copies of each chromosome

Question 14

genetic diffrenecces in meiosis

Answer 14

independent assortment of homologous chromosomeswhere - combinations of chromosomes arrangement
crossing over - chromosomes line up and exchange genetic material

Question 15

meiosis I

Answer 15

prophase I metaphase I anaphase I teleopase I
prophase are relatively the same as mitosis
in metaphase I , each pair of homologous chromosomes align at the equator the postion of each homologous chromosomes is random
in anaphase I the homologous chromosomes separate
in telophase the nucleus envelope reforms around haploid nuclear contains half the number of chromosomes

Question 16

meiosis II

Answer 16

prophase, metaphase, anaphase,telophase II
another of cell division
in anaphase II the centomeres split separating chromatides

Question 17

multicelllar organisms are organised:

Answer 17

cells
tissues
organ
organ system
organism

Question 18

erythrocytes

Answer 18

Structure and function
biconcave shape to increase the surface area for diffusion and to increase the cell flexibility for it to fit through narrow capillaries. These cells have no nucleus so there is more space to hold haemoglobin to increase transport of oxygen.

Question 19

neutrophiles

Answer 19

has a lobed nucleus and granular cytoplasm. The cells are flexible to enable them to surround pathogens and engulf them. They contain lysosomes filled with the hydrolytic enzyme,
lysozyme. Neutrophils are made from stem cells in the bone marrow.

Question 20

sperm cells

Answer 20

The flagellum contains many mitochondria to supply energy for ATP. The acrosome in the head of the cell contains digestive enzymes to so the sperm can penetrate and fertilise the egg cell.

Question 21

palisade cells

Answer 21

Located in the mesophyll tissue layer of leaves. They are rectangular, tightly packed cells that contain many chloroplasts to absorb and maximise light energy for photosynthesis. They have thin cell walls to reduce the diffuse distance of carbon dioxide.

Question 22

guard cells

Answer 22

These pair of cells have flexible walls, more so on one side, which results in the cells bending when turgid to open stomata and closing when flaccid and this helps control water loss by transpiration.

Question 23

squamous epithetial cells

Answer 23

Usually only a single layer of flat cells is in contact with the basement membrane of the epithelium.
This provides a short diffusion distance. e.g. these form the linings of the lungs.

Question 24

cilated epithelial cells

Answer 24

These cells have hair-like projections that sway to move substances, such as mucus, out of the lungs or an egg in the oviduct. Goblet cells are also located within the epithelium and these cells release mucus to trap molecules, such as trapping dust in the trachea.

Question 25

cartilage

Answer 25

A connective tissue that is firm and flexible, located in the outer ear, nose and the end of bones. It provides structural support and it prevents the bones from rubbing together which would damage them. It is made up of elastin and collagen fibres and chondrocyte cells within an extracellular matrix.

Question 26

muscle

Answer 26

Composed of tissues that can contract and relax to create movement. Skeletal muscles cause the skeleton to move and are made up of myofibrils containing the proteins actin and myosin. Smooth muscle is located within organs and cardiac muscle is within the heart. Muscles have multiple fibres connecting with connective tissues in between.

Question 27

xylem

Answer 27

the cells that make up the part of the vascular bundle in plants responsible for transporting water and mineral ions. The tissue is made up of elongated, hollow dead cells, with lignin in the walls to strengthen and waterproof the walls. Xylem tissues are made from the stem cells in the meristem.

Question 28

pholem

Answer 28

The cells that make up the part of the vascular bundle responsible for transporting organic substances made in photosynthesis. It is made of sieve tube element cells, which have perforated end walls and are lacking most organelles to make transport of sugars easier, and companion cells, which contain organelles to provide resources for the sieve tube elements. Phloem sieve tubes are made from the stem cells in the meristem.

Question 29

stem cells

Answer 29

Stem cells are undifferentiated cells that can self-renew (continually divide) and become specialised. Different types of stem cells have different differentiation abilities. These are: • Totipotent • Pluripotent • Multipotent • Unipotent

Question 30

totipotent

Answer 30

Totipotent cells can divide and produce any type ot body cell. During development, totipotent cells translate only part of their DNA, resulting in cell specialisation. Totipotent cells occur only for a limited time in early mammalian embryos.

Question 31

pluripotent

Answer 31

Pluripotent cells are found in embryos and can become almost any type of cell. For this reason, they are used in research with to prospect of using them to treat human disorders. There are issues with this as sometimes the treatment doesn't work, or the stem cells continually divide to create tumours.

Question 32

mulitipotent

Answer 32

Multipotent and unipotent cells are found in maturè mammals and can divide to form a limited number of different cell types. Multipotent cells, such as in bone marrow, can differentiate into a limited number of cells, whereas unipotent cells can only differentiate into one type of cell.

Question 33

uses of stem cells

Answer 33

Stem cells could be used in both research and medicine. These uses include: • Repairing damaged tissues • Treatment of neurological conditions such as Alzheimer's and Parkinson's • Research into biological knowledge e.g. - cells can be grown to test side effects and new medicinal drugs they can be grown and studies to develop diffrent cell types

Question 34

why do some animals reproduce asseually when conditions are favourable

Answer 34

gentically identical offspring offspring produced will be in large numbers/produces more offspring and offspring will find conditions more favourable/ have the same adaptations