Cell Division

Question 1

Eukaryotic cells

Answer 1

Enter cell cycle and divide by mitosis or meiosis

Question 2

Prokaryotic cells

Answer 2

Replicate by binary fusion

Question 3

Viruses

Answer 3

Do not undergo cell division as they are non-living
Instead they replicate inside the host cells they invade

Question 4

3 stages of cell cycle

Answer 4

Interphase (G1 ,s ,G2)
Nuclear division (mitoisis / meiosis )
Cytokinesis final stage

Question 5

Interphase

Answer 5

Is the longest stage in the cell cycle .
When the organelles double , the cells grow and dna replicates

Question 6

Nuclear division - mitosis

Answer 6

4 stages
Prophase
Metaphase
Anaphase
Telophase

One round division
Genetically indentical cells are made
Diploid cells are made
Growth and repair

Question 7

Prophase

Answer 7

Prophase - chromosomes condense and become visible

Centrioles separate and move to opposite poles of the cell , create spindle fibres which are realised from both poles create spindle apparatus.

Plant cells have Spindel apparatus but lack the centrioles

Question 8

Metaphases

Answer 8

Chromosomes align along the equator of cell. Spindle fibres released from the poles now attach to the centromere and chromatid.

Question 9

Anaphase

Answer 9

Spindel fibres retract and pull the centromere and chromotids they are bound to towards the opposite poles . Centromere to divide into two and individual chromotids and pulled pulled to opposite poles . These seperated chromotids now referred as chromosomes .

Stage requires energy in the form atp which is provided by respiration on the mitochondria

Question 10

Telophase

Answer 10

Chromosomes reach poles and become indistinct.
Nuclear envelope reforms and nucleolus reforms
Spindle fibres disintergrate.

Question 11

Cytokinesis - final stage

Answer 11

Cytoplasm splits in two to create two new genetically identical cells

Question 12

Mitotic index

Answer 12

The number of cells in mitosis / the total number of cells x 100

Question 13

Binary fission in prokaryotic cells

Answer 13

Stage 1 : replication of the circular dna and plasmids
Stage 2: division of the cytoplasm to produce to daughter cells each with a single copy of the cichlid dna and a variable number of plasmids

Question 14

Replication of viruses

Answer 14

Can’t undergo cell division non living

Replicate inside the host cells they invade by injecting their nucleus acid into the cell to replicate the virus particles

Question 15

Components of membrane

Answer 15

Cholesterol present in some membranes restrict the lateral movement of other molecules in membrane.
Useful as makes the membrane less fluid at high temperature.
Prevents water and dissolved ions leaking out the cell.

Proteins -

Extrinsic- provide mechanical support.
Connected to proteins or lipids to make glycoproteins and glycolipids. Function of these is cell recognition as receptors

Intrinsic - are protein carries of channel proteins involved in the transport of molecule across the membrane

Question 16

Protein channels or carrier proteins

Answer 16

Protein channels - form tubes that fill with water to enable water soluble ions to diffuse

Carrier protiens - will bind to larger molecules such as glucose and amino acids and change shape to transport them to the other side of membranes

Question 17

Partially permeable

Answer 17

Only lipid soluble substance and small molecules can pass by simple diffusion.