Cells and control

Question 1

How many chromosomes are in the human body?

Answer 1

23 - the 23rd pair are the sex chromosomes, influencing the biological sex of the person.

Question 2

How does mitosis work?

Answer 2

Mitosis is where cells divide for the body to: Grow, repair cells or for organisms like bacteria to reproduce. Mitosis creates 2 identical cells called daughter cells - Each are identical to the parent cell.

Question 3

Describe the cell cycle

Answer 3

Cell growth, DNA Synthesis, Further growth occurs and DNA is checked for errors, Mitosis, Cytoplasm separates - 2 cells are formed, Temporary cell resting period where the cell stops dividing.

Question 4

Length of cell cycle stages equation

Answer 4

Observed number of cells at that stage / Total number of cells observed MULTIPLIED by total length of time of cell cycle

Question 5

Interphase

Answer 5

DNA in chromosomes copies itself ready for mitosis

Question 6

Prophase

Answer 6

DNA in chromosomes and their copies condense. Membrane around the nucleus dissapears

Question 7

Metaphase

Answer 7

Chromosomes and their copies line up in the middle of the cell

Question 8

Anaphase

Answer 8

Chromosomes and their copies are pulled to different ends of the cell

Question 9

Telophase

Answer 9

New membranes form around chromosomes at ends of the cell

Question 10

Cytokinesis

Answer 10

Cell membrane pinches off and divides into 2 cells

Question 11

How does Cancer occur?

Answer 11

Cancer occurs when a cell mutates and divides uncontrollably. The growth cannot be stopped by apoptosis, and grows into a solid block of cells called a tumor

Question 12

Types of Tumor

Answer 12

Benign - Grows within a membrane so can easily be removed. Doesn’t invade other parts of the body
Malignant - Grows quickly and invades neighboring tissue. Can go into the bloodstream. Cancerous cells can form secondary tumors in other parts of the body. This is called metastasis

Question 13

What causes cancer?

Answer 13

Mutations in the cell cause Cancer, several are required to cause a cell to become cancerous.

Question 14

Why do cells differentiate?

Answer 14

In multicellular animals and plants cells must differentiate so that its cells develop features that allow them to fulfil specific roles. Cells that have been differentiated have become specialized.

Question 15

What are stem cells?

Answer 15

Stem cells are cells that have not undergone differentiation. A cell which has not yet been specialized is called undifferentiated.

There are two types of stem cells - Embryonic and Adult stem cells.

Embryonic stem cells can differentiate into any type of cell, whereas adult cells can only differentiate into cells from the tissue they were extracted from.

Question 16

How can people be treated with stem cells?

Answer 16

Stem cells can divide into different cells, and illnesses and diseases that cause loss of cells or damage cells can be treated with stem cells. They can replace those cells that have been damaged - eg: type 1 diabetes, multiple sclerosis etc.

Question 17

Types of Neurones

Answer 17

Sensory, Motor and relay

Question 18

Features of Neurones

Answer 18

They all have an axon which is insulated by the myelin sheath. They also all have dendrons which branch into dendrites at each end - they receive incoming impulses from other neurons

Question 19

What is a synapse?

Answer 19

Where 2 neurones meet there is a gap called a synapse. The electrical signal is converted into a chemical one which is converted back to an electrical one on the other side of the synapse.

Question 20

Process of Synapse transfer

Answer 20

1. An electrical impulse is carried along the first axon
2. This triggers the nerve ending to release neurotransmitters.
3. These diffuse across the synapse and bind with receptor molecules on the membrane of the second neurone
4. The receptor molecules on the second neurone bind only to the specific neurotransmitters released from the first neurone

Question 21

Reflex arc

Answer 21

Sensor, Sensory neuron, Control centre (Spine), Motor neuron, and muscle (effector)