- Created by: Ellome Anistan
- Created on: 28-05-18 10:30
Cells and Control
- Cell replicates organelles and chromosomes
- Each chromosome is made up of 2 sister chromotids.
- Chromosomes condense and become visible
- Both sister chromotids joint at the centromere.
- Nuclear membrane dissipates & spindle fibres form.
- These attach to centromere of chromosome at poles of cell.
- Spindle fibres pull chromosome to line up on equator of cell
- Spindle fibres contract.
- Chromotids pulled apart and move to poles of cell.
- CHROMOTIDS ARE NOW CHROMOSOMES
- New nuclear membranes form around both groups of chromosomes at each pole
- Cytoplasm divides.
- 2 new cells are formed.
Mitosis: The process of cells dividing to produce two diploid daughter cells that are genetically identical to the parents.
Diploid: Have two copies of each type of chromosome. Humans have 23 pairs of chromosomes.
- Mitosis produces identical cells for:
=>repair of damaged cells & worn out tissue
=>asexual reproduction (in strawberries and aphids).
Asexual Reproduction: Producing new organisms from one parent only. They will be genetically identical to the parent.
- The offspring are clones & no variation
- Faster than sexual reproduction
- Mitosis is the production of two daughter cells
- Each with identical sets of chromosomes in the nucleus to the parent cell
- => Formation of two genetically identical diploid body cells.
- Cancer cells are produced through uncontrollable cell division
- Produces tumours that damages the body and results in death.
- Benign: not harmful
- Malignant: dangerous (when moving through metastatis).
Growth in Animals
Growth: A permanent increase in the no. of cells or in the mass or size of an organism (normally by mitosis).
- Nerve Cell=>2m long to carry messages around body.
- Sperm Cell=> Tail to swim
- RBC=> No nucleus for more space for Oxygen.
Why is cell differentiation important for specialised cells?
Differentiation: Where an unspecialised cell turns into a very specific cell, with a specific functions and specific adaptations, it has become specialised.
- Having specialised cells allows multicellular organisms to work more efficiently.
Growth in Animals 2
- Used to assess a child's growth over time to overall pattern in development can be seen
- No. of babies will have that specific mass but be below the percentile line.
- Draw lines from age and mass and see where they meet.
Growth in Plants
- Plants tend to grow at their tips of roots and shoots - meristems
- These are zones of cell division - mitosis
- Then the cell goes through elongation (cell walls loosen links between celluslose molecules) to allow water in => expansion of vacoule and cytoplasm.
- The links reform and walls become rigid again.
- Cells then differentiate into specialised cells that have different functions.
Types of Plant Cell
- Undifferentiated cells in plants
- Can become any type of cell
Growth in Plants 2 - Specialised Cells 2
Specialised Cells 2
Root Hair Cell
- Large surface area to take in more water.
- Thin cell wall to allow easy net movement of water
- No mesophyll (chloroplast tissue)
- Contain chloroplasts to help plant make food by photosynthesis.
- Found in the top of the leaf
- Large surface area to catch as much sunlight as possible
Growth in Plants 3 - Specialised Cells 3
Specialised Cells 3
- Consist of dead cells
- Thick strengthened cell wall with hollow middle
- Involved in movement of water through a plant.
- Found either side of stomata pores on underside of leaf
- Control opening and closing of pores during different times of day and different conditions
- Able to change shape=> opening and closing of pores
Stem Cells: An unspecialised cell that continues to divide by mitosis to produce more stem cells and other cells that differentiate into specialised cells.
- Stem cells are found in early human embryos and in adult bone marrow (or specific places).
Pluripotent: Can become any cell type
Multipotent: Can only become a limited no. of cells.
Adult Stem Cell
- Tissues created from these will not be rejected by the body.
Embryonic Stem Cell
- Found in inner cell mass in the blastocyst.
Stem Cells 2
- Can produce any type of specialised cell
- Shoot => Apical Meristem
- Root/Stem => Lateral Meristem
- Middle of the Stem => Intercalary Meristem
- Can treat many diseases caused by damaged cells like Diabetes I, leukemia and CVD.
- If stem cells continue to divide in the body => cancer
- They can be rejected.
- They can be used to test new drugs on
Brain: The central processing centre of the body
- If there is no activity in the medula oblongata => brain-dead
Brain and Spinal Cord Problems
- X-ray scan
- Beams move in a circle around the head
- Detectors measure the absoprtion of the X-ray
- 3D picture of the brain
- Diagnose conditions
- Moniter conditions after diagnosis
- Positron Emission Tomography
- Patient is injected with radioactive glucose
- The more active the cell, the more glucose it will absorb => respiration
- Radioactive atoms release gamma rays which can be detected by a scanner.
- Shows changes in real time
- Useful for studying disorders that change the brain's activity.
Brain and Spinal Cord Problems 2
Spinal Cord Problems
- Adult Stem cells do not differentiate into neurones in the spinal cord
- Wires are used to stimulate nerves and muscles in quadriplegics.
- Brain tumours can squash parts of the brain and stop it working.
- Cells can be killed by radiotherapy (high energy X-ray beams) and chemotherapy (drugs).
- These can damage body and brain
- Chemo might not work due to blood-brain barrier (natural filter that only allows certain substances from the blood to the brain).
Limitations of CNS Surgery
- Hard to repair damage - no way to repair nervour tissue
- Not possible to surgically remove tumours growing in certain parts of the brain
- Surgery could lead to permanent damage
The Nervous System
- The nervous system is made up of the brain, spinal cord, nerves and sense organs
- A stimulus stimulates a response in the body
- Detected by receptor cells in sense organs
- Receptor cells create electrical signals called impulses.
- Impulses travel from the receptor cells to the brain (voluntary response) or spinal cord (reflex action/ involuntary response) sent along
- Brain processes this and sends impulses to effectors (muscles & glands) to carry out an action.
The Nervous System 2
The Nervous System 3
- Sensory Neurone: Long dendrites => quicker impulse than using many.
- Motor Neurone: Myelin sheath => Electrical Insulator => speeds up impulse
- Relay Neurone: Long Axon => quicker impulse.
- An electrical impulse travels along an axon and to the ends of the neuron.
- End of first neuron releases chemicals =>neurotransmitters
- Chemicals diffuse across synapse (gap) and bind to receptors in 2nd neuron
- Receptors in 2nd neurone only bind with specific chemicals from the first.
- 2nd neurone is stimulated and transmits an electrical impulse down the axon.
- Slowed down because diffusion takes time
The Nervous System 4
- If in danger: signals go from sensory to motor via relay
- Skips CNS but goes through unconscious part of brain.
- The reflex is from receptor to effector
- Thick layer to protect the eye
- Its muscles contract and relax to alter the size of the pupil.
Rod and Cone Cells
- The photoreceptors are sensitive to black and white and colour.
- Cone cells function in bright light and produce detailed vision
- Rod cells function in low light and movement
The Eye 2
- Protein build-up inside the lens and makes it cloudy.
- Full vision can be restored by using a plastic lens.
- Cones don't work properly and cannot be corrected.
- Most common is red-green colour blindness.
- Distant objects appear blurred
- Rays focused in front of retina because the eyeball is too long or cornea is too curved.
- Can be solved using a diverging lens.
The Eye 3
- Caused by eyeball being too short or cornea being less curved.
- Can be fixed by converging lens