Cells And Control Flashcards
What are the stages of mitosis?
Interphase - the DNA copies itself
Prophase – the chromosomes condense so spindle fibres become visible, the nuclear membrane breaks down
Metaphase – chromosomes line up in the middle of the cell
Anaphase – one set of chromatids are pulled to each pole of the cell
Telephase – new nuclear membranes form around the groups of chromosomes
Cytokinesis – the cell membrane divides into two daughter cells
What are stem cells?
- Completely undifferentiated cells
- That can specialise into any type of cell
What are meristems?
- Parts of a plant where growth occurs (root and shoot tips)
- Don’t ever fully differentiate, stay as stem cells
- Can be used to grow clones quickly and cheaply to protect from extinction or if it has desirable features
What are the two types of animal stem cells?
Embryonic - removed from the embryo and can differentiate into any cell type
Adult - found in limited numbers and locations in the body
What are some of the uses for embryonic stem cells?
- Replacing or repairing brain cells to treat Parkinson’s disease
- Replacing the damaged cells in the retina to treat some kinds of blindness
- Grow new tissues in the lab for transplants or drug testing
- To replace insulin producing cells for diabetics
What are the advantages and disadvantages of embryonic stem cells?
Advantages:
- Easy to extract from embryo
- Produce any type of cell
Disadvantages:
- Embryo destroyed when cells removed, some people think embryos have a right to life
What is the risk of all stem cells?
They may not stop dividing so may cause cancer
What are the advantages and disadvantages of adult stem cells?
Advantages:
- No embryo destroyed so not an ethical issue
- If taken from the person treated, it will not cause rejection by the body
Disadvantages:
- Only produces few types of cells
What are some of the functions of the cerebral hemispheres?
- Consciousness
- Memory
- Intelligence
- Visual and sensory processing
- Personality
- Senses
What do the two cerebral hemispheres make up?
Cerebrum
What is the function of a cerebellum?
Controlling fine movements of muscles e.g. coordination and balance
What is the function of the medulla oblongata?
Controls subconscious activities e.g. heart rate, breathing rate, digestion, swallowing and sneezing
How does a CT scan work?
- X-ray radiation is fired at the brain from different angles
- This generates a 3-D image of the brain
How does a PET scan work?
- A radioactive tracer is injected into the blood
- The tracer will build up in areas of rapid respiration and will be highlighted on the scan
How does the nervous system work?
- Receptors convert a stimulus into an electrical impulse
- Impulses travel along sensory neurons to the CNS
- The information is processed and appropriate response is coordinated
- An electrical impulse is sent along motor neurones to effectors
- Effectors carry out the response
What are the stages of the reflex arc?
- Receptors in the skin detect a stimulus and transmit a signal to sensory neurones
- Sensory neurons send electrical impulses to relay neurones in the spine
- They connect sensory neurons to motor neurones
- Motor neurones send electrical impulses to effector
- The effector produces a response
What are the features of sensory neurones?
- Dendrites to receive impulses from receptor cells
- Dendrons and axons to allow fast transmissions over long distances
- Cell body which contains the nucleus
- Myelin sheath that insulates the neuron stopping energy loss and allows impulse to jump between gaps speeding up transmission
- Axon terminals to pass impulses to other neurons
How is an impulse transmitted over a synapse?
- Synapse is a gap between neurons
- An electrical impulse stimulates the release of chemical messengers called neurotransmitters
- Neurotransmitters diffuse across the synapse
- This stimulates an electrical impulse in the next neurone
What is the function of the cornea?
Refracts light onto the retina
What is the function of the iris?
- Muscles that surround the pupil that contract or relax to alter the size of it
- Controls how much light enters the pupil
What is the function of the lens?
Further refracts light to focus it onto the retina
What is the function of the retina?
- Layer of the light-sensitive cells found at the back of the eye that are stimulated when lights hits them
- Contains rod and cone cells which convert light to nerve impulses
What is the function of the optic nerve?
Carries impulses between the eye and brain
What is the function of the ciliary muscles and suspensory ligaments?
- Holds the lens in place
- Control its shape and allow us to focus on objects near or far away
What is the difference between a rod and cone cells?
Rod cells - more sensitive to light so useful for seeing in dim light
Cone cells - sensitive to bright light and allow colour vision
What is accommodation?
The process of changing the shape of the lens to focus on near or distant objects
How does the eye adapt to a near object?
- Ciliary muscles contract
- Suspensory ligaments loosen
- Lens is thicker and more curved
- Light is refracted strongly
How does the eye adapt to a far away object?
- Ciliary muscles relax
- Suspensory ligaments tighten
- Lens becomes thinner
- Light is only refracted slightly
How does the eye adapt to bright light?
- The circular muscles in the iris contract and radial muscles relax
- To make the pupil smaller
- This avoids damage to the retina
How does the eye adapt to dim light?
- Circular muscles in the iris relax and radial muscles contract
- To make the pupil larger
- So more light can enter to create a better image
What is shortsightedness? (+ name)
- Myopia
- The lens is too curved so distant objects appear blurry
What is long sightedness? (+ name)
- Hyperopia
- The lens is too flat so it cannot refract light enough
What are cataracts?
- Clouding of the lens
- Can often occur congenitally (from birth) but can also develop over time
- They restrict vision
How can cataracts be treated?
By removing the lens and replacing with an artificial lens (plastic)
What is colour blindness caused by?
- Occurs when people do not have enough cone cells in their retina
- Usually genetic
What are the causes of shortsightedness?
- Elongated eyeballs, so the distance between lens and retina is too big
- Lens being too thick and curved, so light is focused in front of the retina
What are the causes of long sightedness?
- Eyeball being too short, so the distance between lens and retina is too small
- Loss of elasticity in the lens, meaning it cannot become thick enough to focus
How can shortsightedness be corrected?
By placing a concave lens in front of the eye
How can long sightedness be corrected?
By placing a convex lens in front of the eye
What is laser eye surgery?
- Lasers either used to reduce the thickness of cornea (to refract less light) to treat short sightedness
- Or to change its curvature (to refract light more strongly) to treat long sightedness
What does mitosis produce?
Two genetically identical daughter diploid cells
What is the structure of DNA?
- Polymer made up of monomers called nucleotides
- These are made from 1 sugar molecule, 1 phosphate molecule (which form the backbone) and 1 of the four bases
- These join together forming two strands (double helix)
- The double helix is held together by weak hydrogen bonds between complimentary base pairs
What are the complimentary base pairs?
Adenine and Thymine
Cytosine and Guanine 
What is a gene?
- Short section of DNA
- Each gene codes for a particular sequence of amino acids to make a specific protein
What is the genome?
The entire DNA of an organism
