Topic 2 - Cells and Control Flashcards
Describe mitosis
Mitosis is a step in the cell cycle that cells must undergo in order to divide. Mitosis is the stage where the cell divides.
It’s the process that involves a cell dividing to produce 2 identical cells.
Describe interphase
In this stage the cell grows, organelles (such as ribosome and mitochondria) grow and increase in number, the synthesis of proteins occurs, DNA is replicated and the energy stores are increased.
Describe prophase
The DNA in chromosomes and their copies condenses to become more visible. The membrane around the nucleus breaks down.
Describe metaphase
Chromosomes and their copies line up in the middle of the cell
Describe anaphase
Spindle fibres split the chromosomes down the centre and pull one chromatid to either side of the cell.
Describe telophase
New membranes form around the chromosomes at either end of the cell
Describe cytokinesis
The cell cytoplasm and membrane divides to produce two daughter cells; each new cell has a copy of each of the chromosomes.
Describe the importance of mitosis
It’s important in growth, repair and asexual reproduction.
Describe the division of a cell by mitosis
It is the production of two daughter cells, each with identical sets of chromosomes in the nucleus to the parent cell, which results in the formation of two genetically identical diploid body cells
Describe cancer
The result of changes in cells that lead to uncontrolled cell division
Describe growth in animals (highlighting cell division and differentiation)
In animals, cell division occurs by mitosis, after which cells can differentiate to specialised forms, specially adapted to their function.
Describe growth in plants (highlighting cell division, elongation and differentiation)
Plant cells can grow longer in a specific direction by absorbing water into their vacuoles, and this is controlled by substances called auxins. Mitosis only occurs in meristems in the tips and roots and shoots in plants.
Explain the importance of cell differentiation in the development of specialised cells (?? remove)
In animals, almost all cells differentiate at an early stage and then lose this ability. Most specialised cells can make more of the same cell by undergoing mitosis.
In plants, many types of cells retain their ability to differentiate through life.
Describe what a baby being born at the 50th percentile for mass means
The baby Is heavier than 50% of babies.
Being in a high percentile can indicate a health problem.
Describe the function of embryonic stem cells
-They can differentiate into any type of cell in the body.
-They form when an egg and sperm cell fuse to form a zygote.
-Scientists can close the cells and direct them to differentiate into almost any cell in the body
Describe the function of stem cells in animals
Adult stem cells can differentiate into related cell types only. So bone marrow cells can differentiate into blood cells and cells of the
immune system, but not other cell types.
Describe the function of meristems in plants
-They can differentiate into any type of plant, and have this ability throughout the life of the plant
-Found in root and shoot tips
-Can be used to make clones of the plant - this may be necessary if the parent plant has certain desirable features, for research or to save a rare plant from extinction.
Discuss the potential benefits associated with the use of stem cells in medicine
-Can be used to replace damaged or diseased body parts
-Unwanted embryos from fertility clinics could be used as they would otherwise be discarded.
-Potential for medical research into the process of differentiation.
-Potential for treating patients with currently untreatable conditions
-Potential for growing organs for transplants
Discuss the potential risks associated with the use of stem cells in medicine
-There is no guarantee of how successful these therapies will be, for example in the use of stem cells in healing damage caused by Parkinson’s disease.
-Patients could be exploited by paying for expensive treatments and being given false hope of a cure as stem cell therapies are only in their developmental stages.
-The difficulty in finding suitable stem cell donors.
-The difficulty in obtaining and storing a patient’s embryonic stem cells.
-Cultured stem cells could be contaminated with viruses which would be transferred to a patient.
-People may have religious or ethical objections as it is seen as interference with the natural process of reproduction
Describe the structures and functions of the cerebellum
Large lump-like structure at the bottom of the brain, on the rear side.
It is responsible for controlling minor movements and balance.
Describe the structures and functions of the cerebral hemisphere
The two large cerebral hemispheres (together the cerebral cortex or cerebrum) take up most of the skull and perform a variety of functions including for memory, intelligence, language, conscious thought, voluntary movement.
The left hemisphere of the brain controls the right side of the body and vice versa.
Describe the structures and functions of the medulla oblongata
It is a small elongated structure found in the brainstem, at the base of the brain. It is responsible for involuntary actions such as the heartbeat and breathing.
Explain how the difficulties of accessing brain tissue inside the skull can be overcome by using CT scanning
CT scans use x-ray radiation from several angles to generate a 3D image of the brain. This is useful for examining bleeding within the skull and damage to brain structures.
Explain how the difficulties of accessing brain tissue inside the skull can be overcome by using PET scanning
In PET scans, radioactive glucose / a ‘tracer’ is injected into the blood before the scan. The scan itself shows the area where the tracer builds up to show area with greater blood flow. This can identify cancerous tumours as these use more blood than normal tissue.
Explain some of the limitations in treating damage and disease in the brain and other parts of the nervous system, including spinal injuries and brain tumours
-It is complex and delicate
-It is easily damaged
-Drugs given to treat diseases cannot always reach the brain because of the membranes that surround it
-It is not fully understood which part of the brain does what
-Often, tumours can be buried deep in the brain or spinal cord, making them especially difficult to remove.
Explain the structure and function of a reflex arc
-Sensory receptors on sensory organs detect a stimulus and convert it into an electrical impulse.
-This electrical impulse travels along nerve cells called sensory neurones to the central nervous system where the impulse passes to a relay neurone.
-The impulses are then sent along to a motor neurone.
-It then moves to the effector which carries out an appropriate response.
What are some features of a neurone?
-A long fibre (axon) which is insulated by a fatty (myelin) sheath. They are long so they can carry messages up and down the body.
-Tiny branches (dendrons) which branch further as dendrites at each end. These receive incoming impulses from other neurones.
Describe what happens at synapses.
Synapses are the gaps between two neurones. They control the speed of the impulse.
At the end of an axon of the first nerve cell, a chemical called a neurotransmitter is released into the synapse. This diffuses across the synapse and carries the signal to receptors on the other nerve cell. The receptor generates an electrical impulse that carries on along the nerve cell.
Explain the role of the cornea
Focuses light, is in a fixed shape
Explain the role of the lens
Focuses light, can change shape to refract light
Explain the role of the iris
Coloured part of the eye
Explain the role of the rod cells in the retina
Receptor cells that detect light intensity
Explain the role of the cone cells in the retina
Receptor cells that detect colour
Describe short-sightedness
Short-sightedness is also called myopia and is when light rays are too focused in front of the retina and the cornea refracts light rays too much. The cornea is too convex.
Describe long-sightedness
Long-sightedness is also called hyperopia and is when light rays are too focused behind the retina and the lens doesn’t refract light enough. The eyeball is too short.
Describe cataracts
A build-up of protein in the lens, causing it become cloudy. It restricts vision
Describe colour blindness
The inability to see certain colours. This usually occurs because people with the condition do not have enough cone cells in their retina. This is usually genetic.
Explain how cataracts, long-sightedness and short-sightedness can be corrected
*With spectacle lenses/contact lenses -concave lenses to focus the light on the fovea for short-sightedness and convex lenses to bring the rays together to treat hyperopia
*For cataracts, the lens can be replaced with a plastic one
