Cells and control Flashcards
SB2a Mitosis
Describe the Cell Cycle.
1. Interphase - The diploid cell has 2 sets of chromosomes, these are each copied and they attatch, forming X shapes.
Mitosis
2. Prophase - The nucleus starts to break down and spindle fibers appear.
3. Metaphase - By the end of metaphase, the chromosomes are lined up on the spindle fibres across the middle of the cell.
4. Anaphase - The chromosome copies are separated and moved to either end of the cell on the spindle fibres.
5. Telophase - A membrane forms around each set of chromosomes to form nuclei.
6. Cytokinesis - A cell surface membrane forms to separate the 2 cells during cytokinesis.
- This is also when cell walls form in plants.
SB2a Mitosis
Describe where and why mitosis is needed.
1. Growth - Growth is an increase in size as a result of an increase in number of cells, hence, mitosis is needed.
2. Repair - To replace damaged cells mitosis is needed.
3. Asexual reproduction - Asexual reproduction produces offsprings that are identical clones. Meaning that is relies on mitosis.
SB2a Mitosis
Describe of products of Mitosis.
1. 2 daughter cells, each with identical sets of chromosomes to the parents.
- Results in the formation of: 2 genetically identical diploid body cells.
SB2a Mitosis
Describe what causes the growth of Cancer.
Uncontrollable cell division, this rapid cell division produces lumps of cells called tumours that can damage the body and result in death.
SB2b Growth in animals
Describe what differentiation is and provide how;
A) Sperm Cells are specialised
B) Egg Cells are specialised
C) Red Blood Cells are specialised
1. Differentiation is the process of unspecialised cells become specialised.
A) Sperm Cells
- Long tail for swimming to the egg.
- Lots of mitochondria to provide enough energy for getting to the egg.
- Enzyme on it’s head to get into the egg.
- Haploid - ( 23 Chromosomes ) as egg contains other 23
B) Egg Cells
- Egg cell will only let in 1 sperm cell
- Egg cell has all of the nutrients an embryo will need to grow.
- Haploid - ( 23 chromosomes )
B) Red Blood Cells
- No nucleus, allows for more space to carry oxygen ( Done by red haemoglobin molecules )
- Has a large surface area, allowing oxygen to diffuse in and out quickly.
SB2b Growth in animals
Describe how Percentile Charts can be used to monitor growth
( By providing an example )
1. First, the chart is created by measuring a large amount of babies.
- These measurements would then be split into 100 groups.
2. This allows us to see what percentage of readings are below a certian reading, or percentile.
3. We can then draw a curved lined of their growth as they age, if they stay relatively within the same percentile, they are growing normally, else, something may be wrong.
SB2c Growth in plants
Explain how plants are able to grow.
1. A group of cells near the end of each shoot and root allows the plant to continue to grow.
2. These groups of cells are called the Meristem.
3. The cells in the meristems divide rapidly via mitosis, many of the cells produced can then increase in length ( Elongation ), and differentiate.
SB2c Growth in plants
Describe how;
A) A Xylem Vessel is adapted to it’s functiom
B) A Root Hair Cell is adapted to it’s function
A) Xylem Vessel
1. Thickened walls to withstand water pressure.
2. Tiny pores in walls allows water and mineral salts to enter and leave the vessel
3. Having no cytoplasm means the vessel is empty, this is what allows water to pass through.
B) Root Hair Cells
1. They have long thing projections that stick out into the soil, allowing it to reach more water underground
2. They also have a large surface area to increase rate of absorption.
SB2d Stem cells
A) What are Stem Cells?
B) Describe the difference between Embryonic & Adult Stem Cells.
A) Stem Cells are cells that can divide repeatedly over a long period of time to produce cells that can then go on to differentiate.
B1) Embryonic Stem Cells
- Embryonic stem cells are the cells in the early-life on an embryo that can produce any type of specialised cell.
- As the cells continue to divide the embryo starts to develop different areas that will become the different organs.
B2) Adult Stem Cells
- Adult stem cells are present when the young animal is fully developed, these are much more limited in what they can specialise into.
- Adult stem cells in human tissue allow the tissue to grow and replace old or damaged cells.
SB2d Stem cells
Describe the Benefits & Risks to using Stem Cells in medicine.
Benefits;
1. They can be used to treat patients with currently untreatable diseases.
2. They can also be used for growing organs for transplants
3. They also assist in medical research.
Risks;
1. If stem cells continue to divide inside the body after they have replaced damaged cells, they can cause cancer.
2. Stem cells from one person could be rejected & killed by the immune system of the other.
3. Clinical Issue - Cultured stem cells could be contaminated with viruses which would be transferred to a patient
4. Ethical Issue - Is it right to create embryos for therapy, and destroy them in the process?
- In Therapeutic cloning
SB2e The Brain
Describe the different parts of the Brain.
1. Cerebral Cortex/Hemispheres
- The Cerebrum’s outlayer, and is split into 2 hemispheres, right and left.
- Controls most of our senses, intelligence, personality, conscious thought and high-level functions, such as language and verbal memory.
2. Cerebellum
- Located at the base of brain.
- Controls balance, co-ordination of movement and muscular activity.
- Also controls timing and fine movement.
3. Medulla oblongata
- Controls unconscious activities such as heart rate and breathing rate.
- Also responsible for reflexes, such as sneezing, vomiting and swallowing.
4. Spinal Cord ( Not part of the brain )
- The neurones that make of the medulla oblongata connect the brain to the spinal cord.
- The spinal cord consits of many nerves & is used for information sending.
SB2f Brain and spinal cord problems - Higher
Describe how CT scans are used to investigate the brain.
1. CT scans show the shapes of structures in the brain.
2. An X-ray beam moves in circles around the head, and detectors measure the absortion of the rays.
3. A computer can then use this information to create a series of ‘slices’, showing a view of brain.
4. Differences in the shapes in the brain can be linked to differences in the way people think and act, suggesting the function of those parts.
SB2f Brain and spinal cord problems - Higher
Describe the Advantages of using CT scanning over electrodes in brain surgery.
1. CT scanning allows scientists to get a deeper look into the brain than electrodes could in surgery.
2. It also allows the study of a healthy individual without the risk of damaging the brain.
SB2f Brain and spinal cord problems - Higher
Describe how PET scans are used to investigate the brain.
1. A PET scan shows brain activity.
2. The patient is injected with radioactive glucose.
- More active cells will take in more glucose than less active. ( For respiration )
3. The radioactive atoms emit gamma rays, which the scanner detects.
- More gamma rays come from the parts containing more active cells.
4. Carrying out activites during a PET scan shows which part of the brain is used for what activity.
SB2f Brain and spinal cord problems - Higher
Describe;
A) The effects of Spinal Cord damage
B) The limitations in trying to treat Spinal Cord damage.
A) Damage to the Spinal Cord reduces the flow of information between the brain and lower parts of the body.
- Damage in lower Spinal Cord can result in loss of use in legs, while damage in the neck can result in quadripegia.
B1) Adult stem cells cannot differentiate into neurones in the spinal cord, meaning new neurones cannot be made to repair damage.
B2) Wires can be used to electrically stimulate nerves and muscles below the damage, but patients don’t regain full movement/feeling.
Quadripegia - Loss of use in both arms and legs.
