SB2: Cells and Control Flashcards
What are the two types of cell division?
Mitosis and meiosis
How many pairs of chromosomes are there inside a nuclei?
23 pairs
Describe the two phases in the cell cycle.
Interphase: cell makes extra sub-cellular parts. DNA replication occurs, to make copies of the chromosomes, but they stay attached to each other forming an x shape.
Mitosis: cell splits to form 2 daughter cells, both identical to the parent cell. The cells are genetically identical.
When do cells divide?
- When an organism grows
- When an organism is damaged and needs new cells to repair itself
- For organisms that reproduce asexually
What are the stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
What occurs in prophase?
- nucleus breaks down
- spindle fibres appear
What occurs in metaphase?
Chromosomes are their copies line up on the spindle fibres in the middle of the cell
What occurs in anaphase?
The chromosome copies are separated and moved to either end of the cell on the spindle fibres
What occurs in telophase?
A membrane forms around each set of chromosomes to form a nuclei
What occurs in cytokinesis?
- cell surface membrane forms to separate the 2 cells.
- cell walls form in plants
What are cancer cells?
Cells that divide uncontrollably
What are tumours?
A growth produced by a group of cancerous cells
Define growth
- increase in size as a result of increase in number/size of cells
- long-lasting permanent change
How is the growth of babies recorded?
Measuring:
- mass
- length
- head circumference
What are percentile growth charts?
a chart used to compare the growth of a baby to the growth of other babies
What are specialised cells and what process must they go through to become specialised?
Cells that have adaptations to carry out specific tasks or functions. They must go through differentiation to become specialised
What are the adaptations of a red blood cell?
- biconcave disk shape (increases surface area)
- no nucleus (increases surface area)
- protein called haemoglobin binds to oxygen to carry it easier
What are the adaptations of a fat cell?
- expands to store more fat/ shrinks when it loses it
- not a lot of mitochondria - no need for lots of energy
- can form a layer of fatty tissue around some organs for protection and energy
What are the adaptations of a muscle cell?
- Have proteins that allow the muscle to contract and relax for movement by sliding over each other
- lots of mitochondria
- lots of ribosomes to produce proteins
What are meristems and where are they located?
A group of cells near the end of each root and shoot that allows plants to continue growing ( plant stem cell) for the rest of their lives
What is cell elongation?
The process through which the plant continues to grow in length. Animals do not have this process
What are the adaptations of a root hair cell?
- a large surface area so they can absorb lots of water through osmosis
- thin cell walls so water can easily get in through the roots
- lots of mitochondria
What are the adaptations of a xylem cell?
- hollow
- line up next to each other forming a long hollow tube to carry water and mineral ions from roots and leaves
- thick walls to resist water pressure
- cells empty so no processes occurring which means water only travels upwards
What are the adaptations of a palisade cell?
- only found in leaves
- lots of chloroplasts to trap energy for photosynthesis
- can move to absorb as much light as possible
What are stem cells?
Cells that have not undergone differentiation
What is the difference between embryonic and adult stem cells?
- embryonic: before the baby is born, cells can differentiate into any type of specialised cell
- adults: can only differentiate into the type of specialised cell that is in the tissue around them
What are the advantages of using embryonic stem cells?
- can differentiate into any type of desired cell
What are the disadvantages of using embryonic stem cells?
- hard to obtain
- ethical issues
- risk of rejection with the patient
- may carry diseases with it
- limited supply
- chances of mutations occurring
What are the advantages of using adult stem cells?
- unlimited supply
- no risk of rejection as they are taken from the patient themselves
What are the disadvantages of using adult stem cells?
- may not differentiate into desired stem cell
- chances of mutations occurring
- difficult to obtain and store the stem cells
What are nerves?
Bundles of neurones
What are stimuli and what are they detected by?
Something that sets off a reaction in the nervous system. Detected by receptor cells
Draw a timeline of how information travels through the body from a stimulus to a response
- Stimuli
- Receptor cells in sense organs
- Electrical impulses to CNS
- Electrical impulses to effectors
- Response
What are the three types of neurones and what are their roles?
- sensory neurone: carries impulse from receptor to CNS
- relay neurone: carries impulse from sensory neurone to motor neurone
- motor neurone: carries impulse from relay to effectors
What are the parts of a neurone and what do they do?
- Axon: long fibre so that they can carry messages up and down the body
- Dendron: tiny branches
- Dendrite: smaller branches that span from dendrons. Both receive incoming impulses from other neurones
What is a myelin sheath and what does it do?
A fatty layer surrounds the axon. It insulates neurones from neighbouring ones which stops the impulse from losing energy. Since no energy is lost, the impulse travels faster
What is a neurotransmission?
The travelling/ transmission of impulses
What are effectors and what are some examples of them?
The organ/tissue that produces a response, eg: muscles and glands
What is a synapse?
The gap between two neurones
What happens at a synapse?
- an electrical impulse travels along the first axon
- this triggers the neurone to release chemical messengers called neurotransmitters
- these chemicals diffuse across the synapse and bind with receptor molecules on the membrane of the second neurone
- the receptor molecules on the second neurone bind only to the specific neurotransmitters released from the first neurone
- this stimulates the second neurone to transmit the electrical impulse.
Name one benefit and one drawback of a synapse
Good:
- impulses only flow in one direction because they are only released from axon terminals
- Allows fresh impulses to be generated so the original impulse doesn’t have to split and lose strength
Bad: slows down neurotransmission
What is a reflex arc and how is it different to a normal response?
Pathway down which automatic responses (reflexes) travel. The impulse doesn’t pass through the conscious parts of your mind
Draw a flowchart of the reflex pathway
- Stimulus detected
- Impulses sent along sensory neurone
- In CNS, impulse goes through relay neurone
- Impulses sent to motor neurone
- Impulse reaches an effector resulting in an appropriate response
What do stimulants and depressants do?
Stimulants increase neurotransmissions
Depressants decrease neurotransmissions
Why are reflexes important?
They protect the body
What are the different parts of the brain?
- cerebral cortex/ cerebrum
- cerebellum
- medulla oblongata
What does the cerebral cortex do?
used for:
- senses
- languages
- memory
- behaviour
- thoughts
- emotions
Where is the cerebral cortex located in the brain?
- outer layer of brain tissue: on top of the brain
- divided into two parts
- the right side controls the left hand side of the body
What is the role of the cerebellum?
controls:
- balance
- posture
- muscle activity (fine motor activity)
Where is the cerebellum located?
- base of the brain
- also divided into two parts
What is the role of the medulla oblongata?
- ‘automatic pilot’ of the brain
controls: - breathing rate
- heart rate
- automatic action
Where is the medulla oblongata located?
- towards base of the brain
- neurones here connect to the spinal cord
What are the two scans used to see the brain?
- CT scan
- PET scan
What is the function of the CT scan?
Shows the shapes of the structures of the brain and allows visualisation of tissue damage
How is a CT scan carried out?
- X-ray beam rotates around the brain
- detectors measure the amount of X ray absorbed
- computer creates cross sectional view as ‘slices’ 3d image if possible
What are the limitations of CT scans?
- Frozen pictures
- limited resolution
- harmful X rays: esp. to preggo women and children
- patient must remain still
How do PET scanners work?
- inject patient with radioactive glucose
- patient completes activity = areas of brain active
- these radioactive tracers collect in places with a high blood flow
- this includes cancerous tissues
What is the function of a PET scan?
Shows level of activity within different parts of the brain
How are brain tumours formed?
Cancer cells divide rapidly, forming a lump (tumour)
What effects do brain tumours have?
- squash parts of the brain
- stop functions
How can we treat brain tumours?
- radiotherapy
- chemotherapy
What are the limitations of brain tumour treatments?
- damage to brain and surrounding tissues
- drugs may not get through the blood-brain barrier
What are the effects of spinal cord damage?
- reduces flow of information between the brain and the body
- quadriplegia: loss of arm and leg functions
Why is spinal cord damage so difficult to treat?
- higher the damage = more of the body is affected
- no adult stem cells in that area
What are the advantages of a PET scan?
- can distinguish between begnin and malignant tumours
- not invasive
- no risk of infection
- can detect diseases before they appear
What are the disadvantages of a PET scan?
- causes a person to be temporarily radioactive
- very expensive
