Cells and Control Flashcards
What are the ways of measuring growth?
- Size ( height, length, circumference)
- West mass = includes all the mass in an organism, including water and fluid in the body ( highly variable )
- Dry mass = mass of an organism which has no water present ( scientifically accurate but is a destructive method )
What things happen for growth in plants and animals ?
Plants :
- cell division- the cell divides
- cell elongation-cells fill up with water in the elongation zone and stretch and grow in size
- cell differentiation- when a cell becomes specialised to a certain role, it means multicellular organisms work more efficiently.
What is a stem cell?
Stem cells are cells that can differentiate into nearly any type of cell (They are undifferentiated)
What is an embryonic stem cell?
Embryonic stem cells are found in early human embryos. Embryonic cells are pluripotent and can become almost any cell in the body.
What are adult stem cells?
Adult stem cells are multi potent. This means they can become a limited amount of cells. They are found within certain differentiated tissues such as bone marrow. They are used to grow of replace damaged tissue.
What are the benefits, drawbacks and risk of embryonic stem cells?
Benefits :
-They are pluripotent, so can become a wide range of cells
-Due to techniques such as IVF, it is easy to get them.
-Can be cloned from patient’s own cells to avoid rejection.
Drawbacks :
-ethnical issues ( such as catholic contraception beliefs and murder)
-ethnical concerns ( it is illegal in some countries or restricted by law )
-seen as illegal cloning of humans
Risks :
- Differentiated cells may be rejected in treatment as come from another patient
- cancer and uncontrolled growth
What are the benefits, drawbacks and risks of adult stem cells?
Benefits :
-no ethnical issues
-carry lower rejection rates
Drawbacks :
-difficult to identify and remove from the body ( mixed with differentiated cells)
- less useful as they are multi potent so can only become a limited amount of cells so can only cure a limited amount of diseases.
Risks :
-Risk of rejection if not from patient
- cancer and uncontrolled growth
-disease transmission as the donor may pass on a virus/ get infected.
What is the nervous system made up of ?
CNS ( central nervous system) made up of the brain and spinal cord.
PNS ( peripheral nervous system) made of every nerve in your body other than the brain and spinal cord.
What are the stages of the reflex arc?
SRSSRSMER Stimulus Receptor Sensory neurone Synapse Relay neurone Synapse Motor neurone Effector Receptor
What is meristem?
- Meristem is where cell growth and mitosis occurs in plants.
- Meristem is found in the areas of a plant that are growing ( the tips of roots and shoots)
- Meristem produces unspecialised cells that can divide and form into any cell in the plant (similarly to embryonic stem cells)but they can do this throughout the plants life.
- unspecialised cells go on to form specialised tissues like xylem and phloem.
What structure and function to sensory neurones have?
- One long dendron that carries nerve impulses from receptor cells to the cell body ( located in the middle of the neurone )
- One short axon carries nerve impulses from the cell body to the CNS.
- what impulses are sent along to reach the CNS
What is the structure and function of a motor neurone?
- Many short dendrites carry nerve impulses to the cell body
- One long axon carries nerve impulses from the cell body to the effector cells
( you can get myelinated motor neurones which have a myelin sheath of unmyelinated ones.)
-sends information from the CNS to the effector cells
What is the structure and function of a relay neurone ?
- many short dendrites carry nerve impulses from the sensory neurone to the cell body
- an axon carries nerve impulses from the cell body to motor neurones.
- impulses travel through the CNS along relay neurones
What is a synapse?
A synapse is the gap / connection between two neurones.
What happens at a synapse ?
- At a synapse the nerve signal is transferred by chemicals called neurotransmitters, which diffuse ( move ) across the gap.
- Synapses are there to help filter information. It also ensures that the impulses only travel in one direction.
- electrical impulses travel along a neurone, at a synapse it is transferred to chemical energy and then when transferred into the next neurone it is transferred to electrical energy again.
What is a reflex ?
Reflexes are automatic, rapid responses to stimuli that can reduce chances of being injured. The impulses pass through either the spinal cord or an unconscious part of the brain to create a quicker response. They also travel in the pattern of the reflex arc ( SRSSRSMER)
How does the eye focus on near and distant objects ?
To looks at a distant object the ciliary muscles relaxes which allows the suspensory ligaments to pull tight. This then pulls the lens into a less rounded shape so light is refracted less.
To look at a near object the ciliary muscle contracts which slackens the suspensory ligaments. The lens then becomes a more rounded shape and more light is refracted.
What happens to long sighted people?
Long sighted people are unable to focus on near objects.
- this occurs when the lens is the wrong shape and doesn’t bend the light enough or the eyeball is too short.
- light from near objects is bought into focus behind the retina
- you can use glasses on contact lenses with a convex lenses to correct it.
What happens to short sighted people?
Short sighted people are unable to focus on distant objects
- This occurs when the lens is the wrong shape so bends the light too much or the eyeball is too long
- Light from distant objects is bought into focus in front of the retina
- use a lens with a concave lens to correct it.
What is colour blindness and can it be treated ?
Colour blindness is when cones on the retina aren’t working causing certain colours to not be seen ( most commonly red-green)
There is no cure for colourblindness as at the moment cones cannot be replaced.
What is cataracts and is there a cure?
A cataract is a cloudy part of the lens, which stops light from being able to enter the eye.
Cataracts causes blurred vision and colours can look less vivid. People also struggle to see in bright light.
Cataracts can be cured by replacing the faulty lens with an artificial one.
What is the Brain?
It is protected inside the bones of your skull and encased in protective membranes called the meninges. It is made of billions of interconnected neurones that form different regions. Different regions carry out different functions.
What is the cerebrum?
The largest part, at the front of the brain and is divided into two cerebral hemispheres. The right hemisphere controls muscles on the left of your body and vice versa. Different parts are responsive for different things including movement, intelligence, memory, language
What is the cerebellum?
Responsible for muscle coordinating and balance. Located at the base of the brain.
What is the Medulla / Medulla oblongata ?
Controls unconscious activities such as gut movements, heartbeats and breathing. It connects the brain to the spinal cord.
What is a CT scan?
X-rays are used to produce an image of the brain which shows main structures but not functions, measures how much of the X-rays are absorbed.
-this can show diseased and damaged areas so if the patient has lost a particular function (e.g. sight)the function of that part of the brain can be worked out
what are PET scans ?
- uses radioactive chemicals to show active parts as the scanner detects the gamma rays, more gamma rays more active part of the brain
- shows both structure and function
- by seeing inactive and active parts they are useful for studying disorders that change the brains activity
Why is it hard to treat CNS problems ?
- Damaged tissue in the CNS is hard to repair as CNS neurones don’t readily repair.
- problems in the brain are hard to access so can’t be operated on
- treatment may lead to further permanent damage.
How are red blood cells adapted to their role?
they contain haemoglobin - a red protein that combines with oxygen. they have no nucleus so they can contain more haemoglobin…they have a biconcave shape (flattened disc shape) to maximise their surface area for oxygen absorption
How are root hair cells adapted to their job?
Root hair cells are adapted for this by having a large surface area to speed up osmosis. They also have thick and long roots for stability and balance.
What is stage 2 of mitosis?
Prophase - The chromosomes shorten and the membrane begins to break down.
What is stage 3 of mitosis?
Metaphase - The chromosomes line up in the middle
What is stage 4 of mitosis?
Anaphase - The chromosomes are pulled apart by spindle fibres attached to the centremere from the centriole.
-pulled apart into chromatids to either side of the cell
What is stage 5/6 of mitosis?
Telophase - the cells nucli and membrane begin to reform. The cell begins to split and form a furrow.
Cyctokenisis - the cell splits and forms two nucli.
What are the advantages of asexual reproduction?
- produces lots of offspring very quickly which can allow organisms to colonise a new area very rapidly
- only one parent cell is needed so reproduction isn’t dependent so can reproduce when conditions are most favourable
What are some disadvantages of mitosis (asexual reproduction)?
- there is no genetic variation
- due to no genetic variation if environmental conditions change they may become unfavourable and the whole population may be affected
What is stage 1 of meiosis (sexual reproduction)?
-before decision the DNA duplicates (one arm of the X-shapes chromosome is an exact copy of the other)
What is stage 2 of meiosis (sexual reproduction)?
The chromosomes line up in the centre of the cell from both the father and the mother
What is stage 3 of meiosis (sexual reproduction)?
The pairs are pulled apart so each new cell has a copy of each the mother’s and father’s chromosomes
This is so important as it creates genetic variation
What is stage 4 of meiosis (sexual reproduction)?
In the second division the chromosomes line up again and like mitosis the arms of the chromosomes are pulled apart
What is stage 5 of meiosis (sexual reproduction)?
You get four haploid daughter cells which are the gametes with singles sets of chromosomes that are now genetically different
What are the advantages of meiosis (sexual reproduction)?
- creates genetic variation meaning some individual of that species are more likely to survive if environmental conditions change
- can leave to natural selection and evolution meaning that species is more adapted and fitter
What are some disadvantages of meiosis (sexual reproduction)?
- takes more time and energy so organisms produced fewer offspring throughout their lifetime
- two parents are needed so there can be problems of individuals are isolated (e.g. polar bears)
What is stage 1 of mitosis?
Interphase- Nucleus and organelles duplicate, the cell gets bigger and subcellular structures are made
What are the benefits and risks of stem cells use in medicine?
- can be used to grow and repair damaged tissues and therefore potential new cures
- tumour development and stem cells divide very quickly
- disease transmission past on to the recipient from the donor
- rejection and the drugs taken for this leaves them susceptible to disease
What is the cornea, iris, lens and retina?
- cornea refracts light in the eye
- iris controls how much light enters the pupil
- lens also refracts light but focuses it onto the retina
- retina is the light sensitive part of the eye covered in rods and cones
What are rods and cones?
- Rods are more sensitive in dim light but can’t see colour
- cones are sensitive to different colours but aren’t so good in dim light
How is light detected by the brain?
The information from light is converted into electrical impulses and the optic nerve carries these impulses from the receptors to the brain
What do myelin sheaths do?
Acts as an electrical insulator speeding up the electrical impulse
-having a longer neurone is also quicker than shorter ones
What are dendrons/dendrites and axons?
Dendrons/dendrite carry nerve impulses towards the cell body
-axons carry never impulse away from the cell body
