SB2 - Cells and Control Flashcards
Name the two stages of the cell cycle
Interphase and Mitosis
Name the five stages of mitosis
Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
List the five stages of mitosis in order
Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
Describe what happens during Interphase
The stage when the cell prepares itself for the process of cell division, and DNA replication takes place. The cell also makes more of its sub-cellular structures, and increases in size
Describe what happens during each stage of mitosis
Prophase - the nucleus starts to break down and spindle fibres appear
Metaphase - the chromosomes line up across the middle of the cell
Anaphase - the separated chromosomes move away from each other
Telophase - the chromosomes arrive at opposite ends of the cell and the nucleus membrane reforms
Cytokinesis - the cytoplasm of the cell is separated as the cell membrane is pinched to divide the cell into two daughter cells
Why is mitosis important for an organism?
Mitosis is a process of producing genetically identical, diploid cells, needed for growth
What do we call cells that have one copy of each chromosome?
Haploid
Name and example of a cell with only one copy of each chromosome
Gametes - egg, sperm, pollen
What do we call cells that have two copies of each chromosome?
Diploid
Name and example of a cell with two copies of each chromosome
Any body cell - e.g. muscle, epithelial, nerve etc …
Fruit flies have four types of chromosomes. How many chromosomes are in a diploid fruit fly cell?
8
Explain why the number of mitochondria in a cell doubles during Interphase
So each daughter cell has enough mitochondria / same number of mitochondria as parent cell
What do we call the offspring from asexual reproduction?
Clones
What are spindle fibres and what is their function?
Filaments formed in a cell during mitosis, which help to separate chromosomes
Give a benefit of asexual reproduction
Asexual reproduction produces clones, doesn’t need two parents and is fast method of producing offspring
Give a disadvantage of asexual reproduction
Asexual reproduction does not provide variation, so a whole population could get killed by one disease
Describe how mitosis produces genetically identical, diploid cells
The cell copies each chromosome to produce two sets. Each set of chromosomes move to opposite sides of the cell. The cell then splits into two cells, each with a full set of identical chromosomes
Why is each plantlet that grows along a strawberry runner a clone?
Because they are genetically identical to the parent plant / have the same chromosomes / DNA / genes as the parent plant
Why does asexual reproduction rely on mitosis?
All of the cells of the offspring have to be genetically identical to the parent
How can cancers grow?
The cell cycle goes out of control
Describe what a ‘crown gall tumour’ on a rose plant will look like
A lump (often brown) on the stem
Explain how crown gall tumours develop
There is a change to the cells that causes rapid and uncontrolled cell division
Explain why sperm cells cannot be produced using the cell cycle (2 marks)
- Cell cycle only produces diploid cells / cells with two sets of chromosomes
- Sperm cells / gametes are haploid / contain only one set of chromosomes
What is the definition of growth?
Growth is defined as an increase in size due to an increase in the number or size of cells
What are percentile growth curves used for?
The graph shows the expected rate of growth of babies of different birth weights and is used to check that a child’s growth is normal
What are the three zones of growth in plants?
Zone of cell division (Meristem), zone of elongation and zone of differentiation
Where does cell division happen in the plant?
Meristem - zone of cell division
Name the process that changes less specialised cells into more specialised ones
Differentiation
What is a stem cell?
An undifferentiated cell that can produce any type of cell
Name the two types of stem cells in animals
Embryonic stem cells and adult stem cells
Describe the difference between the two types of animal stem cells
Embryonic stem cells can produce any type of specialised cell whilst adult stem cells can only produce the type of specialised cell that is in the tissue around them
Give two advantages of using stem cells to treat people
- No need to take anti-rejection drugs because cells are genetically identical
- No need to find a donor
- No need for tissue typing
Give two disadvantages of using stem cells to treat people
- The stem cells may cause cancer if they continue to divide inside the body after they have replaced the damaged cells
- Cultured stem cells could be contaminated with viruses which would be transferred to a patient
- There are no guarantees that the therapy will be successful
- Lack of stem cell donors
- Hard to obtain and store a person’s embryonic stem cells - need to be collected near the start of the pregnancy
What are the ethical problems of using stem cells to treat people or during research?
- One source of embryonic stem cells is unused embryos produced by in vitro fertilisation (IVF)
- Is it right to create embryos for therapy, and destroy them in the process?
- Embryos could come to be viewed as a commodity, and not as an embryo that could develop into a person
- When should an embryo be regarded as, and treated as, a person?
What are plant stem cells called?
Meristem cells
Name two parts of a plant where stem cells can be found
Roots and shoots
A cell in the basal layer of the skin contains 46 chromosomes and divides by mitosis to produce new skin cells. After ten successive divisions, how may chromosomes will the basal cell have?
46
Complete the sentence: When chromosomes replicate, they produce ……………
Chromatids
In which three of the following cells is mitosis unlikely to occur? - A sperm cell, an epithelial cell of a villus, a hair cell, a cell in the red bone marrow, a red blood cell, a lymphocyte, a cell in the basal layer of the skin
Sperm cell, red blood cell, lymphocyte
Which structures of a flowering plant give rise to potatoes?
A potato is a tuber formed at the end of an underground stem
Which structures of a flowering plant give rise to the fleshy scales of an onion?
Onion scales are modified leaves containing a food store
In the process of tissue culture in plants, what is needed to induce the formation of a complete plant, in addition to a growth medium with nutrients?
The appropriate plant growth substances (‘hormones’) would need to be added
What is defined as ‘a change in the environment that you might need to respond to’
A stimulus
What is the function of a receptor in the nervous system?
Detect stimuli
List four stimuli which can be detected by the skin
The skin can detect heat, cold, touch and pressure
How de we become aware of a stimulus?
Never impulses travelling from a receptor to the brain make us aware of a stimulus
Name the transparent outer layer found at the front of the eye
Cornea
Name the layer at the back of the eye that contains light receptor cells
Retina
Name the hole in the centre of the eye through which light enters
Pupil
Which part of the eye contains muscles that control the size of the hole in the centre of the eye?
Iris
Name the muscles that control the shape of the lens
Ciliary muscles
Name the nerve that takes information from the eye to the brain
Optic nerve
True or false? When a bright light shines in the eye impulses travel in the optic nerve
True
True or false? When a bright light shines in the eye the radial fibres in the iris contract
False
True or false? When a bright light shines in the eye the retina responds
True
True or false? When a bright light shines in the eye the pupil becomes smaller
True
What is the cause of the blind spot in the field of vision?
There are no sensory cells in the blind spot
Which parts of the eye refract (‘bend’) the light to form an image on the retina?
The curved surface of the cornea, and the lens refract the light
What do you understand by the term ‘accommodation’?
Accommodation is the way the eye can focus either near or distant objects to form a sharp image on the retina
What part does the lens play in the ‘accommodation’ process?
The lens is made thinner so that light from a distant object is refracted less, or fatter so that light from a close object is refracted more
What happens to the ciliary muscle and lens for an eye to focus on a distant object?
The ciliary muscle relaxes and the lens gets thinner
What happens to the ciliary muscle and lens for an eye to focus on a near object?
The ciliary muscle contracts and the lens gets thicker
What type of colour blindness is most common in men?
Red-green colour blindness is the most common form of colour blindness in men
What is a cataract?
A cataract is a cloudy patch on the lens
Explain why cataracts cause blurred vision
Cataracts stop light from entering the eye as normal so less light reaches the retina
What treatment is offered to people with cataracts?
The cataract lens can be surgically removed and is replaced by an artificial lens. Only one eye is done at a time so that the person can have vision
What kind of eye defect can give rise to short-sightedness?
Long eyeballs, large eyeballs, too powerful a lens, or a combination of these defects can give rise to short-sightedness
What type of spectacle lens can help correct long-sightedness?
Converging (convex or meniscus) lenses can help correct long-sightedness
Name the two structures which make up the central nervous system
The central nervous system consists of the brain and spinal cord
Name the nerve fibres which carry impulses from the sense organs to the central nervous system
Sensory
Name the nerve fibres which carry impulses from the central nervous system to glands and muscles
Motor
How can we tell which part of the body a sensory nerve impulse comes from?
Each part of the body is connected to its own region of the brain
What is the function of an axon?
To carry the nerve impulse away from the cell body
Explain why some axons have myelin sheaths
To speed up nerve impulses (it insulates the axon)
Describe the transmission of information from the stimulus of rods and cones in a dog’s eye when it sees a cat, to the dog’s muscles (via the CNS) as it responds and runs after the cat
Rods and cones (stimulus) - sensory - neurone / optic nerve - CNS (relay neurone) - motor neurone - muscle cells (response)
What is a reflex?
A fast, automatic response to a stimulus
Explain why neurones can deliver information very quickly
The signal is transmitted by electrical impulses
Explain why doctors use electrical impulses to stimulate different parts of the brain
To find out what different parts of the brain do
What is the gap between two nerves called?
A synapse
Name the chemicals that are involved in sending signals from one cell to another
Neurotransmitters
How do nerve impulses travel from one nerve to another?
The neurotransmitter is released by the axon of one neurone and diffuses across the gap to the dendrite of the other neurone. The neurotransmitter is absorbed into the dendrite which sets off an electrical impulse down the neurone
Name the reflex reaction that protects the eye from too much light?
Iris reflex - change in size of the pupil of the eye in response to light intensity
Give examples of two other reflex actions
Blinking in response to foreign particles on the cornea, coughing or sneezing in response to irritation of the nasal passages and trachea or bronchi, knee jerk in response to a blow on the tendon of the leg extensor muscle, rapid removal of the hand from a hot or sharp object
Write the order of neurones that a nerve impulse travels through during a reflex arc
Sensory neurone, relay neurone, motor neurone
Which type of neurone has many short dendrites which carry nerve impulses from the CNS to the cell body, and along a long axon to an effector cell?
Motor neurone
Which type of neurone has one long dendron which carries nerve impulses from a receptor cell, past the cell body and down a short axon to the CNS?
Sensory neurone
Which type of neurone has many short dendrites that carry nerve impulses from a sensory neurone to the cell body and along a short axon to a motor neurone?
Relay neurone
What is the receptor in a reflex knee-jerk?
A stretch receptor in the leg extensor muscle
What is the effector in a reflex knee-jerk?
The leg extensor muscle
Name the largest region of the brain
Cerebrum
What is the function of the largest region of the brain?
Right hemisphere controls muscles on left side of body. Left hemisphere controls muscles on right side of body. Different areas of the cerebrum are responsible for different things (e.g. memory, language and vision)
Where is the cerebellum found in the brain?
Back of brain
What is the function of the cerebellum?
Responsible for muscle coordination and balance
Which part of the brain is found at the base of the brain, at the top of the spinal cord?
Medulla oblongata
What is the function of the medulla oblongata?
Control of unconscious activities like breathing and heart rate
Name the two types of scans that doctors can use to study the brain
CT scans and PET scans
Which type of scanner is used to show brain activity?
PET scan
Which type of scanners uses X-rays to produce an image of the brain?
CT scanners
Which type of scanners needs patients to be injected with a radioactive tracer?
PET scans
Which type of scanners can only produce still pictures of the brain?
CT scanners
What can lower spinal cord damage cause?
Loss of feeling and use of the legs
What can damage to the spinal cord in the neck cause?
Loss of use of both arms and legs (quadriplegia)
Explain why a brain tumour can stop parts of the brain from working
As the brain tumour grows, it squashes the parts of the brain around it
How can brain tumours be treated?
Surgery, radiotherapy, chemotherapy
