Topic 2 - Cells And Control Flashcards
What is the cell cycle?
Series of events taking place in a cell
Name some parts of the cell cycle
Cell growth
DNA replication
Cell division
State the three stages of the cell cycle
Interphase
Mitosis
Cytokinesis
What is interphase
Involves cell growth, synthesis of new organelles and DNA replication
What is the longest stage of the cell cycle?
Interphase
What does DNA replication involve?
Double helix unzips
DNA bases align next to complementary bases on strands
Complementary base pairs join
2 identical DNA molecules form
What’s a chromosome?
A DNA molecule tightly coiled around proteins
What happens to chromosomes during DNA replication?
DNA in arm of each chromosome is replicated
What are the arms of the chromosomes called?
Chromatids
What is mitosis?
Form of cell division - forms 2 diploid daughter cells
Genetically identical to parent cell
Why is mitosis important in organisms?
Asexual reproduction
Growth
Repair of damaged cells
Cell replacement
State the 4 stages of mitosis
Prophase
Metaphase
Anaphase
Telophase
Outline prophase
DNA condenses
Chromosomes become visible
Nuclear membrane disappears
Outline metaphase
Chromosomes line up along cell equator
Outline anaphase
Spindle fibres attach to each chromosome
Arms of each chromosome pulled to opposite poles
Chromatids separated
Outline telophase
Nucleus of cell divides
New membrane forms around each set of chromosomes
What does cytokinesis involve?
Division of cell membrane and cytoplasm
2 genetically identical daughter cells produces
A cell divides by mitosis once every 2 minutes. Calculate the number of identical cells present after 10 minutes
10/2=5
5 cell divisions taken place
2⁵ = 32 cells
What is cancer
Non communicable disease
Uncontrolled cell division (due to damaged DNA) results in formation of primary tumour
Tumour cells break off and spread to other tissues forming secondary tumours
What are percentile charts?
Chart used to monitor growth
Measurements can be compared to expected values at certain age
What does the 95th percentile mean?
95% of measurements will be below the value of the 95th percentile
What can doctors determine from percentile charts? (3)
Slower growth than normal (below bottom line)
Faster growth than normal (above top line)
Abnormal growth (irregular growth patterns)
Describe growth in animals
Cell division occurs in all body cells at slower rate in adults than younger animals - growth stops + cell division only required for repairs
Most cells differentiate at early stage + become specialised.
Describe growth in plants
Cell division only occurs in meristematic tissue. Rate remains same through life.
Meristematic stem cells can differentiate into any cell type.
Cell elongation occurs in all cells. They expand and enlarge = growth
What are stem cells?
Cells that are unspecialised and capable of differentiating into a range of different cell types.
What is meant by differentiation?
Process where stem cells become specialised
Why is cell differentiation important?
Enables formation of specialised tissues with specific funtions
What are embryonic stem cells?
Stem cells found in very early embryos that are unspecialised and capable of differentiating into any cell type
What is the function of embryonic stem cells?
Enable growth and development of tissues in human embryos
What are adult stem cells?
Stem cells that can differentiate into a limited range of cell types
Give an example of an adult stem cell
Bone marrow stem cells
What’s the primary function of adult stem cells?
Replacement of dead cells
Eg replacement of red blood cells which only live for 120 days
Where are stem cells found in plants?
Meristems
Where is meristem tissue found?
In regions of the plant where cells are continuously dividing - eg root tips, shoot tips
What are meristematic stem cells?
Stem cells found in meristems that are unspecialised and capable of differentiating into any cell type during the plants life
How can stem cells be used in medicine?
Stem cells collected
Stimulated to differentiate into specific cell types
Specialised cells transplanted into patient
Used to treat damage or disease
Where can embryonic stem cells be collected from?
Donor stem cells removed from embryos grown in vitro
Patients own stem cells removed from the umbilical blood before birth
What are the benefits of using stem cells in medicine? (4)
Treat damage or disease eg: heart disease
Treat diseases that would otherwise be untreatable
Used in scientific research
Growing organs for transplants
What are the risks of stem cell use in medicine? (6)
Transplanted stem cells could cause tumours
Finding suitable donors is difficult
May be rejected by body
Potential side effects
Long term risks unknown
May become contaminated during prep and transmit infections to patient
What are the ethical issues related to the use of stem cells in medicine? (2)
The embryos that were used to provide stem cells are destroyed which is seen as unethical and a waste of human life
May lead to reproductive cloning of humans
What is the central nervous system?
Brain and spinal cord
What is the spinal cord?
A long thin structure composed to neurones that extends from medulla oblongata down spine
What’s the function of the spinal cord?
Connects peripheral NS to brain
Describe structure of brain
3 main regions:
Cerebrum
Cerebellum
Medulla oblongata
Describe the structure of the cerebrum
Largest region of brain
Divided into 2 hemispheres
What is the function of the cerebrum?
Involved in: Intelligence Language Memory Emotion Visual and sensory processes
What is the function of each cerebral hemisphere?
Left receives sensory info from right side of body and controls muscle coordination on right
Right received sensory info from left side of body and controls muscle coordination on left
Where is the cerebellum located?
Lower region of brain
What’s the function of the cerebellum?
Involved in:
Coordination of muscles
Voluntary movement - walking
Non voluntary movement - balance
What’s the function of the medulla oblongata?
Controls automatic processes in the body eg: breathing rate, heart rate
What methods, other than surgery, are used by doctors to observe the brain?
CT scan
PET scan
What is a CT scan?
Procedure that uses X rays to produce 3D cross-sectional images of the brain
Describe how CT scans are useful to investigate brain function
Show damaged regions of brain (areas of swelling/bleeding)
Observations of symptoms can enable scientists to determine function of damaged region
What does a PET scan involve?
Radioactive substance injected into patients bloodstream and taken up by tissues in brain.
Radiated emitted by tissues detected, enabling identification of active and inactive brain regions.
Describe how PET a scans are useful to investigate brain function
Show which areas are active/not
Comparisons between healthy and brain damaged allow determine functions of inactive regions
Why is it difficult to treat damage to the CNS?
Damage to neurones is permanent and can’t be repaired (nerve cells don’t divide by mitosis).
Hard to reach some areas of brain.
Risk of further damage to other areas in surgery.
What is the function of the nervous system?
Allows an organism to rapidly react to environmental and internal changes
What are neurones?
Nerve cells adapted to quickly transmit nerve impulses. The functional units of the NS.
What is the function of the axon?
Carries impulses away from the cell body
Enables transmission of nerve impulses over long distances
What’s the function of the dendrites and dendrons?
Carry impulses towards cell body
Provide large surface area to receive impulses
What’s the role of the myelin sheath?
Electrically insulating layer
Surrounds axon and increases speed of impulses
Outline the function of a sensory neurone
Carries impulses from receptors to the CNS
Describe the structure of a sensory neurone
Long dendron carries impulses from receptor to cell body
Cell body found halfway down neurone
Short axon carries impulses from cell body to CNS
Outline the function of a motor neurone
Carries impulses from CNS to effectors
Describe the structure of a motor neurone
Short dendrites carry impulses from CNS to cell body
Cell body found at one end of the neurone
Long axon carries impulses from cell body to effectors
Outline function of relay neurone
Carries impulses from sensory neurones to motor neurones within CNS
Describe structure of relay neurone
Short dendrites carry impulses from sensory neurones to cell body
Short axon carries impulses from cell body to motor neurones
Describe how the CNS coordinates a response to a stimulus
Stimulus
Sensory receptor detects stimulus
Sensory receptor sends impulses along sensory neurone to CNS
CNS coordinates response
CNS sends info to effector along motor neurone
Effector produces a response to the stimulus
What is a synapse?
A small gap between neurones across which a nerve impulse is transmitted via neurotransmitters
How are nerve impulses transmitted across a synapse?
Nerve impulses reach presynaptic neurone
Triggers release of neurotransmitters
Neurotransmitters diffuse across synapse
Bind to receptors on postsynaptic neurone
Stimulates impulse in postsynaptic neurone
Why do synapses slow down the transmission of nerve impulses?
Takes time for the neurotransmitters to diffuse across the synapse and bind to receptors on the postsynaptic neurone
What is a reflex?
Automatic response to a stimulus by the body
Involuntary - doesn’t involve conscious part of brain
Protective mechanism eg a withdrawal reflex is initiated when a hot object is touched to prevent burns
Describe the reflex arc
Stimulus -> sensory receptor -> sensory neurone -> relay neurone -> motor neurone -> effector -> response
