Topic 2: Cells and Control Flashcards
what are the stages of mitosis
interphase
prophase
metaphase
anaphase
telophase
cytokinesis
2.1: Describe mitosis as part of the cell cycle, including the stages
interphase, prophase, metaphase, anaphase and telophase
and cytokinesis
- Interphase: DNA replicates and forms X shaped chromosomes
- Prophase: DNA in chromosomes condense, becoming more visible. The nuclear membrane breaks down + dissapears and spindle fibres appear. Chromosomes move freely in the cytoplasm.
- Metaphase: The two chromatids line up on spindle fibres across the equator of the cell .
- Anaphase: The two chromatids separate and pulled apart on spindle fibres to opposite cell poles.
- Telophase: New membranes form around each full chromosome set at each pole of the cell -> two nuclei are formed with identical chromosomes. Spindle fibres disappear.
Cytokinesis: the cell splits into two. Cell surface membranes/cell walls form to separate the identical cells.
2.2: Describe the importance of mitosis in growth, repair and asexual reproduction
Mitosis is important in growth + repair as it produces identical cells.
Mitosis is important in asexual reproduction as there’s only one parent. It produces CLONES, whose cells are IDENTICAL to the parent. It is faster + doesn’t need others.
2.3 Describe the division of a cell by mitosis
the production fo 2 daughter cells, each with identical sets of chromosomes in the nucleus to th eparents cell, and that this results in the formation of two genetically identical dploid body cells
2.4 describe cancer
mutations cause a chnage in cells that lead to uncontrolled cell division
2.5 Describe growth in organisms, including:
a) cell division and differentiation in animals
b) cell division, elongation and differentiation in plants
a) Growth happens by cell division (mitosis) and growth often happens when young until full growth.
In younger animals, cell division is at a faster rate -> more growth.
In mature animals, cell division is mostly used for repair not growth.
Cells divided by mitosis eventually DIFFERENTIATE to become different types of SPECIALISED cell.
Most cells stop differentiating at early stages - specialised cells with nuclei divide by mitosis.
b) Growth happens firstly in the MERISTEM at the end of shoots/roots due to rapid cell division
Growth occurs due to cell elongation (zone of elongation) due to intake in water (osmosis) in vacuoles.
Cells also differentiate into specialised cells which have particular functions (zone of differentiation): xylem/phloem, root hair cells.
2.6 Explain the importance of cell differentiation in the development of specialised cells
Differentiation produces specialised cells, adapted/specialised to carrying out specific functions.
They make up a whole multi-cellular organism + specialised cells make them work more effectively
2.7: Demonstrate an understanding of the use of percentiles charts
to monitor growth
Percentile charts measurements (head circumference/length/mass) are divided into 100 groups. We find the percentage of readings BELOW a PERCENTILE.
If the Xth percentile for an N month old baby’s mass is Y kg. X% of N month old babies will have a mass BELOW Y kg.
CURVED LINES show the RATE OF GROWTH of a baby at the SAME PERCENTILE.
Measuring mass regularly + plotting it helps identify if babies are growing normally. Babies should remain NEAR THE SAME PERCENTILE CURVE (varying a small amount)
CONCERNS: over 95th percentile, below 5th (not growing properly) and baby size increases by more than 3 lines.
2.8: Describe the function of embryonic stem cells, stem cells in
animals and meristems in plants
EMBRYONIC STEM CELLS are cells taken from embryos at early stages of division
They can divide to produce any type of specialised animal cell.
(When embryos develop areas - limit to types of specialised cell)
Can replace/repair damaged: brain cells (treat Parkinson’s); retina cells (treat blindness). Used to grow transplants/drug testing tissue.
ADULT STEM CELLS are taken from differentiated tissue in an animal (e.g. bone marrow)
As the animal is fully developed, stem cells lose ability to produce other specialised cells - only produced surrounding tissue stem cells
Can treat leukaemia (bone marrow cancer) + potentially new tissues genetically matched to patients.
PLANT MERISTEM CELLS are taken from rapidly growing parts: root/shoot meristems
Can divide and differentiate to produce any type of specialised plant cell for as long as the plant lives.
Can be used to clone rare plants to stop their extinction
Can produce cloned crop plants for farmers with desirable traits.
2.9: Discuss the potential benefits and risks associated with the
use of stem cells in medicine
ALL STEM CELLS
Benefits: Replace faulty, diseased cells with healthy, specialised ones and stimulate their growth - scientific interest for cures if disease.
Drawvbacks: REJECTION (the immune system can kill cells put in) of cells from another person. CANCER (stem cells don’t stop dividing after replacing damaged ones)
Viruses inside cells can infect cells + if not spotted, could spread.
EMBRYONIC STEM CELLS
Benefits: Easy to extract from embryos + produces any cell type.
Drawbacks: Embryos destroyed when cells are removed - some believe in right to life (ethical issue). Some believe curing patients is important.
ADULT STEM CELLS
Benefits: No embryo destroyed (no ethical/religious issue)
Already used to treat disease by bone marrow transplants which can differentiate into specialised cells
Drawbacks: Produce a narrow range of cell types + only from the tissue around them.
2.10 B: Describe the structures and functions of the brain including
the cerebellum, cerebral hemispheres and medulla oblongata
CEREBELLUM: responsible for balance, posture and muscle coordination as well as timing/fine control of muscles
CEREBRAL HEMISPHERES: Controls voluntary movement, sensory info , consciousness, language, memory and behaviour.
MEDULLA OBLANGATA: unconscious/automatic activities: breathing/ heart rate as well as reflex control: vomiting, sneezing+ swallowing
2.11 B: Explain how the difficulties of accessing brain tissue
inside the skull can be overcome by using CT scanning
and PET scanning to investigate brain function
CT: Patients pass through a ring taking a series of X-rays at different angles around the head. Detectors measure X-ray absorption.
Computers process uses information to build a 3D view of the brain in slices. Shape differences can be linked to the way people think/act so the function can be worked out if the area has lost function.
PET: Patients are given RADIOACTIVE GLUCOSE. MORE ACTIVE cells take in MORE GLUCOSE to respire rapidly, detected by a scanner as radioactive atoms cause GAMMA RAYS. This builds up an image where tracers are most concentrated (highlighted brightly) Activities cause specific areas of the brain to become more active.
Tumour: Areas with UNUSUALLY high levels take in A LOT of GLUCOSE (high levels of METABOLIC REACTIONS)
2.12 B: Explain some of the limitations in treating damage and
disease in the brain and other parts of the nervous
system, including spinal injuries and brain tumours
SPINAL CORD INJURY: REDUCES flow of information between the brain + body parts. It can leas to loss in use of legs (+ arm). NO ADULT STEMS CELLS differentiate into neurones + neurones are specialised so can’t divide to replace damaged cells. The spine protects the spinal cord - hard to access it for surgery. Permanent/further damage could occur.
BRAIN TUMOURS: Cancer cells divide rapidly to form tumours. RADIOTHERAPY and CHEMOTHERAPY can kill cancer cells but this can damage healthy cells. CHEMOTHERAPY may not work due to the BLOOD-BRAIN BARRIER only allowing certain substances to pass (difficult for medicine to enter). The skull protects the brain - hard to access it for surgery.
2.13 Explain the structure and function of sensory neurons
SENSORY NEURONES: Carry impulses from receptor cells to the CNS. Dendrite branches collect impulses from receptor cells. Impulses passed into them are transmitted along a long dendron to the cell body in the middle of the neurone. A short axon transmits impulses away from the cell body to the series of axon terminals, passing impulses to other neurones.
2.13 explain the structure and function of sensory receptors
- groups of cells that can detect a chnage in your environment (stimulus). different receptors detect different stimuli e.g. recpetors in eyes detect light, receptors in skin detect touch and temperature change
