Topic 2 - Cells And Control Flashcards
Interphase
Increases the amount of subcellular structures eg mitochondria , ribosomes. DNA duplicate
First stage of mitosis
Prophase - chromosomes condense, shorter. Membrane around nucleus breaks down and chromosomes lie in cytoplasm.
Second stage of mitosis
Metaphase - spindle fibres attach to centromere. chromosomes line up in middle of cell
Third stage of mitosis
Anaphase - spindle fibres shorten and pull chromatids apart to the poles of the cell.
Fourth stage of mitosis
Telophase - membrane form around each set of chromosomes. These become the nuclei of the two new cells - nucleus has divided.
Final stage of mitosis
Cytokinesis - cytoplasm and cell membrane divide to form two genetically identical diploid cells.
Why is mitosis important?
Used for growth and repair and replace damaged cells. Some organisms use it for asexual reproduction eg plants.
How many chromosomes does each cell have at the end of mitosis?
46 (diploid)
How does cancer happen?
The rate which cells divide by in mitosis is controlled by genes. If there’s a change in one of the genes that controls cells division they start diving uncontrollably.
Cell differentiation (animals & plants)
Cell changes to become specialised for its job. Allows multicellular organisms to work more efficiently.
Cell division (animals & plants)
By mitosis
Cell elongation (plants only)
Plant cell expands, cell gets bigger so plant grows
What is a percentile chart?
Used to monitor growth so any problems highlighted can be seen.
What are stem cells?
Cells that can differentiate into any type of cells. Important for the growth and development of organisms.
What is the function of embryonic stem cells?
Have the potential to develop into any type of cell.
Function of meristem in plants
Produce stem cells. The unspecialised cells go to form specialised tissues like the xylem and phloem
What is the meristem?
Tissue found in areas of plan that are growing eg tips of the roots and shoots
Benefits of using stem cells in medicine?
Able to replace cells which have been damaged by disease or injury. Eg Parkinson’s
Risks of using stem cells in medicine
Tumor could develop as stem cells divide very quickly
Disease could be passed on as viruses live inside cells
Ethical issues as embryo has a potential human life
Reflex arc order
Stimulus, receptor, sensory neurone, synapse, relay neurone, synapse, motor neurone, effector, response
Function of the stimulus
Detects a change in the environment
Function of the receptor
Receptors in skin detect change in environment eg heat
Function of the sensory neurone
Electrical impulse travel along the sensory neurone to the spinal cord/CNS
Function of the synapse (first one)
Neurotransmitters diffuse across the synapse
Function of relay neurone
The impulse is passed to the relay neurone
What happens at the second synapse?
Impulse travels across another synapse
What happens at the motor neurone?
Impulses travel along a motor neurone via a synapse
What happens at the effector?
Impulses passes to the muscle/effector
What happens at the response?
Muscle / effector contracts eg moving hand away from hot pan
When would the reflex arc be used?
In dangerous situations
What is the role of the myelin sheath?
Acts as an electrical insulator, speeds up impulse.
What is an advantage on long neurones?
Speeds up the impulse
What is the role of neurotransmitters?
Chemicals which diffuse across the gap between two neurones. The neurotransmitters then set off new electrical signal in the next neurone.
