Flashcards in Cells And Control Deck (42):
What are chromosomes?
Coiled up lengths of DNA molecules found in the nucleus
What is a diploid cell?
Cell with two copies of each chromosome
What kind of cells undergo the cell cycle?
Body cells in multicellular organisms
The stage of cell cycle when the cell divides. Organisms use mitosis to grow or replace damaged cells or to asexually reproduce
What happens in interphase?
DNA is spread out in long strings, cell growing to increase number of sub-cellular structures. DNA duplicates and forms x shaped chromosomes with identical left and right arms
Describe the events of Mitosis and Cytokenisis
1; prophase: chromosomes condense, lie free in cytoplasm as membrane around nucleus breaks down
2; metaphase: chromosomes form a line at centre of cell
3; anaphase: cell fibres pull chromosomes apart, each arm of each chromosome go to opposite ends of cell
4; telophase: membranes form around each of the sets of chromosomes (these become nuclei of new cells)
cytokinesis; before telophase ends cytoplasm and cell membrane divide to form two separate cells
What does mitosis produce?
Two genetically identical diploid cells
What’s the equation to calculate number of cells after multiple divisions of a cell by mitosis?
Number of cells = 2^number of divisions by mitosis
What is growth?
An increase in size or mass
What’s cell differentiation?
Cell changes to become specialised, allowing multicellular organisms to work more efficiently
How is cell division done?
How do plants grow?
By cell elongation. Plant cells expand, so plant grows. Cell division happens in tips of roots and shoots. Plants grow continuously and continue to differentiate to develop new parts
How do animals grow?
By cell division. In most animals cell differentiation is lost at an early age and cell division for growth stops when animal reaches full growth
Hows cancer caused?
Gene controlling cell division mutates, cells divide uncontrollably, tumour is caused
What do growth percentile charts do? How do they work?
Assess a child’s growth over time, show an overall pattern of development. Three main measurements taken are length, mass and head circumference
The chart shows number of percentiles eg 50th percentile means the mass 50% of babies would’ve reached at a certain age
Doctors are likely to investigate if babies size are above top of below bottom percentile line, size increases/ decreases by 2 or more percentiles or there’s an inconsistent pattern
What are stem cells?
Unspecialised/ undifferentiated cells
What can stem cells do?
Divide by mitosis to become new cells which then differentiate. In adults, they’re found in certain places eg bone marrow, and are used to replace damaged cells
What are embryonic stem cells?
Found in embryos, they have the potential to divide and become any type of cell. They are essential for the growth and development of organisms
Where are unspecialised cells found in plants and what do they do?
They’re found in meristem tissue, which is found in areas of plants that are growing. The unspecialised cells meristems produce can divide into any cell type and can do this for as long as the plant lives. Unspecialised cells can form unspecialised tissues
What are potential risks of stem cell treatment?
Tumour development, disease transmission, rejection, ethical issues
What are neurones?
What are sensory receptors?
Group of cells that detect a stimulus. Different receptors detect different stimulus
What’s a stimulus?
A change in your environment
What happens when a stimulus is detected by your receptors?
Its converted to a nervous (electrical) impulse and sent along sensory neurones to CNS
What’s CNS consist of?
Brain and spinal cord
What’s reaction time?
Time taken to respond to stimulus
List the path of the nervous system
Stimulus > receptor > sensory neurone > CNS > motor neurone > effector > response
What do dendrites and dendrons do?
Carry nerve impulses towards cell body
What are axons?
Carry impulses away from cell body
Some axons surrounded by myelin sheath: acts as electrical insulator, speeds up the electrical impulse
How does a sensory neurone work?
1 long dendron carries nerve impulses from receptor cells to cell body, located in middle of neurone. 1 short axon carries impulses from cell body to CNS
How does a motor neurone work?
Many short dendrites carry nerve impulses from CNS to cell body, 1 long axon carries impulses from cell body to effector cells
How do relay neurones work?
Many short dendrites carry nerve impulses from sensory neurones to the cell body. An axon carries nerve impulses from cell body to motor neurones
What’s a synapse?
A connection between two neurones
How are nerve signals transferred?
By neurotransmitter chemicals. They diffuse across gap, then set off new electrical signals in the next neurone
What are reflexes?
Automatic responses to stimuli
What’s a reflex arc?
The passage of information in a reflex, from receptor to effector
Describe the process of the reflex arc
1; stimulus detected, impulses sent along sensory neurone to a relay neurone in the CNS
2; impulses trigger release of neurotransmitters when they reach a synapse between sensory neurone and relay neurone. Neurotransmitters cause impulses to be sent along relay neurone
3; when impulse reaches synapse between relay neurone and motor neurone, neurotransmitters are released and cause impulses to be sent along the motor neurone
4; impulses travel along motor neurone to effector
5; effector reacts accordingly
Describe the eye protection reflex
Light receptors in eye detect bright light, send message along sensory neurone to brain
Message travels along relay neurone to a motor neurone, which tells circular muscles in iris to contract
What forms the spindle/cell fibres?
What’s the middle of a cell called?
What are the middle bits of chromosomes called?