- Created by: Hinges
- Created on: 13-08-20 16:17
Explain how sperm cells are adapted to their funct
1. They contain lots of mitochondria to provide energy for swimming
2. They have a long tail to swim to the egg cell
3. The acrosomes contain enzymes that digest the cell membranes of the egg cellto enter into
4. They havev haploid nucleus, so when fertilised with egg cell, it yeilds correct no. of chromosomes
Why enzymes have an optimum pH
If the pH is too high or too low, it can change in active site and denature the enzyme
Difference between diffusion and active transport
1. Active transport requires energy whereas diffusion is passive
2. Active transport moves substances against a concentration gradient whereas diffusion moves substances down the gradient
1. Cell grows and increases the subcellular structures
2. Duplicates the DNA
If the tip is cut off a plant shoot, it grows a wh
1. The tip of a plant contains meristems
2. They prduce unspecialised cells that are able to divide and form any cell type in plant
3. The plant is able to produce all different specialised cells it needs to grow.
Sensory neurone -structure and function (3)
1. It has a long dandelion and short axon
2. Cell body in the middle
It carries nerve impulses from receptor cells to CNS
Describe pathway of reflex arc (5)
1. Stimulus is received by the receptor cells
2. Sensory neurone carries the nerve impulses from receptor to CNS
3. Impulse is transferred actoss a synapse to a relay neurone via neurotransmitters
4. It is then transferred to another synapse to a motor neurone
5. Travels to the effector
Stimulus > Receptor cells > Sensory Neurone > CNS > Synaps / neurotransmitters > motor neurone > effector
Purpose of cilia
Cilia are hair like structures on top surface of cell
They move substances along the surface of the tissue
How they function in airway?
They help to move mucus up to the throat so it can be swallowed and it does not reach the lungs.
Advantage of electron microscope over light microscope:
Light microscope uses light whereas electron microscope uses electrons.
Higher magnification and resolution that light microscope
Why is it necessary to use thein sampes when using a light microscope?
How would you convert a measurement from milimeter to micrometer?
Which unit can be expressed in standard form as 10 power -12? (picometer)
Describe the steps to get a focused image of cells
1. Place the slide beneath the objective lens
2. Adjust the focus
3. Adjust the length of the stage till the image is clear
Factors affecting rate of reaction ->
Temperature, pH and substrate concentration
1. Temperature - As the temperature increases, the rate of reaction increases. But, if it get too hold the active site changes and the enzyme get denatured. The enzymes work the best at optimum temperature (usually 37.5)
2. pH -> As the p
As pH increase, the rate of reaction increases too. But,if the pH is too much, then the active site changes and the enzyme is denatured. Works best at optimum pH(7)
3. Substrate concentration -> Higher the concentration, faster the reaction. However, beyond optimum, rate of reaction has no effect even if the concentration increases.
What is a cell cycle?
Body cells in multicellular organisms divide to produce new cells.
Three uses of mitosis:
4 stages of mitosis:
The membrane around the neucleus breaks down
Chromosome lie free in cytoplasm
The chromosomes line up at the center of the cell
Cell fibres pull the chromosomes apart
Chromosomes go to the opposite end of the cell
Membrane formation around the each set of chromosomes
Formation of two new cells
Benefit and Risk associated with stem cells in medicine
1. Cure some diseases. e.g. Sickle cell anaemia can be cured with bon marrow transplant
2. Specialised cells might be used to replace those which are damaged by disease/injury. e.g. cardic muscle cells can be transplanted into someone with heart disease
1. Stem cells divide very quickly. This uncontrolled division can lead into tumour development.
2. The transplanted cells may get rejected by the patient's body. The patient's body may trigger immune response to get rid of them,making the patient susceptible for diseases
3. If the donor cells are infected, the disease could be transmitted into patient's body