What 6 features does a PLANT CELL have?
1. Cell wall - gives plant cell rigid shape
2. Chloroplasts - contain a chemical called chlorophyll to carry out photosynthesis
3. Vacuole - space used to store useful substances
4. Cell Membrane - controls substances entering and exiting the cell
5. Cytoplasm - site of chemical reactions
6. Nucleus - controls cell activities
What 3 features does an ANIMAL CELL have?
1. Cell Membrane - controls substances entering and leaving the cell
2. Cytoplasm - site of chemical reactions
3. Nucleus - controls all cell activities
Diffusion is the movement of a substance from an area of high concentration to area of low concentration until evenly spread. This is the process by which substances like oxygen, water, urea and carbon dioxide enter and leave cells.
Importance to a cell:
Entering a cell - oxygen, water, glucose, amino acids.
Exiting a cell - water, urea, carbon dioxide.
Osmosis is the technical term for the diffusion of water through a selectively-permeable membrane.
Effects of osmosis on cells:
- water in>water out - Bursts
- water in=water out - no change
- water in
- water in>water out - turgid (swollen, but not burst)
- water in=water out - no change
- water in<water out - plasmolysed (shrunk but cell wall rigid).
CELL DIVISION (MITOSIS)
- The division of a cell into two daughter cells.
- The two daughter cells are genetically identical.
- Genetically identical cells are calles clones.
Chromosomes and genes:
- Chromosomes are long thread-like structures in the nucleus
- There are 46 chromosomes in a human nucleus
Stages of mitosis:
- Chromosomes double
- Chromosomes shorten and thicken - 2 chromatids, attatched by a centromere
- Chromosomes line up at the equator - cetromeres attatch to spindle fibres
- Chromatids (1/2 a chromosome) move to opposite poles - spindle fibres pull chromosomes apart
- Nuclei reform and cytoplasm divides - 2 indentical daughter cells are created.
Enzymes are biological catalysts -
- Catalysts speed up the rate of a reaction, but are unchanged themselves.
- Enzymes are proteins found in living cells.
How enzymes work:
- All enzymes work on only one substance - this substance is the enzyme's substrate.
- Enzyme and substrate join
- Shapes of enzyme and substrate fit closely together
- A change occurs in the substrate and the product is released
The enzymes are specific to that substrate.
The optimum rate of an enzyme is the rate at which it works best. This can be affected my PH, temperature etc.
Above about 50 degrees, enzymes are denatured.
Substrate Enzyme Product
- hydrogen peroxide catalase oxygen + water
- starch amylase maltose
- fats lipase fatty acids + glycerol
- protein pepsin polypeptides
- glucose-1-phosphate phosphorlyase starch
The formula for aerobic respiration is:
glucose + oxygen ------> energy + water + carbon dioxide
Food contains the chemical energy we need to fuel out bodies. Fats contain twice as much energy as carbohydrates or proteins.
DENATURED - when an enzyme is destroyed, perhaps because it gets too hot, it is denatured.
OPTIMUM - this is the peak activity rate of an enzyme.
SUBSTRATE - this is the substance upon which an enzyme works.
SPECIFIC - when talking about enzymes and their substrates, enzymes only work on ONE subtance (substrate). The enzyme is SPECIFIC to that substrate.
SYNTHESIS - this is the word used to describe the buildup of a substance from smaller molecules to larger molecules. For example: the enzyme phosphorylase builds up G-1-P and changes it into starch.
DEGRADATION - this is another word for breakdown. It is used when talking about enzymes that DEGRADE their substrate and release their product.
STAINS & INDICATORS
IODINE stains PLANT CELLS (yellow)
METHYLENE BLUE stains ANIMAL CELLS(blue)
BICARBONATE INDICATOR turns RED ---> YELLOW (in presence of carbon dioxide)
BENEDICT'S SOLUTION turns BLUE---> RED (in presence of glucose)
IODINE turns BROWN ---> BLACK (in presence of starch)