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TRANSCRIPT
Intermediate Two Biology
Unit 1: Living Cells Summary Notesa) Cell Structure and Function
Animal CellsAnimal cells have a nucleus, cell membrane and cytoplasm
Plant cellsPlant cells have all animal cell parts plus a cell wall, vacuole and chloroplasts. The presence or absence of a cell wall tells you if it is a plant or animal cell.
Yeast cells
Yeast cells have nucleus, cell membrane, cytoplasm and cell wall. They have no chloroplasts (cannot make their own food). They reproduce by budding.
Functions of cell structures
Structure Function Found inNucleus Contains genetic material.
Controls cells activitiesAll cells (except red blood cells)
Cytoplasm
Nucleus
Cell membrane
Chloroplast
Nucleus
Cell wall
Vacuole
Cell membrane
Cytoplasm Cytoplasm
CytoplasmCell membrane
NucleusCell wall
Cell membrane
Controls movement of substances into and out of the cell
All cells
Cytoplasm Site of chemical reactions All cellsVacuole Contains cell sap (sugary water) PlantsChloroplast Site of photosynthesis Some plant cellsCell wall Gives cell support and shape Plant and yeast cells
Commercial and Industrial uses of cells
Bread Making Uses yeast cells Anaerobic respiration (no oxygen present) of yeast produces carbon
dioxide Carbon dioxide causes dough to rise
Alcohol Production Uses yeast cells Anaerobic respiration
(fermentation) of yeast on sugar produces alcohol (ethanol)
Used to produce beer and wine
Antibiotic Production Uses fungi Fungi produce a wide
range of antibiotics to kill bacteria
Some bacteria are sensitive- the antibiotics prevent growth and destroy bacterial cells
Some bacteria are resistant- the antibiotics do not work
Resistant bacteria are on the increase due to overuse of antibiotics
CO2
Yo
ghurt Production Uses bacteria Bacteria convert lactose sugar in milk into lactic acid Decrease in pH causes curdling (thickening) of milk
Souring of milkLactose Lactic acid
Alternative Fuel Production Biogas
oUses bacteriaoBacteria produce methane gas from anaerobic breakdown of waste
products e.g. sewage Gasohol
oUses yeastoFermentation of sugar cane produced alcohol which is mixed with
petrol
b) Diffusion and Osmosis in plant and animal cellsDiffusion
Movement of substances from a high concentration to a low concentration down a concentration gradient
Food (glucose, amino acids) and oxygen enter cells by diffusion Carbon dioxide and waste products (urea) leave cells by diffusion Important process to cells
o Gain raw materials for respiration and photosynthesiso Removal of waste products
Osmosis
Special case of diffusion involving water only Movement of water across a selectively permeable membrane from an area
of high water concentration to a low water concentration Osmosis causes the change in weight of cells in water solutions Isotonic solutions have the same water concentration as a cell. There is no
net movement of water Hypotonic solutions are weak solutions and have a high water concentration.
Water will move into a cell. Hypertonic solutions are strong solutions and have a low water
concentration. Water will move out of a cell.
Test tubes A and B are hypotonic solutions as potato gained mass from taking in water by osmosis
Test tubes C, D and E are hypertonic solutions as potato lost mass from losing water by osmosis
Test tube B is closest to an isotonic solution because the mass of the potato changed the least
Dissolved food
Oxygen Waste products
e.g. CO2
Test Tube Concentration of sugar (M)
Percentage change in mass of potato
A 0.1 +10B 0.2 +5C 0.3 -10D 0.4 -15E 0.5 -25
Osmotic Effects in Plant cells
Hypertonic solution Isotonic solution Hypotonic solution Water moved out
of cell Cell
plasmolysed Vacuole has
shrunk Cell membrane
came away from cell wall
Flaccid
Cell appears normal
Water has moved into cell
Turgid Vacuole has
increased in size Cytoplasm
pushed against cell wall
Cell wall stretched to a maximum
Osmotic effect in Animal Cells
Hypertonic solution Isotonic solution
Hypotonic solution
Water moved out of cell
Cell shrunk/shrivelled
Cell appears normal
Water has moved into cell Cell has burst as no cell wall to
hold shape
c) Enzyme ActionCatalysts Speed up chemical reactions Lower energy input required for chemical reactions Take part in reactions but remain unchanged and can be used again
Enzymes Biological catalysts Made by all living cells Required for functioning of living cells
Made of protein
Specificity of Enzymes Active site of enzyme is where the
chemical reaction takes place It is complementary to one substrate
(lock and key hypothesis) Enzymes can only react with one
substrate/ perform one reaction
Enzyme reactions Degradation
o Chemical breakdown of a substanceo E.g. catalase breaks down hydrogen peroxide into water and oxygeno E.g. amylase breaks down starch into maltose
Synthesiso Building of a complex molecule from simpler moleculeso E.g. phosphorylase builds up glucose-1-phosphate into starch
Factors affecting enzyme activity Optimum conditions
o Enzymes have a temperature and pH value it works best ato Produces high volume of product at a fast rateo Activity increases to an optimum value then decreaseso Optimum value is peak of enzyme activity graph
Temperatureo Enzymes are made of protein which changes shape at high
temperatures
o This changes the shape of the active site and the substrate can no longer react with the active site of its enzyme
o The enzyme is denatured at high temperatures
pH o Enzymes have a small range of pH values it can work in
d) Aerobic and Anaerobic respiration
Energy release Chemical
energy in a cell is
contained in glucose
Energy released through series of enzyme controlled reactions- respiration
Glucose + oxygen energy + carbon dioxide + water Some energy released as heat Most energy used for cellular activities
Role of ATP
Energy from breakdown of glucose used to make ATP from ADP + Pi ATP used as energy source Used to transfer energy
Aerobic pathway
Glycolysiso First stage of respirationo Does not require oxygeno Glucose split into 2 pyruvic acid moleculeso 2 ATP produced
Oxygen dependant stageso Only occurs if oxygen is presento Pyruvic acid is completely broken down to carbon dioxide and water o 36 ATP producedo Aerobic respiration produces 38 ATP in total
Anaerobic Pathway
Only Glycolysis occurs Animal cells
o Pyruvic acid converted to lactic acido Reversible in presence of oxygen
Repayment of oxygen debt
Anerboic respiration in plant cells
o Pyruvic acid converted to alcohol (ethanol) and carbon dioxideo Carbon dioxide is released into atmosphere
Irreversible
e) Photosynthesis Series of enzyme-controlled reactions Carbon dioxide + water glucose + oxygen
Energy fixation Sunlight source of energy Sunlight trapped by chlorophyll in chloroplasts Converted into chemical energy (ATP) ATP used to produce glucose
Photolysis
Requires light Breakdown of water to produce hydrogen, oxygen and ATP Oxygen is released as by product to atmosphere by diffusion
During time P Anaerobic
respiration Production of lactic
acid
During time Q Repayment of
oxygen debt Lactic acid
converted to pyruvic acid
Hydrogen and ATP is carried to next stage
Carbon fixation
Hydrogen from stage one is joined with carbon dioxide to produce glucose
Uses ATP from photolysis as energy source Glucose stored as
o starch in leaveso cellulose in cell walls
Limiting factors of photosynthesis
Light intensity Carbon dioxide concentration Temperature
Carbon
Limiting factor at point 1: carbon dioxide concentration o Compare rate of photosynthesis with the graph for the higher carbon
concentration, the only difference is the carbon dioxide concentration therefore it must be the limiting factor
Limiting factor at point 2: light intensityo As graph is increasing due to higher concentration of carbon dioxide, it
must be the light intensity which is limiting the rate of photosynthesis
Removing a limiting factor
Use of heaters Use of lamps Adding carbon dioxide
o Increases glucose productiono Plants grow fastero Allows plants to be harvested sooner
Carbon