3 - PLANT NUTRITION AND TRANSPORT 

Minerals for healthy growth 

Deficiencies - 

1 - Nitrates 

• Contain nitrogen for making amino acids and proteins 
• Needed for cell growth 
• Stunted 
• Yellow older leaves 

2 - Phosphates 

• Contain phosphorus for making DNA and cell membranes 
• Needed for respiration and growth 
• Poor root growth 
• Purple older leaves 

3 - Potassium 

• Helps enzymes needed for photosynthesis and respiration 
• Poor flower and fruit growth 
• Discoloured leaves 

4 - Magnesium (small amounts) 

• Needed for making chlorophyll 
• Yellow leaves 

3 - PLANT NUTRITION AND TRANSPORT 

Photosynthesis 

• Produces food for plant (glucose) 
• Happens in the leaves of all green plants 
• Happens inside chloroplasts - in leaf cells and other green parts of plant, contain green pigment (chlorophyll) 
• Chlorophyll - green pigment, absorb sunlight, uses its energy to convert carbon dioxide and water into glucose (oxygen also produced - waste product) 
• Converts light energy to chemical energy (stored in the glucose) 
• Chemical energy released when glucose is broken down during respiration 

Leaves - 

•  Broad - large surface area exposed to light 
• Most chloroplasts found in palisade layer - near top of leaf, more exposure to light 
• Upper epidermis - transparent, light can pass through it to palisade layer 
• Network of vascular bundles - xylem and phloem (transport vessels), deliver water and nutrients, take away glucose produced, support leaf structure 

• Waxy cuticle - reduces water loss by evaporation 
• Adaptions of leaves for efficient gas exchange also make photosynthesis more efficient (eg: lower surface full of small holes - stomata, let carbon dioxide diffuse directly into leaf) 

Rate of photosynthesis  

Limiting factor - 

• Depends on environmental conditions (eg: winter - low temp., night - light etc.) 
• Stop photosynthesis from happening any faster 
• Light intensity, CO2, concentration, temperature 

Limiting factor: light 

• Chlorophyll uses light energy to perform photosynthesis 
• Light intensity increased - rate of photosynthesis increases steadily (only up to a certain point - only limiting factors are then either CO2 levels or temp) 
• Not enough light = slows down rate 

Limiting factor: carbon dioxide 

• CO2 - raw material needed for photosynthesis (only about 0.04% of air, fairly scarce for plants) 
• Increases rate of photosynthesis up to a point 
• Graph flattens out - no longer the limiting facto 

Limiting factor: temperature 

• Affects enzymes involved 
• Temp increases - rate of photosynthesis increases up to a point 
• Too high - denatures enzymes 

Experiments 

Testing leaf for starch - 

• Put in boiling water with tweezers/forceps - stops any chemical reactions happening inside leaf 
• Put in boiling tube with ethanol 
• Heat in water bath - gets rid of any chlorophyll, leaf end up pale/white 
• Rinse leaf in cold water 
• Add a few drops of iodine solution
• Present = blue/black 

Showing whether photosynthesis is taking place (starch tests) - 

1 - Chlorophyll 

• Use variegated leaves - only green parts contain chlorophyll (eg: ivy leaves) 
• Take variegated leaf from plant that has been exposed to light 
• Record which bits are green etc. 
• Test leaf for starch (previous experiment) 
• Present = blue/black (will only occur in green parts of leaf) 
• Only parts of the leaf that contained chlorophyll are able to photosynthesise and produce starch 

2 - CO2 

• Set up plant and dish of soda lime in bell jar (sealed) 
• Light shining through bell jar 
• Soda lime will absorb CO2 out of the air in the jar 
• Test leaf for starch (with iodine solution) after set period of time = none present 
• No starch been made in the leaf, CO2 needed for photosynthesis 

3 - Light 

• Plant that has grown without any light 
• Cut leaf from plant - test for starch using iodine solution 
• Light needed for photosynthesis 

Showing rate of photosynthesis (oxygen production) - 

1 - Light 

• Canadian pondweed used to measure the effect of light intensity on the rate of photosynthesis - rate at which the pondweed produces oxygen corresponds to the rate at which photosynthesis is taking place 
• The faster the rate of oxygen production, the faster the rate of photosynthesis 

1. Source of white light placed at a specific distance from pondweed 

2. Leave to photosynthesise for set time 

3. Syringe draws up gas produced 

4. Record results 

5. Repeat with light at different distances 

• Can be altered to measure effect of temperature or CO2 on photosynthesis 
• eg: put in beaker of water, different concentrations of CO2 bubbled through 
• eg: changing temp of water 

2 - HUMAN NUTRITION 

Alimentary canal 

Mouth - 

- Salivary glands in the mouth produce amylase in saliva 

- Teeth break down food mechanically 

Oesophagus - 

- Muscular tube 

- Connects mouth and stomach 

Liver - 

- Produces bile 

Gall bladder - 

- Stores bile 

Stomach - 

- Pummels food with muscular walls 

- Produces pepsin (protease enzyme) 

- Produces HCl - kills bacteria, right pH for proteas enzyme (pH 2) 

Pancreas - 

- Produces protease, amylase, lipase 

- Releases enzymes into small intestine 

Small intestine -

- Produces protease, amylase, lipase 

- Nutrients absorbed into body 

- Contains villi 

Large intestine - 

- Excess water absorbed by blood 

Peristalsis - 

• Muscular tissue all the way down alimentary canal 
• Squeeze boluses through gut 
• Squeezing action - waves of circular muscle contractions 

Digestive process - 

1. Ingestion 

• Putting food in mouth 

2. Digestion 

• Break-down of large, insoluble molecules to small, soluble molecules 
• Mechanical - teeth and stomach muscles 
• Chemical - enzymes and bile 

3. Absorption 

• Process of moving molecules through the walls of the intestines into the blood 
• Digested food molecules absorbed in small intestine 
• Water mainly absorbed in large intestine 

4. Assimilation 

• Digested molecules have been absorbed, moved into body cells - become part of cells (assimilation) 
• eg: amino acids used by cells to make cellular proteins 

5. Egestion 

• Undigested materials form faeces 
• Egested 

Villi (small intestines) - 

• Small intestine - adapted for absorption of food 
• Very long - time to break down and absorb all food 
• Large surface area for absorption - covered in millions of villi 
• Each cell on surface of villi has microvilli - increase surface area further 
• Villi - single permeable layer of surface cells, very good blood supple for quick absorption 

2 - HUMAN NUTRITION 

Digestive enzymes 

• Break down big molecules into smaller ones 
• Starch, proteins and fats are too big to pass through walls of digestive system and insoluble 
• Sugars, amino acids, glycerol and fatty acids are smaller, soluble and can pass through walls of digestive system 

Amylase - starch to maltose 

Maltase - maltose to glucose 

Protease(s) - proteins to amino acids 

Lipase(s) - lipids to glycerol and fatty acids 

Bile - 

• Produced in liver, stored in gall bladder, released into small intestine 
• Neutralises stomach acid 
• Emulsifies fats 
• HCl in stomach makes pH too acidic for enzymes in small intestine - bile neutralises/makes conditions alkaline 
• Emulsifies fats - breaks fats into tiny droplets (bigger surface area for lipase to break down - speeds up digestion) 

2 - HUMAN NUTRITION 

Balanced diet 

• Gives all essential nutrients in right proportions 
• Carbohydrates, proteins, lipids, vitamins, minerals, water 
• Fibre

Carbohydrates - 

• Pasta, rice, sugar 
• Provide energy 

Lipids (fats and oils) - 

• Butter, oily fish 
• Provide energy 
• Act as energy store 
• Provide insulation 

Proteins - 

• Meat, fish 
• Growth and repair of tissue 
• Provides energy in emergencies 

Vitamins -

1 - Vitamin A 

• Liver 
• Improves vision 
• Keeps skin and hair healthy 

2 - Vitamin C  

• Oranges 
• Prevents scurvy 

3 - Vitamin D 

• Eggs 
• Calcium absorption 

Mineral ions - 

1 - Calcium 

• Milk, cheese 
• Makes bones and teeth 

2 - Iron 

• Red meat 
• Makes haemoglobin 
• Healthy blood 

Water - 

• Food, drink 
• Most bodily functions 
• Homeostasis 
• Replaces water lost through urinating, breathing and sweating etc 

Dietary fibre - 

• Wholemeal bread 
• Movement of food through gut 

Energy requirements - 

• Activity level - active people need more energy 
• Age - children/teenagers need more energy than older people - growth, generally more active 
• Pregnancy - pregnant women need more energy - provide energy baby needs for development 

2 - HUMAN NUTRITION 

Biological molecules 

Carbohydrates - 

• Made up of simple sugars 
• Contain carbon, hydrogen and oxygen 
• Starch and glycogen are large, complex carbohydrates - made up of many smaller units (eg: glucose or maltose molecules) joined in a long chain 

Proteins - 

• Made up of long chains of amino acids 
• Contain carbon, nitrogen, hydrogen and oxygen 

Lipids - 

• Fats and oils 
• Made up of fatty acids and glycerol 
• Contain carbon, hydrogen and oxygen 

Testing for glucose (Benedict's reagent) - 

• Add Benedict's reagent (blue) to a sample (an excess) 
• Heat - do not boil 
• Positive = coloured precipitate (blue-green-yellow-orange-brick red) 
• The higher the concentration, the further the colour change goes - can compare 

Testing for starch (iodine test) - 

• Add iodine solution (iodine dissolved in potassium iodide solution - brown/orange) 
• Present = blue/black 
• No starch = stays brown/orange 

2 - ELECTRICITY 

Circuits

1 - Current

• the rate of flow of charge round the circuit 
• will only flow through a component if there is a voltage across that component 
• unit = amp, A

2 - Voltage

• driving force that pushes the current round 
• 'electrical pressure' 
• unit = volt, V 

3 - Resistance

• anything in the circuit that slows down the flow
• if you add more components to the circuit, there will be a higher overall resistance 
• units = ohm, Ω 

4 - Balance 

• voltage is trying to push the current around the circuit 
• resistance is opposing voltage 
• relative sizes of voltage and resistance decide how big the current will be 

INCREASE VOLTAGE = MORE CURRENT FLOWS 
INCREASE RESISTANCE =  LESS CURRENT FLOWS 

Standard test circuit - 

• Basic circuit used for testing components and getting V-I graphs 
• Component, ammeter and variable resistor all in series (can be put in any order in main circuit) 
• Voltmeter only placed in parallel around component being tested 
• Varying variable resistor alters current flowing - can take several pairs of readings from ammeter and voltmeter 
• Plot current and voltage on V-I graph

1 - Ammeter 

• Measures current (amps) flowing through the component 
• Must be placed in series 
• Anywhere in main circuit, never in parallel 

2 - Voltmeter 

•  Measures voltage (volts) across component 
• Must be placed in parallel 
• Around the component 

Mains supply/battery supply - 

• a.c. (alternating current - constantly changing direction) = mains 
• d.c. (direct current - current keeps flowing in same direction) = battery 
• UK - mains electricity = 230 volts 

Series circuits -

• Different components connected in a continuous line 
• Can't control which components current flows through - flows through all or none 
• If one component is removed/broken, the circuit is broken 
• eg: fairy lights 
• Same current flows through all parts of the circuit 
• A1 = A2 
• Size of current determined by total voltage of the cells and total resistance of circuit (I = V/R)
• Total resistance depends on the number of components and the type of components 

Parallel circuits -

• Each component is separately connected 
• If one component is removed/disconnected, hardly affects others 
• Diagram - each component in its own loop 
• How most things are connected (eg: household electrics - lights) 

Exceptions to series and parallel -

• Ammeters always connected in series 
• Voltmeters always connected in parallel with a component 

LEDs (light emitting diodes) -

• Emit light when a current flows through them in a forward direction 
• Numbers on digital clocks, traffic lights, remote controls 
• Don't have a filament that can burn out 
• Indicate the presence of current in a circuit - often used in appliances to show when they are switched on 

LDRs (light dependant resistors) -

• Type of resistor that changes its resistance based on how much light falls on it 
• Bright light - resistance falls 
• Darkness - resistance is highest 
• Electronic circuits (eg: burglar detectors) 

Thermistors -

• Temperature-dependant resistor 
• Hot - resistance drops
• Cool - resistance increases
• Temperature detectors (eg: car engine temperature sensors) 

Resistance 

VOLTAGE = CURRENT X RESISTANCE (V = I X R) 

Voltage/current graphs -

1 - Metal filament lamp

• As the temperature of the metal filament increases, the resistance increases 
• (x axis = V, y axis = I) 

2 - Wire

• Current through a wire (at a constant temp.) is proportional to voltage

3 - Diode

• Current will only flow through a diode in one direction 

4 - Different resistors

• The current through a resistor (at a constant temp.) is proportional to voltage 
• Different resistors have different resistances - different gradients

Charge, voltage, energy change 

• Current = rate of flow of electrical charge (A) 
• In solid metal conductors (eg: copper wire) charge is carried by negatively charged electrons 
• More charge passes around a circuit when  bigger current flows 
• (time must be in seconds - charge is measured in coulombs, C)

CHARGE = CURRENT X TIME