Biology-Year 10-Organisms and Energy

We inhale oxygen and exhale carbon dioxide and water vapour mostly and nitrogen levels stay the same. 

Limewater turns cloudly when it is mixed with carbon dioxide and we use this to show that we exhale carbon dioxide. Another substance that is used to test for carbon dioxide is Sodium Hydrogen Carbonate Indicator Solution. 

Our exhaled breath is warmer than the surrounding air this is because respiration is an exothermic reation. 

Glucose + Oxygen → Carbon Dioxide + Water + Energy (for the body and heat)

In human cells there are 5 main features:

• Nucleus = controls the cell and contains genetic material
  
• Cell Membrane = holds the cell together & controls what enters and leaves the cell
• Cytoplasm = where many chemical reactions happen
• Ribosomes = where photosynthesis happens
• Mitrochondria = where energy is created by respiration

Aerobic:

Happens when there is plenty of oxygen about, uses oxygen. Happens in humans, plants and animals. It transfers more energy than anaerobic respiration.

glucose + oxygen → carbon dioxide + water

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

Anaerobic:

Happens when there is not a plentyful supply of oxygen and that's why it doesn't need oxygen to happen. It only really happens in us when we do lots of exercise. Happens in humans, plants and animals. It transfers less energy and is less efficient than aerobic respiration.

In animals it is: glucose → lactic acid (lactic acid build up can lead to cramps)

In plants & yeast it is: glucose → ethanol + carbon dioxide

In this experiment you need: woodlice/maggots/germinating peas, a water bath, soda lime granules and a respirometer.     

Add soda lime granules to two tast tubes, the soda lime absorbs CO₂. Put cotton wool over the soda lime because it is corrosive, and put the woodlice on top in one tube and beads of the same mass in the other as a control.

Set up the respirometer as shown. The apparatus is left for a period of time in a water bath. During this time the woodlice will use up the oxygen by respiring and this leads to a decrease in the volume of air in the test tube.

The decrease in the volume leads to a reduce in pressure the test tube causeing the coloured dye to rise up towards the test tube containing woodlice.

The distance moved by the liquid is measured after a given time. The volume of oxygen taken in per minute can be calculated with this information and this is the rate of respiration. Repeat the steps with different temperatures to see how temperature effects the respiration rate.

The higher the temperature the higher the respiration rate because the cells are respiring more and using up the oxygen in the test tube.

There are 3 main factors that effect the rate of diffusion:

• Distance - the shorter the distance the quicker they will diffuse.
• Surface area - the bigger the surface area the larger the amount of particle can diffuse at once, increasing the diffusion rate.
• Concentration difference - substances will diffuse faster if they are going from a high concentration to a low concentration.

Fick's Law

Rate of Diffusion ⋉ Surface Area x Concentration Difference 

                                   Thickness of Membrane

⋉=directly proportional to

To increase the rate of diffusion you can increase the surface area where the particles diffuse or increase the size of the concentration gradient. If you increase the thickness of the membrane (the distance the particles have to travel to diffuse) the rate of diffusion will decrease.

When we breath in, the intercostal muscles contract to move the ribs upwards and outwards. The diaphragm contracts and moves down. The volume inside the chenst increases and the pressure decreases. This causes air to rush into your lungs and they inflate.

When we breath out, the intercostal muscles relax and the ribs move downwards and inwards. The diaphragm relaxes and moves up. The volume inside the chest decreases and the pressure increases, this causes the air to rush out of your lungs and they deflate.

Diffusion = The movement from a high concentration to a low concentration.

When an animal grows the surfaces area increase at a lesser rate than the volume of the animal.

• This makes diffusion of gases into the interior a problem.
• And the animals either have small flattened bodies so that the internal cells are close to the surface or they have a respiratory system and organs (like humans), because the gases can't diffuse through their skin.

Depending on the animals surface area to volume ratio (SA : V) is the way they exchange gases in their body: through their skin/with a respiratory system & organs.

One alveolus, many alveoli.

• They are found in the lungs and the lungs job is to transfer oxygen to the blood and remove the waste carbon dioxide.
• There are millions of alveoli in the lungs and in the alveoli gas exchange happens.
• Blood arriving to the alveoli has come back from the rest of the body and contains mostly carbon dioxide and not much oxygen. This maximises the concentration gradient for the diffusion of both gases.
• The oxygen diffuses out of the air and into the blood and the carbon dioxide diffuse into the lunds and is breathed out. They go from a high concentration to a low concentration.

How alveoli are specialised to maximise the diffusion of O₂ and CO₂:

• Moist lining for dissolving gases.
• Large surface area.
• Very thin walls - shortens the distance of diffusion. And it is permeable.
• Surrounded by blood capillaries to maintain a good blood supply and the concentration of CO₂ and O₂

carbon dioxide + water   ----LIGHT--->   glucose + oxygen

6CO₂ + 6H₂O   ----CHLOROPHYLL--->   C₆H₁₂O₆ + 6O₂                                        

Plants and algae use energy from the sun to make glucose. If a plant can't photosynthesis then it won't make starch which is a product of the process, because the glucose is stored as starch because it is insolable .The reaction is an endothermic reaction because it takes in energy as it occurs. Photosynthesis happens inside chloroplasts that contain chlorophyll which absorbs light, and this energy is transfered into the chloroplasts. 

The glucose produced can make more complex molecules that the plant needs to grow. These make up the organism's biomass - living material. The energy in the biomass works its way up the food chain as animals eat the organism and each other, the biomass is why we get energy from the things we eat and biomass is there because of photosynthesis. 

The rate of photosynthesis is affected by light intensity, concentration of CO₂ and temperature, these limiting factors prevent photosynthesis from happening faster.

            A      B       C

A = At the beginning the light intensity is directly proportional to the rate and it is the limitling factor but as the line levels out something else becomes the limiting factor like the amount of CO₂ or the temperature, and the rate is no longer increasing.

B = Temperature is usually a limiting factor because it is too low and the enzymes that are used during photosynthesis work slowly is low temperatures. But as the temperture gets too hot the plant becomes denatured and dies, it happens at 45°C. 

C = At the beginning there is a plentyful amount of CO₂. But increasing the CO₂ level will only increase the rate to a certain point (like light intensity) and when the line flattens out something else is the limiting factor.

Pondweed is put into water containing some sodium hydrogencarbonate this is so that there is enough carbon dioxide in the water for the plant to photosynthesise. 

A light source is places a specific distance from the pondweed, you can then count the amount of oxygen bubbles produced a minute or leave it for a set amount of time with a syringe collecting the oxygen produced, this would give you the volume of oxygen produced.  Repeat the process with the light at different distances from the pondweed, to see how the light intensity affects the rate of photosynthesis. Any other limiting factors should be controled.

The rate can be calculated by volume produced ÷ time taken.

The lower the light intensity (the further the lamp was away from the weed) the less oxygen is produce therefore the slower photosynthesis happens.

The distance from the lamp and the light intensity is inversely proportional to each other this means, as distance increases light intensity decreases. But light intensity decreases in proportion to the square of the distance. This is the inverse square law.

Light intensity ⋉ 1 ÷ distance²

This means that is you halve the distance the light intensity will be 4 times greater. And is you double the distance you will make the light intensity 4 times smaller.       

Osmosis = the net movement of water molecules across a semi-permeable membrane from a place of high water concentration (lower solute concentration) to a place of low water concentration (higher solute concentration). 

The membrane has small holes that allow only small molecules to pass through and not bigger molecules (e.g. sucrose). Water molecules can pass both ways through the membrane, but there is usually more water molecules on one side of the membrane and because of this there is a steady net flow of water molecules into the part with a lower water concentration and a high solute concentration.

In this experiment we put slices of potato into different sucrose solutions of different concentrations. 'M' is the unit that measures concentration, 0.0M is pure water.

The potato slices should be the same size and from the same potato, to make it a fair test. Other things you should keep the same: the amount of sucrose solution, the amount of drying and the type of potato (if it is not the same potato).

Put 3 slices into each solution but measure their mass before you put them in the solutions. Leave the potatos in the solution for at least 40 minutes, all for the same amount of time. Take out the potatos and pat them dry to remove excess water on the surface of the potato. Measure the mass of each group, this is the final mass.

Claculate the percentage change in mass with the before and after weights.

percentage change = final mass - initial mass      X 100

                                              initial mass 

Find the percentage change in mass: a positve is gain in mass and a negative is loss in mass. 

The overall tread is that the lower the concentration of sucrose solution the heavier the potato will be after, potatoes in water 0.0M will gain weight and the potatoes in the sucrose solution will lose weight.

This show that the water with a high sucrose concentration was hypertonic compared to the potato and this means that the potato shrank as the water in the potato went into the solution, so it lost weight.

The water is hypotonic compared to the potato, so the potato increased in mass as the water in the pot went into the potato because the potato had a higher sucrose concentration than the water.

Hypertonic = High concentration, contains lots of sucrose compared to something else. Makes cells lose water and they dehydrate, wilt or die.

Hypotonic = Low concentration, contains less sucrose compared to something. Makes cells gain water can cause they to swell, fill up, become turdid or burst. 

Active Transport is the movement of particles across a membrane against a concentration gradient (i.e. from an area of lower to an area of higher concentration) using energy transfered during respiration.

Active transport happens in plants root cells as well as osmosis. The root cell has a large surface area and thin walls to make it easy to collect plenty of water. There is no chloroplasts in the root hair cell as there is no light underground. The concentration of mineral ions is higher in the root hair cell than in the soil so the mineral ions are absorbed by active transport. 

In plants mineral ions are useful and in animals they need glucose and amino acids as well as the mineral ions. There are lots of mitochondria (because this is were respiration happens) and the energy made there is used for the cell to transport what is needed, via active transport (which needs energy to happen). The energy is used to move a particle through a protein against the direction of diffusion.

Active transport requires effort and energy (like pushing some thing up a hill) were as passive transport requires no effort or energy (like letting something roll down a hill).

The order is: Root Hair cell, Epidermis, Root Cortex, Endodermi and Xylem Vessel.

The water enters the root by osmosis and the water travels up the xylem to the leaves by transpiration.

Water travels up the Xylem, and the Phloem transports dissolved food around the plant. 

Phloem: Cells are alive, transports up and down the plant, transports sucrose and other organic materials, takes nutrience to storage, cellulose walls.

Xylem: Transports water and minerals, cells are dead, lignified walls, cellulose walls, transports up the plant, is a major role of support in the plant.

Vascular tissue is xylem and phloem and there are certain features of the tissue.

• The dead hollow cell have lumen inside.
• Lignin is inside cell walls and it adds strength & waterproofing.
• Lignin is in rings, spirals and coils and this makes the stem rigid.
• Tiny pores allow water to enter and leave.
• There is no cytoplasm or nuclei.
• It is relatively long and thin.

Stoma is the singular, Stomata is the plural.

In the light water enters the guard cells because of osmosis and this water expands the cells and they become turgid. As they expand the stoma is squeezed and bends outwards making a 'banana' shape. 

In the dark, photosynthesis doesn't happen so water leaves the guards cells and they become flaccid and turgor, therefore the guard cells no longer press on the stoma and it closes.

Transpiration is caused by the evaporation and diffusion of water from a plant's surface. Transpiration happens mostly in the leaves. The loss of water leads to a slight shortage of water in the leaves, so more water is drawn up from the xylem vessles to replace it. This then draws up the more water from the roots, and there is a constant transpiration stream of water through the plant. This transpiration stream carries mineral ions that dissolve into the water.

• Light Intensity = the brighter the light, the greater the tramspiration rate. This is because in the dark photosynthesis is not needed so the stomata don't open up to let out CO₂, and when they are closed they don't let out a lot of water.
• Temperature = the warmer it is, the faster transpiration happens. When it is warm the water particles have more energy and evaporate/diffuse out of the stomata.
• Air Flow = the better the air flow (strong wind) the greater the transpiration rate. If air flow is bad, the water vapour surrounds the leaf and dosen't move away. This means that there is a high concentration of water on the outside of the leaf as well as inside so diffusion doesn't happen.

A potometer is used to measure the plant's rate of transpiration using its rate of water uptake as an equivalent. Approximately 99% of water absorbed by the root hair cells is transpired through stomata. Only 1% is used by the plant for photosynthesis. 

Rate of transpiration = distance moved by the air bubble

                                  time taken to move that distance

• Waxy cuticles - Reduces exapouration of water from the surface.
• Guard cells - Open and close the stomata depending on the gases required and water avaliability. 
• Tightly packed palisade cells near the top of the leaf - These all contain chlorophyll to absorb light energy.
• Air spaces - Allows gases to come into contact which a greater surface areas of many cells.
• Leaves are thin - To reduce the distance gases have to diffuse.
• Leaves are broad and flat - To increase the surface area to absorb light.

A xerophyte plant is adapted to survive in an enviroment with little liquid water.

• Thick cuticle - Stops unwanted evaporation through leaf cells.
• Small leaf surface area - Less surface area for evapouration.
• Low stomata density - Smaller surface area for diffusion.
• Sunken stomata, Stomatal hairs & Rolled Leaves - Maintains humid air around stomata.
• Extensive roots - Maximise water uptake.