Lipids:
- Lipids (fats) contain carbon, hydrogen, and oxygen as well but never in the same ratio as carbs.
- Lipids contain very little oxygen
- They are usually insoluble in water
- Lipids includes, fats, oils, waxes and steroids
- Fats contain twice as much energy as carbohydrates. More energy efficient storage molecules.
Proteins:
- Made up of carbon, hydrogen, oxygen, nitrogen and sulfur atoms.
- Used in structure, storage, movement and transport of cells.
- Proteins are the most abundant organic molecules in cells. They assist in growth and repair.
- Enzymes are important proteins that control reactions in the cell.
- Proteins are large molecules made up of smaller molecules called amino acids, joined by peptide bonds to form a polypeptide.
- Proteins are made up of one or more poly peptide bonds.
Nucleic Acids
- Hereditary material found in cells and viruses.
- Consist of sub-units called nucleotides consisting of a sugar, a phosphate and a nitrogenous base.
- The 2 kinds of nucleic acids.
- RNA (ribonucleic acid)
- DNA (deoxyribonucleic acid)
- Plan, choose equipment ore resources and perform a first hand investigation to gather information and use available evidence to identify the following substances in tissues:
- Glucose
- Starch
- Lipids
- Proteins
- Chloride ions
- Lignin
Experiment: Chemicals in Cellular Tissue
Aim: To use diagnostic tests to determine wether the following chemicals are present in apple, potato and tuna cellular tissue: glucose, starch, lipids as oils, protein, sodium chloride salt, and lignin.
Hypothesis: Apple, potato and tuna do not contain any of the above chemicals.
Method:
- The cellular tissue will need to be mashed into pulp. A small amount of distilled water will need to be added to this pulp ONLY FOR glucose sodium and chloride tests.
- record colour changes in a table.
- Test glucose by adding a few drops of benedict’s solution to a sample of apple in a test tube then lightly heat over flame.
And so on…
- Describe the current model of membrane structure and explain how it accounts for the movement of some substances into and out of cells.
The cell membrane is a thin sheet composed of two layers of phospholipids. The sheet is very fluid and flexible. Other lipids such as cholesterol are also found within the membrane. The fatty acid tails are hydrophobic and so face the inside of the membrane. The phospholipid head if hydrophilic and so faces the outside of the membrane. Proteins are scattered between the phospholipid bilayer. Proteins are capable of movement between the membrane. The membrane has been shown through the fluid mosaic model.
Fluid Mosaic Model
- Compare the processes of diffusion and Osmosis
Diffusion: Diffusion occurs when molecules of a particular substance move from region of high concentration to region of low concentration and involves random movement of particles. When a substance is transported in this manner it is said to be the diffusion gradient.
Osmosis: is the Diffusion of water across a semi-permeable membrane from a high concentration to region of lower concentration until even. So imagine water moving from a dilute concentration to a higher concentration. Osmosis is a passive process (occurs slowly).
Diagram explaining Osmosis
Osmosis is the movement of only a solvent through a semi-permeable membrane. However, diffusion is the spreading of any molecule, whether liquid or gas, and diffusion occurs whether or not a membrane exists.
- Perform a first hand investigation to investigate the difference between osmosis and diffusion.
Observing Diffusion
Aim: To model diffusion of water in sugar
Hypothesis: The colour from the skittles will disperse throughout the petrii dish and will mix.
Method:
Set up the perti dishes in the following way.
In the first petri dish place one skittle in the centre of the dish and carefully fill with water. Once filled with water do not move the dish.
In the second dish set up four different coloured skittles in each quarter of the petri dish and carefully fill with water. Do not obstruct.
Results: Colour slowly spreads throughout petri dish. The whole perti dish for test one. Colours spread until they meet another in test 2 and then slow right down. They do eventually mix but do not spread to the extent that test one did.
Conclusion: The rate of diffusion is based on concentration. Diffusion slows right down between the two dyes because they have a very similar concentration.
Observing Osmosis
Aim: To model the function of a cell membrane
Method:
- Tie one end of a dialysis tube with string
- Fill the dialysis tube with starch solution
- Rinse outside of tube with water to remove any starch solution
- Place dialysis tube in a large beaker of water
- Add 10mL of iodine to the water and observe what happens
- Draw experiment set up before and after experiment.
Conclusion:
Dialysis tube is semi-permeable therefore the iodine can pass through via osmosis. Osmosis and diffusion are both passive processes.
- Explain how the surface area to volume ratio affects the movement in and out of cells.
When and object is small (e.g. a cell) it has a large surface area in comparison to its volume. So as an object gets smaller its surface area to volume ratio increases. As an object becomes larger its surface area to volume ratio becomes smaller and diffusion is no longer efficient. For this reason cells need to be very, very small with the effectiveness of diffusion being the controlling factor. Cells obtain their nutrients and release wastes by diffusion through the cell membrane, or the whole surface area of the cell. A large SA:V is better for cells because then there is enough surface area to supply the volume of the cell with nutrients and remove wastes at a rate that is fast enough to keep the cell alive.
2cm Cube
SA= 2x2x4=24cm2 V= 2x2x2=24cm3 SA to V= 24 to 8= 3:1
- Perform a first hand investigation to demonstrate the effect of surface area to volume ratio on rate of Diffusion
Rate of Diffusion Test
Aim: to determine the rate of diffusion in potato cubes of different sizes.
Hypothesis: the larger cubes should have less iodine diffuse through them than the smaller cube.
Method:
- Cut 3 cubes of potato (no skin)
- Place all cubes in a 250mL beaker.
- Fill with iodine solution until it just covers the largest cube
- Cover with watch glass to prevent evaporation
- Leave for 24 hours
- Cut cubes in half to view how far iodine has diffused through potato
Results:
Conclusion: The larger the SA:V ratio is the more efficient diffusion is. Therefore cells need to be small in order to gain the nutrients they need.
- Identify some examples that demonstrate the structural relationship between cells, tissues, organs and organ systems in multicellular organisms.
Organism
Organ System
Organs
Tissues
Cells
In plants
Organ system: Shoot system
Organ: vascular system
Tissue: vascular tissue (vascular bundles) transports food, water, hormones and minerals within the plant. Vascular tissue includes xylem, phloem, parenchyma, and cambium cells.
Phloem cells conduct food from leaves to rest of the plant. Found in veins along with Xylem
- Distinguish between autotrophs and heterotrophs in terms of nutrient requirements.
Autotrophs- make their own organic material (energy) from inorganic substances, typically using the energy from sunlight through the process of photosynthesis. These include all plants, algae, and some bacteria.
Heterotrophs- all animal, fungi and some bacteria that exploit a wide variety of foods to provide their energy and organic matter needs. This means they eat plants and/or other animals.
- Identify the materials required for photosynthesis and its role in ecosystems.
In order to produce their own food, plants need a few raw materials H2O, CO2, light energy from the sun, and the pigment chlorophyll. The chemical energy stored in this food fuels the reactions that sustain life (metabolism). Heterotrophs rely on producer either indirectly or directly for their energy. The photosynthesis that occurs in the oceans is vital to the Earth’s functioning providing oxygen and absorbing carbon dioxide.
- Identify the General word equation for photosynthesis and outline this as a summary of a chain of biochemical reactions.
CARBON DIOXIDE + WATER GLUCOSE + OXYGEN
6CO2 + 6 H2O C6H12O6 + 6O2
Radiant energy from sunlight is absorbed by the chlorophyll pigments in the chloroplasts of green plant cells and is converted to chemical energy. Some of this is used to split water molecules to hydrogen and oxygen.
light
Water Hydrogen + Oxygen
Light independent reactions:
Hydrogen released from light reactions combines with carbon dioxide to form sugars. This process is a chain of biochemical reactions requires energy. This energy is supplied by some of the energy absorbed by light in light reactions or from energy stores ATP in the plant.
light
Hydrogen + Carbon Dioxide Sugars
These reactions occur in the stroma.
- Light reaction
Radiant energy is absorbed by the chlorophyll pigments and is converted into chemical energy. Some of the energy is used to split water molecules into hydrogen and oxygen. This reaction occurs on the internal membranes of the chloroplast, the thylakoids.
- Dark reaction
The hydrogen released from the first reaction combines with carbon dioxide to form sugar, the energy used to form sugar is used from the absorption of light. This reaction occurs in the stroma of chloroplasts.
- Explain the relationship between the organisation of the structures used to obtain water and minerals in a range of plants and the need to increase the surface area available for absorption.
In an aquatic environment, water and minerals can be absorbed across the whole surface of the plant. In most terrestrial plants, water and minerals, are obtained through the root systems, which also anchor the plants in the soil. Plant roots need to increase the surface area over which absorption can occur. They achieve this by having a branching structure, and root hairs just behind the root tips.
- Explain the relationship between the shape of leaves, the distribution of tissues in them and their role
The shape of the leaf and distribution of tissue depends on the environment in which the plant lives i.e. a dry terrestrial plant will have different distribution of tissues than an aquatic plant. Terrestrial plants have large numbers of chloroplasts in special photosynthesising cells called palisade cells, the arrangement of palisade cells vary in different plants to utilise the light available.
- Describe the role of teeth in increasing surface area of complex foods for exposure to digestive chemicals
Teeth grind and physically break up food in the mouth where the digestive process first begins. Grinding food into smaller pieces increases the rate of reaction and therefore saliva is absorbed faster, food can be swallowed easier and will break down faster throughout the digestive process.
- Perform a first-hand investigation to gather information and use available evidence to demonstrate the need for chlorophyll and light for photosynthesis
Aim: To demonstrate the effect of light and chlorophyll on starch production in leaves (photosynthesis)
Method:
Part A- Testing starch content
- Collect 2 soft green leaves form a plant in sunlight
- Place in a 600mL beaker half filled with boiling water. Boil for 2 minutes to break down cell membrane the remove.
- Place each leaf in a 100mL beaker of methylated spirits. Remove and place back in large water beaker.
- Heat for 5 minutes then remove, wash with cold water and place each leaf into a petri dish. Describe
- Cover with iodine. Describe
Part B- the effect of chlorophyll on the production of starch
- Collect variegated leaves exposed to sunlight
- Draw patterns on leaves. Predict where starch may be present
- Repeat Part A. Describe, compare
Part C- effect of light on production of starch
- Collect leaves off 2 plants, one that has been exposed to full sunlight and one that had been kept in a dark cupboard for 48 hours.
- Repeat procedure in part A. Describe appearance of leaves from each plant
- Compare the digestive systems of mammals, including a grazing herbivore, carnivore and a predominantly nectar feeding animal.
- Dog
- Digestive system relatively small & simpler compared to herbivores.
- Large stomach to produce enzymes for the breakdown of meats.
- Fast and efficient digestion process.
- Very little caecum
- Cow
- Fermentation occurs in caecum, the caecum is very large
- Ruminant herbivores
- It is as if they have ‘four stomach’
- More efficient than the hindgut fermentation in other herbivores (eg. rabbit)
3. Human
- Omnivores
- Digestive system proportionally larger than a carnivore’s and smaller than a herbivores.
- Teeth structure different
- Very small caecum
4.Honey Possum
- Very specialised diet
- Small unspecialised and simple digestive system
- Very small caecum and stomach
- Compare the roles of a respiratory, circulatory and excretory systems
- Identify and compare the gaseous exchange surfaces in an insect, a fish, a frog and a mammal.
-
Mammals have lungs and breathe atmospheric air. The respiratory surface is called the alveoli is where most gaseous exchange occurs. The alveoli provide a large respiratory surface area and gases readily diffuse across the thin cell layer.
-
Fish have gills that exchange dissolved gases with water around them. Fish take in water through the mouth and release it out the gills. The gill contains many stacked layers, which provides a large surface area.
- Frogs and tadpoles have soft moist skin. They have a good blood supply right under their skin so gases are efficiently exchanged directly through the skin surface.
-
Insects have a tracheal system that enables individual cells (rather than a whole system) to exchange gases. Air is passed through a network of tubes deep into the insect’s tissues. Air enters through openings called spiracles that are spaced along the insect’s body. Trachea divide into tiny branches called tracheoles. They have a large SA:VR and are moist to allow diffusion. The trachea is lined with chitin, which is impermeable and keeps the airways open.
- Explain the relationship between the requirements of cells and the need for transport systems in multicellular organisms.
In multicellular organisms, cells have a range of difficulties in exchanging substances with the external environment. Transport systems help cells to overcome this. The circulatory system collects materials and delivers them to places within the organism where they are needed. At the same time, the circulatory system collects wastes and transports them to places where they can be excreted.
- Outline the transport system in plants.
Absorb water and minerals from the soil.
Takes water and mineral from surrounding cells and conducts it upwards.
Carries food, mainly sugar, made by the leaves onto the root cells.
Stomata are important for gas exchange and transpiration. Each stoma is surrounded by two guard cells which contain chloroplasts. The guard cells control the size of the stomatal opening, and thus control the amount of gas exchange and transpiration.
- Identify mitosis as a process of nuclear division and explain it’s role
Mitosis is the process in which identical nuclei for new cells form. The cell’s chromosomes in the nucleus replicate and two daughter cells are created. Mitosis is essential in both unicellular and multicellular organisms for growth and repair. The different phases of mitosis is explained on the next page.
- Explain the need for cytokinesis in cell division
Cytokinesis is the division of the cytoplasm cell that usually accompanies a nuclear division. Although mitosis divides a nucleus into two new nuclei, cytokinesis ensures that each new nucleus is embedded in cytoplasm containing essential organelles and surrounded by a cell membrane.
S- Shorten chromosomes
T- Thicken
R- Replicate
E- Equator (line up)
S- separate (chromosomes pull apart, nucleus divides)
S- Split
