Sin título

Structures and Functions in Living Organisms

2.1 Level of organisation

• Organelle (e.g. cytoplasm): subcellular structures found within living cells
• Cell (e.g. muscle cell / palisade cell): basic structural unit of a living organism
• Tissue (e.g. muscle tissue / palisade tissue): group of similar cells working together to carry out a particular function
• Organ (e.g. stomach / leaf): group of different tissues working together to carry out a particular function
• Organ system (e.g. digestive system / shoot system): group of organs working together to carry out a particular function
• Organism (e.g. human / sunflower): a form of life

2.2-2.6 Cell Structure

• Nucleus: stores genetic material
• Cytoplasm - where chemical reactions take place
• Cell membrane: controls which substances can pass in and out of the cell
• Mitochondria: provides energy for the cell through respiration
• Ribosomes: site of protein synthesis
• Rigid cell wall (plants): provides support and structure
• Chloroplasts (plants): carry out photosynthesis with chlorophyll absorbing light from the sun
• Permanent vacuole (plants): contains cell sap (sugars, salts, water)

2.7-2.14 Biological molecules

• Carbohydrates: carbon, hydrogen, oxygen, starch and glycogen from simple sugars (e.g. glucose, fructose)
• Proteins: carbon, hydrogen, oxygen, nitrogen, proteins from amino acids
• Lipids: carbon, oxygen, hydrogen, lipids from 3 fatty acids + glycerol
• Glucose test: benedict's solution + water bath, blue to brick-red
• Starch test: iodine, brown to blue-black
• Protein test: biuret A + biuret B, blue to purple
• Fat test: ethanol + distilled water, colourless to milky white emulsion
• Enzyme: biological catalysts which increase the rate of reaction
• Enzymes + temperature: rate increases as temperature increases (particles have more kinetic energy so move faster and higher chances of collision), optimum 37
• Enzymes + high temperature: bonds are broken, active site changes shape, enzyme cannot bind with the substrate, enzyme is denatured
• Enzyme + temperature exp: heat starch to set temperature, add amylase, add iodine to each well after a minute, measure time till iodine stops turning blue-black
• Enzyme  + temperature exp: independent - temperature, dependent - rate of starch breakdown, control - volume of starch, concentration of starch
• Enzymes + pH: rate increases as neutrality increases (particles have more kinetic energy so move faster and higher chances of collision), optimum 7
• Enzymes + high pH: bonds are broken, active site changes shape, enzyme cannot bind with the substrate, enzyme is denatured
• Enzyme + pH exp: heat starch + amylase + pH solution, add a drop of the solution to each well with iodine after 10 seconds, measure time till solution turns orange
• Enzyme + pH exp: independent - pH, dependent - rate of starch breakdown, control - temperature, volume of starch, concentration of starch

2.15-2.17 Movement of substances into and out of cells

• Diffusion: the net movement of particles from an area of high concentration to an area of low concentration
• Diffusion example: single-celled organisms use diffusion to transport molecules into the body from the air as they have a large surface area : volume ratio
• Diffusion + concentration gradient: the greater the difference in concentration, the quicker the rate of diffusion (more particles are moving down the gradient)
• Diffusion + temperature: the greater the temperature, the quicker the rate of diffusion (particles have more kinetic energy so move faster and collide frequently)
• Diffusion + surface area : volume ratio: the greater the surface area, the quicker the rate of diffusion (particles have more space to move through)
• Diffusion + distance: the lower the distance particles need to travel, the quicker the rate of diffusion
• Active transport: the movement of particles from an area of low concentration to an area of high concentration using energy
• Active transport example: root hair cells use diffusion to take mineral ions from the soil using energy as cells have a higher concentration of mineral ions
• Diffusion exp: cut out 1cm cubed agar cube, place in HCl, remove + wash the cube, cut cube in half, measure diffusion distance, use different concentrations of HCl

2.18-2.33 Nutrition

• Carbohydrates: bread, pasta, potatoes, for energy
• Proteins: meat, fish, eggs, for growth and repair
• Lipids: butter, oil, cheese, for energy and insulation
• Fibre: vegetables, bran, for pushing food down the gut + preventing constipation
• Vitamin A: carrots, for vision
• Vitamin C: citrus fruits, for absorbing iron + preventing scurvy
• Vitamin D: margarine, for absorbing calcium
• Calcium: milk, for bone and teeth strength + preventing rickets
• Iron: red meat, for haemoglobin + preventing anaemia
• Water: water, juice, milk, for cell reactions to take place
• Age: energy requirements increase when approaching adulthood then decreases as adults age
• Activity levels: energy requirements increase because you need energy for movement
• Pregnancy: energy requirements increase to support growth of the foetus
• Mouth: mechanical when teeth break down food pieces, chemical when amylase breaks down starch, salivary glands produce saliva to lubricate the food bolus
• Oesophagus: tube from mouth to stomach, bolus moves down due to wave-like contractions (peristalsis) which squeeze the food down
• Pancreas: produces carbohydrates, protease and lipase and secretes these enzymes into the stomach and small intestine
• Stomach: pepsin breaks down proteins, hydrochloric acid kills bacteria, muscular walls churn food
• Liver: produces bile (alkaline) to neutralize HCl and to emulsify fat which increases surface area and it is broken down quicker, stored in gall bladder
• Small intestine: enzymes break down food, molecules diffuse into the bloodstream via the villi, bile enters via the bile duct
• Villi: thin walls decreases diffusion distance, rich capillary network to carry digested food, microvilli to increase surface area, small intestine is long
• Large intestine: absorbs water, produces faeces, faeces are stored in the rectum, faeces are removed through the anus
• Carbohydrates: starch to maltose by amylase, maltose to glucose by maltase, broken down in mouth + small intestine
• Proteins: proteins to amino acids by proteases, broken down in stomach + small intestine
• Lipids: lipids to glycerol + 3 fatty acids by lipases, broken down in small intestine
• Energy exp: measure temperature of cold water, measure mass of food sample, heat food till it catches fire, put sample under water, measure temperature of water
• Energy exp: independent - food sample, dependent - temperature rise, control - volume of water, distance from food to calorimeter
• Energy equation: Energy transferred (J) = Temperature increase (degrees C) x Mass (g) x 4.2 (J/g/degrees C)

2.34-2.39 Respiration

• Respiration: release of energy within the cell either aerobically or anaerobically
• Aerobic: Glucose + Oxygen > Water + Carbon Dioxide (C6 H12 O6 + O2 > CO2 + H2O), uses oxygen, full breakdown of glucose, releases energy used to make ATP
• Anaerobic (animals): Glucose > Lactic acid, very low energy release, partial breakdown of glucose, very less ATP produced
• Anaerobic (plants + fungi): Glucose > Ethanol + Carbon Dioxide (C6 H12 O6 > C2 H5 OH + CO2), low energy release, partial breakdown of glucose, less ATP produced
• Energy: ATP is used for other processes in the cell (e.g. active transport, protein synthesis, muscle contraction)
• Evolution of CO2 exp: flask 1 limewater, flask 2 germinating seeds, flask 3 limewater, connect flasks with capillary tubes
• Evolution of CO2 exp: flask 1 remains clear - air doesn't have enough CO2 to affect limewater, flask 3 goes cloudy - organisms are respiring + producing CO2
• Evolution of CO2 exp: independent - living or not living, dependent - colour of limewater in flask 3, control - temperature, volume and concentration of limewater
• Evolution of heat exp: flask 1 germinating seeds, flask 2 dead seeds, measure initial temperature, leave for few days, measure end temperature
• Evolution of heat exp: temperature will increase for live germinating seeds as they release heat from aerobic temperature
• Evolution of heat exp: independent - living or not living, dependent - temperature, control - number of seeds

2.40-2.50 Gas Exchange

• Ribs: bone cage surrounding the lungs to provide protection of internal organs
• Intercostal muscles: muscles found between the ribs that control inhalation and exhalation
• Diaphragm: dome at the bottom of the thorax that changes the pressure to control inhalation and exhalation
• Trachea: the windpipe where air enters the thorax and flows to the lungs
• Bronchi: two tubes to each lung
• Bronchioles: smaller tubes that connect to the alveoli
• Alveoli: tiny air sacs that are the place of gas exchange
• Pleural membranes: found on the outside of the lungs to lubricate them (reduce friction while breathing)
• Inhalation: intercostal muscles contract, the ribcage moves up and out, the diaphragm contracts downwards, pressure decreases, air moves in
• Exhalation: intercostal muscles relax, the ribcage moves down and in, the diaphragm relaxes upwards, pressure increases, air moves out
• Alveoli: thin walls so short diffusion distance, large surface area so more space for molecules to travel through, good blood supply so maintains the concentration
• Exercise exp: We'll change whether the student has exercised or not. The students will be of the same age, gender, size and general fitness. We'll repeat the investigation several times to ensure our results are reliable. We'll measure the change in breathing rate. Immediately after exercise and each minute for the subsequent 5 minutes. We'll control the type of exercise carried out, the temperature of the environment, the food intake of the students prior to the investigation.

2.51-2.69 Transport

• Unicellular organisms: diffusion to transport molecules, high surface area to volume ratio, more space for molecules to travel at once + short diffusion distance
• Multicellular organisms: transport system to transport molecules, low surface area to volume ratio, less space for molecules to travel at once + larger distance

2.83-2.92 Coordination + control

• Homeostasis: maintenance of constant internal environment (stimulus, receptor, coordinator)
• Positive phototropism: shoot tip accumulates more auxin + cells elongate faster on shaded side, shoot bends towards the light
• Negative phototropism: root accumulates more auxin on shaded side, auxin inhibits cell elongation, root bends downwards
• Positive geotropism: root accumulates more auxin on lower side, auxin inhibits cell elongation, root bends downwards
• Negative geotropism: shoot tip accumulates more auxin + cells elongate faster on lower side, shoot bends upwards
• Conjunctive: lubricates and protects the surface of the eye
• Sclera: tough outer layer that protects the eye
• Cornea: transparent layer that refracts light into the eye
• Iris: controls the diameter of the pupil + how much light enters the eye
• Pupil: the hole in the middle
• Lens: focuses light onto the retina
• Retina: light-sensitive part covered in in rods and cones
• Bright light: circular muscle contracts, radial muscle relaxes, smaller pupil, less light in
• Dim light: circular muscle relaxes, radial muscle contracts, larger pupil, more light in
• Distant objects: ciliary muscle relaxes, suspensory ligaments contract, thin lens, less refraction of light
• Near object: ciliary muscle contracts, suspensory ligaments slacken, fat lens, more refraction of light
• Adrenaline: fight or flight response (adrenal glands)
• Insulin: blood sugar levels (pancreas)
• Glucagon: blood sugar levels (pancreas)
• Testosterone: male sexual development (testes)
• Progesterone: female sexual development (ovaries)
• Oestrogen: female sexual development (ovaries)
• ADH: water levels (pituitary gland)
• FSH: menstrual cycle (pituitary gland)
• LH: menstrual cycle (pituitary gland)