Curriculum Portal

neurologyYou need to know

• Animal cells contain a nucleus, cytoplasm, a cell membrane, mitochondria and ribosomes.
• The nucleus contains genetic material and controls the cell’s activities, the cytoplasm is where most chemical reactions happen, the cell membrane controls movement into and out of the cell, mitochondria are the site of aerobic respiration, and ribosomes are where proteins are made.
• Plant cells contain the same structures as animal cells and also have a cellulose cell wall, chloroplasts and a large permanent vacuole.
• The plant cell wall strengthens and supports the cell, chloroplasts contain chlorophyll for photosynthesis, and the permanent vacuole contains cell sap which helps keep the cell turgid.
• Bacterial cells are prokaryotic and usually contain cytoplasm, a cell membrane, a cell wall, circular DNA and plasmids, and some also have a slime capsule or a flagellum.
• Prokaryotic cells are smaller and simpler than eukaryotic cells, and they do not have a nucleus or other membrane-bound organelles.
• Eukaryotic cells, such as plant and animal cells, have genetic material enclosed in a nucleus.
• Unit conversions for microscopy are that 1 centimetre equals 10 millimetres, 1 millimetre equals 1000 micrometres, and 1 micrometre equals 1000 nanometres.
• Magnification is how many times larger the image is than the real object, and resolution is the ability to distinguish two points that are close together as separate points.
• The microscopy formula is `magnification = \frac{image\ size}{real\ size}`, so `image\ size = magnification \times real\ size` and `real\ size = \frac{image\ size}{magnification}`.
• Electron microscopes have a much higher magnification and a much higher resolution than light microscopes, so they can show much smaller sub-cellular structures in greater detail.
• Sperm cells are adapted for fertilisation by having a flagellum to swim, many mitochondria to release energy, and an acrosome containing enzymes to penetrate the egg cell.
• Nerve cells are adapted to carry impulses by having a long axon, branched connections to other cells, and an insulating sheath to speed up transmission, while muscle cells are adapted to contract by containing protein fibres and many mitochondria.
• Root hair cells are adapted for absorbing water and mineral ions by having a long extension that increases surface area and many mitochondria for active transport, xylem cells are dead and hollow with lignified walls for water transport and support, and phloem cells transport sugars using sieve tubes and companion cells.
• In multicellular organisms, specialised cells form tissues, tissues form organs, and organs work together in organ systems.
• Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient.
• Diffusion happens faster when the concentration gradient is steeper, the temperature is higher, the surface area is larger, and the diffusion distance is shorter.
• A large surface area to volume ratio increases the rate of exchange by diffusion because more surface is available compared with the amount of material inside the organism or cell.
• Exchange surfaces are adapted by being large, thin and well supplied: the small intestine has villi and microvilli, the lungs have many alveoli with a good blood supply, fish gills have filaments and lamellae, roots have many root hair cells, and leaves are broad with stomata and internal air spaces.
• Osmosis is the net movement of water molecules through a partially permeable membrane from a dilute solution to a more concentrated solution, plant tissue gains mass in a more dilute solution and loses mass in a more concentrated salt or sugar solution, and active transport moves substances from a lower concentration to a higher concentration against the concentration gradient using energy from respiration, such as mineral ion uptake by root hair cells and glucose absorption in the small intestine.

• Label diagrams of animal, plant and bacterial cells accurately and match each structure to its function.
• Convert measurements between centimetres, millimetres, micrometres and nanometres correctly by multiplying or dividing by 10 or 1000 as needed.
• Calculate magnification, image size or real size using `magnification = \frac{image\ size}{real\ size}` and keep all values in the same unit before substituting.
• Prepare a microscope slide by placing the specimen in a drop of water, adding stain if needed, and lowering the coverslip at an angle to avoid trapping air bubbles.
• Focus a light microscope by starting on the lowest magnification, using the coarse focus first, then the fine focus, and only moving to a higher magnification once the image is clear and centred.
• Draw a biological specimen from a microscope using clear single outlines, no shading, correct proportions, straight label lines and a labelled magnification scale bar.
• Relate the structures of specialised animal cells, plant cells and exchange surfaces to their functions using precise cause-and-effect statements.
• Calculate surface area to volume ratio from measurements and use the result to predict how quickly a cell or organism can exchange substances by diffusion.
• Plot and interpret a graph of plant tissue mass change in different salt or sugar concentrations using labelled axes and a sensible scale, and identify where there is little or no net mass change.
• Calculate percentage change in mass using `percentage\ change = \frac{final\ mass - initial\ mass}{initial\ mass} \times 100` and use the sign of the answer to show mass gain or mass loss.