GCSE Biology · 24 flashcards
Cell Biology and Microscopy Flashcards
24 cell biology terms every GCSE paper expects you to define
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All 24 GCSE Biology Cell Biology and Microscopy flashcards
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- Cell membrane
- A partially permeable barrier around every cell that decides which substances may pass in or out.For example: Oxygen crosses it freely, while large starch molecules cannot.
- Cytoplasm
- The jelly-like fluid filling a cell, where most chemical reactions of the cell take place.For example: Anaerobic respiration happens here rather than in an organelle.
- Nucleus
- The organelle holding the cell's DNA as chromosomes, controlling the cell's activities and how it develops.For example: A red blood cell loses its nucleus to make room for haemoglobin.
- Mitochondrion
- The organelle where aerobic respiration takes place, transferring energy from glucose for the cell to use.For example: Muscle and liver cells hold thousands because their energy demand is high.
- Ribosome
- A tiny structure in the cytoplasm where amino acids are joined together to build proteins.For example: Cells that secrete enzymes are packed with them.
- Cell wall
- A rigid outer layer made of cellulose in plants, giving the cell strength and stopping it bursting when full of water.For example: Present in plant and algal cells; absent from all animal cells.
- Chloroplast
- A green organelle containing chlorophyll, where a plant absorbs light energy to carry out photosynthesis.For example: Root cells have none because no light reaches them underground.
- Permanent vacuole
- A large sac of cell sap in a plant cell that pushes outwards to keep the cell firm and hold its shape.For example: When it loses water the plant wilts.
- Prokaryotic cell
- A cell with no nucleus, whose genetic material floats free in a single loop, plus small extra rings called plasmids.For example: All bacteria are prokaryotic.
- Eukaryotic cell
- A cell whose genetic material is enclosed inside a nucleus, and which contains membrane-bound organelles.For example: Plant, animal and fungal cells are all eukaryotic.
- Plasmid
- A small circular ring of DNA in a bacterium, separate from its main chromosome and often carrying antibiotic-resistance genes.For example: Genetic engineers use plasmids to carry genes into bacteria.
- Magnification
- How many times larger an image appears than the real object, calculated as image size divided by actual size.For example: An image 50 mm across of a 0.5 mm object is magnified 100 times.
- Resolution
- The smallest distance between two points that can still be seen as separate, which sets how much detail an image shows.For example: Raising magnification without resolution gives a bigger but blurrier image.
- Light microscope
- An instrument using light and glass lenses to view specimens, typically up to about 2000 times with limited resolution.For example: Enough to see a nucleus and chloroplasts, not ribosomes.
- Electron microscope
- An instrument using a beam of electrons instead of light, giving far higher magnification and resolution than a light microscope.For example: It revealed the internal structure of mitochondria for the first time.
- Differentiation
- The process by which a cell gains a specialised structure and function suited to one particular job.For example: A cell developing long extensions to become a nerve cell.
- Stem cell
- An undifferentiated cell able to divide repeatedly and develop into one or more different specialised cell types.For example: Bone marrow stem cells replace worn-out blood cells.
- Meristem
- A plant tissue at root and shoot tips whose cells keep dividing and can become any plant cell type throughout life.For example: Gardeners take cuttings from meristem tissue to clone a plant.
- Mitosis
- A type of division in which one cell copies its chromosomes and splits into a pair carrying exactly the same genes.For example: Healing a cut relies on it, as does replacing worn-out skin.
- Cell cycle
- The repeating sequence in which a cell grows, copies its DNA and organelles, then divides in two.For example: Chromosomes are duplicated before division begins, not during it.
- Diffusion
- The net movement of particles from a higher to a lower concentration, spreading them out without any energy input.For example: Carbon dioxide moving into a leaf through the stomata.
- Osmosis
- The movement of water across a partially permeable membrane, from a dilute solution towards a more concentrated one.For example: Root hair cells draw water from damp soil this way.
- Active transport
- Movement of substances against a concentration gradient, from low to high, which requires energy released by respiration.For example: Root hair cells absorbing mineral ions from dilute soil water.
- Surface area to volume ratio
- The surface area of an organism divided by its volume; as something grows larger this ratio falls, slowing exchange.For example: Why large animals need lungs while a single cell does not.