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Biology · Edexcel Paper 1

Cells and Microscopy

How living things are built from cells: the structures inside animal, plant and bacterial cells, how microscopes show them, and how specialised cells are adapted to their jobs. It includes magnification calculations, the units used for tiny things and the core practical on using a microscope. Matches Edexcel GCSE Biology Topic 1, points 1.1 to 1.6 and 2.6. Every lesson is for both Combined Science and separate Biology, at Foundation and Higher.

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Key terms in this chapter

All 39, gathered from every lesson.

Eukaryotic cell
A cell whose genetic material is enclosed in a nucleus, such as an animal or plant cell.
Prokaryotic cell
A cell with no nucleus, whose genetic material lies free in the cytoplasm, such as a bacterium.
Nucleus
The part of a eukaryotic cell that contains the genetic material and controls the cell's activities.
Cytoplasm
The jelly-like substance inside a cell where most chemical reactions happen.
Cell membrane
A thin layer around the cell that controls what enters and leaves.
Cell wall
A rigid layer outside the cell membrane that supports the cell. In plants it is made of cellulose.
Plasmid
A small ring of DNA, separate from the main loop, found in bacteria.
Standard form
A way of writing very large or very small numbers as \(A \times 10^{n}\), where A is between 1 and 10.
Order of magnitude
A factor of ten. One order of magnitude is 10 times, two is 100 times.
Micrometre (µm)
One millionth of a metre, the unit most cells are measured in.
Sub-cellular structure
A structure inside a cell, such as the nucleus or a mitochondrion.
Mitochondria
Structures where aerobic respiration takes place, releasing energy for the cell.
Ribosome
A tiny structure where proteins are made.
Chloroplast
A structure in plant cells that contains chlorophyll and carries out photosynthesis.
Chlorophyll
The green pigment that absorbs light energy for photosynthesis.
Permanent vacuole
A space in a plant cell filled with cell sap.
Cell sap
A solution of sugars and salts stored in the permanent vacuole.
Cellulose
The strong material that plant cell walls are made of.
Aerobic respiration
A chemical reaction that uses oxygen to release energy from glucose.
Photosynthesis
The process in which plants use light to make glucose.
Magnification
How many times bigger an image is than the real object.
Resolution
The ability to see two points that are close together as separate. Also called resolving power.
Light microscope
A microscope that uses light and glass lenses to magnify a specimen.
Electron microscope
A microscope that uses a beam of electrons, giving much higher magnification and resolution.
Eyepiece lens
The lens you look through, usually ×10.
Objective lens
The lens just above the specimen, giving different magnifications.
Stage
The platform on which the slide is placed.
Stain
A coloured chemical, such as iodine, that makes parts of a cell easier to see.
Specimen
The object being looked at under a microscope.
Specialised cell
A cell that has a structure suited to its particular job.
Differentiation
The process by which a cell changes to become specialised.
Adaptation
A feature of a cell that helps it carry out its function.
Acrosome
The part of a sperm cell that contains enzymes to break into the egg.
Axon
The long extension of a nerve cell that carries impulses.
Myelin sheath
A fatty layer around a nerve cell's axon that insulates it and speeds up impulses.
Root hair cell
A cell on the surface of a root with a long projection that absorbs water and minerals.
Xylem
Tubes made of dead cells that carry water and mineral ions up a plant.
Phloem
Living tubes that carry dissolved sugars around a plant.
Tissue
A group of similar cells that work together to do a particular job.