Edexcel GCSE Biology Topic 1: Key Concepts Cells & Microscopy

Vocabulary flashcards covering Topic 1: Key Concepts in Biology from the Edexcel GCSE syllabus, including cell structures, microscopy, enzymes, food tests, and transport mechanisms.

Nucleus

The organelle in an animal cell that contains DNA and controls cell activity.

Mitochondria

The site of aerobic respiration within a cell where ATP production occurs.

Ribosomes

The cellular organelle that serves as the site for protein synthesis.

Cell wall

A plant cell structure made of cellulose that provides structural support.

Chloroplasts

Organelles in plant cells that contain chlorophyll and are the site of photosynthesis.

Vacuole

A plant cell organelle that stores cell sap and maintains turgor.

Chromosomal DNA

A single circular loop of DNA found free in the cytoplasm of bacterial (prokaryotic) cells.

Plasmid DNA

Small extra loops of DNA found in prokaryotic cells.

Flagella

A tail-like structure that enables movement in bacterial and sperm cells.

Prokaryotic cells

Cells that lack a nucleus and membrane-bound organelles; their DNA floats freely in the cytoplasm.

Acrosome

A specialized part of a sperm cell containing enzymes to digest the egg membrane.

Haploid nucleus

A nucleus containing $23$ chromosomes, characteristic of sperm and egg cells.

Ciliated epithelial cells

Cells with hair-like projections called cilia that beat to move mucus and pathogens away from the lungs.

Light microscope

A microscope that uses light, has a resolution of approximately $200\,nm$, and can view living cells.

Electron microscope

A microscope that uses electrons, has a resolution of approximately $0.1\,nm$, and reveals sub-cellular structures in far greater detail than light microscopes.

Magnification Formula

$$\text{Magnification} = \frac{\text{image size}}{\text{actual size}}$$

Microscope slide (wet mount) stains

Dyes like iodine or methylene blue added to specimens to make structures more visible under a microscope.

Milli (m)

A unit prefix representing a power of $10^{-3}$.

Micro ($\mu$)

A unit prefix representing a power of $10^{-6}$.

Nano (n)

A unit prefix representing a power of $10^{-9}$.

Pico (p)

A unit prefix representing a power of $10^{-12}$.

Standard Form (Cell size)

A way of writing small measurements, e.g., $0.000007\,m$ is expressed as $7 \times 10^{-6}\,m$.

Lock-and-key model

A model of enzyme action where the substrate fits into a specific, complementary active site to form an enzyme-substrate complex.

Enzyme specificity

The property of an enzyme to only catalyse one specific reaction because only the correct substrate fits the shape of its active site.

Denaturation

An irreversible change in the shape of an enzyme's active site, caused by high temperature or extreme pH, that prevents it from functioning.

Optimum temperature (Human)

The temperature at which human enzyme activity is highest, approximately $37\,^{\circ}\text{C}$.

Stomach enzyme optimum

The condition where pepsin functions best, which is at $pH\,2$.

Rate of enzyme activity

$$\text{Rate} = \frac{1}{\text{time (s)}}$$

Carbohydrases

Enzymes like amylase that break down starch into maltose and eventually glucose.

Proteases

Enzymes like pepsin and trypsin that break down proteins into amino acids.

Lipases

Enzymes that break down lipids into fatty acids and glycerol.

Benedict's test

A food test for reducing sugars that involves heating a sample with Benedict's solution until a brick-red precipitate forms.

Biuret test

A food test for proteins using potassium hydroxide and copper sulfate; a positive result is a mauve/purple colour.

Ethanol emulsion test

A food test for lipids involving ethanol and water; a positive result is the formation of a milky-white emulsion.

Calorimetry Formula

$$\text{Energy (J)} = \text{mass of water (g)} \times 4.2 \times \text{temperature rise ($^{\circ}\text{C}$)}$$

Diffusion

The passive movement of particles from an area of high concentration to an area of low concentration.

Osmosis

The passive movement of water molecules across a partially permeable membrane from high water potential to low water potential.

Active transport

The movement of substances from low to high concentration (against a gradient) using energy (ATP) and carrier proteins.

Percentage change in mass

$$\text{\% change} = \frac{\text{change in mass}}{\text{original mass}} \times 100$$