Cell Transport and Biological Molecules Vocabulary

Vocabulary flashcards covering cellular transport mechanisms (diffusion, osmosis, active transport) and biological molecules (carbohydrates, proteins, lipids, DNA, and food tests) based on Edexcel GCSE Biology source materials.

Diffusion

The movement of molecules from a region of higher concentration to a region of lower concentration down a concentration gradient as a result of their random motion and kinetic energy.

Concentration Gradient

The difference in the concentration of a substance between two regions.

Equilibrium

The state reached when molecules become evenly distributed throughout an available space, resulting in no net movement in any direction.

Partially Permeable Membrane

A membrane that allows certain smaller molecules to pass through while preventing larger molecules from crossing.

Water Potential ($\Psi$)

The measure of the tendency of water molecules to move from one region to another, measured in kilopascals ($\text{kPa}$).

Pure Water Water Potential

The highest possible water potential value, which is equal to $0\,\text{kPa}$ at atmospheric pressure.

Osmosis

The movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) across a partially permeable membrane.

Plasmolysis

The shrinkage of a plant cell's protoplast away from its cell wall when placed in a hypertonic solution due to water loss by osmosis.

Turgid

The firm state of a plant cell when water enters it by osmosis in a hypotonic solution, causing the vacuole to expand and push against the cell wall.

Crenation

The shrinking or shriveling of an animal cell when water leaves the cell after being placed in a hypertonic solution.

Cytolysis

The swelling and bursting of an animal cell placed in a hypotonic solution due to water intake in the absence of a supporting cell wall.

Active Transport

The movement of particles across a cell membrane from a region of lower concentration to a region of higher concentration against a concentration gradient, requiring energy (ATP) and carrier proteins.

Carrier Protein

A protein embedded in the cell membrane that binds to specific molecules and uses energy released during cellular respiration to transport them across the membrane against a concentration gradient.

Monomer

A single basic molecular subunit that chemically binds with other identical or similar subunits to form a larger polymer.

Polymer

A large complex molecule composed of two or more repeating monomer units chemically joined together.

Glycosidic Bond

The type of chemical bond that joins simple sugar monomers together to form carbohydrates such as starch and glycogen.

Peptide Bond

The chemical bond that links individual amino acid monomers together to build proteins.

Ester Bond

The chemical bond formed between a glycerol molecule and fatty acid molecules in lipids.

Benedict's Test

A chemical test for reducing sugars where heating a sample with Benedict's reagent produces a color change from blue to green, yellow, orange, or red depending on concentration.

Iodine Test

A chemical test used to identify starch, which produces a characteristic blue-black color upon adding iodine solution.

Biuret Test

A chemical test for proteins where adding equal amounts of $\text{NaOH}$ and a few drops of $1\,\%\,\text{CuSO}_4$ solution to a sample turns the solution from blue to purple or mauve in the presence of peptide bonds.

Ethanol Test

A test for fats and oils where the sample is dissolved in ethanol and mixed with water to form a cloudy white emulsion if lipids are present.

DCPIP Test

A quantitative test for Vitamin C where a blue DCPIP solution turns colorless as it is reduced by Vitamin C.

Nucleotide

The monomer of nucleic acids like DNA, consisting of a deoxyribose sugar, a phosphate group, and a nitrogenous base.

Chargaff's Base Pairing Rule

The rule stating that in DNA, adenine always pairs with thymine (A-T) and cytosine always pairs with guanine (C-G) via hydrogen bonds.

Double Helix

The double-stranded, twisted ladder structure formed by two complementary strands of DNA.

Euchromatin

Loosely packed, active chromatin within eukaryotic cells.

Heterochromatin

Densely packed, inactive chromatin within eukaryotic cells.

Codon

A specific sequence of three nucleotides in nucleic acids that corresponds to a particular amino acid during protein synthesis.