Level 2 Life Processes at a Cellular Level

Active site

A region on an enzyme that binds to a substrate during a reaction.

Active transport

The movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.

Aerobic respiration

An enzyme-controlled process which requires oxygen to produce energy from the breakdown of glucose.

Anaerobic respiration

An enzyme-controlled process in the absence of oxygen in which glucose is broken down forming lactic acid to produce energy.

ATP (Adenosine Triphosphate)

The molecule in all living cells that stores and releases energy for cellular processes.

Catalyst

A substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

Cell

Basic building block/unit of life. The smallest structural and functional unit of an organism. Typically microscopic.

Cell cycle

The sequence of events a cell undergoes from its formation to its division into two daughter cells.

Cell membrane

(see plasma membrane)

Cell wall

A rigid structure that provides support to plant cells and is composed of cellulose.

Channel protein

Transmembrane proteins that form pores in the cell membrane, allowing specific molecules or ions to pass through by diffusion.

Chlorophyll

A green pigment essential for photosynthesis in plants, algae, and some bacteria. It absorbs light energy, particularly in the blue and red regions of the spectrum, which is then used to convert carbon dioxide and water into glucose (sugar) and oxygen.

Chloroplast

Organelle found in the cytoplasm of photosynthetic organisms, which is the site of photosynthesis.

Coenzyme

Another name for an organic cofactor.

Cofactor

A substance that many enzymes need to work properly. They can be ions (such as Mg2+, Cu2+, Fe2+) or organic molecules (such as coenzyme Q10, haem, etc).

Cristae

(singular - crista) The folds in the inner mitochondrial membrane where the electron transfer chain occurs.

Cytoplasm

A jelly-like substance found in cells containing all the organelles, excluding the nucleus.

Cytosol

The liquid or fluid component of the cytoplasm.

Denature

To alter the shape of a complex molecule (such as a protein or a nucleic acid) by breaking the bonds holding it together. This renders it unable to carry out its function.

Deoxyribonucleic acid

Full name for DNA. Present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.

Diffusion

The passive movement of molecules or particles along a concentration gradient, or from regions of higher concentration to regions of lower concentration.

DNA replication

The biological process of creating two identical DNA molecules from one original DNA molecule.

Endoplasmic reticulum

Network of membranes found throughout the cytoplasm of cells which are involved in processing proteins (Rough ER) and lipids (Smooth ER).

Enzyme

A protein produced by a living organism which acts as a catalyst to speed up a specific biochemical reaction.

Eukaryote

A cell or organism that possesses a clearly defined nucleus.

Facilitated diffusion

Transport of substances across a membrane from an area of higher concentration to an area of lower concentration by means of a carrier molecule.

Flaccid

A state where cells lack turgor pressure, meaning they are soft, limp, and lacking firmness.

G1 phase

The stage of interphase where the cell grows rapidly while performing routine metabolic processes. It makes proteins needed for DNA replication and copies some of its organelles in preparation for cell division. A cell typically spends most of its life in this phase.

G2 phase

The stage of interphase where the replicated chromosomes are checked for errors, and any repairs required are made. The cell also makes additional proteins, organelles and final preparations to divide.

Golgi body

Network of folded/flattened membranes found in the cytoplasm of cells which are involved in packaging molecules like proteins for secretion.

Thylakoids

Stacks of flattened, membranous sacs found within chloroplasts. Where the light-dependent reactions of photosynthesis occur.

Hypertonic solution

A solution with a comparatively higher concentration of solutes compared to another.

Hypotonic solution

A solution with a comparatively lower concentration of solutes compared to another.

Induced fit model

The model of enzyme action that states that since enzymes are flexible structures, binding of the substrate to the enzyme alters the configuration of both the enzyme and the substrate, providing a better fit.

Inhibitors

Poisons that bind to, or distort, the active site and prevent the enzyme from catalysing reactions.

Interphase

The phase of the cell cycle in which cells grow, accumulating nutrients needed for mitosis and replicating their chromosomes.

Isotonic solution

A solution with the same concentration of solutes compared to another.

Lock and key model

The model of enzyme action that states the substrate fits into the enzyme's active site (like a key fitting into a lock) to form an enzyme-substrate complex.

Lysosome

Sac like organelles which contain digestive enzymes. They are involved with the digestion of cellular invaders (e.g. Bacteria) and waste molecules.

Mitochondrial Matrix

The innermost compartment of a mitochondrion, enclosed by the inner mitochondrial membrane. It contains various enzymes and other essential components involved in cellular respiration and ATP production.

Mitochondria

Organelles found in the cell's cytoplasm which are the site of cellular respiration.

Mitosis

A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent cell.

Nucleotide

The basic building block of DNA. It is made up of a base, a sugar, and a phosphate group.

Organelle

An organised and specialised structure found within cells.

Osmosis

The movement of water molecules from an area of high concentration to an area of low concentration through a semi-permeable membrane.

Palisade layer

A layer of columnar cells rich in chloroplasts found beneath the upper epidermis of leaves. Where most photosynthesis occurs.

Passive transport

Transport of a substance across a cell membrane by diffusion; expenditure of energy is not required.

Phagocytosis

The process of engulfing and ingestion of particles by the cell.

Photosynthesis

The enzyme-controlled process that occurs in plants using energy from sunlight to convert carbon dioxide and water into glucose and the waste product oxygen.

Plasma membrane

The cells outer membrane. Formed from a double layer (bilayer) of phospholipids and associated proteins.

Pinocytosis

A process of taking in fluid into the cell by forming narrow channels through its membrane that pinch off into vesicles.

Prokaryote

A single-celled organism whose cell lacks a nucleus and other membrane-bound organelles.

Protein

A large molecule comprised of one or more long chains of amino acids folded into a specific shape.

Ribosome

Small organelles found in the cytoplasm or on the surface of endoplasmic reticulum which are the site of protein synthesis.

S phase

The stage of interphase where the chromosomes are replicated.

Semi-conservative replication

The name given to the DNA replication process to describe the fact that each new DNA double helix consists of one original (parental) strand and one newly synthesised strand.

Semi-permeable membrane

A membrane that allows some substances to pass through it but not others.

Stroma

The fluid filling up the inner space of the chloroplasts, which encircles the grana and the thylakoids. Where the light-independent reactions of photosynthesis occur.

Substrate

A molecule upon which an enzyme acts.

Tissue

A group of cells that have a similar structure and that function together as a unit.

Tonicity

Describes the ability of a solution to affect the volume of a cell by osmosis. It refers to the relative concentration of solutes (dissolved substances) on either side of a cell membrane.

TurgidSs

Refers to cells or tissues that are swollen from water uptake.

Solution

The final uniform mixture created when the solute has thoroughly dissolved into the solvent.

Solute

The substance that gets dissolved into a liquid in a solution

Solvent

A liquid substance capable of dissolving other substances