AS91156 Cells Vocabulary

Activation energy

The energy required for a chemical reaction to occur.

Active site

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

Active transport

Movement of ions or molecules across a membrane by proteins, against a concentration gradient. Requires energy.

Aerobic Respiration

An enzyme-controlled process that occurs in the mitochondria and produces energy in the form of ATP in the presence of oxygen. Glucose + oxygen → carbon dioxide + water + energy (36 ATP).

Allele

An alternative form of a gene.

Anabolic

Reactions that join substrates together.

Anaerobic respiration

Glucose is broken down in the absence of oxygen into lactic acid and ATP in the cytoplasm. Glucose-> Lactic acid + 2ATP.

Anti-parallel

Describes how the two backbones of DNA run in opposite directions - one 3'-5' and the other 5'-3'. Explains why there is a leading strand and a lagging strand in DNA replication.

ATP (Adenosine Triphosphate)

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

Autosomes

Chromosomes other than those concerned with sex determination.

Catabolic

Reactions that break molecules down. For example, digestion.

Cell membrane

Semi-permeable, phospholipid bilayer that controls entry and exit of substances into and out of cells.

Cell wall

Hard structure made of cellulose that gives plant cells support.

Centrioles

A pair of structures in animal cells involved in making the spindle during cell division.

Centromere

The region where two sister chromatids are joined and attach to the spindle during cell division.

Characteristics

A feature of an organism (trait/phenotype).

Chlorophyll

A green pigment essential for absorbing light energy during photosynthesis.

Chloroplast

Organelle in some plant cells that is involved in photosynthesis

Chromosome

A unit of genetic material made of DNA wound around histone proteins.

Coenzyme

An organic molecule that is necessary for an enzyme to function and participates in the chemical reaction but is left unchanged after the reaction.

Co-factor

A metal ion that completes an enzyme's active site.

Compartmentalisation

In both mitochondria and chloroplasts, specific chemical reactions are isolated by membranes from other reactions to increase the efficiency of the reaction.

Cristae (singular: crista)

The folds in the inner mitochondrial membrane increase the surface area where the electron transfer chain occurs.

Cytoplasm

Jelly-like material in the cells of plants and animals, composed of water, salts, and various organic molecules.

Denature

Where an enzyme, due to heat or pH, has its active site permanently altered so that substrates can no longer 'fit' the active site, and the biological reaction stops.

Diffusion

The random, passive movement of particles from an area of high concentration to an area of low concentration until they reach equilibrium.

DNA/Deoxyribonucleic acid.

Genetic material in the form of a double-stranded, helix shaped molecule containing the genetic code. Contains a deoxyribose sugar and phosphate backbone, and bases A,T,G,C.

DNA Replication

Process prior to cell division where DNA is copied so that new daughter cells will have the same genetic information.

Electron Transport Chain

Occurs in the cristae of the mitochondria. Hydrogen produced in the Krebs cycle is passed along a chain to form a large amount of ATP. Oxygen is required to pick up the hydrogen ions at the end to form water.

Endocytosis

The process by which cells take in substances from outside the cell by engulfing them in a vesicle. A form of active transport.

Endoplasmic reticulum

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

Enzyme

A globular protein which acts as a biological catalyst to speed up the rate of a chemical reaction in an organism.

Exocytosis

A vesicle membrane fuses with a cell membrane to expel its contents out of the cell.

Facilitated diffusion

Passive transport of substances through channel proteins across a membrane from an area of higher concentration to an area of lower concentration.

Flaccid

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

Fertilisation

The combining of the sperm and egg to form a single-celled zygote.

Gametes

Sex cells containing half the chromosomes of the parent.

Gene

A section of DNA that codes for a protein.

Genetic diversity/ variation

The total number of different alleles in the genetic makeup of a breeding population.

Glycolysis

Glucose is broken down in the cytoplasm without the presence of oxygen and two molecules of ATP are made.

Golgi apparatus

Organelle that processes and packages proteins into a usable form to be exported out of the cells.

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 shape of both the enzyme and the substrate, providing a better fit and, in so doing, reducing the activation energy for the reaction required.

Inhibitor

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

Ion pumps

A form of active transport where plasma membranes can pump ions against a concentration gradient. E.g. Na+ and K+.

Isotonic solution

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

Krebs cycle

A part of aerobic respiration where the product of glycolysis enters the matrix of the mitochondrion and undergoes a series of enzymatic reactions. Hydrogen is removed and carbon dioxide is excreted.

Lactic acid

A toxic compound produced in animals during anaerobic respiration.

Lagging strand

The daughter strand of DNA that is copied in segments called Okazaki fragments during DNA replication against the direction that the replication fork is moving, due to the anti-parallel nature of the DNA helix.

Large vacuole

Large, water-filled organelle within a plant cell cytoplasm.

Leading strand

The daughter strand of DNA that is copied continuously during DNA replication in the direction that the replication fork is moving.

Light-dependent reaction

Stage of photosynthesis that occurs in the thylakoid where water is split using light energy.

Light-independent reaction

Enymatic reactions that occur in the stroma of the chloroplast during photosynthesis that do not rely on energy from sunlight.

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.

Lysis

Cell membrane bursts due to excessively high water pressure.

Lysosome

Organelle containing digestive enzymes that will recycle chemicals and worn-out organelles.

Metabolism

All of the biochemical reactions happening in the cells of an organism.

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.

Meiosis

Cell division during sexual reproduction, where gametes are formed by halving the genetic information of the original cell and creating different combinations of alleles from the parents, introducing variation.

Mitochondrion

Organelle in animals and plants where respiration takes place to release energy for the cell.

Mitosis

Cell division for growth, repair, and maintenance in somatic cells, where one parent cell divides into two genetically identical daughter cells.

Nuclear membrane

Double-layered membrane with pores to allow transfer of substances between the nucleus and the cytoplasm.

Nucleus

An organelle that holds the chromosomes and controls cell activity.

Offspring

The resulting individuals of reproduction.

Okazaki fragments

The name of the lagging strand fragments made during DNA replication.

Organelle

An organised and specialised structure found within cells.

Osmosis

The passive diffusion of water from an area of higher water concentration to an area of lower water concentration, across a semi-permeable membrane.

Passive transport

Includes diffusion, osmosis, and facilitated diffusion. No energy is required for this to occur, and particles move from high to low concentration.

Phagocytosis

A form of active transport where particles are engulfed by a membrane that wraps around them, taking them into the cell in vesicles.

Pinocytosis

A form of active transport where liquid is engulfed by a membrane wrapping around it and taking it into the cell in vesicles.

Phenotype

How a gene is expressed as a protein/characteristic/trait.

Photosynthesis

The process of plants making glucose with light energy in the chloroplasts. Water + carbon dioxide -light-> glucose + oxygen

Plasmolysis

The irreversible process whereby plant cells lose too much water, causing the cell membrane to shrink away from the cell wall.

Respiration

Cellular process in the mitochondria where glucose is broken down to release energy in the form of ATP.

Ribosomes

Made of RNA and used in the production of proteins.

Rough E.R

Studded with ribosomes, this region produces proteins which are then transported to other organelles in the cell.

Semi-permeable membrane

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

Stomata

Microscopic openings on a leaf surface that permit gas exchange.

Stroma

The fluid that fills 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. (Reactant(s) of an enzyme-catalysed reaction).

Semi-conservative replication

New DNA molecules after replication consist of one parental strand from the original molecule and one newly synthesized daughter strand.

Sex chromosomes

Chromosomes involved in sex determination. E.g., X and y in mammals.

Sexual reproduction

The combining of genetic information from two parents resulting in genetically unique offspring.

Smooth E.R.

Involved with lipid metabolism, steroid synthesis, and detoxification in the liver.

Tonicity

It refers to the relative concentration of solutes (dissolved substances) on either side of a cell membrane in osmosis.

Turgid

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

Trait

A feature of an organism (protein/phenotype/characteristic).

Vacuole

These organelles store materials like water and starch granules. Larger and more numerous in plants.

Water potential

The concentration of water in a solution. It can be high, low, or in equilibrium.

Zygote

The fertilised egg/ovum.