IB BIO SL GLOSSARY

Cell theory

theory that states that all organisms are composed of cells, and that all cells come from pre-existing cells, smallest compoenent of life

Growth

an increase in physical size.

Homeostasis

the process in which an organism regulates activities within cells and their bodies to keep conditions stable.

Reductionism

an approach to science that holds that a complex system can be best understood as the sum of its parts, and that variables can be studied in isolation.

Histone

a protein associated with DNA that plays a role in gene expression and the packing of DNA.

Palisade mesophyll

photosynthetic tissue below the epidermis in a leaf.

Resolution

the ability to see adjacent objects or structures as distinct from each other.

Peripheral proteins

proteins on the surface of the plasma membrane.

Permeability

the rate of passive diffusion of molecules through the membrane, which depends on the electric charge, size, and polarity of the molecule.

Endocytosis

the process in which the cell takes in materials from the outside by infolding of the membrane to form a vesicle.

Semi-permeable membrane

membrane that allows some substances to diffuse through but not others. Transport pumps proteins in the plasma membrane that use ATP to move substances across the membrane

Covalent bonds

a chemical bond formed by the sharing of one or more electrons, especially pairs of electrons, between atoms.

Peptide bonds

a covalent bond that joins amino acids, at the carboxyl group of one amino acid to the amino group of the other amino acid, with the release of a molecule of water.

Saturated fat

a fatty acid with all potential hydrogen binding sites filled.

Protein

organic molecule composed of polymers of amino acids joined together by peptide bonds and taking a particular three-dimensional shape.

Rhodopsin

a visual pigment consisting of retinal and opsin.

Catalase

an enzyme found in the blood, and in most living cells, that catalyses the decomposition of hydrogen peroxide into water and oxygen.

Degenerate code

there are more codons (64) than there are amino acids to be coded, so most amino acids are coded by more than one code.

Chromosome

A structure within the cell that bears the genetic material

Genome

The total genetic material of an organism

Haemoglobin

The oxygen-carrying pigment of red blood cells

Down syndrome

A genetic disease resulting from having an extra chromosome 21

Naked DNA

The DNA in prokaryotic cells that is not associated with proteins

Diploid

A cell containing two sets of chromosomes

Clones

A group of genetically identical cells or individuals

Mesocosm

Experimental tool that brings a small part of the natural environment under controlled conditions

Sustainable communities

Communities capable of being maintained without exhausting resources or causing ecological damage

Trophic level

Position in a food chain occupied by organisms with similar feeding modes

Fossilised organic matter

Remains of organisms preserved in fossil form

Ozone (O3)

Gas made up of three atoms of oxygen

Selective breeding

the intentional breeding of organisms with desirable traits in an attempt to produce offspring with similar desirable characteristics or with improved traits.

Platelet

a small fragment of red blood cells found in the blood plasma that functions to promote blood clotting.

Thrombin

a protease in blood that facilitates blood clotting by converting fibrinogen to fibrin.

Inspiration

when the air moves from higher pressure (outside the body) to the lower pressure (inside the lungs).

Spirometer

an instrument for measuring the volume of air entering and leaving the lungs.

Surfactant

a substance composed of lipoprotein that is secreted by the alveolar cells of the lung and serves to maintain the stability of pulmonary tissue by reducing the surface tension of fluids that coat the lung.

Cholinergic synapse

a junction between two cells that employs acetylcholine as its transmitter substance.

Repolarization

the change in membrane potential that returns the membrane potential to a negative value after the depolarization phase of an action potential.

Resting potential

the potential difference between the two sides of the membrane of a nerve cell when the cell is not conducting an impulse.

Metabolic rate

the chemical processes occurring within a living cell or organism during a certain period.

tympanic membrane (eardrum)

the membrane at the end of the ear canal that relays vibrations into the middle ear

malleus (hammer)

a small bone in the middle ear that transmits vibrations of the eardrum to the incus.

Differentiation

the alteration of a cell's morphology and physiology through changes in gene expression.

Emergent property

a property of a system that emerges from the interaction of the elements of the system.

Gene expression

the synthesis of a functional gene product, often protein, but also rRNA, tRNA, or snRNA.

Magnification

ratio of image size to actual size.

Metabolism

the sum of all of the chemical reactions that occur within an organism or within a cell.

Objective lens

the part of the microscope that gathers light from the specimen and focuses it to produce a real image.

Paramecium

genus of single-celled ciliated organisms.

Response

in behavioural science, the behaviour that is the consequence of a stimulus.

Scale bar

a means of visually indicating the magnification of an image.

Stargardt's disease

a degenerative eye disease that has been the target of stem cell research.

Stem cell

a relatively undifferentiated cell that can give rise to other types of cells and retains the ability to divide.

Surface area to volume ratio

a variable that decreases as cells grow, so that it sets a limit to the size of cells.

System

a level of organization that emerges due to the interaction of elements.

Tissue

a group of cells with a common function and structure.

70S

the size of prokaryotic ribosomes.

80S

the size of eukaryotic ribosomes.

Archaea

a domain of prokaryotes.

Binary fission

method of prokaryotic cell division.

Cell wall

non-living carbohydrate-based extracellular material.

Compartmentalization

seen in eukaryotes; consequence of organelles being membrane-bound.

Endoplasmic reticulum (ER)

site of synthesis of proteins destined for export or for secretion.

Eukaryote

organisms with membrane-bound nuclei.

Exocrine glands

glands that secrete their products into ducts.

Extracellular matrix

a network of material that is secreted by cells that serves to support, strengthen, and organize cells.

Flagellum

a relatively long extension of the cell used in locomotion.

Golgi body

a eukaryotic organelle that modifies proteins after translation.

Lysosome

a cellular organelle involved in cellular digestion.

Nucleoid

a region of the prokaryotic cell where DNA is located.

Nucleus

membrane-bound organelle found in eukaryotes that contains DNA; it is the site of replication and transcription.

Organelle

a sub-cellular structure or membrane-bound compartment with a distinct structure and function.

Pilli

extensions of the prokaryotic cell surface membrane used for reproduction.

Prokaryote

category of a cell without a membrane-bound nucleus: archaea and bacteria.

rough ER

ER with ribosomes attached.

Soft ER

endoplasmic reticulum that synthesizes new membrane and does not have ribosomes attached.

Scanning electron microscope

an electron microscope that generates a three-dimensional image.

Transmission electron microscope

an electron microscope that produces two-dimensional images.

Ultrastructure

the detailed structure of a biological entity.

Amphipathic

molecule that has hydrophobic and hydrophilic regions.

Cholesterol

a lipid that prevents the membrane from becoming too and also prevents it from crystalizing.

Davson-Danielli model

model of the cell membrane in which the phospholipid bilayer is between two layers of protein.

Electron carriers

proteins arranged in chains on the membrane to allow the transfer of electrons from one carrier to another.

Fluid mosaic model

a model conceived by S.J. Singer and Garth Nicolson in 1972 to describe the observed structural features of biological membranes.

Fluidity

refers to the viscosity of a lipid bilayer of the membrane that allows it to change shape.

Glycoproteins

proteins that contain oligosaccharide chains.

Hormone-binding sites

proteins on the outside of the membrane that allow specific hormones to bind.

Integral proteins

proteins embedded in the phospholipid bilayer.

Phospholipid bilayer

two layers of phospholipids arranged so that their hydrophobic tails are projecting inwards while their polar head groups are on the outside surfaces.

Singer-Nicholson model

current model of membrane structure that incorporates a fluid mosaic structure in a discontinuous lipid bilayer.

Transport pumps

proteins in the plasma membrane that release energy and use it to move substances across the membrane.

Active transport

movement of substances across membranes using energy in the form of ATP.

ATP (adenosine triphosphate)

The energy molecule.

Concentration gradient

a gradient resulting from an unequal distribution of ions across the cell membrane.

Diffusion

Diffusion is the net movement of molecules from a region of high concentration to a region of low concentration

Exocytosis

the process in which the cell releases materials to the outside by discharging them as membrane-bounded vesicles that pass through the cell membrane.

Facilitated diffusion

diffusion through a membrane that requires proteins.

Hypertonic

a more concentrated solution relative to another fluid.

Hypotonic

a less concentrated solution relative to another fluid.

Isotonic

refers to two solutions having the same osmotic pressure across a semipermeable membrane.