The ratio of the surface area of an object to its volume. In cells, as the ratio decreases, the exchange of materials becomes less efficient.
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Geometry Formulas
Mathematical formulas used to calculate the surface area and volume of cells.
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Organisms
Living things made up of cells that can be affected by the surface area-to-volume ratio concept.
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Heat-Exchange
The transfer of heat between an organism and its surroundings.
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Small Organisms
Organisms with a high surface area-to-volume ratio, resulting in more efficient heat-exchange with their surroundings.
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Larger Organisms
Organisms with a lower surface area-to-volume ratio, resulting in less efficient heat-exchange with their surroundings.
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Light Microscopes
Used to study stained or living cells and can magnify the size of an organism up to 1,000 times.
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Electron Microscopes
Used to study detailed structures of a cell that cannot be easily seen or observed by light microscopy.
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Prokaryotic Cells
A type of cell that lacks a nucleus and other membrane-bound organelles.
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Eukaryotic Cells
A type of cell that contains a nucleus and other membrane-bound organelles.
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Prokaryotic Cell
A type of cell that is smaller and simpler than eukaryotic cells. Examples include bacteria and archaea. The genetic material is one, circular DNA molecule found in the nucleoid. They have a cell wall made of peptidoglycans and a plasma membrane. Prokaryotes lack membrane-bound organelles.
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Eukaryotic cells
Cells that are more complex and have many smaller structures called organelles.
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Organelles
Small structures within eukaryotic cells that perform specific functions.
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Fungi, protists, plants, and animals
Examples of eukaryotes - organisms made up of eukaryotic cells.
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Prokaryotic cells
Cells that lack a nucleus and organelles, and are generally smaller and simpler than eukaryotic cells.
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Plasma membrane
The outer envelope of the cell, made up of mostly phospholipids and proteins, that regulates the movement of substances into and out of the cell.
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Semipermeable
A characteristic of the plasma membrane that allows certain substances to pass through while blocking others.
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Peripheral proteins
Proteins associated with the cell membrane that are loosely bound to the lipid bilayer and located on the inner or outer surface of the membrane.
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Integral proteins
Proteins firmly bound to the plasma membrane that are amphipathic, meaning they have both hydrophobic and hydrophilic regions.
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Transmembrane proteins
Integral proteins that extend all the way through the membrane, allowing them to transport substances across the membrane.
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Fluid-mosaic model
The arrangement of phospholipids and proteins in the plasma membrane, which is constantly in motion and resembles a mosaic.
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Nucleus
The largest organelle in the cell that directs cell activities and is responsible for the cell's ability to reproduce.
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DNA
The hereditary information that is organized into large structures called chromosomes and located in the nucleus.
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Chromosomes
The structures that organize DNA in the nucleus.
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Nucleolus
The visible structure within the nucleus where rRNA is made and ribosomes are assembled.
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Ribosomes
Sites of protein synthesis in the cell that manufacture all proteins required by the cell or secreted by the cell.
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Large Subunit
One of the two subunits that make up a ribosome, composed of ribosomal RNA (rRNA) and proteins.
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Small Subunit
One of the two subunits that make up a ribosome, composed of ribosomal RNA (rRNA) and proteins.
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Free Floating Ribosomes
Ribosomes that are not attached to the endoplasmic reticulum (ER) and are found in the cytoplasm of the cell.
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Attached Ribosomes
Ribosomes that are attached to the endoplasmic reticulum (ER) and are involved in protein synthesis for export out of the cell.
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Endoplasmic Reticulum (ER)
A continuous channel in the cytoplasm that provides mechanical support and transportation.
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Rough ER
The region of ER that compartmentalizes the cell and has ribosomes attached to it.
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Smooth ER
The region of ER that lacks ribosomes and makes lipids, hormones, and steroids, and breaks down toxic chemicals.
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Rough ER
An organelle involved in protein synthesis that has ribosomes attached to its surface.
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Golgi complex
An organelle that modifies, processes, and sorts proteins synthesized by the rough ER and packages them into vesicles.
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Vesicles
Little sacs that are used for packaging and transporting materials within the cell or to the plasma membrane.
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Plasma membrane
The outer layer of a cell that separates it from its environment and regulates the movement of materials in and out of the cell.
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Mitochondria
Organelles responsible for converting energy from organic molecules into ATP for the cell
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ATP
The most common energy molecule in the cell, produced by mitochondria through the conversion of organic molecules
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Lysosomes
Organelles containing digestive enzymes used to break down old organelles, debris, and large ingested particles.
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Apoptosis
Programmed cell death that involves the use of lysosomes.
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Vacuoles
Fluid-filled sacs that store water, food, wastes, salts, or pigments in plant cells.
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Peroxisomes
Organelles that detoxify various substances, producing hydrogen peroxide (H2O2) as a byproduct.
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Cytoskeleton
A network of protein fibers that determines the shape of a cell, including microtubules and microfilaments.
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Microtubules
Protein fibers that participate in cellular division and movement, made up of the protein tubulin.
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Microfilaments
Thin, rodlike structures composed of the protein actin, important for cell movement.
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Cilia and Flagella
Locomotive structures in single-celled organisms, with a beating motion that allows movement.
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Transport
Traffic of molecules across the cell membrane.
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Semipermeability
Property of the plasma membrane that allows only certain molecules to pass through.
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Facilitated transport
Assistance required for hydrophilic substances to pass through the hydrophobic central zone of the bilayer.
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Aquaporins
Channels that allow specific transport of water molecules across the membrane.
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Membrane proteins
Proteins that transport glucose and ions such as Na+ and K+ across the plasma membrane.
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Polarisation
Condition of the membrane as ions move across it.
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Passive Transport
The movement of substances across a cell membrane without the need for energy.
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Simple Diffusion
The movement of small non-polar molecules across a cell membrane without the need for assistance.
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Facilitated Diffusion
The movement of molecules across a cell membrane with the help of channel-type proteins.
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Osmosis
The movement of water across a cell membrane from an area of high water potential to an area of low water potential.
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Tonicity
The measure of osmotic gradients between a cell and its environment.
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Isotonic Solution
A solution with the same solute concentration as the cell.
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Hypertonic Solution
A solution with a higher solute concentration than the cell.
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Hypotonic Solution
A solution with a lower solute concentration than the cell.
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Water Potential
The measure of potential energy in water that describes the eagerness of water to flow from an area of high water potential to an area of low water potential.
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Pressure Potential
The component of water potential that measures the impact of pressure on water movement.
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Solute Potential
The component of water potential that measures the impact of solutes on water movement.
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Active Transport
Movement of molecules against the natural flow, powered by ATP, to maintain a concentration gradient.
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Sodium-Potassium Pump
A special protein that uses ATP to transport three sodium ions out of the cell and two potassium ions into the cell.
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Primary Active Transport
The direct use of ATP to transport molecules across the cell membrane.
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Secondary Active Transport
The use of energy captured from the movement of another substance flowing down its concentration gradient to actively transport something.
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Endocytosis
The process by which a portion of the cell membrane engulfs a substance to form a vacuole or vesicle.
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Pinocytosis
The type of endocytosis where the cell ingests liquids.
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Phagocytosis
The type of endocytosis where the cell takes in solids.
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Receptor-Mediated Endocytosis
The type of endocytosis that involves cell surface receptors that work in tandem with endocytic pits lined with clathrin.
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Bulk Flow
The one-way movement of fluids brought about by pressure, for example, the movement of blood through a blood vessel and the movement of fluids in xylem and phloem of plants.
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Dialysis
Diffusion of solutes across a selectively permeable membrane, used for blood filtration in kidney dialysis.