Unit 2: Cell Structure and Function (copy)

Cell

Life’s basic unit of structure and function.

Surface area-to-volume ratio

As cells increase in volume, this ratio decreases, making material exchange less efficient.

Prokaryotic cells

Simpler, smaller cells without membrane-bound organelles; examples include bacteria and archaea.

Eukaryotic cells

More complex cells with membrane-bound organelles, including fungi, protists, plants, and animals.

Plasma membrane

Outer envelope of the cell regulating substance movement; made mostly of phospholipids and proteins.

Fluid-mosaic model

Description of the plasma membrane's structure, comprising phospholipids and proteins.

Nucleus

Largest organelle in the cell that directs cellular activities and contains DNA.

Ribosomes

Sites of protein synthesis composed of rRNA and proteins.

Endoplasmic Reticulum (ER)

Continuous channel providing mechanical support and transportation within the cell.

Golgi complex

Modifies, processes, and sorts proteins for export from the cell.

Mitochondria

Power stations of the cell converting energy from organic molecules into ATP.

Lysosomes

Sacs carrying digestive enzymes to break down waste materials and old organelles.

Vacuoles

Fluid-filled sacs that store various substances; more prominent in plant cells.

Peroxisomes

Organelles that detoxify substances and break down hydrogen peroxide.

Cytoskeleton

Network of protein fibers maintaining cell shape and aiding movement.

Microtubules

Protein fibers involved in cellular division and movement.

Microfilaments

Thin structures composed of actin essential for cell movement.

Cilia and Flagella

Structures that provide locomotion to single-celled organisms.

Cell wall

Rigid layer outside the plasma membrane providing support in plant cells.

Chloroplasts

Organelles in plant cells that carry out photosynthesis and contain chlorophyll.

Passive transport

Movement of molecules across the membrane without energy input, includes diffusion.

Osmosis

Diffusion of water across a semipermeable membrane.

Tonicity

Describes osmotic gradients affecting cell water movement.

Active transport

Movement of substances against their concentration gradient, requiring energy.

Endocytosis

Process by which a cell engulfs large particles to bring them inside.

Pinocytosis

Type of endocytosis where the cell ingests liquids.

Phagocytosis

Type of endocytosis where the cell takes in solids.

Receptor-mediated endocytosis

Endocytosis that involves receptor proteins binding to ligands.

Exocytosis

Process of expelling waste or secretion products from the cell.

Bulk flow

One-way movement of fluids driven by pressure.

Dialysis

Diffusion of solutes across a selectively permeable membrane.

Hydrophobic

Refers to substances that do not mix with water, typically passing through the membrane easily.

Facilitated diffusion

Passive transport of substances across a membrane with the help of channel proteins.