PowerPoint 3b - The Cell copy

Selectivity

The property of the cell membrane to control what enters and exits the cell.

Selective permeability

A feature of cell membranes that allows some substances to pass through while blocking others.

Phospholipid

A molecule comprising a hydrophilic head and hydrophobic tails that make up cell membranes.

Phospholipid bilayer

A double layer of phospholipids that forms the basic structure of cell membranes.

Integral membrane proteins

Proteins that span the membrane and can be either alpha-helices or beta-sheets.

Peripheral proteins

Proteins that are associated with the outer or inner surface of the membrane, rather than spanning it.

Fluid mosaic model

A model that describes the structure of the plasma membrane as a mosaic of various proteins floating in or on the fluid lipid bilayer.

Passive transport

Movement of molecules across the cell membrane without the use of energy.

Active transport

Movement of molecules against their concentration gradient, requiring energy, often in the form of ATP.

Endocytosis

The process by which cells internalize substances, englobing them in vesicles.

Exocytosis

The process by which substances are expelled from a cell through vesicles that fuse with the membrane.

Peptidoglycan

A polymer that composes the bacterial cell wall, providing tensile strength.

Gram-negative bacteria

Bacteria characterized by a thin layer of peptidoglycan and an outer membrane containing lipopolysaccharides.

Gram-positive bacteria

Bacteria characterized by a thick peptidoglycan layer and the absence of an outer membrane.

Teichoic acids

Carbohydrate chains embedded in the peptidoglycan layer of Gram-positive bacteria that provide structural support.

Mycolic acids

Waxy substances found in the cell walls of some Gram-positive bacteria, providing protection against desiccation.

Cytoskeleton

An infrastructure within the cell made up of microfilaments, intermediate filaments, and microtubules that provides shape and support.

Flagella

Long, whip-like structures that aid in the locomotion of some bacteria.

Cilia

Short, hair-like structures that can help in cell movement or in moving substances across the cell surface.

Chloroplast

An organelle found in plants and some algae where photosynthesis occurs.

Mitochondria

Organelles known as the powerhouses of the cell, where aerobic cellular respiration occurs to produce ATP.

Extracellular matrix (ECM)

A complex network of proteins and carbohydrates outside the cells that provides structural and biochemical support.