Chapter 2

cell membrane

regulates the passage of substances into and out of the cell

What molecules make up the cell membrane?

lipids and proteins

types of lipids

phospholipidscholesterol glycolipids

phospholipids

bilayer with hydrophilic heads on the outside and hydrophobic heads on the inside

amphipatic

both hydrophilic and hydrophobic

integral proteins

span the cell membrane and can form channels, transporters, receptors, while others are enzymes

peripheral proteins

attached to either the outer or inner surface of the cell membrane & form cytoskeletal anchors or act as enzymes

functions of a cell membrane

Communication Shape & protectionSelective permeability

maintenance of electrochemical gradient

the cell membrane creates both a chemical and electrical gradient across the membrane

What kind of entities contribute to the development of the electrical gradient across the membrane?

ions and other charged molecules

simple diffusion

Movement of molecules from a region of high concentration to an area of low concentration: does not require an input of energy, a cell membrane, or transport/carrier proteins

facilitated diffusion

Movement of molecules from a region of high concentration to an area of low concentration: does not require an input of energy, but does require transport/carrier proteins in the cell membrane

osmosis

Movement of water molecules or solvent molecules from a region of high water concentration to an area of low water concentration: does not require an input of energy, does not require pores in the cell membrane

active transport

Movement of molecules from a region of low concentration to an area of high concentration: does require and input of energy & transport/carrier proteins in the cell membrane

endocytosis

Transport of large molecules into the cell due to the �engulfing� action of the cell membrane & the subsequent formation of a membrane bound vesicle

Phagocytosis

�cellular eating� of solid matter

pinocytosis

�cellular drinking� of predominantly extracellular fluid

Exocytosis

Reverse of endocytosis - secretory vesicles formed within the cell fuse with the cell membrane, emptying their contents into the extracellular environment

Receptor-mediated endocytosis

specific pathway in which a molecule must bind to a specific receptor in the cell membrane to initiate an endocytotic event. Once within the cell, the receptors & molecules separate with the receptors returning to the cell membrane, while the specific molecules are processed

cytoplasm

all cellular contents between the cell membrane & the nucleus - it includes the cytosol, organelles

cytosol

thick fluid composed of 75% - 90% water with the remaining composed of soluble & insoluble molecules & ions

organelles

organs" of cells that have specific functions

nucleus

�Control center� of a cell, contains hereditary material (DNA) arranged as genes on chromosomesSurrounded by a double-membrane nuclear envelope which contain nuclear pores to allow the movement of moleculesbetween the cytoplasm & nucleusContain nucleoli for the assembly of ribosomes necessary for protein synthesis

ribosomes

Composed of ribosomal RNA (rRNA) & proteins Sites for protein synthesis May be free-floating in the cytoplasm or bound to endoplasmic reticulum

endoplasmic reticulum

Smooth ER is continuous with the nuclear envelope & is involved in Reticulum (ER) lipid metabolism & detoxification Rough ER has ribosomes attached to it & is involved in modification, storage, & transportation on proteins

golgi complex

Composed of flattened, stacked sacs called cisternae It processes, sorts, packages, & delivers proteins & lipids to the plasma membrane & forms lysosomes & secretory vesicles

protein route for exocytosis

ribosomes, RER, transport vesicles, Golgi complex, secretory vesicles, exocytosis

lysosomes

Contain digestive enzymes Digestion includes processes such as autophagy - digestion of organelles & autolysis - digestion of their host cell

peroxisomes

Contain oxidizing enzymes, like catalaseDetoxification function

mitochondria

Site for cellular respiration, production of ATP

cytoskeleton

Cellular shape & movement

flagella

Long, whip-like structure for movement

cilia

Short, hair-like structures for movement

centrioles

Forms the mitotic spindle for cell division & is involved in the formation & regeneration of flagella & cilia

cell cyle

interphase and mitosis

interphase

Composed of G1, S, & G2 phasesGrowth & preparation for division (mitosis) occur during the G phasesDNA replication occurs during the S phase

Mitosis

Prophase, Metaphase, Anaphase, & Telophase

prophase

chromosomal condensation, nuclear envelopedisintegration, and spindle formation

metaphase

�lining up� of the chromatid pairs on the metaphase (equatorial) plate

anaphase

chromatid separation

telophase

reverse of prophase