Anatomy of a cellAnatomy of a cell

Chapter 3Chapter 3

Typical CellTypical Cell

Cells vary due to function. The Cells vary due to function. The typical cell exhibits the most typical cell exhibits the most important characteristics of many important characteristics of many distinctive cell types.distinctive cell types.

Examples of cell types:Examples of cell types:

Nerve cells, muscle cells, red blood Nerve cells, muscle cells, red blood cells, gland cells, and immune cellscells, gland cells, and immune cells

Functional Anatomy of CellsFunctional Anatomy of Cells

Cell structuresCell structures Plasma membranePlasma membrane——separates the cell from separates the cell from

its surrounding environmentits surrounding environment CytoplasmCytoplasm——thick gel-like substance inside of thick gel-like substance inside of

the cell composed of numerous organelles the cell composed of numerous organelles suspended in watery cytosol; each type of suspended in watery cytosol; each type of organelle is suited to perform particular organelle is suited to perform particular functions functions

NucleusNucleus——large membranous structure near large membranous structure near the center of the cellthe center of the cell

Cell MembranesCell Membranes

Each cell contains a variety of Each cell contains a variety of membranes:membranes: Plasma membrane Plasma membrane Membranous organellesMembranous organelles——sacs and sacs and

canals made of the same material as the canals made of the same material as the plasma membraneplasma membrane

Cell MembranesCell Membranes

Fluid mosaic modelFluid mosaic model——theory explaining theory explaining how cell membranes are constructedhow cell membranes are constructed Molecules of the cell membrane are Molecules of the cell membrane are

arranged in a sheetarranged in a sheet The mosaic of molecules is fluid; that is, the The mosaic of molecules is fluid; that is, the

molecules are able to float around slowlymolecules are able to float around slowly This model illustrates that the molecules of This model illustrates that the molecules of

the cell membrane form a continuous sheetthe cell membrane form a continuous sheet

Cell MembranesCell Membranes

Primary structure of a cell membrane Primary structure of a cell membrane is a double layer of phospholipid is a double layer of phospholipid moleculesmolecules Heads are hydrophilic (water-loving)Heads are hydrophilic (water-loving) Tails are hydrophobic (water-fearing)Tails are hydrophobic (water-fearing) Molecules arrange themselves in bilayers in waterMolecules arrange themselves in bilayers in water Cholesterol molecules are scattered among the Cholesterol molecules are scattered among the

phospholipids to allow the membrane to function phospholipids to allow the membrane to function properly at body temperatureproperly at body temperature

Most of the bilayer is hydrophobic; therefore water or Most of the bilayer is hydrophobic; therefore water or water-soluble molecules do not pass through easilywater-soluble molecules do not pass through easily

Plasma Membranes and Plasma Membranes and ProteinsProteins

A cell controls what moves through A cell controls what moves through any section of membrane by means any section of membrane by means of proteins embedded in the of proteins embedded in the phospholipid bilayer.phospholipid bilayer.

The protein acts as a gate allowing The protein acts as a gate allowing water-soluble molecules to pass water-soluble molecules to pass through the membrane.through the membrane.

Cytoplasm and OrganellesCytoplasm and Organelles

CytoplasmCytoplasm——gel-like internal gel-like internal substance of cells that includes many substance of cells that includes many organelles suspended in watery organelles suspended in watery intracellular fluid called cytosolintracellular fluid called cytosol

Cytoplasm and OrganellesCytoplasm and Organelles

Two major groups of organelles:Two major groups of organelles: Membranous organelles are specialized Membranous organelles are specialized

sacs or canals made of cell membranessacs or canals made of cell membranes Nonmembranous organelles are made of Nonmembranous organelles are made of

microscopic filaments or other microscopic filaments or other nonmembranous materialsnonmembranous materials

OrganellesOrganelles

Endoplasmic reticulum (Highway Endoplasmic reticulum (Highway system of the cell)system of the cell) Made of canals with membranous walls Made of canals with membranous walls

and flat, curving sacs arranged in and flat, curving sacs arranged in parallel rows throughout the cytoplasm; parallel rows throughout the cytoplasm; extend from the plasma membrane to extend from the plasma membrane to the nucleusthe nucleus

Proteins move through the canalsProteins move through the canals

ERER

Two types of ER:Two types of ER:

1) Rough ER: Ribosomes on the outer 1) Rough ER: Ribosomes on the outer surface of the organellesurface of the organelle

2) Smooth ER: 2) Smooth ER: Synthesizes certain Synthesizes certain lipids and carbohydrates and creates lipids and carbohydrates and creates membranes for use throughout cellmembranes for use throughout cell

nonmembranous structurenonmembranous structure

Ribosomes in the endoplasmic reticulum Ribosomes in the endoplasmic reticulum make proteins for make proteins for ““exportexport”” or to be or to be embedded in the plasma membrane; embedded in the plasma membrane; free ribosomes make proteins for the free ribosomes make proteins for the cellcell’’s domestic uses domestic use

Golgi apparatusGolgi apparatus

Golgi apparatus (UPS of cell): flat-like Golgi apparatus (UPS of cell): flat-like pancake organelle that packages and pancake organelle that packages and delivers proteins and other organic delivers proteins and other organic molecules throughout the cell.molecules throughout the cell.

LysosomesLysosomes

Lysosomes (miniature stomach)- Lysosomes (miniature stomach)- enzymes in lysosomes digest the enzymes in lysosomes digest the protein structures of defective cell protein structures of defective cell parts, including plasma membrane parts, including plasma membrane proteins, and particles that have proteins, and particles that have become trapped in the cellbecome trapped in the cell

MitochondriaMitochondria

Mitochondria (power plant of cell)- Mitochondria (power plant of cell)- mitochondrial enzymes catalyze series mitochondrial enzymes catalyze series of oxidation reactions that provide of oxidation reactions that provide about 95% of cellabout 95% of cell’’s energy supplys energy supply

Each mitochondrion has a DNA molecule, Each mitochondrion has a DNA molecule, allowing it to produce its own enzymes allowing it to produce its own enzymes and replicate copies of itselfand replicate copies of itself

NucleusNucleus

Consists of nuclear envelope Consists of nuclear envelope (composed of two membranes each (composed of two membranes each with essentially the same molecular with essentially the same molecular structure as plasma membrane) structure as plasma membrane) surrounding nucleoplasm; nuclear surrounding nucleoplasm; nuclear envelope has holes called nuclear envelope has holes called nuclear porespores

CytoskeletonCytoskeleton

The cellThe cell’’s internal supporting s internal supporting framework made up of rigid, rodlike framework made up of rigid, rodlike pieces that provide support and allow pieces that provide support and allow movement and mechanisms that can movement and mechanisms that can move the cell or its parts (Figure 3-move the cell or its parts (Figure 3-13)13)

CentrosomeCentrosome

An area of the cytoplasm near the An area of the cytoplasm near the nucleus that coordinates the building nucleus that coordinates the building and breaking of microtubules in the cell- and breaking of microtubules in the cell- Important in cell divisionImportant in cell division