CELL STRUCTURE

CELL STRUCTURE Enormous variety in the size and shape

of different cells Smallest cells belong to group of

organismsMycoplasma Only about 0.2 µm in diameter So small that often beyond the limit of

resolution of light microscopes

CELL STRUCTURE Large cells (giant amoeba)Chaos chaos

About 1000 µm in diameter

Larger cellsyolks of bird eggs Single cells containing stored food for the

developing bird for the most part, cells are between 5 &

50 µm in diameter

CELL STRUCTURE certain structures are common to most

cells plants, animals, and related organisms

have 3 basic structures: cell membrane-outer boundary nucleus-control center cytoplasm-material between the cell membrane

and nucleus

CELL MEMBRANE all cells are separated from their

surroundings by a cell membrane regulates what enters and leaves the cell aids in the protection and support of the

cell similar to cell walls that surround a house

CELL MEMBRANE it must communicate with other cells, take

in food, and water and eliminate wastes composed of several kinds of molecules

lipids, proteins, cho’s

LIPIDS• double layer of lipid molecules, known as a

‘bilayer’ forms the basic unit from which cell membranes are constructed

PROTEIN some proteins stick to the surface of

the lipid bilayer, others are free to move around within the bilayer

some act as channels through which molecules can pass

others act like small pumps, actively pushing molecules from one side of the membrane to the other

CARBOHYDRATES cho’s are attached to proteins or lipids

at the membrane surface many act like chemical id cards,

allowing cells to recognize and interact with each other

CELL WALL in organism such as plants, algae, and

some bacteria, the cell membrane is surrounded by a cell wall

helps to protect and support the cell very porouswater, oxygen, carbon

dioxide, and other substances can pass through easily

made up of two or more layers layers form in a series of steps

PRIMARY CELL WALL 1st layer to form develops where two

plant cells meet Contains a gluey substance called

pectin, that helps hold the cells together

Each of these cells then forms a primary cell wall on its side of this gluey layer

Made up of cellulose (a fibrous material)

Make the cell wall elasticstretch as it grows

SECONDARY CELL WALL Plants that have woody stems,

another layer secondary cell wall, develops

Composed of cellulose and lignin Lignin makes cellulose more rigid Wood consists mainly of secondary

cell walls

NUCLEUS Nucleus-info center of the cell

Seen in many cells as a large dark structure

1st described by Robert Brown Not all cells have nuclei Small unicellular organismbacteria and

several other kinds of organisms, do not have nuclei

PROKARYOTES / EUKARYOTES The absence or presence of a nucleus can

be used to divide organisms into two categories:

Prokaryotes-lack nuclei Eukaryotes-contain nuclei

Karyon=nucleus Pro=before Eu=true

PROKARYOTES Prokaryotic organism

Bacteria and their relatives Usually small and unicellular

EUKARYOTES Eukaryotic organisms

Both unicellular and multicellular

NUCLEUS Nucleus is the information center of the

cell Contains DNA=instructions for making

thousands of different molecules Directs all the activities that occur in a

living cell

NUCLEUS Nuclear envelope

Composed of two membranes that form boundary around nucleus

Insidedozens of nuclear pores Molecules move in and out of nucleus through

nuclear pores

NUCLEUS Nucleolus

Most nuclei contain a small region called nucleolus

Made up of RNA and proteins Where ribosomes are made

NUCLEUS Chromosomes

The DNA in the nucleus of eukaryotic cells is attached to special proteins and forms large structures called chromosomes

Contain genetic information that must be passed to each new generation of cells

CYTOPLASM Cytoplasm

Area between the nucleus and the cell membrane

Contains important structures

TOMORROW We will discuss the organelles found

within the cytoplasm!!!!!!!!!!!!