Cells

9/25/09

A Brief HistoryRobert Hooke – In 1664, he saw the 1st cell and named it a cell (cork); used a microscope

Anton van Leeuwenhoek – 1st person to observe living cells; refined lenses to magnify images

Schleiden, Schwann, and Virchow – made up cell theory.

Cell Theory

1. All living things are made up of cells

2. Only cells can make cells. 3. Cells are the basic units of structure and function in an organism.Two types of cells

– Prokaryotes – cell that lacks membrane-bound organelles. No nucleus. Primitive – ex. Bacteria

– Eukaryotes – cell that has organelles protected by membranes. More complex.

Endosymbiotic theory• Evidence to support the idea that prokaryote cells developed 1st

and eukaryote cells resulted when prokaryotic cells ingested each other.

• Prokaryotic cells lack a nucleus and membrane-bound organelles.– All cells share certain characteristics.

• Cells tend to be microscopic.• All cells are enclosed

by a membrane.• All cells are filled with

cytoplasm.• All cells contain genetic

information (DNA).

Bacterium(colored SEM; magnification 8800x)

cell membrane

cytoplasm

Types of Eukaryotic Cells

Plant – has cell wall, large vacuole, plastids (ex. Chloroplast), no centrioles

Animal – no cell wall, small vacuole, centrioles, no plastids

Eukaryotic cells have a nucleus and membrane-bound organelles.

Eukaryotic Membranes

Parts of Cell --- organelle – “little organ”Plasma or cell membrane – outer membrane. Phospholipid (P+O+fat)Cell wall – outer membrane of plants. Made up

of cellulose (we can’t digest)

Nucleus – control center of cell. a. nuclear membrane – outside edge of

nucleus. b. nucleolus – makes ribosomal RNA c. chromosomes – contains genetic material

(DNA) d. nucleoplasm – fluid inside nucleus. Used

to protect organelles within nucleus.

Eukaryotic Nucleus

What differences do you notice between the cells?

Cell Wall No cell Wall

Rigid shape Round shape

Large Vacuole Small Vacuole

Green Color! Lacks chloroplast (plastids)

No centrioles Centrioles

• Cell membranes are composed of two phospholipid layers.1. Phospholipid bilayer.2. Other molecules embedded in the membrane.3. The fluid mosaic model describes movement in membrane.

cell membrane

protein

cholesterol

proteincarbohydratechain

protein channel

Fluid Mosaic Model

1. The phospholipid bilayer behaves like a fluid more than it behaves like a solid– Like a boat on an ocean!

2. The mosaic consists of lipids and proteins in the cell membrane constantly changing.

Membrane ProteinsIntegral protein – any protein embedded into the membrane

Transmembrane proteins – extend across the plasma membrane

Peripheral proteins – aid in conformational changes

Video!

Organelles in Plant and Animal Cells

9/28/09

Cytoplasm – clear fluid inside cell. Acts as shock-absorber to protect contents of cell.

Endoplasmic reticulum (ER) – channels used for transporting things within cell (highway system). a. smooth ER – contains no ribosomes b. rough ER – contains ribosomes. Used for transporting molecules needed in protein making.

Ribosomes – makes proteins

Golgi body or apparatus – packages and “labels” proteins and lipids sent to different parts of the cell.

Golgi Apparatus

Ribosomes

Rough ER

Rough ER

Smooth ER

Smooth ER function – detoxification of drugs and poisons, production of steroid hormones, release of calcium

Mitochondria - “powerhouse of cell” – makes energy by cellular respiration. Has many folds called cristae that increases the surface area.

Vacuole – storage area for food, water and waste. Larger in plant cells.

Lysosomes – “suicide sac” – contains enzymes used to digest foreign materials and sometimes the cell itself.

Microtubules (bigger) and microfilaments (smaller) - used for structural support – called cytoskeleton.

Microtubule Organization in Plants Microfilament Arrangement in Bundles

Centrioles – only in animal cells. Used during cell reproduction.

Cilia ( hair –like projections) & flagella (long tail-like whip) – structures some cells have for cell movement.

Protist Ciliate E. Coli bacterium with flagella

• Plant cells have cell walls that provide rigid support.

Chloroplasts– convert solar energy to chemical energy. – plastids that hold chlorophyll (green pigment used for

making food in plants)