Lecture 122-124

Types of Cells

·       All life is composed of cells

·       Microscope was improved by Antonie von Leeuwenhoek 1600’s

·       First person to see, describe, and name cells was Robert Hook 1655

·       Matthias Schleiden and Theodor Schwann developed cell theory

o   all orgs are composed of one or more cells

o   cells are basic unit of structure and function in organisms

o   all cells come from pre-existing cells

·       in 400bc, a lot of people believed in spontaneous generation

Cell size

·       Plant cells range in size from 10-100 µm

·       Cells need to be small so that there is a large surface area/volume ratio

·       As the size of the cell increases volume increases by cube and SA by a square

Microscopes

·       Need a microscope to see most cells

o   A light microscope goes to approx. 0.2µm

o   Electron microscope goes to approx. 0.5nm

Cells

Cells differ in shape, size and activities, but share 4 characteristics

1.     Plasma membrane

2.     Dna- Containing region

3.     Cytoplasm- semifluid of water, dissolved subst and solids

a.     Doesn’t include DNA containing region

4.     Ribosome- sites of protein synthesis

Two types of cells

1.     Prokaryotic

2.     Eukaryotic

Prokaryotic- lacks internal membrane compartments & and therefore nucleus (lacks organelles)

Eukaryotic- (true nucleus)

·       Has internal membrane bound compartments or organelles

·       Allows many separate activities

Prokaryotic cell

·       Have a cell wall

·       Many surrounded by capsule or gelatinous sheath

·       Lack any internal membrane bound organelles

·       Lack a nucleus, have a nucleoid

·       Many have some accessory rings of DNA called plasmids

·       Flagellum (some not all)

·       Ribosomes

Eukaryotic Cell

·       Nucleus- membrane-bound sphere containing DNA in chromosomes

o   Contains DNA

o   Stored differently than in PK cell

·       Nuclear envelope- has two lipid layers

·       Chromosomes- coiled bodies of DNA, bound with proteins

·       Nucleolus- dense area within nucleus

o   Components of ribosomes are produced

Nucleolus

Plant Vacuole- gen maintenance of cell

·       Membrane sac larger than vesicles

·       Plants lg central vacuole

o   Funct in storage AA, sugars & wastes

o   Maintaining turgor pressure and rigidity in plants

Animal vacuole- Contractile Vacuole

·       Found in single-celled organisms

·       Regulation of water balance

Mitochondria

·       All euk cells

·       Powerhouse of cells

·       Produce ATP

·       Participate in aerobic respiration

Chloroplasts (only photosynthetic euk; plants and protists)

·       Photosynthesis

·       Photo pigments located in grana

Endomembrane system:

·       Complex system of tubes, sac, and vesicles involved in the synthesis and distribution of metabolic products throughout the cell.

Cytoskeleton:

·       Interconnected system of fibers, threads & tubules that extend between nucleus, plasma membrane, & organelles

·       Provides structure and movement capabilities

Fibers:

1.     Microtubules- long hollow tubules of tubulin

·       Compose cilia and flagella

·       Movement of chromosomes and other structures

Flagella:

·       long whip-like struct involved in movement or locomotion of
single-celled org. Usually occur 1-2 in number

Cilia:

·       short hair-like struct involved movement of food particles or
water currents. Usually occur many in number