Download Ch 3 - Fort Bend ISD

Cell Structure
and
Function
Chapter 3
There are 2 types of cells
1. Prokaryotes
2. Eukaryotes
Prokaryotes
• Do NOT have a membrane surrounding
genetic material, therefore, can make
proteins simultaneously when reading
genetic code.
• Lack some structures found in Eukaryotic
cells
Eukaryotes
• Have a membrane surrounding their DNA,
forming a NUCLEUS
• Contain numerous internal membranes
that have specific functions, called
ORGANELLES
External Structures – Bacteria
• Glycocalyces – Sugar based external
surrounding firmly attached to cell’s
surface.
• Flagella – Tail like structure that propels
bacteria (also found on sperm cells). Flow
of hydrogen and sodium ions allows
movement.
• Fimbriae and Pili – Hair like structures
that adhere to surfaces to move bacterium.
Cell Walls
• Found in most prokaryotes – allows
attachment to other cells and resistance to
antimicrobial drugs.
• Eg. Penicillin attacks cell walls of microbes
• Peptidoglycan – Polysaccharide, divides
cells into two types:
1. Gram-Positive (Thick layer of
peptidoglycan)
2. Gram-Negative (Thin layer of
peptidoglycan)
Cytoplasmic Membrane
• Made up of a PHOSPHOLIPID BILAYER:
outside is hydrophilic and inside is
hydrophobic
• Selectively Permeable, but naturally
impermeable to large objects
• Concentration Gradient – Concentration
of sodium ions can attract and repel
charged substances into and out of cells.
Diffusion
• Simple Diffusion - When a small, nonpolar molecule passes through a lipid
bilayer.
• Channel Diffusion - Channel proteins
where material moves through an open,
aqueous pore.
• Facilitated diffusion - Type of passive
transport that is dependent on single
transport protein carriers.
Osmosis
• Movement of water across a selectively
permeable membrane driven by a
difference in solute concentrations on the
two sides of the membrane.
Cytoplasm
• Gelatinous material inside of a cell
• Liquid portion is called CYTOSOL
• Contains INCLUSIONS– Deposits of small
compounds within the cytoplasm
Endospores
• Produced by Bacillus and Clostridium
• NOT FOR REPRODUCTION
• Constitute a defensive strategy for hostile
or unfavourable conditions
Nonmembranous Organelles
• Ribosomes – Sites of protein synthesis
• Cytoskeleton – Structure of proteins which
gives cells structure and movement:
1. Microfilaments: Fine, thread-like protein
fibers, 3-6 nm in diameter
2. Microtubules: Cylindrical tubes, 20-25 nm
in diameter
3. Intermediate filaments are about 10 nm
diameter and provide tensile strength for the
cell.
Archaea Glycocalyces
• Same characteristics as bacterial
glycocalyces
Archaea Flagella
• Similar to bacterial flagella
• About half the thickness (10-14 nm)
Fimbriae and Hami
• Fimbriae – nonmotile, rodlike, sticky
projections
• Hami – Fimbria of archaea. Filament frays
into 3 hooks. Used for attachment
Eukaryotic Glycocalyces
• Most animal and protozoan cells lack cell
walls
• Glycocalyces are anchored through
covalent bonds
Eukaryotic Cell Walls and
Membranes
• Cell walls of plants are made of cellulose
• Cell walls of fungi are made of chitin or
glucomannan
• Cell walls of algae are made of cellulose,
proteins, agar, carrageenan, silicates,
algin, calcium carbonate, or a combination
of the aforementioned
• ALL have cytoplasmic membrane
Centrioles and Centrosome