5.1 All organisms are composed of cells

5.1 All organisms are composed of cells

neuron

skeletal muscle

amoeba

sperm & egg

3 main features: plasma membrane nucleus or nucleoid cytoplasm

A plasma membrane surrounds

all cells

bilayer fluid mosaic

Singer, Nicolson 1972

Genetic Information

prokaryotes

DNA

eukaryotes

nucleoid

plasmids

DNA as chromosomes during cell division

1 Circular chromosomal DNA

2 Extra-chromosomal plasmid DNA

Cell Discovery/Theory

cells are the unit of structure and function

cells fromcells

cell walls of cork ‘little

animicules’

Why are cells small?

As an object increases in size…

Volume increases as the cube (x3) of its diameter

while

surface area increases as the square (y2)

The membrane (surface) must allow for sufficient & rapid exchange to support the cell contents

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Prokaryotic vs Eukaryotic

small & simpleribosomes, nucleoidpeptidoglycan wall3.5bya

large & complex organelles, chromosomescytoskeleton1.5bya

Features in common

Unique to eukaryotes, organelles allow for division of labor

Prokaryotes: so what?

Decomposition nutrition

disease sewage treatment digestion

soil contamination clean upnutrient recycling symbiosis normal flora

Energy transformers history of life genetic engineering human health

An amphipathic molecule

Charged phosphate creates a polar ‘head’

H-C tails are non-polar, hydrophobic

The Plasma Membrane is built primarily of Phospholipids

Phospholipid molecules self-organize, tails avoiding water of both the cytoplasm and the environment

creates a bilayer

tails a barrier to charged ions and polar molecules

channels, carriers, aquaporins

membrane stability

relay information in/out of cell

facilitate rxns

Membrane proteins

move molecules across

bind cells tightly together

keeps molecules from ‘escaping’ from tissues

TIGHT JUNCTIONS

Steroids – cholesterol in animal cells – modify the fluidity of the membrane so it stays intact at both warm and cold temperatures.

Membrane as Mosaic

Glycoprotiens and glycolipids function in cell to cell attachment, recognition, and cell signaling