Cells
Chapter 3
Early investigation of cells
• Robert Hook, 1665, coined term “cells” after observing
cork cells
• Malpighi, Grew and Leeuwenhoek, late 1600’s described
various plant tissues and Protistans
• Jean Baptiste de Lamarck, all living things composed of
cells
• Robert Brown, 1831, discovered nuclei
• Schleiden and Schwann, 1838-9, developed Cell Theory
• Rudolf Virchow, 1858, argued against spontaneous
generation
• Louis Pasteur, 1862, demonstrated spontaneous
generation did not occur
Prokaryotic vs Eukaryotic
• Prokaryotic – have no nuclei, or other
membrane-bound organelles
• Eukaryotic – possess both nuclei and other
membrane-bound organelles
• Domains Archaea and Bacteria, prokaryotic
• Domain Eukarya, all eukaryotic
includes Kingdoms Protista, Fungi, Plantae
and Animalia
Cell Structure
• Protoplasm – all the material inside the
cell wall
• Cytoplasm – all the material between the
plasma membrane and nucleus
• Cytoplasm consists of the liquid cytosol
and the organelles
Cell Wall
• primarily composed of cellulose
• Middle Lamella – layer of pectin between two
adjacent cell walls
• Primary cell wall – laid down first, more flexible
• Secondary cell wall – deposited inside primary,
more rigid due to lignin
• Plasmodesmata – strands of cytoplasm that
extend through the cell walls of adjacent cells
Plasma Membrane
• outermost membrane surrounding cells
• immediately inside cell wall
• phospholipid bilayer with imbedded
proteins, glycolipids and glycoproteins
Nucleus
• surrounded by nuclear envelope (membrane)
• contains much of the cell’s DNA
Chromatin – thin strands
Chromosome – condensed, precedes
cellular reproduction
• Nucleoli, spherical structures in nucleus, consist
of proteins and RNA; site of rRNA synthesis
and ribosome subunit assembly
Endoplasmic Reticulum
• Rough ER – ribosomes present; site of
protein synthesis, transport and storage
• Smooth ER – site of lipid synthesis and
transport
Ribosomes
• lack surrounding membrane
• Present in prokaryotic and eukaryotic cells
• site of protein synthesis
Dictyosomes
• aka Golgi Bodies in animal cells
• receive, modify and package molecules
Plastids
• Chloroplast – site of photosynthesis
• Chromoplasts – contain various pigments
• Leucoplasts
Amyloplasts – synthesize starch
Elaioplasts – synthesize oils
Chloroplasts
• surrounded by a double membrane
• contain some DNA and ribosomes
• Grana – stacks of thylakoid membranes;
contain chlorophyll; site of light-dependent
reactions of photosynthesis
• Stroma – liquid surrounding the grana; site
of the light-independent reactions of
photosynthesis
Mitochondria
• consist of an outer membrane and much
in-folded (cristae) inner membrane
• site of aerobic respiration
• contains some DNA and ribosomes
Endosymbiont Hypothesis
• suggests chloroplasts and mitochondria
were initially free-living, bacteria-like
organisms that parasitized or were
captured by early eukaryotic cells
• supporting evidence
– bacteria-like inner membranes
– bacteria-like DNA
– bacteria-like ribosomes
Vacuoles
• Central Vacuole – large, centrally located
• storage site of various molecules
• promotes rapid increase in volume of cell
following cell reproduction
Cytoskeleton
• Microtubules – composed of protein;
involved in cell wall formation, cell division,
movement of cilia and flagella
• Microfilaments – also protein, but thinner
than microtubules; play a role in
cytoplasmic streaming (cyclosis)
Cell Reproduction
• will be covered later