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, , 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