Chapter 3 Structure and Function of Plant Cells

Scales of Microscopic Observation Sizes either metric or as magnifications mag = nx The human eye is 1x Lenses increase magnification, series even more (ex. Compound light microscope) Total mag is achieved by multiplying the powers: 5x X 10x = 50x The light microscope: x mag. The electron microscope: >100,000x mag. Resolving Power (most cells cannot be seen unaided)

Cytology = the study of cell structure and function Tools used:light microscope electron microscope stains special scopes Electron microscopy: TEM and SEM Cell freeze fractionation and organelles Biochemical cytology Cell Organization Prokaryote vs. Eukaryote Cell defined: (bag of sugary water?) Cell size: surface area to volume ratio; limits on distance and transport

The Plant Cell Eukaryotic cells and compartmentalization! Parts of a typical plant cell:  Plasma (cell) membrane  Cytoplasm  Nucleus  Ribosomes  Cytoskeleton  Organelles  Cell wall

Membranes and Cell Compartments Plasma membrane  Surrounds cell, partially fluid  Semi(selectively)permeable  Barrier that protects cell, gives cell support and some shape  Allows passage of gases and nutrients into and out of cell only at surface  Metabolic activities occur in or on membranes

Organelles = “tiny organs”  Small internal spaces or compartments inside a cell surrounded by additional membrane  Compensate plasma membrane  Increases surface area  Compartments maintain different environments for different types of reactions  Perform own special functions Internal Membrane Systems

The endomembrane system - network of membranes that interconnect organelles for the synthesis, packaging and transport of substances Consists of: Plasma membrane Endoplasmic reticulum (ER) – two types Rough ER Smooth ER Dictyosomes (Golgi bodies) Flattened membrane sacs Primarily for secretion Major shipment center

Vesicles Vacuoles Large central vacuole and turgor pressure Microbodies Ex. Peroxisomes and glyoxysomes Connections between cells Plasmodesmata (plasmodesma) - open channel for movement of material from one cell to the next - show picture

The Nucleus  Is an organelle  Very very large  Genetic control center  DNA and chromosomes  Nuclear envelope  Nuclear pores  Nucleolus and ribosomes  Cytosol and nucleoplasm Ribosomes Not an organelle Site of protein synthesis Made up of protein and RNA