Cell Structure and Function Chapter 7
Dec 25, 2015
Microscopes : windows to the world of the cell Cells are the basic unit of
life. The invention and
improvement of microscopes in the 17th century led to the discovery and early study of cells
Robert Hooke observed “cells” in a slice of cork
1800’s Schwann –Animal tissues are composed of cells
Schleiden – Plant materials are composed of cells
Virchow - All tissues from living organisms are composed of cells
History of Cells
The Cell Theory
All living things are composed of cells
Cells are basic units of structure and function
All cells come from pre-existing cells
Types of Microscope
Light: uses light and lenses to magnify image
Electron: uses magnets and electrons to magnify image
MagnificationTo calculate:
Power of objective lens x Power of Eyepiece
Do these calculations: Eyepiece = 10xObjective = 10x; 40x; 100x
Electron Microscope Uses magnets and
electrons to magnify images
Magnifies 1000x better than a light microscope
Specimen cannot be living
Types of Electron Microscopes
Transmission Electron Microscope: internal structures
Scanning Electron Microscope: surface structures
Major Type of CellsThere are two basic types of cells
Prokaryotic & EukaryoticA major difference between prokaryotic and eukaryotic cells is the location of chromosomes.
Prokaryotic Cells Lacks a nucleus
and most other organelles
DNA concentrated in nucleoid region
Bacteria and Archae
1-10 micrometers Appear earliest in
earth’s fossil record
Eukaryotic Cells Nucleus surrounded
by its membrane Internal organelles
bounded by membranes
10 – 100 micrometers
Protists, Fungi, Plants, Animals
Cytoplasm
Fluid portion of the cellAll cellular organelles are
suspended in itOrganelles specialized
structures that perform various functions
Nucleus & it’s Contents
Chromosomes carry the cell’s genetic informationAlways remain in the nucleus
RNA carries this message from the nucleus to the ribosomes moves through the nuclear pores
Storage, Cleanup and Support
Vacuolesstore water, salts, carbohydrates & proteins
Lysosomes filled with enzymes breakdown of macromolecules
Cytoskeleton maintains shape & helps in movement
Microtubule Hollow structures made of
tubulin Maintain shape in many cells Centrioles in animals cells
made of tubulin help organize cell division not present in plant cells
Project from the surface cilia & flagella movement
Centriole
Cilia
Capture and Release Energy
The cellular machinery constantly needs energy to function.
Supplied by two organelles the Chloroplasts & Mitochondria
Mitochondria Convert chemical
energy in food to a form that the cell can useATP
All mitochondria come from the cytoplasm of the egg cell inherited from the mother
Endosymbiosis Chloroplasts and mitochondria are
similar to prokaryotes Lynn Margulis in 1960 evidence
that chloroplasts and Mitochondria evolved as endosymbiontsBoth have DNA, RNA and Ribosomes
that prokaryoticThey replicate their own DNADivide by binary fission
RNA World
Miller & Urey 1953, organic molecules necessary for life have arisen from simpler compounds
Origin of life RNA evolved before DNA
Cellular Boundaries
Cell WallsProvides supportConfers shapeProtects the cellPresent in plants and prokaryotes
Cell MembranesRegulates what enters and leaves the cellSelectively Permiable
Cell/Plasma Membrane Boundary that separates the
interior of a living cell from it’s surroundings and regulates the traffic of chemicals into and out of the cell
Phospholipid BilayerProtein “icebergs” float in a
“sea” of phospholipids
Phospholipid Molecule
Composed of proteins and a type of lipid called phosopholipid (glycerol+2 fatty acids)
Function of Cell MembranesMaterials need to move in and out of the cell
Function like gatekeepers, letting some molecules through, but not others “Selectively Permeable”
Diffusion The spread of molecules
from areas of high concentration, to areas of low concentration.
Equilibrium when the molecules are even throughout a space
Concentration Gradient difference between concentrations in a space.
Passive Transport Diffusion Some
substances are allowed to move freely
Facilitated diffusion transport proteins
Osmosis The diffusion of
water (across a membrane)
Water will move in the direction where there is a high concentration of solute and low water concentration
OsmosisDissolved molecules ( ions,
organic molecules, etc) are called solutes
Most solutes cannot cross membranes
As solute conc increases “free” H2O decreases
Hypertonic high [solute]Hypotonic low [solute]
•Water flow equal in both directions
•Net water flow into the cell which can burst (Hemolysis)
Net water flow out of cell which shrinks(Crenation)
Water Balance in Animal Cells
Active Transport Cell expends energy to move
molecules or ions across the membrane
A specific transport protein pumps solute across a membrane
The chemical energy is supplied by the mitochondria
Example Na+(Sodium) K+(Potassium) pump.
Transport of Large Molecules
Large molecules have to be packaged to be transported in and out of the cell
Vesicles (membranes sacs) are formed to move the substances ExocytosisEndocytosis