Cell Structure and Function Chapter 7

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

History of Cells 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

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

How Cells are Studied Microscopy Cell Fractionation

Microscopes An instrument used observe minute objects Enlarges images of small objects

Types of Microscope Light: uses light and lenses to magnify image Electron: uses magnets and electrons to magnify image

Parts of a Microscope (Eyepiece)

Magnification To calculate: Power of objective lens x Power of Eyepiece Do these calculations: Eyepiece = 10x Objective = 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

The Eukaryotic Animal Cell

The Eukaryotic Plant Cell

Major Type of Cells There are two basic types of cells Prokaryotic & Eukaryotic A 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

Cell Structure Section 7.2

Cell Organization Cytoplasm Nucleus / Nuclear region Cytoplasmic inclusions Nucleus / Nuclear region Cell Membrane/Wall

Cytoplasm Fluid portion of the cell All cellular organelles are suspended in it Organelles specialized structures that perform various functions

Nucleus & it’s Contents

Nucleus & it’s Contents Chromosomes carry the cell’s genetic information Always remain in the nucleus RNA carries this message from the nucleus to the ribosomes moves through the nuclear pores

Storage, Cleanup and Support Vacuolesstore water, salts, carbohydrates & proteins Lysosomes filled with enzymes breakdown of macromolecules Cytoskeleton  maintains shape & helps in movement

Microfilaments Threadlike structures made of actin Forms an extensive network Helps cells move

Microtubule Hollow structures made of  tubulin Centriole 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 Cilia

Building Protein Ribosomes Endoplasmic Reticulum Golgi Apparatus

Ribosome

Endoplasmic Reticulum (rough & smooth)

Protein Synthesis

Golgi Body

Capture and Release Energy The cellular machinery constantly needs energy to function. Supplied by two organelles the Chloroplasts & Mitochondria

Chloroplasts Sunlight to Chemical energy

Mitochondria Convert chemical energy in food to a form that the cell can useATP 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 endosymbionts Both have DNA, RNA and Ribosomes that prokaryotic They replicate their own DNA Divide 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 Walls Cell Membranes Provides support Confers shape Protects the cell Present in plants and prokaryotes Cell Membranes Regulates what enters and leaves the cell Selectively Permiable

Cell/Plasma Membrane Phospholipid Bilayer 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 Bilayer Protein “icebergs” float in a “sea” of phospholipids

Phospholipid Molecule Composed of proteins and a type of lipid called phosopholipid (glycerol+2 fatty acids)

Protein “icebergs” in a “sea” of phospholipids

Plasma Membrane

Cell Transport Section 7.3

Function of Cell Membranes Materials need to move in and out of the cell Function like gatekeepers, letting some molecules through, but not others  “Selectively Permeable”

Passive Transport Active Transport Types of Transport Diffusion Facilitated Transport Active Transport

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

Osmosis Dissolved 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]

Isotonic- means the same

Hypotonic- less solute

Hypertonic- high solute

Water Balance in Animal Cells Net water flow into the cell which can burst (Hemolysis) Water flow equal in both directions Net water flow out of cell which shrinks (Crenation)

Water Balance in Plant Cells Turgid Flaccid

Plasmolysis Shrinking of cytoplasm in both plant and 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.

Active Transport

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 Exocytosis Endocytosis

Exocytosis & Ednocytosis

More Exo & Endo