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

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

How Cells are Studied

A. MicroscopyB. 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)

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

The Eukaryotic Animal Cell

The Eukaryotic Plant Cell

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

Cell Structure

Section 7.2

Cell Organization

CytoplasmCytoplasmic inclusions

Nucleus / Nuclear regionCell Membrane/Wall

Cytoplasm

Fluid portion of the cellAll cellular organelles are

suspended in itOrganelles specialized

structures that perform various functions

Nucleus & it’s Contents

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

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

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

Building Protein

RibosomesEndoplasmic ReticulumGolgi 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 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)

Protein “icebergs” in a “sea” of phospholipids

Plasma Membrane

Cell Transport

Section 7.3

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”

Types of Transport

Passive TransportDiffusionFacilitated 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

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]

Isotonic- means the same

Hypotonic- less solute

Hypertonic- high 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

Turgid Flaccid

Water Balance in Plant Cells

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 ExocytosisEndocytosis

Exocytosis & Ednocytosis

More Exo & Endo