Cell

Cell Theory

Plant And Animal Cells

Transport

History of the Cell Theory• 1500s-Eyeglass makers-several lenses magnifies

objects• Anton van Leeuwenhoek: First to describe cells.

“Animalcules” (bacteria)• Robert Hooke: Studied cork (dead cells of oak tree);

monastery; cells born.• Robert Brown (1833): Dark structure near the center

of the cell (nucleus)• Matthias Schleiden(1838): Plants made of cells• Theodore Schwann (1839): Animals are made of

cells.• Rudolf Virchow (1855): Cells come from pre-existing

cells

Hooke

Cell Theory

• All organisms are composed of one or more cells.

• Basic unit of organization of organisms.

• All cells come from pre-existing cells.

Modern Cell Theory

The cell contains hereditary information which is passed on from cell to cell during cell

division.

All cells are basically the same in chemical composition and metabolic activities.

Cell Size

• 5 to 50 micrometers in diameter– Smallest Mycoplasma bacteria (0.2

micrometers across)– Giant amoebas Chaos chaos (1000

micrometers/1 mm) in diameter; unaided eye

Cell membrane/plasma membrane

• Thin flexible barrier

• Many cells in direct contact with fluid portion of blood called plamsa.

Nucleus (plural: nuclei)

Large membrane enclosed structure that contains genetic material in the form of DNA and controls cell’s activities.

Prokaryotic vs. EukaryoticPROKARYOTES

PRO- “Before”•Generally smaller and simpler (exceptions)

•Do not separate genetic material in a nucleus.

•All characteristics of life.

•Single Cells

•Lack organelles

•Ex. bacteria

EUKARYOTES

EU- “True”•Larger, more complex

•Dozens of structures

•Internal membranes

•Highly specialized

•Genetic material in nucleus

•Single celled, multicellular

•Ex. Plants, animals, fungi

Eukaryotic and Prokaryotic Cells

Organelles: Membrane bound structures.

Microscopes-use lenses to magify the image of an object by focusing light or electrons

Compound Light Microscope: Uses two or more lenses that lets light throught to magnify objects.Used to examine living cells, small organisms and

preserved cells.See cells and structures as small as 1 millionth of

a meterMagnification: Up to 1500 x

Compound Microscope

• Objective lens-just above specimen-enlarges image

• Ocular lens-eyepiece-further magnifies image

• Most living things nearly transparent :: use dyes.– Toluidine blue-cell boundaries and nuclei– Fluorescent-give off light of a particular color

when viewed under specific wavelengths of light.• Fluorescence microscopy-identify locations of

molecules and watch movement.

Electron Microscope: beam of electrons that are focused by a

magnetic fieldMagnify object up to 500,000x Produce realistic, 3-D pictures.

Electron Microscopes

• Transmission and scanning

• Explore cell structures and large protein molecules.

• Electrons pass through thin samples-cells and tissues must be cut ultrathin.

• Electrons scatter::uses a vacuum

• Chemically preserved samples

• Nonliving cells and tissues only

Scanning Tunneling Microscope: Probe is brought near specimen. Electrons flow between the tip of

the probe and atoms on the specimen’s surface. As probe follows surface contours, 3-D image is

created on a computer.Magnification: hundred million times

Transmission Electron Microscope: Aims a beam of electrons through a

specimen. Denser objects allow fewer electrons to pass through.

Magnification: hundreds of thousands of times

                      

 

Cell structures and functions

Cell Boundaries

Cell MembraneCell Wall (PLANTS ONLY)

Plasma/Cell Membrane• Structure: A lipid bilayer with protein

molecules and carbohydrate chains embedded throughout the bilayer

• Function: A selectively permeable membrane which controls what enters and leaves the cell.

FLUID MOSAIC

1. Flexible

2. Phospholipids move like water molecules in a current of a lake

Selective Permeability: Process by which the plasma membrane of a cell allows some molecules into the cell

while keeping others out.

Phospholipids: Lipids with a phosphate group attached to them.

Phospholipids

•Glycerol backbone

•Two fatty acid chains

•Phospate group

Cholesterol

•Stabilize phospholipids

•Prevents fatty acid chains from phospholipids from sticking together

Transport Proteins

•Allows substances and waste to move through the plasma membrane.

•Examples: Protein Channels and Carrier Proteins

Proteins and Carbohydrates

• Stick out of cells to help cells identify one another

Cell Wall• Structure: Fairly rigid structure located outside

the plasma membrane.• Function: Shape, support and protection.• Found in plants cells, fungi, most bacteria, and

some protists.• Cellulose.

Cilia And Flagella

Cilia• Structure: Short,

numerous, hairlike projections, that move in a wavelike motion.

• Function: Aid in locomotion and feeding.

Flagella• Structure: Long

projections that move in a whip-like motion.

• Function: Major means of cell locomotion—unicellular organisms.

Cellular Control CenterNucleus

Nucleus• Structure: Center of the Cell• Function : Control center of the cell; Contains

the direction to make proteins and other important molecules (DNA).

• Prokaryotes: DNA in cytoplasm• Plant and animal cells

Chromatin

• Structure: Strands of genetic material, DNA; Forms Chromosomes

• Function: Master set of directions for making proteins.

Nucleolus

• Structure: Prominent structure in the nucleus.• Function: Make Ribosomes (RNA and

Proteins)

Nuclear Envelope• Structure :Separates the nucleus from

the cytoplasm; Double membrane made of two phospholipid bilayers contain pores for substances to pass through.

• Function: Allow materials in and out of nucleus.

Cytoplasm• Structure: Clear, gelatinous fluid inside the

cell. Area between cell membrane and nucleus. Dissolved in Cytosol are salts, minerals, and organic compounds.

• Function:Contains various cell organelles.

• Organelles that Build Proteins

RibosomesEndoplasmic ReticulumGolgi Apparatus

Ribosomes

• Structure: Most numerous in cell; no membrane; found free and attached; among smallest of organelles; Made up of RNA and Proteins

• Function: Protein Assembly (DNA directions)

Endoplasmic Reticulum• Structure:Complex system of folded membranes

suspended in the cytoplasm.• Function:

– transportation system between the nucleus and the cytoplasm

– Site of chemical reactions– Prepares proteins for export (rER)– synthesizes steroids – regulates calcium levels– breaks down toxic substances (sER)

• Smooth (No Ribosomes); Rough (Ribosomes)

Golgi Apparatus/Body• Flattened system of tubular membranes.

Flattened stack of pancakes.

• Modifies, sorts, and packages proteins and lipids for storage and transport (Cell’s Post Office)

Organelles that Store, Clean-UP, and Support

Vacuoles/VesiclesLysosomes

CytoskeletonCentrioles

Vacuole Vacule in plants/Vesicle in animals

• Structure: Sac surrounded by a membrane.

• Function: Stores food, enzymes and other materials needed by the cell, and some vacuoles store waste products.

Plastids

• Function: Stores starches and lipids;

• Example chloroplast (one type) transfers energy from light to organic compounds.

In plants, plastids may differentiate into several forms, depending upon which function they need to play in the cell.

Chloroplasts: for photosynthesisChromoplasts: for pigment synthesis and storage Amyloplasts: for starch storage Statoliths: for detecting gravityElaioplasts: for storing fatProteinoplasts: for storing and modifying protein

Lysosomes• Structure: Small spherical organelles

that enclose hydrolytic enzymes within a single membrane.

• Function: Digest molecules, old organelles, and foreign substances (engulfs viruses or bacteria)

Cytoskeleton

• Structure: Support structure made of tiny rods and filaments.

• Function: Form a framework for the cell.

Microtubules and MicrofilamentsAssist in cell shape and assist organelles in moving from place to place within the cell.

Microtubules: Thin hollow cylinders made of proteins.

Microfilaments: Thin, solid protein fibers.

Centrioles

•Pair of cylinder-shaped bodies found in the cells

•Organize cell division

•Animal Cells ONLY

Organelles that capture and release energy

• Chloroplasts (PLANT ONLY)

• Mitochondria

Chloroplast (PLANTS ONLY)• Structure:Disc shaped (ability to change shape

and position in the cell as light intensity changes) Contains pigment in the inner series of thylakoid membranes.

• Function: Convert solar energy to chemical energy stored in food.

Chlorophyll• Function: Traps light energy and gives

leaves and stems their green color.

Mitochondria

• Structure: Granular and rod shaped, with an inner membrane that forms long, narrow folds.

• Function: Convert chemical energy in food to usable compounds (ATP).

Animal Cell

Diffusion—Movement of particles from an area of higher

concentration to an area of lower concentration

Slide 59

Net MovementNet Movementmovement which changes movement which changes

concentrationconcentration

Slide 60

Slide 61

Factors that affect diffusionFactors that affect diffusion

Particle size and shapeParticle size and shapeTemperatureTemperatureConcentration gradient—Difference in Concentration gradient—Difference in

concentration.concentration.Cytoplasmic streaming—Continuous Cytoplasmic streaming—Continuous

movement of materials in cytoplasm.movement of materials in cytoplasm.

Slide 62

Diffuse in MembranesDiffuse in Membranes1.1.

Passive TransportPassive TransportMoving of materials across cell membrane Moving of materials across cell membrane

without using cellular energy.without using cellular energy.•Diffusion (phospholipids) Diffusion (phospholipids)

•Facilitated Diffusion (transport proteins) Facilitated Diffusion (transport proteins) Uses Channel ProteinsUses Channel Proteins

Active TransportActive TransportMoving of materials across cell membrane Moving of materials across cell membrane

using cellular energyusing cellular energyUses Carrier ProteinsUses Carrier Proteins

Slide 63

Osmotic PressureOsmotic Pressure

• Force produced by the net Force produced by the net movement of water out of or movement of water out of or

into a cellinto a cell• Water moves from an area of Water moves from an area of

HIGH water concentration (low HIGH water concentration (low solute) to an area of LOW solute) to an area of LOW water concentration (high water concentration (high

solute)solute)

Slide 64

AquaporinsAquaporins

Water channel proteinsWater channel proteins

Slide 65

OsmosisOsmosis

Slide 66

Osmotic PressureOsmotic PressureForce produced by the net movement of Force produced by the net movement of

water out of or into cell.water out of or into cell.Result:Result:Turgid pressure-plants straight upTurgid pressure-plants straight upWater purification (reverse osmosis)Water purification (reverse osmosis)Desalinates Salt WaterDesalinates Salt Water

Slide 67

Osmotic Condition—Cell Osmotic Condition—Cell concentrations versus concentrations versus environmental solution environmental solution

concentrations.concentrations.

IsotonicIsotonicHypotonicHypotonicHypertonicHypertonic

Slide 68

IsotonicIsotonic“Iso” means same“Iso” means same

Solution concentrations inside is the same as Solution concentrations inside is the same as outside.outside.

No net movement of water.No net movement of water.Animal cells: NormalAnimal cells: NormalPlant Cells: FlaccidPlant Cells: Flaccid

Slide 69

Solute concentrations outside is Solute concentrations outside is less than cell concentration.less than cell concentration.

Animal Cell : LysedAnimal Cell : LysedPlant Cell: TurgidPlant Cell: Turgid

““Hypo” - underHypo” - under

Slide 70

Slide 71

Solute concentration outside is Solute concentration outside is greater than cell concentration.greater than cell concentration.

Animal Cell: ShrinkAnimal Cell: ShrinkPlant Cell: PlasmolyzedPlant Cell: Plasmolyzed

““Hyper” - aboveHyper” - above

Slide 72

This is why it is dangerous to drink sea water - its a myth that drinking sea water will cause you to go insane, but people marooned at sea will speed up dehydration (and death) by drinking sea water.

This is also why "salting fields" was a common tactic during war, it would kill the crops in the field, thus causing food shortages.

Slide 73

Slide 74

Hypertonic, Isotonic and Hypertonic, Isotonic and HypotonicHypotonic

Slide 75

Slide 76

Slide 77

AActive ctive TTransransPPortort

Using a protein molecule to move Using a protein molecule to move particles up the concentration particles up the concentration

gradient.gradient.Requires ATP (Adenosine Requires ATP (Adenosine

Triphosphate)Triphosphate)

Slide 78

Example of how the cell Example of how the cell uses Active Transportuses Active Transport

Pump—Proteins that use active Pump—Proteins that use active transport to move particles transport to move particles

between the interior and exterior between the interior and exterior of the cell.of the cell.

e.g. Sodium/Potassium pump: e.g. Sodium/Potassium pump: Used to move sodium and Used to move sodium and

potassium ions across nerve potassium ions across nerve membranes.membranes.

Slide 79

Active Transport Versus Active Transport Versus Passive TransportPassive Transport

Slide 80

Large MoleculesLarge Molecules

Slide 81

Endocytosis: Cell membrane Endocytosis: Cell membrane indents around molecule and indents around molecule and

forms a vesicle.forms a vesicle.

Pinocytosis—Uptaking fluid moleculesPinocytosis—Uptaking fluid moleculesPhagocytosis—Uptaking solid moleculesPhagocytosis—Uptaking solid molecules

Slide 82

Pinocytosis and PhagocytosisPinocytosis and Phagocytosis

Slide 83

ExocytosisExocytosis

Vesicles fuse with cell membrane Vesicles fuse with cell membrane to release materials.to release materials.

Slide 84

Endocytosis and ExocytosisEndocytosis and Exocytosis

Slide 85

Homeostasismaintain internal physical and

chemical conditions

Unicellular organisms• Grow

• Respond to environment

• Transform energy

• Reproduce

Multicellular organisms

• Cells become specialized (move, react, produce substances) – particular tasks – communicate with one another

Levels of Organization• Cell-basic unit of life (muscle cell)

• Tissue-Cells working together to perform particular function (smooth muscle tissue)

• Organ-Group of tissues working together (heart, stomach)

• Organ System-organs working together to perform specific function (stomach, pancreas, intestines form digestive system)

• Organism-organisms working together; division of labor

Cellular Communication

• Receptors-on or in cell, a specific protein to whose shape fits that of a specific molecular messenger (hormone)