What are cells?How many types are there?How Cells Are Put Together?

What are cells?How many types are there?How Cells Are Put Together?

Chapter 4

We shall cover the first part today and the rest next time

Chapter 4

We shall cover the first part today and the rest next time

It is the….

Smallest unit of life

Can survive on its own (or can do so if it

has to)

Is highly organized for metabolism

Senses and responds to environment

Has potential to reproduce

It is the….

Smallest unit of life

Can survive on its own (or can do so if it

has to)

Is highly organized for metabolism

Senses and responds to environment

Has potential to reproduce

What is a CellWhat is a Cell

Structure of CellsStructure of Cells

All start out life with: Plasma membrane Region where DNA

is kept Cytoplasm

All start out life with: Plasma membrane Region where DNA

is kept Cytoplasm

Two types of cells exist:

ProkaryoticEukaryotic

Why Are Cells So Small?Why Are Cells So Small?

Cells absorb stuff across their membranes…

Surface-to-volume ratio

The bigger a cell is, the less surface area there

is per unit volume

Above a certain size, material cannot be moved

in or out of cell fast enough

Cells absorb stuff across their membranes…

Surface-to-volume ratio

The bigger a cell is, the less surface area there

is per unit volume

Above a certain size, material cannot be moved

in or out of cell fast enough

Remember ElephantsRemember Elephants

Why don’t we see 90 foot high elephants. It would be better for them.

They would need ears as big as sail ship sails to cool themselves based on their lack of surface area…

Why don’t we see 90 foot high elephants. It would be better for them.

They would need ears as big as sail ship sails to cool themselves based on their lack of surface area…

Surface-to-Volume RatioSurface-to-Volume Ratio

Mid 1600s - Robert Hooke observed and

described cells in cork

Late 1600s - Antony van Leeuwenhoek

observed sperm, microorganisms

Mid 1600s - Robert Hooke observed and

described cells in cork

Late 1600s - Antony van Leeuwenhoek

observed sperm, microorganisms

Early DiscoveriesEarly Discoveries

Cell TheoryCell Theory

1) Every organism is composed of one or more

cells

2) Cell is smallest unit having properties of life -

therefore viruses are not considered living

3) Continuity of life arises from growth and division

of single cells - we are all related to the very first

life forms on this Planet

1) Every organism is composed of one or more

cells

2) Cell is smallest unit having properties of life -

therefore viruses are not considered living

3) Continuity of life arises from growth and division

of single cells - we are all related to the very first

life forms on this Planet

Create detailed images of

something that is otherwise too

small to see

Light microscopes Simple or compound

Electron microscopes Transmission EM or Scanning EM

Create detailed images of

something that is otherwise too

small to see

Light microscopes Simple or compound

Electron microscopes Transmission EM or Scanning EM

Tools of Biology - MicroscopesTools of Biology - Microscopes

Limitations of Light MicroscopyLimitations of Light Microscopy

Wavelengths of light are 400-750 nm

If a structure is less than one-half of a wavelength long, it will not be visible

Light microscopes can resolve objects down to about 200 nm in size

Wavelengths of light are 400-750 nm

If a structure is less than one-half of a wavelength long, it will not be visible

Light microscopes can resolve objects down to about 200 nm in size

Tools - Electron MicroscopyTools - Electron Microscopy

Uses streams of accelerated electrons rather than light

Electrons are focused by magnets rather than glass lenses

Can resolve structures down to 0.5 nm

Uses streams of accelerated electrons rather than light

Electrons are focused by magnets rather than glass lenses

Can resolve structures down to 0.5 nm

Electron Microscope

Electron Microscope

incoming electron beam

condenser lens (focuses a beam of electrons onto specimen)

specimen

objective lens

intermediate lens

projector lens

viewing screen (orphotographic film)

Main component of cell membranes

Gives the membrane its fluid properties

Two layers of phospholipids

Main component of cell membranes

Gives the membrane its fluid properties

Two layers of phospholipids

The cells skin - The Lipid Bilayer

The cells skin - The Lipid Bilayer

Fluid Mosaic ModelFluid Mosaic Model

Membrane is a mosaic of Phospholipids Glycolipids Sterols Proteins

Most phospholipids and some proteins can drift

through membrane MOVIE link above

Membrane is a mosaic of Phospholipids Glycolipids Sterols Proteins

Most phospholipids and some proteins can drift

through membrane MOVIE link above

Membrane ProteinsMembrane Proteins

Adhesion proteins - GLUES

Communication proteins - INFO

Receptor proteins - INBOUND

Recognition proteins

Adhesion proteins - GLUES

Communication proteins - INFO

Receptor proteins - INBOUND

Recognition proteins

Continue…How are cells put together?

Continue…How are cells put together?

Watch me please!Watch me please!

Include just Archaea and eubacteria

DNA is not enclosed in nucleus

DNA is not enclosed in nucleus

DNA is not enclosed in nucleus

DNA is not enclosed in nucleus

Generally the smallest, simplest cells

No organelles

Include just Archaea and eubacteria

DNA is not enclosed in nucleus

DNA is not enclosed in nucleus

DNA is not enclosed in nucleus

DNA is not enclosed in nucleus

Generally the smallest, simplest cells

No organelles

Prokaryotic CellsProkaryotic Cells

Prokaryotic StructureProkaryotic Structure

bacterial flagellum pilusplasma membrane

DNA in nucleoid region

cytoplasm, with ribosomes

Most prokaryotic cells have a cell wall outside the plasma membrane, and many have a thick, jellylike capsule around the wall.

bacterial flagellum

Eukaryotic CellsEukaryotic Cells

Have a nucleus and other organelles

Eukaryotic organisms Plants Animals Protistans Fungi

Have a nucleus and other organelles

Eukaryotic organisms Plants Animals Protistans Fungi

Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery of cytoplasm

Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells

Keeps the DNA molecules of eukaryotic cells separated from metabolic machinery of cytoplasm

Makes it easier to organize DNA and to copy it before parent cells divide into daughter cells

WHY HAVE AN NUCLEUS?Functions of Nucleus

WHY HAVE AN NUCLEUS?Functions of Nucleus

Nuclear EnvelopeNuclear Envelope

Two outer membranes (lipid bilayers) Innermost surface has DNA attachment sites Pores span bilayer

Two outer membranes (lipid bilayers) Innermost surface has DNA attachment sites Pores span bilayer

one of two lipid bilayers (facing nucleoplasm)

NUCLEAR ENVELOPE

one of two lipid bilayers (facing nucleoplasm)

nuclear pore (protein complex that spans both lipid bilayers)

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

http://video.search.yahoo.com/video/play?vid=1079578458&vw=g&b=0&pos=1&p=endomembrane+system&fr=yfp-t-501

SEE IT!

Group of related organelles in which lipids are assembled and new polypeptide chains are modified

Products are sorted and shipped to various destinations

POST OFFICE OF THE CELL

Group of related organelles in which lipids are assembled and new polypeptide chains are modified

Products are sorted and shipped to various destinations

POST OFFICE OF THE CELL

Canals inside cellsEndoplasmic Reticulum (ER)

Canals inside cellsEndoplasmic Reticulum (ER)

Components of Endomembrane System

Components of Endomembrane System

Endoplasmic reticulum

Golgi bodies

Vesicles

Endoplasmic reticulum

Golgi bodies

Vesicles

Endoplasmic ReticulumEndoplasmic Reticulum

In animal cells, continuous with nuclear

membrane

Extends throughout cytoplasm

Two regions: rough and smooth

In animal cells, continuous with nuclear

membrane

Extends throughout cytoplasm

Two regions: rough and smooth

Rough ERRough ER

Arranged into flattened sacs Ribosomes on surface give it a

rough appearance Some polypeptide chains enter

rough ER and are modified Cells that specialize in secreting

proteins have lots of rough ER

Arranged into flattened sacs Ribosomes on surface give it a

rough appearance Some polypeptide chains enter

rough ER and are modified Cells that specialize in secreting

proteins have lots of rough ER

Smooth ERSmooth ER

A series of interconnected tubules No ribosomes on surface Lipids assembled inside tubules Smooth ER of liver inactivates

wastes, drugs Sarcoplasmic reticulum of muscle

is a specialized form

A series of interconnected tubules No ribosomes on surface Lipids assembled inside tubules Smooth ER of liver inactivates

wastes, drugs Sarcoplasmic reticulum of muscle

is a specialized form

Golgi BodiesGolgi Bodies

Put finishing touches on proteins and lipids that arrive from ER

Package finished material for shipment to final destinations

Material arrives and leaves in vesicles

Put finishing touches on proteins and lipids that arrive from ER

Package finished material for shipment to final destinations

Material arrives and leaves in vesicles

VesiclesVesicles

Membranous sacs that move

through the cytoplasm

Lysosomes

Peroxisomes

Membranous sacs that move

through the cytoplasm

Lysosomes

Peroxisomes

Central VacuoleCentral Vacuole

Fluid-filled organelle Stores amino acids, sugars, wastes As cell grows, expansion of vacuole as

a result of fluid pressure forces cell wall to expand

In mature cell, central vacuole takes up 50-90 percent of cell interior

Fluid-filled organelle Stores amino acids, sugars, wastes As cell grows, expansion of vacuole as

a result of fluid pressure forces cell wall to expand

In mature cell, central vacuole takes up 50-90 percent of cell interior

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

ATP-producing powerhouses

Double-membrane system

Carry out the most efficient energy-

releasing reactions

These reactions require oxygen

Similar to Ancient bacteria in chemistry

ATP-producing powerhouses

Double-membrane system

Carry out the most efficient energy-

releasing reactions

These reactions require oxygen

Similar to Ancient bacteria in chemistry

MitochondriaMitochondria

Mitochondrial StructureMitochondrial Structure

Outer membrane faces cytoplasm Inner membrane folds back on itself Membranes form two distinct

compartments ATP-making machinery is embedded in

the inner mitochondrial membrane

Outer membrane faces cytoplasm Inner membrane folds back on itself Membranes form two distinct

compartments ATP-making machinery is embedded in

the inner mitochondrial membrane

ChloroplastsChloroplasts

Convert sunlight energy to ATP through photosynthesisConvert sunlight energy to ATP through photosynthesis

Like Bacteria?Like Bacteria?

Both mitochondria and chloroplasts

resemble bacteria

Have own DNA, RNA, and ribosomes

Both mitochondria and chloroplasts

resemble bacteria

Have own DNA, RNA, and ribosomes

Plant Cell FeaturesPlant Cell FeaturesCENTRAL VACUOLE

LYSOSOME-LIKE VESICLE

GOLGI BODY

SMOOTH ER

ROUGH ER

RIBOSOMES

NUCLEUS

CHLOROPLAST

CYTOSKELETON

MITOCHONDRION

PLASMODESMA

PLASMA MEMBRANE

CELL WALL

Animal Cell FeaturesAnimal Cell Features

CYTOSKELETON

MITOCHONDRION

CENTRIOLES

LYSOSOME

GOLGI BODY

SMOOTH ER

ROUGH ER

RIBOSOMES

NUCLEUS

PLASMA MEMBRANE

Present in all eukaryotic cells

Basis for cell shape and internal organization

Allows organelle movement within cells and, in some cases, cell motility

Present in all eukaryotic cells

Basis for cell shape and internal organization

Allows organelle movement within cells and, in some cases, cell motility

CytoskeletonCytoskeleton

Length of microtubules or microfilaments can change

Parallel rows of microtubules or microfilaments actively slide in a specific direction

Microtubules or microfilaments can shunt organelles to different parts of cell

Length of microtubules or microfilaments can change

Parallel rows of microtubules or microfilaments actively slide in a specific direction

Microtubules or microfilaments can shunt organelles to different parts of cell

Mechanisms of Movement Mechanisms of Movement

Structural component that wraps around the plasma membrane

Occurs in plants, some fungi, some protistans

Structural component that wraps around the plasma membrane

Occurs in plants, some fungi, some protistans

Cell WallCell Wall

Primary cell wall of a young plant

Plasma membrane

Plant Cell WallsPlant Cell Walls

Primary cell wall

Secondary cell wall(3 layers)

Plant CuticlePlant Cuticle

Cell secretions and waxes accumulate at plant cell surface

Semi-transparent

Restricts water loss

Cell secretions and waxes accumulate at plant cell surface

Semi-transparent

Restricts water loss

Matrixes between Animal CellsMatrixes between Animal Cells

Animal cells have no cell walls

Some are surrounded by a matrix of cell

secretions and other material

Animal cells have no cell walls

Some are surrounded by a matrix of cell

secretions and other material

Cell Junctions - [molecular staples]

Cell Junctions - [molecular staples]

Plants Plasmodesmata

Animals Tight junctions Adhering junctions Gap junctions

Plants Plasmodesmata

Animals Tight junctions Adhering junctions Gap junctions

plasmodesma

Animal Cell JunctionsAnimal Cell Junctionsfree surface ofepithelial tissue(not attached to any other tissue)

examplesof proteinsthat make up tightjunctions

gapjunctions

basement membraneadhering junction