Microscopes and the CellThursday, October 17th

What is “cell theory”?

Who helped developed the cell theory?• 1665

• Robert Hooke• Observed cork under a primitive

microscope• Coined the term “cell”

• Looked like monks cells

Who helped developed the cell theory?• 1674

• Antonie van Leeuwenhoek• Observed and described the first microscopic

organisms• Father of microbiology• Improved the light microscope

• Made more than 25 different types

Who helped developed the cell theory?

• 1830’s– Schleiden (PLANTS) & Schwann (ANIMALS)– Worked independently but upon meeting, made important

connections in regards to the cell nucleus– Summarized many observations into what is now know as

the cell theory

• 1840’s– Virchow– Studied bacteria and disease– Claimed that bacteria was also made of cells

What is “cell theory”?

• Cell Theory (3 parts)1. All living things are made of cells. (Hooke)2. Cells are the basic unit of structure and

function in organisms. (Schleiden & Schwann)3. All cells come from other cells. (Virchow)

ELECTRON MICROSCOPES

LIGHT MICROSCOPE

UNAIDED EYES

What are the different types of microscopes?

• Light (or Optical)Microscope• Light passes through one or more lenses to enlarge

• Magnification = the ability to make things larger

• Resolution = the measure of clarity of an image

• Can magnify images:• 40x - 100x - 400x

Light Microscope

• Electron Microscopes (EMs) – Allows scientists to view a universe too small to

be seen with a light microscope

– Forms an image using a beam of electrons

– Focus a beam of electrons through a specimen (TEM) or onto its surface (SEM)

What are the different types of microscopes?

• Scanning Electron Microscope (SEM)– Provides for detailed study of the

surface of a specimen

– Creates a 3D image

– Cannot view living specimens

What are the different types of microscopes?

Surface of Tongue

Head louse clinging to a human hair

Eyelash hairs growing from the surface of human skin

The surface of a strawberry

Cut human hairs and shaving foam between two razor blades

Household dust – pollen, human hair, pet dander, leaf litter

Toothbrushbristle

Snowflake

• Transmission electron microscope (TEM)– Provides for detailed study of the internal

structure of cells– Electrons are passed through thin

specimens– 2 dimensional

What are the different types of microscopes?

TEM vs. SEM

Viruses leaving a cell

Cell Structure and Function

What are the common features of ALL cells?

• Cell Membrane: AKA plasma membrane– Encloses the cell– Separates the inside from the outside– Regulates what goes in & out of cell

• DNA– Genetic code

• Cytoplasm: the “fluid” inside of the cell– Provide support of internal structures– Site of cellular reactions

What are prokaryotes?

• Single celled organism that lack nuclei

• More primitive; appeared first in the geologic record

• Many have flagella, that help

them move

• Bacteria

What are eukaryotes?

• Have a nucleus– Compartment that

houses the DNA– Controls all functions of

the cell

• Have organelles– structures that carries

out specific jobs in the cell

What’s found in the nucleus?

• Nuclear envelope• A double membrane which encloses the nucleus– Has pores that regulate molecular traffic in and out

of the nucleus

• Chromosomes• Condensed and coiled DNA– Each species has characteristic chromosome

number

What is the cytoskeleton?

• Skeletal system of the cell membrane– Gives the cell its shape & structure– Involved with transport AND cell division

• Microtubules– Long hollow cylinders– Movement of chromosomes during

cell division

Cell membrane

Endoplasmicreticulum

Microtubule

Microfilament

Ribosomes Michondrion

Go to Section:

Cytoskeleton

What organelles are found within eukaryotes?

Endoplasmic Reticulum (ER)• Moves proteins/other substances through the

cell• Makes proteins from the ribosomes

– Rough ER is covered with ribosomes• Connected to the nucleus

– Smooth ER makes lipids (fats)• Ribosomes: structures that make

proteins

What organelles are found within eukaryotes?

• Golgi Apparatus/ Golgi Body• Packaging and distribution center• Modifies lipids and proteins from the ER• Ships out the new products to their final

destinations

• Vacuoles: Storage containers that can also provide structure

What organelles are found within eukaryotes?

• Mitochondria– Organelle that takes energy from sugar and turns

it into ATP (energy) that the cell can use– Has its own DNA

What are the organelles found only in plant cells?

• Cell wall– Made of proteins & carbohydrates– Helps keep the cell’s shape – Provides rigid support– Protects from cell damage– Connects the cell with adjacent cells

• Chloroplasts– Organelle that uses light energy to make

carbohydrates through photosynthesis

What are the organelles found only in plant cells?

• Central Vacuole– Large membrane covered space that

stores water and other substances

Plant Cell

An Animal Cell

Rough ER Smooth ER

Centrioles

CYTOSKELETON

Microfilaments

Microtubules

Lysosome

Golgi apparatus

Ribosomes

In animal cells but not plant cells:LysosomesCentriolesFlagella (in some plant sperm)

Flagella

ENDOPLASMIC RETICULUM (ER)

Mitochondrion

Nucleolus

DNA

Nuclear envelope

Plasma membrane

NUCLEUS

A Plant Cell

In plant cells but not animal cells:ChloroplastsCentral vacuoleCell wall

CYTO-SKELETON

Ribosomes (small brown dots)

Central vacuole

Micro-filaments

Micro-tubules

Rough endoplasmic reticulum

Smooth endoplasmic reticulum

DNANUCLEUS

Nuclear envelopeNucleolus

Chloroplast

Cell wall

Golgi

Plasma membrane

Mitochondrion

What are the 2 different cell types?

• Prokaryotic vs Eukaryotic– YOU are eukaryotic

• Larger cells• Found in all other kingdoms• Often multicellular• Nucleus• Contains membrane bound

organelles• Linear DNA• Asexual OR sexual

reproduction

• Small cells• Bacteria types• ALWAYS unicellular• No nucleus• No membrane bound organelles• Circular DNA• Asexual reproduction

EukaryoticProkaryotic

The Cell Membrane

What is the cell membrane made of?

• Provides protection and support for cells– Separates the cell from the outside environment

• Phospholipid– Molecule that allows the CM to be selectively

permeable • Certain substances can pass in and out of the cell

• Lipid Bilayer (2 layers)– Phospholipids - phosphate and 2 fatty acids

Cell Membrane

What is the cell membrane made of?• They are SELECTIVELY impermeable

• Some substances (not all) can pass across the membrane

• Hydrophobic tails…– Water HATING– Fats & oils

• Hydrophilic heads...– Water LOVING

What is the cell membrane made of?

• Protein channels– Allow nutrients (sugars or amino acids) to enter

the cell– Allow products of metabolism to leave (waste

products)– These channels are quite specific

• Recognize only a limited group of chemical substances to pass through the membrane

What is the function of the cell membrane?

• Gives the cell a flexible structure

• Forms a barrier between the cell and its environment

• Anchors the cytoskeleton to provide shape to the cell

• Attaches to the extracellular matrix to help group cells together (tissues)

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel

Lipid bilayer

Carbohydratechains

What is the Structure of the Cell Membrane?

What is the Structure of the Cell Membrane?

• Carbohydrates– Act like chemical ID cards– Allows individual cells to identify one another

• Membrane allows the following materials in and out of the cell:– Water, Glucose (sugars), Oxygen, chemical compounds

& wastes

How do things pass in and out of the cell?

• Concentration– # of molecules

present

• Diffusion– Spreading of

molecules OUT into available space

– From MORE concentratedto LESS concentrated

How do things pass in and out of the cell?

• Concentration– # of molecules

present

• DIFFUSION– Spreading out of

molecules into available space

– From MORE concentratedto LESS concentrated

DRAW THIS!

How do things pass in and out of the cell?

• Notice it’s not the MOLECULES THAT MOVE

• IT’S THE WATER/LIQUID SOLUTION

• Passive transport clip

DRAW THIS!

How do things pass in and out of the cell?

• Diffusion depends on random particle movements– Doesn’t require cellular ENERGY– Called PASSIVE TRANSPORT

Equilibrium

How do things pass in and out of the cell?

• Osmosis– The diffusion of WATER through a cell membrane

How do things pass in and out of the cell?

• Isotonic = Same strength– Concentrations are the same on either side of the

membrane• Hypertonic = Above strength

– More concentrated solution OUTSIDE of cell membrane

• Hypotonic = Below strength– Less concentrated solution OUTSIDE of cell

membrane

DRAW THIS DIAGRAM

Cellmembrane

Higher Concentrationof Water

Lower Concentrationof Water

Water molecules

Sugar molecules

Osmosis Video

Osmosis vs Diffusion

Diffusion Osmosis

Water? Doesn’t need Needs water for movement

What it is Spontaneous movement of molecules from high to low concentration

Spontaneous movement of WATER across a semipermeable mebrane, from high to low conc.

Process Mainly occurs in gases and liquids

Occurs when the medium (liquid) around a cell has a higher WATER concentration than the cell

What is another example of passive transport?

• Facilitated Diffusion– Passage of molecules

with transport proteins across a membrane

– Uses channels

– Does NOT require ENERGY

What is Active Transport?

• Movement of a substance against its concentration gradient with the use of ENERGY• Moving in the OPPOSITE direction• From LOW to HIGH concentration

• Active transport uses MOST of the energy a cell has for daily activities

• Active transport clip

What is Active Transport?

• Cells try to accumulate high concentrations of molecules they need:• Ions• Glucose (sugar)• Amino acids (proteins)

• Carried out by protein channels

What are the types of Active Transport?

• Exocytosis– Molecules EXIT through

the cell membrane

• Endocytosis– Molecules ENTERING

the cell through the membrane

– VIDEO

How is Passive different from Active Transport?

Passive Active

Does not use any type of energy

Uses energy (Active)

Examples: Examples:

Diffusion Exocytosis

Osmosis Endocytosis

Specialization vs Differentiation• SPECIALIZATION - Multicellular organisms have cells

that perform SPECIFIC jobs • Ex – blood cells carry nutrients, skin cells

protect the interior of the body– Cells work together to perform a specific function

for TISSUES• Similar tissue types make up ORGANS• Organs function together make up ORGAN

SYSTEMSCells Tissues Organs Organ Systems Organisms

Specialization vs Differentiation

• DIFFERENTIATION– Normal process where less specialized cells

develop to perform a function– A fertilized egg (zygote) will develop into an

adult human being– Stem cells will develop into neurons,

somatic cells and germ cells