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UNIT 3: CELLS

T H E O RY, T Y P E S , S T R U C T U R E S , M O V E M E N T

UNIT 3 TOPIC 1: THE CELL THEORY

By the end of this topic, I will be able to…

1. List the three components of the cell theory

2. Describe the importance of each of the contributors to the cell

theory

– Virchow, Schleiden, Schwann, Leeuwenhoek, Hooke

3. Relate the invention of the microscope to the development of the

cell theory

THE CELL THEORY

Three components:

1. All living things are composed of cells

2. Cells are the basic unit of structure and function in living

things

3. All cells come from preexisting cells

HOW DID WE GET THE CELL THEORY?

What tool do we need to see most cells?

The microscope!

People you should know involved with this tool:

• Anton van Leeuwenhoek – he used to grind lenses and

assemble them together to make microscopes

• Robert Hooke – he observed fleas and cork; while looking at

cork, he saw what he called cells. He discovered plant cells (he

did not know this) AND coined the term cell.

– Why did he call them “cells?”

• When he looked at the cork (in 1665), he saw what looked like

thousands of chambers, or little boxes, and called them cells (like a prison

cell or monastery cell, where monks live)

WHAT HOOKE SAW (HIS DRAWINGS)

Fleas

Flies

Snowflakes

Cells

LEEUWENHOEK(1678)

• Worked on ways to make superior lenses (again, he would grind and

reassemble lenses together)

– Did NOT invent the microscope (it was invented nearly 40 years before he was born- in

the 1590s)

• Developed a lens tube with a magnifying power of 270x

• He was the first to see and describe bacteria, yeast, and “animalcules” (little

animals)

– Observed the animalcules in pond water and on his own dental scrapings (plaque)

– His observations are among the first observations ever recorded for bacteria

WHAT LEEUWENHOEK SAW

YEARS AND YEARS OF NO PROGRESS….

Nothing really drastic happens between the work of Hooke/Leeuwenhoek and our next

scientists for close to two centuries

Why?

Likely, because people believed in spontaneous generation and were unwilling to believe anyone

telling them otherwise.

What’s that?

The belief that something living can come from something non-living. We will revisit this in

evolution later this year!

LOUIS PASTEUR

Finally put an end to the debate on where living things come from and disproved spontaneous

generation with his famous experiment:

Living things only come from living things

1838-1839

Two German scientists, Matthias Schleiden and Theodor Schwann, continue studying living things.

• 1838 – Matthias Schleiden (botanist, so studies plants) concluded that all plants are made of

cells

• 1839 – Theodor Schwann (physiologist) concluded that all animals are made of cells

AND FINALLY, VIRCHOW

1855: Rudolph Virchow concluded that all cells come from

preexisting cells (part 3 of the cell theory)

THE CELL THEORY

The 3 Basic Components of the Cell Theory were now complete:

1. All organisms are composed of one or more cells. (Schleiden &

Schwann)(1838-39)

2. The cell is the basic unit of life in all living things. (Schleiden &

Schwann)(1838-39)

3. All cells are produced by the division of preexisting cells.

(Virchow)(1858)

LANGUAGE TARGET: 30-ISH MINUTES

• In the small space in your notes, sketch a timeline highlighting development of

the cell theory

• After you have the dates/people/events/images set out, create your timeline on

the slip of paper available to you in the front

• When done, work on microscope parts handout

Timeline Component Value (points)

Date (Year) 2.5 (.5 points per date)

Person with description of work 5 (1 point per person with description)

Image (COLORED) relating to work 2.5 (.5 points per image)

UNIT 3 TOPIC 1 ENRICHMENT: THE MICROSCOPE

By the end of this topic, you should be able to…

1. Label a microscope and explain the function of each part

2. Bring a specimen into focus when using a compound light

microscope

3. Write about the history of the microscope

HISTORY OF THE MICROSCOPE

• The first microscope is believed to have been invented in/around the 1590s by

Hans and Zacharias Jansen

– Zacharias was a spectacle maker that is credited with inventing the first microscope.

However, he was born ~1580, so he would have been very young in 1590.

– It is believed his father, Hans, assisted him in the building of the first microscope.

HOOKE & LEEUWENHOEK

• These two made improvements on the microscope by modifying the lenses.

• Leeuwenhoek's instruments consisted of simple powerful magnifying glasses,

rather than the compound microscopes (microscopes using more than one

lens) of the type used today or in Zacharias Jansen's original microscope

design.

• Leeuwenhoek's design is extremely simple, using a single lens mounted in a tiny

hole in a brass plate that makes up the body of the instrument. The specimen

was then mounted on a sharp point that sticks up in front of the lens. Its

position and focus could be adjusted by turning the two screws. The entire

instrument was only 3-4 inches long, and had to be held up close to the eye,

requiring good lighting and great patience to use.

TODAY’S MICROSCOPEPLEAS E NOTE … WE WI LL ONLY BE DI S CUS S I NG THE COMPOUND LI G HT MI CR OS COPE (WE MAY A DDR ES S THE S EM AND TEM L ATER I N THE COUR S E)

• The scopes we use in class are compound microscopes

– Have more than one lens

• Convex lenses are used to build the microscopes (and glasses)

– These lenses bend light and focus it in one spot

– Bending Light: The objective (bottom) convex lens magnifies and focuses (bends) the image inside

the body tube and the ocular convex (top) lens of a microscope magnifies it (again).

Ocular Lens

(Magnifies Image)Objective Lens

(Gathers Light,

Magnifies

And Focuses Image

Inside Body Tube)

Body Tube

(Image Focuses)

PARTS OF THE MICROSCOPE• Objective lenses

• Body tube

• Ocular lens

• Nosepiece

• Stage clips

• Diaphragm

• Light source

• Arm

• Stage

• Adjustment knobs

• Base

TOP FUNCTIONS

• Ocular Lens (eyepiece): magnifies the specimen (typically 10x) and what you

look through to observe the specimen

• Body Tube: holds the objective lens(es) the proper distance from the ocular

lens

• [Revolving] Nosepiece: holds the objective lens(es); turn this to switch

objective/magnification

• Arm: holds the body tube/nosepiece/objective lenses; used to support the

microscope; always carry with one hand on the arm

• Objective Lenses: increase/decrease magnification; change power; use the

nosepiece to switch between objective lenses

MIDDLE FUNCTIONS

• Stage: flat surface used to hold the specimen/slide

• Stage clips: two clips used to hold the slide/specimen in place; always use

these!

• Diaphragm: controls the amount of light coming through the

specimen/slide

• Coarse adjustment knob: moves the stage up and down (quickly) for

focusing your image

– This is the larger of the two adjustment knobs

– Never use this on high power!

BOTTOM FUNCTIONS

• Fine adjustment knob: this is the smaller of the two adjustment

knobs and it is used to move the stage slightly to sharpen the image

• Light source: projects light upwards through the slide/specimen,

diaphragm, and lenses

– Usually a light, though can be a mirror

• Base: supports the microscope; always carry with one hand on the

base

MAGNIFICATION

• To determine your magnification…you just multiply the ocular lens by the

objective lens

• Ocular 10x Objective 40x:10 x 40 = 400

Objective Lens have

their magnification

written on them.

Ocular lenses usually magnifies by 10x

So the object is 400 times “larger”

CARING FOR A MICROSCOPE

• Clean only with a soft cloth/tissue

• Make sure it’s on a flat surface

• Don’t bang it

• Carry it with 2 HANDS…one on the arm and the other on the base

USING A MICROSCOPE

• Start on the lowest magnification

• Don’t use the coarse adjustment knob on high

magnification…you’ll break the slide!!!

• Place slide on stage and lock clips

• Adjust light source

• Use fine adjustment to focus

UNIT 3 TOPIC 2: CELL TYPES AND STRUCTURES


1. Discuss similarities and differences between prokaryotic and eukaryotic cells

2. Identify a cell as being prokaryotic or eukaryotic based on cellular components

3. Explain the function of cellular organelles

4. Compare and contrast plant and animal cells

5. Explain how cells work together in multicellular organisms

TYPES OF CELLS• There are MANY types of cells (skin, brain, liver…), but cells are generally classified as

either prokaryotic or eukaryotic.

• Some things that all cells, regardless of type, have in common are:

1. Water- nearly 70% of the mass of each cell is water

2. Macromolecules-

1. Every cell contains a genetic code (nucleic acids)

2. Every cell has hundreds of proteins with unique functions, like cellular

communication or transport or structure (keratin)

3. Every cell contains lipids that are used for energy storage, cell communication,

and protective barriers (cell membrane contains lipids, as does nuclear membrane)

4. Every cell contains carbohydrates, also used in cellular communication, energy

storage, and used for structural support

3. Cell membrane, cytoplasm, and ribosomes

REVISITING UNIT 2 ☺

BEFORE CONTINUING…• What is the monomer for:

– Carbohydrates:

– Lipids:

– Proteins:

– Nucleic acids:

• Explain what the phrase “water is polar” means

– How does this allow water to dissolve so many solutes?

• Describe how invention of the microscope helped scientists understand cells

ANSWERS• What is the monomer for:

– Carbohydrates: monosaccharides/simple sugars

– Lipids: fatty acids/ triglycerides

– Proteins: amino acids (build a polypeptide)

– Nucleic acids: nucleotides







There is an uneven distribution of electrons, giving one side (the oxygen) a partially negative

charge and the other side (the hydrogen) a slightly positive charge


The negative end attracts positive molecules and the positive end attracts negative

molecules










Before the microscope was invented, cells could not been seen. Once the microscope was

invented, scientists could see individual cells as well as what is inside of them.

EXAMPLES OF CELLS

Amoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

TYPES OF CELLSAgain, there are two general types:

1. Prokaryotic: pro means before, kary refers to karyon (kernel)

1. Before kernel (before nucleus)

2. Older, simpler, smaller… bacteria

2. Eukaryotic: eu means true

1. True kernel (true nucleus)

2. Younger, more complex, larger… animal, plant, protist, fungi

PROKARYOTIC CELLS

• Smaller than eukaryotic cells (smaller surface area to volume ratio)

– Size is important because the smaller the cell, the easier it is to have nutrients

reach inner parts of the cell (they also get through the cell quicker)

• Eukaryotic cells have organelles that assist in moving nutrients/waste

• DNA is circular and located in the cytoplasm (“nucleoid region”)

• Less complex than eukaryotic cells (no membrane bound organelles)

– Do contain ribosomes (site of protein synthesis)

• Surrounded by a cell wall outside of the cell membrane

EVOLUTION OF CELLS• Prokaryotic cells likely appeared on earth

approximately 3.8 billion years ago

– We will look at how these cells could have

developed later in the year (evolution unit)

• It involves conditions of earth’s early

atmosphere (lacked oxygen) and the

synthesis of organic molecules

– Photosynthetic bacteria evolved ~3 billion years

ago (oxygen released into atmosphere)

• Eukaryotic cells evolved around 2.7 billion years ago

– Endosymbiotic theory

• Multicellular organisms evolved roughly 1.7 billion

years ago (plants & animals)

CELLSNote that

archaebacteria and

eubacteria are both

closer to eukaryotic

cells than they are to

one another. Scientists

have found that

archaebacterial genes

are more similar to

eukaryotic genes than

they are to eubacterial

genes, suggesting that

archaebacteria share a

common line of

evolutionary descent

with eukaryotes.

ENDOSYMBIOTIC THEORY

Define theory (again): A well-substantiated explanation of some aspect of the

natural world, based on a body of facts that have been repeatedly confirmed

through observation and experiment.

The endosymbiotic theory explains how scientists believe that eukaryotic cells

evolved from prokaryotic cells

ENDOSYMBIOSIS

What is happening?

Essentially, a larger prokaryotic cell engulfs (but does not digest) a smaller

prokaryotic cell. The smaller cell is then living within the larger cell and

operating as a specialized organelle.

EUKARYOTIC CELLS• Larger than prokaryotic

• More complex

– Contain specialized organelles

• Exist either as single-celled organisms or as part of multicellular organelles

– Human body is made of more than 200 kinds of cells! These cells work together to make up five main types of tissue: epithelial, connective, blood, nervous, and muscle tissue.

– Recall: cells of the same organism contain the same DNA, but not all of the genes are activated in every type of specialized cell

• Each type of cell is modified to work in the way the organism needs it to (may differ in size, shape, or function)

SPECIALIZED CELLSA stem cell is a non-

specialized cell that can

either replicate itself

(produce more stem cells)

or differentiate into a

specialized cell. A stem cell

can differentiate into a liver

cell, but a liver cell cannot

change into a nerve cell. A

cell specializes (often) during

interphase before cell

division. Stem cells are

either embryonic (derived

from an embryo) or can be

adult stem cells

(undifferentiated cells from a

mature organism).

GENERAL EUKARYOTIC CELL

• Cell membrane

• Cilia/flagella

• Cytoplasm

• Cytoskeleton

• Nucleus

• Ribosomes

• Endoplasmic Reticulum

• Golgi Body

• Mitochondria

• Lysosome

• Vacuole

• Chloroplast

• Cell wall

PLANT V ANIMAL CELL

PLANT ANIMAL

Chloroplasts/ Cell wall/ Large Vacuole Lysosome

CELL MEMBRANE• Also referred to as the plasma

membrane

• Surrounds the cytoplasm

• Is the outermost part of animal

cells, but not for plant cells

• Plays a large roll in cell transport

(topic 3 this unit)

– Controls movement of

materials into and out of the

cell

– Selectively permeable (does

not allow all things into the

cell)

CILIA/FLAGELLA

• Used for cell movement

• Cilia:

– Shorter/greater in number

– Move fluids using sweeping

motion

• Flagella:

– Longer and typically one per

cell

– Propels cell using whip-like

motions

CYTOPLASM

• Suspends the organelles

• Jelly-like fluid within the cell

membrane

• Also known as the cytosol

CYTOSKELETON• A structure that maintains the shape and size of cells

• A network of microtubules (thicker) and microfilaments (thinner)

– Long protein strands

NUCLEUS• The control center of the cell,

housing the DNA (master copy of

a cell’s genetic material)

• The nucleus is surrounded by the

nuclear membrane, which has lots

of little pores (RNA exits through

these)

• Within the nucleus is the

nucleolus, and this is where

ribosomes are produced

RIBOSOME

• Small particles of RNA and protein scattered

throughout the cytoplasm

• This is the site of protein synthesis (proteins are

made here)

ENDOPLASMIC RETICULUM• An interconnected network of flattened sacs

• Joins with the outer membrane of the

nucleus

• Two types:

– Rough ER: coated in ribosomes (makes

proteins)

– Smooth ER: lacks the ribosomes on its

exterior

• Known as the “highway” or the

transportation system because it folds and

moves proteins

– Sends them to the golgi apparatus/body

GOLGI APPARATUS (GOLGI BODY)

• Made of membrane-bound sacs

• Processes, sorts, and packages cellular

components (proteins and lipids) “Post

Office”

• Can produce lysosomes

• Works directly with the ER

MITOCHONDRIA• Acts as the powerhouse of the cell

– Produces ATP, the energy currency of

the cell

• Contains DNA (not unique to an individual

though, runs through the family- get it from

your mom because it is carried in the

female egg)

• Double membrane

• Varies from 1 to 10,000 mitochondria in a

single (specialized) cell

– Muscle cells contain lots of

mitochondria. Why? Need lots of energy!

LYSOSOME• Membrane-enclosed organelles with lots

of enzymes used to break down polymers

– Lysis = to break or to burst

• Functions as the digestive system of the

cell

• Maintain an acidic pH within the

lysosome

• Debate as to whether this is only found

in animal cells… leaning towards this

organelle being found in both animal and

plant cells

VACUOLE• Fluid filled organelle that stores enzymes,

waste, and water

• Often the largest organelle in plant cells- can

take up to 80% size of the cell (much smaller in

animal cells)

CHLOROPLAST• Found only in plant cells, this

is the location of

photosynthesis

– Converts light energy to

chemical energy

• Double membrane

• Contains DNA

• Green in color because it

contains the pigment

chlorophyll

CELL WALL

• Found in plant cells (and

bacteria and fungi), not in

animal cells

• Located outside the cell

membrane

• Leads to plant cells having a

square/rectangular shape

• Supports and protects the cell

• Made of cellulose (in plant

cells)

– Remember, this is a

polysaccharide!

CENTRIOLES

• Only found in animal cells-

located near nucleus

• Assists in cell division

– Develops spindle fibers

ANIMAL CELL

Mitochondria

Nucleus

Golgi

Cytoplasm

ER

Ribosomes

Cell Membrane

PLANT CELL

Cytoplasm

Vacuole

Cell wall

Cell membrane

Chloroplast

Nucleus

Mitochondria

ER

Ribosome

Golgi body

UNIT 3 TOPIC 3: CELL TRANSPORT


1. Label a cell membrane with its components and explain the function of each component

(carbohydrates, phospholipid head/tail, proteins)

2. Explain what “a cell membrane is selectively permeable means”

3. Explain why the cell membrane is known as the Fluid Mosaic Model

4. Compare and contrast passive transport (diffusion, facilitated diffusion, osmosis) with active

transport (endocytosis, exocytosis)

5. Discuss the importance of surface area to volume ratio

THE CELL MEMBRANE

• Task: regulate movement

into and out of the cell

• Parts you need to know:

1. Lipid bilayer

2. Carbohydrate

3. Proteins (integral and

peripheral)

4. Cholesterol

ARRANGEMENT OF LIPID BILAYER• 2 sheets of phospholipids (a lipid with a head &

two tails)

– Head = hydrophilic

• Hydro: water

• Philia: love, fondness, affinity for

– Arranged on the outsides of the

bilayer due to it’s love for water

(constant contact)

– Tails = hydrophobic

• Hydro: water

• Phobia: fear of or aversion to

– Arranged on the inside of the bilayer

so it is away from water

OTHER COMPONENTS, 1• Carbohydrates

– Attach as a chain to membrane proteins

or lipids

• Glycoprotein- carbohydrates

attached to protein

• Glycolipid- carbohydrates attached

to lipid

– Protect the cell

• These are used for cell recognition

– Differentiate between things that

can enter the cell and things that

cannot enter the cell

OTHER COMPONENTS, 2• Proteins

– Allow for interactions between cells and

transport of materials

– Integral proteins: embedded within the cell

membrane

• Usually transmembrane (extends the length

of the membrane to connect the inside of

the cell with the outside)

• Can act as pathways for materials to enter

and exit the cell

– Peripheral proteins: attached to the exterior

(outside) of the lipid bilayer (or other

membrane)

• Wingmen for other membrane proteins

(partner with other proteins- can be used

for transport from one part of the cell to

another by attaching to these other

proteins)

OTHER COMPONENTS, 3• Cholesterol

– Maintains the integrity of cell

membranes

• Without cholesterol, cell

membranes would be too

fluid and too permeable

– Used to maintain fluidity

of the cell membrane by

preventing crystallization

of the tails in the bilayer

– Involved with cell to cell

communication (due to closeness

with proteins on the cell

membrane)

FLUID MOSAIC MODEL• Fluid combination of

phospholipids, cholesterol, and

proteins

– Separate but loosely attached

molecules

– Different parts of the

membrane float in a fluid-like

space

– Dynamic and scattered with

these different molecules

(mosaic-like)

SO HOW DO THINGS GET INTO AND OUT OF CELLS?• By moving across a concentration gradient (moving from one side of the cell

to the other)

– Concentration: mass of solute in a given volume of solution

• Cell transport

– Passive: no energy required, solutes move down the concentration gradient

– Active: energy required, solutes move up the concentration gradient

SIMPLE DIFFUSION

• Molecules move down the concentration

gradient

– from an area of high concentration to

an area of low concentration

• Passive

– No energy required

• Oxygen and carbon dioxide move

through cells using simple diffusion

FACILITATED DIFFUSION• Some substances, like glucose,

are too large to fit through the

cell membrane without

assistance

• These larger molecules must

use channel proteins to be

carried across the cell

membrane

• Still moving down the

concentration gradient and still

a passive process

OSMOSIS

• This is the movement (diffusion) of

water across a cell membrane

• Passive process

• Molecules move down the

concentration gradient

– Movement depends on type of

solution (hypertonic, isotonic,

hypotonic)

SOLUTION TYPES

HYPERTONIC

Solution outside the cell has a higher solute

concentration and lower water

concentration than inside the cell

• Water LEAVES the cell

HYPOTONIC

Solution outside the cell has a lower solute

concentration and higher water

concentration than inside the cell

• Water ENTERS the cell

SOLUTION TYPES, CONT.

ISOTONIC

The concentration of solute (and water) is

the same outside the cell as inside the cell

• Water moves equally in both directions

• No NET movement

REAL LIFE EXAMPLE: RED BLOOD CELLS

• Red blood cells

• Plant cells

REAL LIFE EXAMPLE: PLANT CELL

ACTIVE TRANSPORT• Movement up the concentration gradient

– From areas of low concentration to areas of high concentration

• Active because this requires energy (ATP)

• Molecular pumps are used to transport materials across the membrane

– Each pump moves one type of molecule

ENDOCYTOSIS AND EXOCYTOSIS

• Endocytosis

– Endo = within

– Cyto = cell

• Movement INTO the

cell

• Exocytosis

– Exo = exit/leave

– Cyto = cell

• Movement OUT OF

the cell

ENDOCYTOSIS• Two types: phagocytosis and pinocytosis

– Phagocytosis: essentially, cell eating

(bringing solids into the cell)

• Ph sounds like fuh… same start

as food (solid)

– Pinocytosis: essentially, cell drinking

(bringing liquids into the cell)

• Think pina colada, which is a

drink!

• In either case, the material is brought into

the cell through vesicles that form around

the material

EXOCYTOSIS

• Products of the ER are

packaged into vesicles at

the Golgi and are then sent

to and released at the cell

membrane

SURFACE AREA TO VOLUME RATIO• Each part of the cell relies on the cell surface. As a

cell grows, its volume grows and the cell membrane

expands. The volume increases quicker than the

surface area.

– Surface area available to pass materials to a unit

volume of the cell steadily decreases.

• If the cell grows too big, not enough material can

come into the cell to accommodate the larger cell

volume.

– cell must divide into smaller cells with favorable

surface area/volume ratios, or cease to function.

• The important point is that the surface area to the

volume ratio gets smaller as the cell gets larger.

unit 3: cells - weebly · the 3 basic components of the cell theory were now complete: 1. all...

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