IB Topic 2.1-2.3

Prokaryote and

Eukaryote Cells

Cell Theory

A. There are 3 main points

1. All living organisms are composed of cells.

2. Cells are the smallest unit of life.

3. All cells come from pre-existing cells

Cell theory: history and evidence

A. The discovery of cells is linked to technological advancements (microscopes)

B. 1590-Jansen developed the compound microscope (it had two lenses)

C. 1665-Robert Hooke discovered the cell1. Looking at cork

D. 1675-Leeuwenhoek discovered unicellular organisms

E. 1838-Mathius Schleiden

discovered all plants are

made of cells

F. 1839-Theodore Schwann

discovered all animals are

made of cells

G. 1855-Rudolph Virchow discovers all organisms are made of cells

**organism=any living thing

Characteristics of Life: (single cell or multi-cell)

1. Order (organization) – from small to large

-Ex: Organelles make up cells.

Cell make up tissues.

Tissues make up organs.

Organs make individuals.

2. Metabolism- organisms take in and release energy

3. Response (to the environment)- response to stimuli

4. Growth and development- heritable programs of DNA direct growth and development (change in one’s shape during life)

5. Homeostasis- organisms have regulatory mechanisms to maintain their internal environments

Examples: body temperature, blood sugar, osmoregulation

6. Reproduction- the ability to reproduce ones own kind

7. Evolutionary adaptation- life evolves as a result of interaction between organisms and their environment

Multicellular organismsA. Multicellular organisms show emergent

properties

B. Emergent properties arise from interaction of the components:

- The whole is greater than the parts (Ex: a heart cannot function without the whole body)

- A single cell can do nothing on its own, but when you put all of the cells together they can perform many functions

Multicellular organisms and differentiation

A. Multicellular organisms differentiate to carry out specialized functions

B. All cells originated from the same place and all carry the genetic information to perform any function (your toe cell could have been a brain cell)

C. In each cell there is only a small amount of activated genetic material

Ex: All cells have the genes for taste. The only cells with activated ‘taste’ genes are on your tongue.

Stem Cells1. Have ability to reproduce and

differentiate

1. Embryo cells all start out as stem cells

2. Valuable for scientific research

3. May be able to differentiate stem cells to desired cell type

4. These may replace damaged cells

Sources:• Embryonic – cells from human blastocysts• Fetal – cells from aborted fetuses• Umbilical cord stem cells – cells from the umbilical cord of

newborns• Placenta derived stem cells – cells from the placenta and

amniotic fluid of newborns• Adult – cells from adult tissue (bone marrow, fat...)

Homework-Outline one therapeutic use of stem cells for humans or some other

animal.

DO NOT USE WIKIPEDIA AS YOUR RESOURCE!!

You may use any government or university website. Their websites generally end

in .edu or .gov.

Viewing Cells1. Light microscopes :

- See color images

- have a larger field of view

- prepare samples easily

- observe living and non-living material

**We cannot see most cell organelles

2. Electron microscopes: - must be dead and no real colors

Scanning Electron (SEM):

- electron beams that bounce off the specimen

Transmission Electron (TEM):

- Used electron beams that pass through specimen

(more detail because they have a higher resolution)

Transmission Microscope (guess what these structures are...)

Scanning Microscope

Microscope Vocabulary

1. Resolution- describes clarity of pictures

-higher resolution = more detailed pictures

2. Magnification- makes objects larger

3. An increase in magnification may reduce the resolution

Calculating Linear Magnification

A. The formula-

Magnification = size of image

size of specimen

B. Example-the object is magnified by two

This is the magnified image.

This is the original object.

Diameter of the image=4cmDiameter of the specimen=2 cm Find the magnification.

Common SI Unit Conversions

1nm (nanometer) = 1 x 10-9 m

1ųm (micrometer) = 1 x 10-6 m

1mm (millimeter) = 1 x 10-3 m

1cm (centimeter) = 1 x 10-2 m

1m (meter) = 1m

1km (kilometer) = 1 x 103 m

Calculating linear magnification• Take a measurement of the drawing (width or

length)• Take this same measurement of the specimen  • Remember to convert units if needed to• Place your values into the equation• Magnification = length of drawing / length of

actual specimen• You can also calculate the length of the

specimen if this is unknown: length of the drawing / magnification.

VIDEO: http://www.youtube.com/watch?v=L1d-02yRsRE

Limitations to Cell Size

A. Cells cannot grow indefinitely

B. They reach a maximum size and divide.

C. Bigger cells are less efficient.

-They have to transport materials further.

-The smaller the surface area to volume ratio the harder it is for the cell.

How Big Is A Cell?OBJECT SIZE

Eukaryotic 10-100 μm

Prokaryotic 1-5 μm

Nucleus 10-20 μm

Chloroplast 2-10 μm

Mitochondrion 0.5-5 μm

Large virus (HIV) 100 nm

Ribosome 25 nm

Cell membrane 7.5 nm

DNA dbl. helix 2 nm

H atom 0.1 nm

Diagram of a typical prokaryote

Prokaryote organelles1. Cell wall- gives the cell structure and strength (covered by sticky

capsule)

2. Plasma membrane- separates the internal features from the outside environment

3. Cytoplasm- holds cell’s organelles and

enzymes

4. Pili- help the cell hold on to other

structures and aid in movement

5. Flagella- aid in organism movement

6. Ribosomes- make protein from mRNA

7. Nucleoid- area containing naked DNA

(ring)

8. Slime capsule- a protective barrier

around the cell (may help shield it from

antibiotics)

An electron micrographs of E. coli

** For IB you must be able to identify the structures on a micrograph.

http://www.cellsalive.com/index.htm

(b) A thin section through the bacterium Bacillus coagulans (TEM)

Pili: attachment structures onthe surface of some prokaryotes

Nucleoid: region where thecell’s DNA is located (notenclosed by a membrane)

Ribosomes: organelles thatsynthesize proteins

Plasma membrane: membraneenclosing the cytoplasm

Cell wall: rigid structure outsidethe plasma membrane

Capsule: jelly-like outer coatingof many prokaryotes

Flagella: locomotionorganelles ofsome bacteria

(a) A typical rod-shaped bacterium

0.5 µmBacterialchromosome

Prokaryote reproduction

1. Most prokaryotes divide by binary fission

Eukaryote Cells

Eukaryote Information

1. All eukaryotes have enclosed nuclei and other membrane bound organelles

2. Eukaryotes are true cells (‘eu’ = true)3. Eukaryotic cells are present in protists,

plants, fungi and animal4. Animal cells have a secretory vesicle

-It secretes glycoproteins that makeup the extracellular matrix-The extracellular matrix functions in support, adhesion and movement

Animal Cell Organelles:• Nucleus: contains genetic material, controls the cell• Ribosome: synthesizes proteins from mRNA.

– Free floating, rough ER, chloroplast and mitochondria.• Rough ER: synthesizes proteins to be excreted by the

cell• Smooth ER: synthesizes lipids and carbs• Golgi Apparatus: modifies, packs and ships via vesicles• Lysosome: digestion (enzymes)• Peroxisome: produces and breaks down hydrogen

peroxide• Mitochondrion: aerobic respiration, converts chemical

energy into ATP using oxygen

• A animal cell

Rough ER Smooth ER

Centrosome

CYTOSKELETON

Microfilaments

Microtubules

Microvilli

Peroxisome

Lysosome

Golgi apparatus

Ribosomes

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

Nucleolus

Chromatin

NUCLEUS

Flagelium

Intermediate filaments

ENDOPLASMIC RETICULUM (ER)

Mitochondrion

Nuclear envelope

Plasma membrane

Figure 6.9

Plant CellsOrganelles found in plants only:- cell wall:

-provides rigid support for the cells-made mostly of cellulose-plays important role in turgor (hardening of cells by the intake of water)-prevents cells from taking in too much water

- chloroplasts- organelle required for photosynthesis

- vacuole- membrane bound sac used for storage of organic compounds

• A plant cell

In plant cells but not animal cells:ChloroplastsCentral vacuole and tonoplastCell wallPlasmodesmata

CYTOSKELETON

Ribosomes (small brwon dots)

Central vacuole

Microfilaments

Intermediate filaments

Microtubules

Rough endoplasmic reticulum Smooth

endoplasmic reticulum

ChromatinNUCLEUS

Nuclear envelope

Nucleolus

Chloroplast

PlasmodesmataWall of adjacent cell

Cell wall

Golgi apparatus

Peroxisome

Tonoplast

Centrosome

Plasma membrane

Mitochondrion

Figure 6.9

Summary of differences between eukaryotes and prokaryotes!

Prokaryotic Cells Eukaryotic cells

small cells (< 5 mm) larger cells (> 10 mm)

always unicellular often multicellular

no nucleus or any membrane-bound organelles

always have nucleus and other membrane-bound

organelles

DNA is circular, without proteins (naked)

DNA is linear and associated with proteins to form

chromatin (not naked)

ribosomes are small (70S) ribosomes are large (80S)

no cytoskeleton always has a cytoskeleton

cell division is by binary fission

cell division is by mitosis or meiosis

reproduction is always asexual

reproduction is asexual or sexual