2.2 PROKARYOTIC CELLS2.3 EUKARYOTIC CELLSAND MICROSCOPE ANATOMY!

IB Bio SL

2.2 Prokaryotic Cells

� Please use your text to complete the handout on the Prokaryotic cell outcomes

2.3 Eukaryotic Cells

� Please use your text to complete the worksheet on the Eukaryotic Cell outcomes

What is a Prokaryotic Cell?

� Are cells that lack membrane bound organelles or any type of cells nucleus.

� They are cells that are

much smaller and

simpler than Eukaryotic

cells.

� In fact most Prokaryotic

cells are less than one

micrometre in

diameter!

The beginning of life

� Prokaryotic cells are thought to be the first to have appeared on earth.

� Prokaryotic cells still play a large role in the world

today. Bacteria is a good example.

Features of Prokaryotic Cells

� The features of the Prokaryotic cell that you will have to identify are:

� Cell wall

� Plasma membrane

� Pili &Flagella

� Ribosomes

� Nucleoid

Cell wall

� Protects and maintains the shape of the cell.

� In most prokaryotes the cell wall is composed of a carbohydrate-protein

complex called

peptidoglycan.

� Some bacteria have an

additional layer outside

the cell wall that allows

them to stick to teeth,

skin and food.

Plasma membrane

� Controls the movement of materials into and out of the cell.

� It also plays a role in binary fission (stay tuned)

Pili

� Are hair-like growths on the outside of the cell wall.

� They are used for attachment.

� Their main function is in

joining bacteria cells in

preparation for the

transfer of DNA.

(sexual reproduction)

Flagella

� Are hair-like growths (longer than pili) that are used for cell motility.

Ribosomes

� Function as the sites of protein synthesis.

� Ribosomes typically

occur in very large

numbers in cells

with high protein

production.

� The ribosomes in prokaryotic cells are small (70s)

Nucleoid Region

� Because bacteria cells are non-compartmentalized and contain a single, long, continuous, circular thread of DNA...

� This region is involved

in the control of the

cell as well as

reproduction.

Binary Fission

� Is the simple process by which prokaryotic cells divide.

1. The circular DNA is copied

2. Two daughter chromosomes become attached to different regions on the plasma memberane.

3. The cells divide into two genetically identical daughter cells.

� The process includes; elongating of the cell, and partitioning of the newly produced DNA.

Binary Fission

Endosymbiotic Theory

� http://learn.genetics.utah.edu/content/begin/cells/organelles/

� We’ll revisit this idea in the evolution unit!

Global Connections...

� Prokaryotes and clean water resources

� Lifesaver bottle with Michael Pritchard

� http://www.ted.com/talks/lang/eng/michael_pritc

hard_invents_a_water_filter.html

2.3 Eukaryotic Cells What do you need to know?

� Draw a diagram of a liver cell including...

� Free ribosomes

� rough endoplasmic

reticulum

� lysosome

� Golgi apparatus

� mitochondrion

� nucleus

Free Ribosomes

� very small structures (about 80S) that carry out protein synthesis in the cell.

� Free ribosomes are found floating in the cytoplasm and others are found attached to the rough ER.

� Ribosomes are composed

of RNA and protein and are

larger in eukaryotic cells

than prokaryotic cells.

Eukaryotic ribosomes

are composed of two subunits.

Endoplasmic reticulum

� an extensive network of channels that stretches from the nucleus to the plasma membrane.

� Its function is to transport materials through the cell.

� There are two types of ER, rough ER and smooth ER.

� The rough ER is

distinguished by the

ribosomes attached

to its exterior surface.

� The advantage of having ribosomes attached to ER is that as the ribosomes synthesize proteins they can be transported by the ER to become parts of cell membranes, enzymes for the cell or messengers between cells.

� The smooth ER has many functions such as production of membrane phospholipids, production of sex hormones, breaks down harmful substances, stores calcium ions, transports lipid based compounds, and aid liver cells in releasing glucose into the blood when needed.

Lysosome

� single membrane bound organelles produced by the Golgi apparatus that contain strong hydrolytic enzymes which break down biological molecules.

� They can contain up to 40 different enzymes and can also break down worn out

cell parts that are no longer

functioning properly.

� Lysosomes are involved in

breaking down materials

brought into a cell via

phagocytosis.

Golgi apparatus

� this organelle is composed of many flattened sacs called cisternae which are stacked on top of each other and it is normally located between the ER and plasma membrane.

� The Golgi apparatus collects, packages, modifies and distributes materials throughout the cell.

� It is located close to the ER to receive products transported by the ER and close to the plasma membrane so it can discharge materials needed outside the cell.

� This organelle is found in high numbers in cell that produce and secrete substances (i.e. pancreas cells).

Mitochondrion

� very large, double membrane bound rod-shaped organelles that are found scattered in the cytoplasm and contain their own DNA.

� Their outer membrane

is smooth while their

inner membrane is highly

folded into cristae which

increase the surface area

of the inner mitochondria

for cellular respiration, the

main function of the mitochondria.

� Due to its size and ability to produce energy in the form of ATP, mitochondria also have their own ribosomes.

� Mitochondria are found in high numbers in cells that have high energy needs (i.e. muscle cells).

Nucleus

� eukaryotic DNA is housed inside the double membrane or nuclear envelop of the nucleus.

� The double membrane allows the DNA to remain separate from the rest of the cell and carry out its functions without interference from the other parts of the cell.

� The nuclear membrane

contains pores that allows

for communication with

the rest of the cell.

� DNA is contained in the form of chromosomes within the nucleus.

� The nucleus is normally located in the center of the eukaryotic cell but is often pushed to the side in plant cells due to the large vacuole.

� Most cells have one nuclei but some have multiple nuclei while others have

none (i.e. red blood cells).

� If there is no nucleus the

cell cannot reproduce.

� Most nuclei often have a

nucleolus a dark area inside

the nucleus where ribosomes

are manufactured.

See inside a cell!

� http://learn.genetics.utah.edu/content/begin/cells/insideacell/

� http://www.cellsalive.com/cells/3dcell.htm

Comparison between prokaryotic and eukaryotic cells

Feature PROKARYOTIC CELLS EUKARYOTIC CELLS

Genetic material Contain a naked loop of DNA. Sometimes referred to as

a nucleoid.

Contain four or more chromosomes consisting of strands of DNA

associated with protein.

Location of genetic material

Naked DNA found in region of the cytoplasm called nucleoid.

Located inside the double membrane of the nucleus;

sometimes referred to as the nuclear envelop.

Cont’dFeature PROKARYOTIC CELLS EUKARYOTIC CELLS

Mitochondria Prokaryotes do not contain

mitochondria. The surface of the cell membrane and the

mesosome are used to produce cellular energy.

Eukaryotic cells all contain

hundreds of mitochondria.

Ribosomes Ribosomes are smaller in prokaryote cells. (70S)

Ribosomes are larger in eukaryote cells. (80S)

Membrane bound organelles or

internal membranes

Few or none are present. Eukaryotic cells contain several membrane bound organelles

such as ER, Golgi apparatus and lysosomes.

Size Measure less than 10

micrometers.

Measure more than 10

micrometers.

Difference between plant and animal cells

FEATURE ANIMAL CELL PLANT CELL

Cell wall No cell wall. Cells have a

plasma membrane only.

Contains a cell wall with a

plasma membrane just inside.

Chloroplasts Not found in animal cells. All plants that carry out

photosynthesis contain

chloroplasts.

Carbohydrate

storage

Animal cells store

carbohydrates in the form of

glycogen.

Plant cells store carbohydrates

in the form of starch.

Cont’d

FEATURE ANIMAL CELL PLANT CELL

Vacuole Not normally present in animal

cells. Some small vesicles are

sometimes formed.

Plant cells contain one large

central fluid filled vacuole.

Shape Usually a rounded shape but the

plasma membrane is flexible and

can change shape.

Plant cells have a fixed shape

due to the cell wall. Often box-

like or angular in shape.

Centrioles Contains centrioles within a

centrosome area.

Do not contain centrioles within

a centrosome area.

Extracellular components

� Extracellular components are structures outside the plasma membranes of cells.

� One commonly known example is the cell wall in plant cells.

� Another example of an extracellular component is the extracellular matrix of animal cells as well as

bone and cartilage.

The Cell Wall

� The cell wall is composed of cellulose microfibrils which form a thick wall surrounding the entire cell.

� The cell wall grows with the cell, continually adding more cellulose to maintain its thickness.

� The cell wall protects the plant cell and helps to maintain its shape.

� The cell wall also protects the cell from too much water entering and helps the cell maintain osmotic balance.

� Since it is made of cellulose, the plant cell can use the cell wall to store carbohydrates.

Extracellular matrix of animal cells

� The extracellular matrix of animal cells is composed of glycoproteins and collagen fibres.

� Together they form a fibre-like structure that anchors the matrix to the plasma membrane.

� The ECM adds strength to the plasma membrane, allows cell to cell interactions, and allows adjacent cells to attach to one another

� Cartilage is made of cells with a lot of extracellular material which gives cartilage its firm, resilient structure

Light Microscopes

• The ocular lens in the eyepiece magnifies and transmits the image to your eye

• The magnification of the ocular lens is 10X

• To find the total magnification of the microscope you are using, multiply the magnification of the objective lens by the magnification of the ocular lens.

• For example: 40X (objective lense) x 10X (ocular lense) = 400X magnification

The Parts of a Light Microscope

• Light source: Could be a mirror, but most likely it is a bulb built into the base

• Diaphragm: Adjusts the amount of light striking an object

• Objective lens: Gathers light and magnifies image

• Ocular lens (eyepiece): Magnifies objects and focuses light to your eye

• Stage: Holds slide– Can be moved using the coarse or fine

adjustment knobs to bring the object into focus

• Stage clips: Hold slide in place

• Base and arm: Structural support for the microscope

Can you name the parts?Start on the left side and work from the top down. Then go to the right side

and work from the top down.

Nice Job !

Objective Lenses

Stage

Diaphragm

Light Source

Base

Fine adjustment

Course adjustment

Stage clip

Arm

Ocular lens (eyepiece)

Images Produced by Light Microscopes

Amoeba Streptococcus bacteria Anthrax bacteria

Human cheek cells Plant cells Yeast cells

Fun in the lab!

� Cells that you eat! Yumm!

� You will examine several plant and animal cells under the light microscope – super-fun!