Cell TheoryTopic 2.1

Assessment Statements2.1.2 Outline the cell theory.2.1.2 Discuss the evidence for the cell theory2.1.3 State that unicellular organisms carry out all the

functions of life2.1.4 Compare the relative sizes of molecules, cell

membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit

2.1.5 Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification

2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size

2.1.7 State that multicellular organisms show emergent properties

2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others

2.1.9 State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways

2.1.10 Outline one therapeutic use of stem cells

Cell theory

1. All organisms are composed of one or more cells

– Cells 1st observed in 1665 by Robert Hooke while observing cork with a microscope he built

– Antonie van Leeuwenhoek observed 1st living cells, “animacules”

– In 1838 Mathias Schleiden stated that plants are made of “independent, separate beings” called cells

– In 1839 Theodor Schwann made a similar statement about animals

2. Cells are the smallest units of life– No living entity found has not been made

of at least one cell

3. All cells come from pre-existing cells– Supported by Louis Pasteur in 1860s

through experiments that disproved spontaneous generation

• Possible exceptions?

Functions of life

1. Metabolism (all chemical reactions that occur within an organism)

2. Growth 3. Reproduction

(hereditary molecules that can be passed to offspring)

4. Response 5. Homeostasis

(maintenance of a constant internal environments)

6. Nutrition (providing a source of compounds that can be broken down to provide organism with energy and nutrients)

Cells and sizes

• Most cells are up to 100 μm (micrometers)

• Organelles are up to 10 μm

• Bacteria are up to 1 μ

• Viruses are up to 100 nm (nanometers)

• Membranes are 10 nm thick

• Molecules are near 1 nm

• All objects are 3-D

Calculating size

• Know the diameter of the microscope’s field of vision using a simple ruler

• Size of specimen can then be calculated in the field

Types of microscopes• Light microscope

– type found in most schools (including ours), uses compound lenses and light to magnify objects

– The lenses bend, or refract the light, which makes the object beneath them appear closer. 

– Magnifies objects up to 2000 times. 

– Two dimensional images– Poor resolution– Bonuses:  Relatively

inexpensive, can view living organisms in color

• Electron microscope– use electrons (negatively

charged electrical particles) to view the specimen

– Types:• Scanning

– 3D images– Magnifies 50,000 X– Non-living specimens

• Transmission– 2D images– Magnifies 2,000,000 X– Non-living specimens

– High magnification and resolution

Limiting cell size

• Why must cells be small?• Surface area to volume ratio• Homeostasis dependent upon volume• Greater surface area able to move more

materials in and out• A large cell has relatively less surface are

than a small cell• What about large cells?

Calculating SA/V of a sphere

• SA=4πr2

• V=(4/3) πr3

Cell reproduction and differentiation

• Allows possibility of growth and replacement of damaged or dead cells

• Multicellular organisms begin as a single cell that reproduces at a rapid rate

• Resulting cells go through differentiation as a result of the expression of genes

• Some cells lose ability to reproduce once they become specialized

Stem cells

• What are stem cells?• Populations of cells that retain their

ability to divide and differentiate into various cell types

• Ex. Meristematic tissue in plants, embryonic (pluripotent) in animals

• Cannot be distinguished by appearance; only by behavior

Stem cell research

• Directed towards growing large numbers of embryonic stem cells in culture

• Used to replace differentiated cells lost due to injury and disease

• Parkinson’s disease and Alzheimer’s disease are caused by loss of brain cells and it is hoped that implanted stem cells could replace many of these lost brain cells

• Other examples: diabetes, leukemia

Ethical issues

• What is the controversy?

• Where do you stand in the debate?

• How do you feel about the source of pluripotent stem cells?

Prokaryotic CellsTopic 2.2

Assessment Statements

2.2.1 Draw and label a diagram of the ultrastructure of Escherichia coli as an example of a prokaryote

2.2.2 Annotate the diagram with the functions of each named structure

2.2.3 Identify structures from 2.2.1 in electron micrographs of E. coli

2.2.4 State that prokaryotic cells divide by binary fission

What is a prokaryotic cell?

• Most are less than 1 μm in diameter

• DNA not enclosed within a membrane and is one circular chromosome

• DNA not attached to proteins

• Lack membrane-bound organelles

• Cell wall made of peptidoglycan

• Divide by binary fission

E. Coli ultrastructure

• Be able to draw and label:– Cell wall

– Plasma membrane

– Flagella

– Ribosomes

– Nucleoid (region containing free DNA)

Cell wall

• Protects and maintains the shape of the cell

• Composted of carbohydrate-protein complex called peptidoglycan

• Some bacteria have an additional layer of polysaccharide (capsule) outside cell wall which makes it possible for some to adhere to structures

Plasma membrane

• Just inside cell wall • Controls movement of materials in and out of

the cell• Plays a role in binary fission• Cytoplasm occupies the interior of the cell and

is location for all cellular processes• Most visible structure is single chromosome

Pili

• Hair-like growths on outside of the cell wall

• Used for attachment

• Main function is joining bacterial cells in preparation for the transfer of DNA from one cell to another

Flagella

• (sing.) or flagellum (pl.)

• Longer than pili

• Allow cell motility

Ribosomes

• Occur in all prokaryotic cells

• Function as sites of protein synthesis

• Occur in very large numbers in cells with high protein production

Nucleoid region

• Non-compartmentalized• Contains a single, long, continuous, circular

thread of DNA• Involved in cell control and reproduction• Cell may also contain plasmids which replicate

independently of the chromosomal DNA• Plasmids are not required but may help the cell

adapt to unusual circumstances

Binary fission

• Process by which prokaryotes divide– DNA is copied– 2 daughter chromosomes become attached to

different regions on the plasma membrane– Their movement is aided by fibers made of

protein called FtsZ– Cell divides into two genetically identical

daughter cells

Paul the Prokaryote

• While watching the clip list as many facts about prokaryotes that you see depicted

Eukaryotic CellsTopic 2.3

Assessment Statements

2.3.1 Draw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell

2.3.2 Annotate the diagram with the functions of each named structure

2.3.3 Identify structures from 2.3.1 in electron micrographs of liver cells

2.3.4 Compare prokaryotic and eukaryotic cells2.3.5 State three differences between plant and animal

cells2.3.6 Outline two roles of extracellular components

What is a eukaryotic cell?

• Range in diameter from 5 to 100 μm

• Noticeable nucleus

• Compartmentalized due to presence of organelles (non-cellular structures which carry out specific functions)

Common organelles

• Endoplasmic reticulum• Ribosomes• Lysosomes• Golgi apparatus• Mitochondria• Nucleus• Chloroplasts• Centrosomes• Vacuoles

Typical Animal Cell

Liver Cell

Typical Plant Cell

Cytoplasm

• Within plasma membrane

• Fluid between organelles is called cytosol

Endoplasmic reticulum

• Extensive network of tubules or channels

• Transports materials throughout the internal region of the cell

• Two types:– Rough (has ribosomes

attached)– Smooth (lacks ribosomes)

• Rough– Involved in protein

development and transport– Closer to nuclear membrane

• Smooth– Produces lipids, sex

hormones– Detoxifies drugs– Stores calcium ions – Transports lipid-based

compounds– Aids liver in release of

glucose

Ribosomes

• Carry out protein synthesis

• May be free or attached to ER

• Composed of RNA and protein

• Larger and denser than those found in prokaryotes

Lysosomes

• Digestive centers that arise from the Golgi apparatus

• Contains enzymes that break down proteins, nucleic acids, lipids and carbohydrates

Golgi apparatus

• Made of flattened sacs called cisternae

• Collects, packages, modifies and distributes materials synthesized in the cell

Mitochondria

• Produces usable cellular energy called ATP through process of cellular respiration

• Has its own DNA and ribosomes

• Capable of reproducing independent of cell

Nucleus

• Region where DNA is located• Bordered by nuclear envelope which has

numerous pores that allows communication with the cell’s cytoplasm

• DNA occurs in form of chromosomes or chromatin

• Some cells extrude their nucleus and are more specialized for a specific function

• Nucleolus within nucleus produces ribosomes

Chloroplasts

• Occur only in plant and algae cells

• Contains its own DNA in the form of a ring

• Includes grana, thylakoids, and stroma

• Carries out photosynthesis

• Capable of reproducing independent of cell

Centrosome

• Pair of centrioles at right angles to one another

• Involved in assembling microtubules which provide structure and movement of cell

Vacuoles

• Formed from Golgi apparatus

• Store potential food, metabolic wastes, toxins, and water

• Enable plants to have higher surface area to volume ratios even at larger sizes

• In plants, they provide rigidity when filled with water

Prokaryotic vs. Eukaryotic

Prokaryotic cells

• DNA in a ring w/out protein

• DNA free in cytoplasm

• No mitochondria

• 70S ribosomes

• No internal compartmentalization

• < 10 μm

Eukaryotic cells

• DNA with proteins as chromosomes/chromatin

• DNA enclosed

• Mitochondria present

• 80S ribosomes

• Internal compartmentalization

• > 10 μm

Prokaryotic AND Eukaryotic

• Both have outer boundaries that always involves a plasma membrane

• Both carry out all the functions of life

• Both have DNA

Plant vs. Animal

Plant cells

• Exterior of cell includes cell wall

• Chloroplasts present

• Large central vacuole

• Store carb. as starch

• Do not contain centrioles

• Has a fixed, often angular shape

Animal cells

• Only plasma membrane; no cell wall

• No chloroplasts

• Vacuoles not present or small

• Store carb. as glycogen

• Contain centrioles

• Cell is flexible and more likely to be rounded in shape

Outermost regions

• Bacteria– Cell wall of

peptidoglycan

• Fungi– Cell wall of chitin

• Yeasts– Cell wall of glucan

and mannan

• Algae– Cell wall of cellulose

• Plants– Cell wall of cellulose

• Animals– No cell wall

– Extracellular matrix made of glycoproteins

Functions of extracellular components

• Cell wall – maintains cell shape– Helps regulate water

intake

• Extracellular matrix (ECM)

– Composed of collagen and glycoproteins

– Strengthens plasma membrane

– Allows for cell-to-cell interaction, possibly altering gene expression

– Directs stem cells to replicate

– Cell migration and movement