CellsCytology

I. The Cell Theory 2.1.1

Made up of three parts:1. All living things are made up of cells2. Cells come from other cells3. Cells are the basic unit of structure

of all living things

THE CELL THEORY 2.1.2

Evidence to support the cell theory:

1. Robert Hooke first views “cells” in cork (1665)2. Anton von Leeuwenhoek views living cells in

algae (1674)3. Schwann and Schleiden study plants and

come up with the theory (1838)4. Improved microscopes have allowed for a

more exact study of living things, and no organism has been discovered that is not made of cells

Arguable “EXCEPTIONS” to the Cell Theory: Some tissue has extracellular material (like

tooth dentine), and the cells make up only a tiny percentage of the total tissue volume

Skeletal muscle “cells” contain hundreds of nuclei each (and can be 30 cm in length)

Hyphae cells in fungus are continuous due to septa, and have many nuclei

Viruses are non-cellular (and thus debatably “non-living”

Consist of only DNA or RNA surrounded by a protein coat

Unicellular organisms are unique (and argued by some to be “acellular”) because they carry out all the Functions of Life within a single cytoplasm… (2.1.3)

Functions Of Life

1. Metabolism – chemical reactions necessary for life

2. Response 3. Homeostasis – maintenance of

internal stability (equilibrium)4. Growth5. Reproduction6. Nutrition

Stem Cells (2.1.9 & 2.1.10)

There are between 10 and 100 trillion cells in a human body. There are also approx half as many bacteria in there as well. Each cell has ~ 30,000 genes, and about 3 billion nucleotide pairs. There are ~100 billion neurons in the brain, and about 25 times as many support cells (glia.)

There are between 10 and 100 trillion cells in a human body. There are also approx half as many bacteria in there as well. Each cell has ~ 30,000 genes, and about 3 billion nucleotide pairs. There are ~100 billion neurons in the brain, and about 25 times as many support cells (glia.)

•Stem Cells are unique cells that are undifferentiated, meaning that they don’t yet have an identity, or function. •Depending on the type of stem cell, they may be induced to become any particular type of cell.•Due to the work of Christopher Reeve, stem cells are now being use to regrow neural tissue (in mice.)

10 mm 100 µm 1 µm 10 nm 0.1 nm

1 mm 10 µm 100 nm 1 nm

Every step to the left represents an increase of 10X

The size of a molecule (DNA = 2nm)

Thickness of a cell membrane 2.1.5

Size of a virus

Average bacteriaSize of

organelles (varies)

Eukaryotic cells

1 mm = 1 x 10-3 meters =1 “millimeter”

1 µm = 1 x 10-6 meters = 1 “micrometer”

1 nm = 1 x 10-9 meters = 1 “nanometer”

(1 angstrom)

Resolution of human eye

II. Importance of Surface Area to Volume ratio in determining cell size (2.1.6)

•Cells can not keep growing – they reach a maximum size and then divide

Sides S.A. Vol Ratio

1 cm 2 cm 3 cm 4 cm 5 cm

For a cube…

As the cell gets larger, the surface area to volume ratio gets SMALLER

Sides S.A. Vol Ratio

1 cm 6 cm2 2 cm 24 cm2 3 cm 54 cm2 4 cm 96 cm2 5 cm 150 cm2

For a cube…

As the cell gets larger, the surface area to volume ratio gets SMALLER

Sides S.A. Vol Ratio

1 cm 6 cm2 1 cm3 2 cm 24 cm2 8 cm3 3 cm 54 cm2 27 cm3 4 cm 96 cm2 64 cm3 5 cm 150 cm2 125 cm3

For a cube…

As the cell gets larger, the surface area to volume ratio gets SMALLER

Sides S.A. Vol Ratio

1 cm 6 cm2 1 cm3 6 2 cm 24 cm2 8 cm3 3 3 cm 54 cm2 27 cm3 2 4 cm 96 cm2 64 cm3 1.5 5 cm 150 cm2 125 cm3 1.2

For a cube…

As the cell gets LARGER, the surface area to volume ratio gets SMALLER

…cell size, cont’d

The rate that things can enter and leave a cell depend on the surface area

The metabolic rate depends on volume Cells that get too large can’t take in

essential materials (food!) or excrete wastes quickly enough

The same principle holds true for heat – cells must be able to release it

•Small cells are the most efficient, because they can easily transport materials throughout the cell…

1) 4 cm2) 2 cm

3) 1 cm

All blue/black

Example: Potato cubes (starch) in Iodine

III. Prokaryotic vs. Eukaryotic

“Before” “Nucleus” “True” “Nucleus”

A. Prokaryotic Cell = “bacteria”

Cell WallSlime CapsuleRing-shaped chromosome (DNA)“Naked DNA”… (only loosely associated with proteins)

Plasmid (DNA)

PlasmaMem-brane

RibosomeMesosome

p5 in IBRB – 2.2.1

cytoplasm

1.

3.

5.

6.

7.

2.

4.

8.

Basal Body

9.

10.

...diagram explanation 2.2.2

Ribosome – protein synthesis; 70s Mesosome (extra)– increases the

surface area of the plasma membrane for more ATP production; might move naked DNA to different ends of the cell during bacterial cell division (called binary fission)

Slime Capsule – protection; adhesion (tooth plaque)

Flagellum – movement

Make sure you can label these things in an E. coli micrograph – use the IBRB! 2.2.3

Cell Wall – protects from bursting or shrinking Plasma Membrane – controls passage of

material in and out of cells Naked DNA (nucleoid)– stores genetic

information; located in an area of the cell called the nucleoid; DNA not associated with histone proteins like eukaryotic DNA (thus naked)

Cytoplasm – contains enzymes to catalyze reactions important for metabolism

Pili- used for adhering to surfaces as well as joining to other bacteria in order to conjugate- that means SEX!!

Multi-cellular organisms vs. Unicellular organisms

Multicellular organisms All cells have the same DNA but… differentiated cells carry out specialized functions by expressing some of their genes but not others 2.1.8 “cell differentiation” – when

cells become specialized in structure and function

Unicellular organisms carry out all of the functions of life within a single cell 2.1.3

• Multicellular organisms show “emergent properties” (2.1.7)– When a number of simple entities

(in this case cells) come together to form a more complex collective

Cardiac muscle cells

form this cardiac TISSUE

Cardiac tissue comes

together to form the heart (an ORGAN)

The heart is a single organ that comes together to

form the cardiovascular system (an

ORGAN SYSTEM)

B. Eukaryotic Cells Nucleus – stores genetic material in chromatin

(DNA mixed with proteins); during cell division the chromatin clumps into chromosomes; membrane bound

Ribosomes (free and rough)– make proteins, ribosomes have no membranes; 80s In the cytoplasm or on the ER depending on what sort

of proteins they produce (for the cell or to be secreted) Endoplasmic reticulum – network of

interconnecting tubes; continuous with the nuclear membrane; detoxifies molecules, produces lipids, metabolizes carbs, makes membranes …

*Make sure you can label and annotate a diagram! 2.3.1, 2.3.2,2.3.3

Golgi body (apparatus) – accepts vesicles from the ER that contain proteins needing to be processed and exported from the cell (as glycoproteins, lipoproteins… glycolipids) cis – end nearest to the nucleus and the ER trans – face nearest to the cell membrane Vesicles – membrane-bound “packages” in the

cell used to transport molecules around safely… Mitochondria – enclosed in an envelope of

two phospholipid bilayers; site of cellular respiration (making ATP through catabolism)

Lysosomes – contains hydrolytic digestive enzymes to break the 4 major biological molecules down (so their parts can be used elsewhere)

•Using all of the eukaryotic organelles, explain their functions as they work together to produce some cellular product.

C. Prokaryotic vs. Eukaryotic

See p. 6 in IBRB (differ in type of DNA, location of DNA,

presence of mitochondria for ATP synthesis, size of ribosomes (.70S vs .80S), and membrane-bound organelles) 2.3.4

See p. 6 in IBRB (differ in presence of cell wall, chloroplasts,

and vacuole, type of carbohydrate used for storage, and shape) 2.3.5

D. Plant vs. Animal Cell

E. Extracellular components – the plant cell wall 2.3.6

(wall protects, maintains shape, and prevents

excessive water uptake)

Microfibrils (bundles) of CellulosePectin

(DON’ T WRITE): Pectin is an adhesive which helps to hold plant cells together (it is added to jam as a thickener, and removed from fruit juice with pectinase to keep it from solidifying)

Cell wall is 10X-100X thicker than plasma membrane

•Animal cell extracellular component: glycoproteins

These carbohydrate-protein molecules aid in support, adhesion (for cell-to-cell connection), and movement

IV. Movement in and out of cells 2.4.4

A. Diffusion – random movement of molecules from a high concentration to a low concentration

B. Osmosis- movement of water across a semi-permeable membrane from a low solute to a high solute concentration 2.4.4

10% sucrose90% water… bag is hypertonic

1% sucrose99% water… water is hypotonicBag will GAIN water.

Osmotic pressure is the pressure that water puts on something when it wants to cross a membrane

Molecules will always diffuse with respect to their own concentration gradient…

Here, water wants to move left, down its concentration gradient.

Red circles want to move right, down their concentration gradient.Here, water wants to move left, down its concentration gradient

Green circles want to move left, down their concentration gradient.

Purple circles want to move right, down their concentration gradient.

*DON’T WRITE:

This membrane is permeable to H2O, but not to the sugar molecules floating in it… what will happen?

*DON’T WRITE:

…water will diffuse until the two sides are isotonic (in equilibrium)

*DON’T WRITE:

Isotonic – both solutions have the same concentration of solute

Potato0.5 M glucose

0.5 M Solution of glucose

There is NO net movement of glucose or water (equilibrium)

Solutions can be compared to others using two RELATIVE terms: Hypertonic – higher solute concentration Hypotonic – lower solute concentration

Water will always try to move towards the HYPERTONIC solution

Practice:

Q: Cell will shrink or swell? A: Shrink, because the solution is

hypertonic!

5% salt95% water

1% salt99% water

*DON’T WRITE:

examples…

In animal cells: blood cells

In plants:

RBC

RBC

In hypotonic solution… water goes in

In hypertonic solution,

In hypotonic solution…water goes in

In hypertonic solution,water leaves

-could have plasmolysis!

CELL BURSTS …LYSIS!

Cell wrinkles

Turgid

Wilted

The phospholipid bilayer has fluidity, which allows it to change shape…

the hydrophobic and hyrophilic properties of each phospholipid help to maintain the bilayer’s structure… 2.4.1, 2.4.2 Hydrophilic portion of the

phospholipid will remain exposed to the water

Hydrophobic portion will stay away from the water, towards the middle

Cholesterol molecules are also embedded along with hydrophobic tails (for structure)INTEGRAL PROTEIN

PERIPHERAL PROTEIN

Functions of membrane proteins 2.4.3

Hormone binding sites – transmit a signal when a hormone is present

Enzymes Electron carriers – pass electrons along Channels for passive transport – allow a

single substance to pass Passive tranport = no energy necessary

Pumps for active transport – use ATP (ATP ADP + P) as energy to push things through (oftentimes against their gradient)

p7 in IBRB

FACILITATED DIFFUSION (IBRB p8) – passive diffusion through a channel protein

ACTIVE TRANSPORT (IBRB p8) – unlike facilitated diffusion, it can be used to move substances into or out of the cell AGAINST their concentration gradient (this takes ATP energy and can be done through by protein pumps)

2.4.5 and 2.4.6

Phospholipid-bound bubbles called “vesicles” are used to transport materials within the cell… (2.4.6)

ENDOCYTOSIS – bringing things into the cell via vesicles

EXOCYTOSIS – secreting things out of the cell via vesicles

In exocytosis… (2.4.7, 2.4.8) Vesicles transport materials Rough ER Golgi membrane