Cells

The parts of a basic light microscope and function of each

eyepiece: lens you look through (10X)

tube: connects the eyepiece to the objective lenses

Illuminator: steady source of light

Stage: flat surface for slides

Nosepiece: holds the objective lenses together, rotated to change power

Diaphragm: changes the amount of light

Coarse: focus the microscope, center the object, always used first with low power

Fine: focus the microscope, used with the high power, sharp focus

Calculate total magnification of a light microscope given the magnifications

Multiply the power of the eyepiece lens (10x) with the power of each of the objective lenses (4X, 10X, 40X)

Use of the compound light microscope

Uses lenses and light to enlarge the image, also called an optical or light microscope. Has two systems of magnification: the ocular/eyepiece lens that you look into; the objective lens, the lens closest to the object

Calculate magnification and estimate size of magnified images and objects

Magnification=Image size/actual size

Use and interpret scale bars

-measure length of specimen in mm

-measure length of scale bar in mm

-divide length of specimen by scale bar

-multiply the scale bar length by the answer

Clear and focused image of a sample under high power magnification

Never use the coarse adjustment, only the fine adjustment

Prepare a wet mount slide

Place the object that will be magnified on a long glass slide, add 1 drop of water and take a square of plastic covering and lay it against the object starting from one side and finishing on the other to ensure no air bubbles are formed

Tenets of cell theory

1. The cell is the smallest living unit in all organisms

2. All living things are made of cells

3. All cells come from other pre-existing cells

limits to cell size

A larger cell is less efficient in moving nutrients and waste materials across the cell membrane (exchange of materials)

Ratio of surface area to volume is important because larger cells would not have enough supply of required substances. Small: 6:1, (has 6O2 and uses 1O2) large:6:10 (has 6O2 uses 10O2)

SA: how fast cell membrane can transport nutrients/waste in & out of cell

V: use of stuff, production of waste

Differences between prokaryote and eukaryote cells

• eukaryote cells have a nuclei (with DNA in it) and prokaryote cells do not

-eukaryote cells have membrane-bound organelles and prokaryote cells do not

• prokaryote cells are smaller (unicellular), simpler than eukaryote cells

-they both have DNA, cytoplasm, ribosomes, cell membrane

Prokaryote: bacteria, eukaryote: animal & plant cells, protists, fungi

Organelle

A tiny cell structure with a specialized function inside a cell inside an eukaryotic cell

Differences between plant and animal cells

Animal cells do not have rigid cell walls, chloroplasts. Plant cells have chloroplasts and contain chlorophyl, cell wall and have a larger central vacuole

Fluid mosaic structure of cell membranes

model of cell membrane structure- diverse mosaic of protein molecules suspended in a fluid bilayer of phospholipid molecules

Four functions of membrane proteins

1. membrane transport (shuttle/channel large polar molecules & charged ions across cell membrane)

2. cell recognition (glycoproteins)

3. receptor proteins (communication-signals to cells)

4. enzymatic reactions

5. Attachment to supporting fibers

How membranes exhibit selective permeability

Allows membranes to regulate the passage of substances across them. Non polar substances pass through easily, large polar molecules and charged ions need transport proteins

How the structure of phospholipid molecules is related to the structure and properties of cell membranes

The phospholipids line up so that they're heads point outward toward the water (hydrophilic) and their tails point inward away from the water (hydrophobic). This allows non polar molecules to easily diffuse across cell membrane.

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration (air, water, or in/out of cell)

Concentration gradient

A region along which the density of a chemical substance increases or decreases. Eventually, both sides will have equal concentrations (dynamic equilibrium)

Why some molecules can diffuse through the phospholipid bilayer (simple diffusion) and some cannot

Due to selective permeability. Hydrophobic tails allow non polar substances and small polar molecules to diffuse slowly (water-osmosis) But large polar molecules (glucose) and charged ions need help from transport proteins.

Compare and contrast active and passive transport

Passive: Without energy, movement is done and from high to low

Active: With energy, movement is done and from low to high

Compare and contrast simple diffusion and facilitated diffusion

In simple diffusion, the substance passes between the phospholipids on its own, no energy used, (high to low)

In facilitated diffusion, type of passive transport, does not require energy, assisted transport through a transport protein (channel-polar or carrier-ions) down its concentration gradient (high to low) a.simple, b.carrier, c & d.channel

Compare and contrast exocytosis and endocytosis

SIMILARITIES:

º both used to transport large particles / large

quantities of material (1)

º both involve (phospholipid) membrane vesicles (1)-membrane surrounds the particle

-both examples of active transport

DIFFERENCE:

º exocytosis is export/release and endocytosis is import of material (1)

Osmosis

the diffusion of free water across a selectively permeable membrane

Tonicity

the ability of a surrounding solution to cause a cell to gain or lose water

Hypertonic, hypotonic and isotonic solutions

Isotonic: solutions have equal solute concentrations.

Hypertonic: solution has a higher solute concentration than the other solution.

Hypotonic: solution has a lower solute concentration than the other solution.

Explain how animal and plant cells respond to changes in tonicity

Animal cells:

-isotonic: the cell volume stays the same, water goes in and out at same rate

-hypotonic: cell gains water, swells and may burst (lysed)

-hypertonic: water moves out of cell, shrivels and can die

Plant cells:

-hypotonic: plant cell is very firm, as water enters, it swells, the cell exerts back pressure, stays turgid (normal), prevents it from not bursting

-isotonic: water moves in and out, the cell is limp and may wilt (flaccid)

-hypertonic: looses water, membrane moves away from the cell wall (plasmolysis), causes plant to wilt