CHAPTER 9-Cell Boundaries

-Cell Environments-Transport

(both passive and active)

Cell Membrane regulates what enters and leaves the cell and also provides protection and support.

The membrane is selectively permeable. Often referred to as the Fluid Mosaic Model. Cell membrane is composed of:

1. Phospholipid bilayer: gives flexibility and protection2. Proteins: act as Channels/Pumps, Markers or Receptors3. Carbohydrates: act as identification tags (like the marker

proteins)

Hydrophobic (phobia?)Hydrophilic

Cytoskeleton is a network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is also involved in movement.

Composed of:1. Microfilaments –

threadlike structures made of actin.

• Provides support• Cytoplasmic Streaming

2. Microtubules – hollow structures made up of tubulins.

• Maintain cell shape• Cilia & Flagellum• Centrioles & spindle

fibers

Cell Wall provides support and protection for the plant cell.

Cell Wall is composed of:1. Cellulose - gives strength & elasticity2. Pectin - gives ability to resist compression3. Cross-linking glycans increases tensile strength4. Lignin - hard, gives strength (2o wall = bark)

Very porous

Is made of multiple layers.

1. Passive Transport: High to Low: No Energy

required2. Active Transport: Low to

High; Energy required

1. Diffusion2. Osmosis3. Facilitated Diffusion

Go on a ‘date’ with someone, switch @BELL. Pick TWO questions you guys can compare, and

check over, see what you think is ‘right.’ If things seem odd or wrong, ask me, or wait to

meet with your next date to see what they found!

OVERALL GOAL: See if you can find out whether other not you understood the videos from homework.

Diffusion The movement of

particles from an area where they are highly concentrated to an area where they are in low concentration.

This means movement is along a concentration gradient.

Osmosis the diffusion of water through a

selectively permeable membrane from high to low concentration

TERMINOLOGY – “tonicity”Isotonic Solution: the concentration of

solutes is the same inside and outside the cell; means “same strength”

Hypertonic Solution: the solution has a higher solute concentration than the cell; means “above strength”

Hypotonic Solution: the solution has a lower solute concentration than the cell; means “below strength”

Equilibrium: when the concentration of the solute is the same throughout a system

The Effects of Osmosis on Animal Cell

Lysis: breaks apartEquilibrium: when the concentration of the solute is the same throughout a system

Cell will shrivel up.

The Effects of Osmosis on a Plant Cell

Plasmolysis: when a plant cells membrane shrinks away from its cell wall

Turgor Pressure: the buildup of water within the plant cell

Flaccid: indicates that the cell, although it contains water, does not have enough internal turgor pressure to provide structural support

Tonicity

Facilitated Diffusion – when a particular substance crosses through a selectively permeable membrane with the help of a channel protein

FD is for molecules that are too large or too strongly charged to cross the membraneEx. Glucose – too largeEx. Water – too

charged (must enter through aquaporins)

FD is fast and specific.

1. Protein Pumps2. Endocytosis 3. Exocytosis

Protein Pumpswhen small molecules

and ions are carried across membranes by proteins in the membrane that act like energy-requiring pumps

Ex. Ca2+, and the Na+/K+

Changes in protein shape is necessary, therefore energy is used.

These systems enable cells to concentrate substances in a particular location.

Endocytosis – process of taking material into the cell by means of infoldings, or pockets, of the cell membrane

Types:Phagocytosis:

taking large food particles into the cell

Pinocytosis: taking liquids into the cell

Exocytosisprocess of

removing material from the cell by means of a vacuole surrounding the material fusing with the cell membrane, forcing the contents out of the cell