Ch 5 cell membrane and transport
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Ch. 5 Cell Membrane and Transport. LIPID BILAYER. cytoplasm. extracellular fluid. Cell Membrane —thin, flexible membrane that surrounds all cells. . Selectively permeable - regulates what enters and exits the cell. Made up of a phospholipid bilayer . Double layer of phospholipids

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Ch. 5 Cell Membrane and Transport

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Ch. 5 Cell Membrane and Transport

LIPID BILAYER

cytoplasm

extracellular

fluid


Cell Membrane—thin, flexible membrane that surrounds all cells.

  • Selectively permeable - regulates what enters and exits the cell.

  • Made up of a phospholipid bilayer.

    • Double layer of phospholipids

    • Gives cells flexible but strong barrier between itself and its surroundings.


Phospholipids

Hydrophilichead

  • Phospholipids are a lipid that have a

    • Glycerol

    • Phosphate

    • Two fatty acid chains

Hydrophobictail


Hydrophilic

Hydrophobic


PhospholipidBilayer

hydrophilic

head

hydrophobic

tails

Water (outside of cell)

hydrophilic

head

Water (inside of cell)


Fluid mosaic model


Fluid mosaic model

Fibers of extracellular matrix

Carbohydrate (of glycolipid)

Glycolipid

Glycolipid

Phospholipid

Microfilaments of cytoskeleton

Protein

Steroids


Membrane Proteins

  • > 50 kinds of proteins found in human red blood cells so far

  • Carry out many different functions

    • Structural, external, identification tags, form junctions between cells

    • Enzymes – catalytic teams for molecular assembly lines

    • Receptors – receive chemical messages from other cells

      • Message transfer is called signal transduction

    • Help move substances across membrane


Cell Transport: movement of substances across the cell membrane based on concentration gradient.

Concentration Gradient: Difference in concentration over a distance.

No Gradient

HIGH concentration

LOWconcentration

Gradient


How the Cell Membrane does its thing…

  • Two categories of cell transport:

    • Passive transport – Requires NO energy

      • High to low concentration

    • Active transport – Requires energy

      • Low to high concentration


3 types of passive transport:

  • Simple Diffusion

    • High to low concentration

    • Small, lipid soluble molecules like CO2 and O2

    • Example:

      • Oxygen enters bloodstream from the lungs


2) Facilitated Diffusion

  • Large, charged, or polar substances move across membrane in this way.

  • Always moves from high to low concentration

  • Requires a transport protein

Transport Protein


2) Facilitated Diffusion

  • Water can move through because it is small, buttransport is slow, aquaporins allow for faster diffusion

Transport Protein


3) Osmosis:

  • Diffusion of water through a selectively permeable membrane until equilibrium occurs.

  • High to low concentration

  • Water will cross membrane until solute concentrations(molecules/mL) are _______________on both sides of membrane


What words do you know that start with……

  • Iso______________

    • Definition:

  • Hyper___________

    • Definition:

  • Hypo____________

    • Definition:


Tonicity

  • A term used to describe the tendency of a cell in a given solution to lose or gain water.


Isotonic Solution—Concentration of solutes is equal in and out of the cell.

  • No net movement of water.

  • Cell maintains shape.


Hypertonic Solutions—Concentration of solutesis higher outside the cell.

  • Water exits the cell.

  • Animal Cell: shrinks which is known as crenation

  • Plant Cell: cell membrane collapses away from cell wall. This is known as plasmolysis.


D. Hypotonic Solution—Concentration of solutes is lower outside the cell.

1. Water enters the cell.

2. Animal cell swells and

may burst which is known as Cytolysis.

3. Plant cell—cell wall prevents breaking. (Turgor Pressure)


Tonicity in animals

  • Osmoregulation: or an animal to survive changes in salinity it must have a method to prevent excessive uptake of water or excessive loss of water

    • Ex: freshwater fish live in hypotonic environment

    • Ex: saltwater fish live in a ___________________ environment


  • Have evolved to have kidneys and gills that constant work to flush water out of the body


Tonicity in plants

  • Turgidity: When a plant cell has a net inflow of water.

  • Plasmolysis: When a plant cell loses water, plasma membrane pulls away from cell wall.

    • Also happens in bacteria and fungi


HYPOTONIC HYPERTONIC

ISOTONIC


What type of solution is each cell in?

HYPERTONIC

HYPOTONIC

ISOTONIC


Ticket out Quiz

2M sucrose

solution

1 liter of

pure water

10M sucrose

solution

2M sucrose

solution

1)

2)

3)

HYPOTONIC

CONDITIONS

HYPERTONIC

CONDITIONS

ISOTONIC

CONDITIONS

Fig. 5.14, p. 88


Active Transport

  • Substances move against

    concentration gradient

    -low to high concentration

  • Requires energy (ATP)

  • Requires a transport protein.


How do LARGE molecules enter and exit the cell?

  • BULK TRANSPORT: Movement of particles into or out of a cell without passing through the plasma membrane.

  • Requires energy!


Endocytosis – Large materials move into cell.

  • Cell engulfs large materials such as macromolecules.


Phagocytosis

  • Cell engulfs large particles, microbes, and cellular debris

  • “Cell eating”


Pinocytosis

  • Cells receive bulk amounts off liquid

  • “Cell drinking”


  • Exocytosis - vesicle fuses with the membrane and exits the cell.

    • Expels materials such waste and hormones.


Lorenzo’s Oil

ALD

Can not digest FAT

Fat builds up and destroys his nerves

Fat enters body in 2 ways – food and biosynthesis

Oil stops biosynthesis!

Oil keeps the body from building up the bad fat

COMPETITIVE inhibition


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