Bellringer-December 5, 2014 (Label the letters)

Cytoplasm

Extracellular Fluid

December 5, 2014

1) What types of molecules passes easily?2) What types of molecules does not pass easily

and needs assistance?

Answers1) a-glycoprotein2) B-glycolipid3) C-Oligosaccharide chains (attached to glycoprotein)4) D-nonpolar tails (fatty acid tails) (hydrophobic tails)5) E-Phosopholipid bilayer6) F-Polar heads (hydrophilic heads) (phosphate head)7) G-Peripheral protein8) H-cholesterol9) I-Integral Protein10) J-Cytoskeleton

Cell Movement: PassiveTransport

Honors BiologyMs. Kim

Membrane structure LEADS TO selective permeability

• A cell must exchange materials with its surroundings–a process controlled by the selectively permeable plasma membrane

Cell Transport• Means moving things INTO and OUT

of the cell• Cells need to take in –Food–Get rid of waste products (excretion) –Give out such useful substances as

hormones and enzymes (secretion).

Permeability and Cell Transport• Hydrophobic (non polar) molecules– Are lipid soluble (can dissolve) – can pass through membrane easily• Ex: Hydrocarbons, CO2, O2

• Hydrophilic (Polar) molecules– Are NOT lipid soluble (can’t dissolve)• Lipid INsoluble

– Do not cross membrane easily• Ex: Na+, Cl- , Glucose/ other sugars–NOTE: CHARGED molecules need “help” to cross

membrane–NOTE: LARGE molecules, POLAR molecules need

“help”

Types of Cellular Transport

• Passive Transport cells do NOT use energy

1. Diffusion2. Facilitated Diffusion3. Osmosis

• Active Transportcells DO use energy

1. Protein Pumps2. Endocytosis3. Exocytosis

high

low

This is going to be hard!

high

low

Weee!

1) Diffusion• Diffusion: • Movement of molecules from a high

concentration to a lower concentration– Does not use energy– Can occur in non-living systems (ex: dye)

• Concentration: – Number of molecules of a substance in a given

volume• Concentration gradient: – Difference in concentration of a substance from

one location to another10

Types of Passive Transport

Diffusion is the tendency for a population of molecules (of ANY substance) to spread out evenly into available space–A “net” movement • Ex: Perfume, a fart , tea, food coloring in

water (see demo) • http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion2.gif• http://www.biosci.ohiou.edu/introbioslab/Bios170/diffusion/Diffusion.html

DIFFUSION • In absence of other forces…–Molecules move (diffuse) from area of HIGH [ ]

to an area of lower [ ] –A.k.a. Molecules move DOWN its OWN

concentration gradient•No chemical work (ATP energy) is used diffusion is spontaneous!

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Substances diffuse down their OWN concentration gradient

Net diffusion

Net diffusion

Net diffusion

Net diffusion Equilibrium

Equilibrium

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Diffusion of Liquids

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Factors Affecting Diffusion

1. Temperature• Higher temperature more kinetic

energy molecules move faster2. Pressure• Higher pressure molecules move faster• ExampleTea: Higher temperature and

more pressure (twirling/stirring) it around) makes diffusion happen faster.

2) Facilitated Diffusion• Molecules move down (not against) a

concentration gradient with the aid of special proteins (channel or carrier proteins)– Speeds up the process– Proteins CAN change SHAPE

• Does NOT use energy (NO ATP NEEDED) = type of passive transport

• Moves things from high to low concentrations–Moves POLAR molecules can NOT

easily pass through the membrane on it’s own. • Example: ions, smaller polar molecules (ex: sugar)

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Channel proteins-Provide “tunnels”

EXTRACELLULARFLUID

Channel proteinSolute

CYTOPLASM

A channel protein (purple) has a channel through which water molecules or a specific solute can pass.

(a)

• Channel Proteins animations

Carrier proteins-Undergo a subtle change in shape “carry” solute across the

membrane

Carrier protein Solute

3. Osmosis• Osmosis: – diffusion of water across a

membrane• Water moves across a semi-permeable membrane

from an area of high water concentration to an area of low water concentration

• If water can cross a membrane, but the solute cannot, then…

– The water moves towards the side with MORE solute to balance the concentrations

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Effects of Osmosis on Water Balance

Osmosis

• The movement of water (water diffusion) across a semipermeable membrane– Involves the movement of FREE water

molecules down a water [ ] gradient• High solute low “free” water [ ] or….• Low solute high free water [ ]

Osmosis is affected by the concentration gradient of dissolved substances (solutes)

Osmosis animation

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OSMOSIS

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Diffusion of H2O Across A Membrane

High H2O potentialLow solute concentration

Low H2O potentialHigh solute concentration

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Osmoregulation• Osmoregulation – control of water balance

• Turgor pressure – pressure inside a cell

• Tonicity – tendency of a cell to lose or gain water based on the solution it is in

3 Types of solutions: – Isotonic– Hypotonic– Hypertonic

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3 Different Types of SolutionsRecall: SOLUTION = a uniform mixture of 2 or more

substances** compare solutions OUTSIDE cell to inside cell

• 1. ISOTONIC-Solution has same concentration of dissolved particles as the cell (same amount of solute outside and inside the cell)

• Water moves into and out of cell at equal rates and cell size remains constant• Cell does not change shape– There will be NO net movement of

water

ISOTONIC SOLUTION

Result: Water moves equally in both directions and the cell remains same size! (Dynamic

Equilibrium)

2. If a solution is hypertonic• Solution has a higher concentration of dissolved

particles than the cell (more solute outside of the cell than it is inside the cell)– Water flows OUT of the cell – The cell shrivels up and turgor pressure decreases – “hyper” means more

» (high [solute])• Ex: when salinity increases in lake, fish can

die!

The water will move out of the fish towards the area with MORE solutes (ocean) to balance the concentrations! Poor fish…

NaCl

HYPERTONIC SOLUTION

Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

3. If a solution is hypotonic• Solution has a lower concentration of

dissolved particles than the cell (less solute outside of the cell than it is inside the cell)– Water flows INTO the cell– The cell swells/gets big! – Ex. Happens with distilled water

• Animals:• Cytolysis (when a cell BURSTS!)

–“hypo” means “less” – (low [solute])

– Think: Hypo- sounds like hippo…hippos are big & round; cells in hypotonic solutions get big & roundAlso, think “hypo” is “low” meaning “low” solutes

SURROUNDING cell

“Hypo” is LOW!!!

HYP0TONIC SOLUTION

Result: Water moves from the solution to inside the cell): Cell Swells and bursts open

(cytolysis)!

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Cell in ___________ Solution

CELL

10% NaCL90% H2O

10% NaCL90% H2O

What is the direction of water movement?

The cell is at ____________________.Dynamic equilibrium

ENVIRONMENT

NO NET MOVEMENT

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Cell in ____________ Solution

CELL

10% NaCL90% H2O

20% NaCL80% H2O

What is the direction of water movement?

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ENVIRONMENT

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Cell in ___________ Solution

CELL

15% NaCL85% H2O

5% NaCL95% H2O

What is the direction of water movement?

ENVIRONMENT

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http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm

• Osmosis Animations for isotonic,

hypertonic, and hypotonic solutions

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Real life examples

Water Balance of Cells with Walls

• Cell walls–Help maintain water balance

• Cell walls are in:–Plants–Prokaryotes–Fungi–Some protists

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Plant Cells & Solutions• Isotonic (Flaccid)

• Plant cells at isotonic solutions are flaccid (can also be in hypertonic solution)• Cells are limp

• Hypotonic (Turgid)• Plant cells prefer hypotonic solutions because the cell wall provides more

support and plant cells are less likely to lyse (burst)• Turgor pressure increases (vacuole fills with water)• It is very firm• A healthy state in most plants

• Hypertonic (Plasmolysis)• Plants wilt, undergo plasmolysis• The cytoplasm and plasma membrane begin to pull

away from the cell wall• Causes cell with walls to wilt & can be lethal.

Water balance in cells with walls

Plant cell. Plant cells are turgid (firm) and generally healthiest in a hypotonic environment, where the uptake of water is eventually balanced by the elastic wall pushing back on the cell.

H2OH2OH2OH2O

Turgid (normal) Flaccid Plasmolyzed

Types of Cellular Transport

#1 • Passive Transport–DOES NOT require chemical energy (ATP)

#2 • Active Transport–DOES require chemical energy (ATP)

Exit Slip-December 5, 2014

1) Draw 3 cells in the following solutions AND draw water direction the water is moving (draw dots to represent the SOLUTE):

1) Hypertonic solution2) Hypotonic solution3) Isotonic solution