Today is Thursday Feb. 14th

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Please take w/s unit 1 plant & animal cells and complete

What’s the answer to number 2?

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1. A2. C3. G4. I

What was the answer to number 15?

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1. B2. F3. J4. K

Cell Membrane &

its function

Cell Membrane

Thin layer that surrounds cells

Allows certain materials to enter & exit cellSelective permeable

Provides protection & support

Found in both plant & animal cells

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Cell Membrane

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Cell Membrane

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Structure of Cell Membrane

Some Terms to KnowPermeable –

ability to pass through

Impermeable – inability to pass through

Equilibrium – equal concentration on either side of a membrane

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Membrane ProteinsDifferent types of cells contain different types

of membrane proteins

Integral proteins – embedded into the hydrophobic core of lipid bilayer, can go all the way through membrane

Peripheral proteins – on surface of membrane

Types of Membrane ProteinsTransport

Channel/ Carrier proteins (hydrophilic tunnel) allow polar molecules and ions to pass through hydrophobic layer

Channel and Carrier proteins are specific for the substance they transport

EnzymaticSignal Transduction (chemical messages)

Receptor proteins transmit information from outside of the cell to inside of the cell

Cell Recognition ID tags – glycolipids or glycoproteins – allow a particular

type of cell to be recognized by other cells and moleculesIntercellular joining

Join together adjacent cellsCell Support

Attach to cytoskeleton or extra-cellular matrix for stability

Cell membrane purpose:

The main function of the cell membrane is to keep track of what enters or exits the cell

Cell transport- Two types

• Passive• Active

What is the cell membrane’s main purpose?

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1. Hold the cell together

2. Tracks what comes in/out of the cell

3. Gives support/structure

4. All of the above

The cell membrane is made of

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1. Lipid bilayers2. Carbs 3. Ribosomes4. mitochondria

Which molecule is NOT part of the membrane’s structure?

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1. Carbs2. Lipids3. Proteins4. Hydrogen

True/False: All cells’ outer layer is the cell membrane.

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1. True2. False

How many ways can a cell transport?

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1. 12. 23. 34. 45. 5

Passive TransportPassive Transport - Movement across the cell

membrane that does not require energy

Diffusion – movement of particles from an area of high concentration to an area of low concentration until an equilibrium is reached (go with/ down its concentration gradient)

Happens easily Particles move arbitrarily between 2 sides

Concentration gradient – the difference in the concentration of a substance across a space

Equilibrium – conc. of a substance is equal throughout a space (doesn’t stop moving)

OsmosisMovement of WATER

from an area of greater concentration to lesser concentration through a selectively permeable membraneOnly certain

molecules can passWater passes through

most membranes

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Osmoregulation in Cells w/o cell walls (animal)

Osmoregulation – control of water balanceTonicity – ability of a solution to cause a

cell to gain or lose water

Isotonic solution Iso ~ equal no net movement of water across the cell membrane solutions are equal in concentration

Hypertonic solution Hyper – many Tonicity – Tone - solid more free water inside the cell therefore the cell will

lose water to its environment, and shrivel More solutes (stuff ) on 1 side of membrane vs. other more concentrated, more solutes

More terms to knowHypotonic solution

Hypo –low, fewless free water inside

the cell therefore the water will enter cell, it will swell

less concentrated, less solutes

1 w/few solutes (stuff ) on 1 side of membrane vs. other

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More on Osmosis

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Osmoregulation of Cells w/ wallsPlant cells are healthiest in a hypotonic

solution, osmotic pressure keeps cell wall turgid (very firm)

Plant cells are flaccid (limp) in an isotonic solution

In a hypertonic solution, the cell membrane will shrink and pull away from the cell wall…called plasmolysis (wilt)

Facilitated DiffusionSome molecules

cannot pass freely across membraneToo largeToo strongly

chargedRequire helper

proteinFacilitates or aids

in diffusion

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Facilitated Diffusion: Passive Transport aided by proteinsChannel Proteins – hydrophilic

passagewaysSome are always open for diffusionRate of movement is determined by conc. Gradient(+) charged ions more likely to diffuse INTO cell(-) charged ions morel likely to diffuse out of the cellSome ion channels have gates and can be opened

by: Stretching of cell membrane Change in electrical charge Binding of specific molecule

Voltage Gated Channels Nerve Cells transmit electrical signals by

opening a series of Na+ gated channels1. Channel is closed2. Area changes voltage3. Channel opens briefly4. Na+ flood into cell – voltage changes5. Channel closes and electrical signal passes

on to the next voltage channel

Chemically Gated Channels Nerve cells send out

a neurotransmitter called acetylcholine (ACh) to nearby muscle cells to signal muscle to contract

1. ACh binds to ACh receptor protein

2. Receptor gate opens for a microsecond to allow Na+ in

3. Na+ sets off muscle contraction

Facilitated Diffusion: Passive Transport aided by proteins Carrier Proteins

1. Specific substance binds to carrier protein

2. Protein changes shape and transports substance across cell membrane

3. Molecules is released into the cell, and carrier protein returns to its original shape

How many different types of transport do not require energy?

1. 12. 23. 34. 45. 5

How does active transport differ from passive transport?

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1. Active require energy; passive does not

2. Passive requires energy; while active does not

3. Active takes longer

4. There is no difference

Which passive transport transports water in/out of the cell?

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1. Diffusion2. Osmosis3. Facilitated

Which passive transport transports molecules out/in the cell?

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1. Diffusion2. Facilitated3. Osmosis

Hypotonic solution cells

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1. swell.2. shrivel up.3. have equal

distribution.

Isotonic cells

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1. swell.2. shrivel up.3. have equal

distribution.

Hypertonic solution cells

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100%1. swell.2. shrivel up.3. have equal

distribution.

Which passive transport is aided by proteins?

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1. Osmosis2. Diffusion3. Facilitated

Active TransportActive Transport - uses energy to move solutes

AGAINST conc. GradientMolecules move from lesser concentration to higher concentration

Requires EnergyAccomplished via pumps found inside the

membraneCarrier proteins act as “pumps” powered by ATP

Endocytosis & exocytosisShape of membrane gets changedExamples

Sodium Potassium pumpProton PumpCotransport

Sodium Potassium pumpPumps 3 Na+ out of

the cell and 2 K+ into the cell

Actively transports both ions against their conc. Gradient, powered by ATP

Prevents Na+ from accumulating in the cell

1. 3 Na+ and a P (from ATP) bind to inside protein pump

2. Pump changes shape transporting 3 Na+ across membrane and out

3. 2 K+ bind to pump and are transported across membrane

4. 2 K+ and P are released inside of cell

Proton PumpActively transports protons (H+) through the

internal membranes of mitochondria and chloroplasts

Cotransport (Coupled Transport)Cotransport – an ATP powered pump

that transports a specific solute, can indirectly drive the active transport of several other solutesEx. As proton pump pumps H+ out, H+ diffuse

back into the cell pulling sucrose molecules into the cell with it!

Bulk Transport: Substances that are too large to be transported by carrier proteins

Exocytosis (export)

Exo ~ exit~ outsidereleasing of materials out of cellMembrane fuses w/material & forces contents o/s of

cellContractile vacuole removing waterSecretion of macromolecules by fusion of vesicle with

membrane, releasing the contents outside of cell

Bulk Transport Endocytosis

Endo ~ inMaterials are taken into cellEnvelope of membrane forms @ substance

Cell membrane engulfs particles and pinches off to form vesicle inside the cell. Vesicle may fuse w/ lysosomes or other organelles

What is the movement of water molecules across a membrane that does allow all material to pass through?

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1. Exocytosis2. Pumping3. Endocytosis4. Diffusion

Exocytosis

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1. Releases materials out of the cell

2. Allows materials in the cell

3. Does both4. Does neither

Which pump uses H+ protons?

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40%

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40%1. Osmosis2. Proton pump3. Cotransport4. Sodium

potassium pump

Which pump requires energy to pump specific substances?

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1. Osmosis2. Proton pump3. Cotransport4. Sodium

potassium pump

Which transport needs energy, K, and Na to work?

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1. Osmosis2. Proton pump3. Cotransport4. Sodium

potassium pump

Endocytosis

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80%1. Releases materials out of the cell

2. Allows materials in the cell

3. Does both4. Does neither

Assignment:

Complete review questions