Today is Thursday Feb. 14th Do now : Please take w/s unit 1 plant & animal cells and complete

What’s the answer to number 2? 1. A 2. C 3. G 4. I

What was the answer to number 15? 1. B 2. F 3. J 4. K

Cell Membrane & its function

Cell Membrane Thin layer that surrounds cells Allows certain materials to enter & exit cell Selective permeable Provides protection & support Found in both plant & animal cells 5

Cell Membrane 6 Fluid-mosaic model/Lipid bilayer (2 layers) outer Heads on outside by water Hydrophilic heads Like water Inner Tails inside hydrophobic tails do not like water makes membranes flexible

Cell Membrane 7 Many different molecules Lipids Large C & H molecule Proteins Different types of cells contain different types of membrane proteins Examples (integral, peripheral) Carbs Cholesterol maintains fluidity – acts as temperature buffer Less fluid as temp increases by restricting movement More fluid as temp decreases by maintaining space

Structure of Cell Membrane

Some Terms to Know Permeable – ability to pass through Impermeable – inability to pass through Equilibrium – equal concentration on either side of a membrane 9

Membrane Proteins Different 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 Proteins Transport 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 Enzymatic Signal 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 molecules Intercellular joining Join together adjacent cells Cell 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? 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 1. Lipid bilayers 2. Carbs 3. Ribosomes 4. mitochondria

Which molecule is NOT part of the membrane’s structure? 1. Carbs 2. Lipids 3. Proteins 4. Hydrogen

True/False: All cells’ outer layer is the cell membrane. 1. True 2. False

How many ways can a cell transport?

Passive Transport Passive 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)

Osmosis Movement of WATER from an area of greater concentration to lesser concentration through a selectively permeable membrane Only certain molecules can pass Water passes through most membranes 19

Osmoregulation in Cells w/o cell walls (animal) Osmoregulation – control of water balance Tonicity – 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 know Hypotonic solution Hypo –low, few less 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 21

More on Osmosis 22

Osmoregulation of Cells w/ walls Plant 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 Diffusion Some molecules cannot pass freely across membrane Too large Too strongly charged Require helper protein Facilitates or aids in diffusion 25

Facilitated Diffusion: Passive Transport aided by proteins Channel Proteins – hydrophilic passageways Some are always open for diffusion Rate of movement is determined by conc. Gradient (+) charged ions more likely to diffuse INTO cell (-) charged ions morel likely to diffuse out of the cell Some 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 channels 1. Channel is closed 2. Area changes voltage 3. Channel opens briefly 4. Na + flood into cell – voltage changes 5. 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?

How does active transport differ from passive transport? 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? 1. Diffusion 2. Osmosis 3. Facilitated

Which passive transport transports molecules out/in the cell? 1. Diffusion 2. Facilitated 3. Osmosis

Hypotonic solution cells 1. swell. 2. shrivel up. 3. have equal distribution.

Isotonic cells 1. swell. 2. shrivel up. 3. have equal distribution.

Hypertonic solution cells 1. swell. 2. shrivel up. 3. have equal distribution.

Which passive transport is aided by proteins? 1. Osmosis 2. Diffusion 3. Facilitated

Active Transport Active Transport - uses energy to move solutes AGAINST conc. Gradient Molecules move from lesser concentration to higher concentration Requires Energy Accomplished via pumps found inside the membrane Carrier proteins act as “pumps” powered by ATP Endocytosis & exocytosis Shape of membrane gets changed Examples Sodium Potassium pump Proton Pump Cotransport

Sodium Potassium pump Pumps 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 Pump Actively 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 solutes Ex. 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~ outside releasing of materials out of cell Membrane fuses w/material & forces contents o/s of cell Contractile vacuole removing water Secretion of macromolecules by fusion of vesicle with membrane, releasing the contents outside of cell

Bulk Transport Endocytosis Endo ~ in Materials are taken into cell Envelope of membrane 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? 1. Exocytosis 2. Pumping 3. Endocytosis 4. Diffusion

Exocytosis 1. Releases materials out of the cell 2. Allows materials in the cell 3. Does both 4. Does neither

Which pump uses H+ protons? 1. Osmosis 2. Proton pump 3. Cotransport 4. Sodium potassium pump

Which pump requires energy to pump specific substances? 1. Osmosis 2. Proton pump 3. Cotransport 4. Sodium potassium pump

Which transport needs energy, K, and Na to work? 1. Osmosis 2. Proton pump 3. Cotransport 4. Sodium potassium pump

Endocytosis 1. Releases materials out of the cell 2. Allows materials in the cell 3. Does both 4. Does neither

Assignment: Complete review questions