AP Biology AP Biology Movement across the Cell

AP Biology

Movement across the Cell Membrane AP Biology 2007 -2008

The Cell Membrane AP Biology 2007 -2008

Cell membrane defines cell § Cell membrane separates living cell from aqueous environment u thin barrier = 8 nm thick § Controls traffic in & out of the cell u allows some substances to cross more easily than others § hydrophobic (nonpolar) vs. hydrophilic (polar) AP Biology

I. Cell Membrane A. General 1. Flexible and allows a unicellular organism to move AP Biology

B. Function 1. Maintain a high concentration of materials in the cell. 2. Keep harmful materials out. 3. Control the movement of materials into and out of the cell. 4. Let the cell sense its environment. AP Biology

5. Protective barrier 6. Regulate transport in & out of cell (selectively permeable) 7. Allow cell recognition 8. Provide anchoring sites for filaments of cytoskeleton AP Biology

C. Maintains homeostasis 1. Balanced internal condition of cells. Also called equilibrium 2. Maintained by plasma membrane controlling what enters & leaves the cell. AP Biology

D. Structure of the Cell Membrane AP Biology *

§ Vocabulary development: § - Semi-permeable membrane = is selective about the substance that can pass through a porous barrier or membrane. AP Biology

FLUID MOSAIC MODEL 1. FLUID- because individual phospholipids and proteins can move around freely within the layer, like it’s a liquid. 2. MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above. AP Biology

Lipids § Function: u energy storage § very concentrated § twice the energy as carbohydrates! cell membrane u cushions organs u insulates body u § think whale blubber! AP Biology 2003 -2004

B. Lipids (Fats) 1. Fats, oils, waxes, steroids 2. Chiefly function in energy storage, protection, and insulation 3. Contain carbon, hydrogen, and oxygen but the H: O is not in a 2: 1 ratio 4. Tend to be large molecules -- an example of a neutral lipid is below AP Biology

Structure of Fat not a chain (polymer) = just a “big fat molecule” AP Biology 2003 -2004

AP Biology

5. Neutral lipids are formed from the union of one glycerol molecule and 3 fatty acids 6. 3 fatty acids + glycerol ----> neutral fat (lipid) 7. Fats -- found chiefly in animals 8. Oils and waxes -- found chiefly in plants 9. Oils are liquid at room temperature, waxes are solids 10. Lipids along with proteins are key components AP Biology

Saturated vs. unsaturated AP Biology 2003 -2004

Other lipids in biology § Cell membranes are made out of lipids phospholipids u heads are on the outside touching water u § “like” water u tails are on inside away from water § “scared” of water u AP Biology forms a barrier between the cell & the outside 2003 -2004

Cell membrane AP Biology

Phospholipids § Phosphate head u “attracted to water” hydrophilic § Fatty acid tails u Phosphate hydrophobic § Arranged as a bilayer Fatty acid “repelled by water” Aaaah, one of those structure–function examples AP Biology

Arranged as a Phospholipid bilayer § Serves as a cellular barrier / border sugar polar hydrophilic heads nonpolar hydrophobic tails H 2 O salt impermeable to polar molecules polar hydrophilic heads waste AP Biology lipids

Cell Membrane Hydrophobic The cell membrane is made of 2 layers of molecules pass phospholipids called the easily; hydrophillic lipid bilayer DO NOT AP Biology

AP Biology

Cell membrane is more than lipids… § Transmembrane proteins embedded in phospholipid bilayer u create semi-permeabe channels lipid bilayer membrane AP Biology protein channels in lipid bilyer membrane

Why are proteins the perfect molecule to build structures in the cell membrane? AP Biology 2007 -2008

H+ H+ Examples Retinal chromophore NH 2 aquaporin = water channel in bacteria Porin monomer H 2 O b-pleated sheets Bacterial outer membrane Nonpolar (hydrophobic) a-helices in the cell membrane COOH H+ H + Cytoplasm proton pump channel in photosynthetic bacteria H O AP Biology 2 function through conformational change = protein changes shape

Cell membrane § http: //study. com/academy/lesson/cellmembrane-functions-rolestructure. html § https: //translate. google. com/translate? s l=es&tl=en&js=y&prev=_t&hl=en&ie=UT F 8&u=https%3 A%2 F%2 Fwww. youtube. c om%2 Fwatch%3 Fv%3 DQQg. Xfu. Fy. KM 4& edit-text=&act=url AP Biology

Many Functions of Membrane Proteins “Channel” Outside Plasma membrane Inside Transporter Enzyme activity Cell surface receptor Cell adhesion Attachment to the cytoskeleton “Antigen” AP Biology Cell surface identity marker

Membrane Proteins § Proteins determine membrane’s specific functions u cell membrane & organelle membranes each have unique collections of proteins § Classes of membrane proteins: u peripheral proteins § loosely bound to surface of membrane § ex: cell surface identity marker (antigens) u integral proteins § penetrate lipid bilayer, usually across whole membrane § transmembrane protein § ex: transport proteins w channels, permeases (pumps) AP Biology

Cell membrane must be more than lipids… § In 1972, S. J. Singer & G. Nicolson proposed that membrane proteins are inserted into the phospholipid bilayer It’s like a fluid… It’s like a mosaic… It’s the Fluid Mosaic Model! AP Biology

Membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer Glycoprotein Extracellular fluid Glycolipid Phospholipids Cholesterol Peripheral protein AP Biology Cytoplasm Transmembrane proteins Filaments of cytoskeleton 1972, S. J. Singer & G. Nicolson proposed Fluid Mosaic Model

Membrane carbohydrates § Play a key role in cell-cell recognition u ability of a cell to distinguish one cell from another § antigens important in organ & tissue development u basis for rejection of foreign cells by immune system u AP Biology

§ https: //translate. google. com/translate? s § l=es&tl=en&js=y&prev=_t&hl=en&ie=UT F 8&u=https%3 A%2 F%2 Fwww. youtube. c om%2 Fwatch%3 Fv%3 DQQg. Xfu. Fy. KM 4& edit-text=&act=url https: //highered. mheducation. com/sites /0072495855/student_view 0/chapter 2/an imation__how_osmosis_works. html AP Biology

Any Questions? ? AP Biology

Movement across the Cell Membrane AP Biology 2007 -2008

TRANSPORT § - Passive transport § Energy…NO § - Active transport § Energy…YES AP Biology

TRANSPORT across membrane § - Passive transport = is the ability of a § substance to travel from an area of high concentration (quantity) of that substance to an area of low concentration of that substance without applying energy. - Active transport = is the ability of a substance to travel from an area of low concentration (quantity) of that substance to an area of high concentration of that substance with applying energy. AP Biology

§ - Gradient = is the difference in measurement of § two different ends or side of a parameter. - Equilibrium = is when the situation is stabled or evenly balanced. It can be when there is no concentration gradient. AP Biology

§ - Equilibrium = is when the situation is stabled or evenly balanced. It can be when there is no concentration gradient AP Biology

AP Biology

Diffusion § Diffusion u AP Biology movement from HIGH LOW concentration

Simple Diffusion § Move from HIGH to LOW concentration § No Energy needed “passive transport” movement of water u no energy needed u AP Biology diffusion osmosis

Facilitated Diffusion § Diffusion through protein channels u u channels move specific molecules across cell membrane facilitated = with help no energy needed open channel = fast transport HIGH LOW AP Biology “The Bouncer”

Active Transport § Cells may need to move molecules against concentration gradient u u u conformational shape change transports solute from one side of membrane to other protein “pump” “costs” energy = ATP LOW conformational change ATP HIGH AP Biology “The Doorman”

Active transport § Many models & mechanisms ATP AP Biology ATP antiport symport

Transport summary simple diffusion facilitated diffusion active transport AP Biology ATP

The Special Case of Water Movement of water across the cell membrane AP Biology 2007 -2008

Osmosis is just diffusion of water § Water is very important to life, § so we talk about water separately Diffusion of water from HIGH concentration of water to LOW concentration of water u AP Biology across a semi-permeable membrane

Getting through cell membrane § Passive Transport u Simple diffusion § diffusion of nonpolar, hydrophobic molecules w lipids w HIGH LOW concentration gradient u Facilitated transport § diffusion of polar, hydrophilic molecules § through a protein channel w HIGH LOW concentration gradient § Active transport u diffusion against concentration gradient § LOW HIGH u u AP Biology uses a protein pump requires ATP

AP Biology

Concentration of water § Direction of osmosis is determined by comparing total solute concentrations u Hypertonic - more solute, less water u Hypotonic - less solute, more water u Isotonic - equal solute, equal water AP Biology hypotonic hypertonic net movement of water

AP Biology

Managing water balance § Cell survival depends on balancing water uptake & loss AP Biology freshwater balanced saltwater

1 Managing water balance § Hypotonic u a cell in fresh water u high concentration of water around cell § problem: cell gains water, swells & can burst § example: Paramecium w ex: water continually enters KABOOM! Paramecium cell § solution: contractile vacuole w pumps water out of cell ATP w ATP u plant cells No problem, here § turgid = full § cell wall protects from bursting AP Biology freshwater

2 Managing water balance § Hypertonic I’m shrinking, a cell in salt water I’m shrinking! u low concentration of water around cell u § problem: cell loses water & can die § example: shellfish § solution: take up water or pump out salt I will u AP Biology plant cells § plasmolysis = wilt § can recover survive! saltwater

3 Managing water balance § Isotonic u u animal cell immersed in mild salt solution That’s perfect! no difference in concentration of water between cell & environment § problem: none w no net movement of water flows across membrane equally, in both directions I could w cell in equilibrium be better… n w volume of cell is stable § example: blood cells in blood plasma w slightly salty IV solution in hospital AP Biology balanced

§ https: //translate. google. com/translate? s l=es&tl=en&js=y&prev=_t&hl=en&ie=UT F 8&u=https%3 A%2 F%2 Fwww. youtube. c om%2 Fwatch%3 Fv%3 DQQg. Xfu. Fy. KM 4& edit-text=&act=url AP Biology

AP Biology

AP Biology Justify how these are not examples of osmosis providing evidence from the pictures

Guided hints: Q. 11) * Water is not shown in the picture. * Read carefully to see which molecules can pass through the membrane. Q. 12) *Molecules move through/across the membrane based on their size. * Look carefully and figure out which molecules are small and which are big. AP Biology

AP Biology

Diffusion across cell membrane § Cell membrane is the boundary between inside & outside… u separates cell from its environment Can it be an impenetrable boundary? NO! OUT IN food carbohydrates sugars, proteins amino acids lipids salts, O 2, H 2 O AP Biology OUT IN waste ammonia salts CO 2 H 2 O products cell needs materials in & products or waste out

How about large molecules? § Moving large molecules into & out of cell through vesicles & vacuoles u endocytosis u § phagocytosis = “cellular eating” § pinocytosis = “cellular drinking” u AP Biology exocytosis

Endocytosis phagocytosis fuse with lysosome for digestion pinocytosis non-specific process receptor-mediated endocytosis triggered by molecular signal AP Biology

Contractile vacuole in Paramecium § https: //translate. google. com/translate? s § l=es&tl=en&js=y&prev=_t&hl=en&ie=UT F 8&u=https%3 A%2 F%2 Fwww. youtube. c om%2 Fwatch%3 Fv%3 Dvk 5 NFSvp 8 l. Y&e dit-text= http: //study. com/academy/lesson/contr actile-vacuole-definition-function. html AP Biology

Pumping water out § Contractile vacuole in Paramecium ATP AP Biology

Do you understand Osmosis… . 05 M . 03 M Cell (compared to beaker) hypertonic or hypotonic Beaker (compared to cell) hypertonic or hypotonic AP Biology Which way does the water flow? in or out of cell

Any Questions? ? AP Biology

Diffusion through phospholipid bilayer § What molecules can get through directly? u fats & other lipids inside cell NH 3 § What molecules can lipid salt NOT get through directly? u polar molecules § H 2 O u outside cell sugar aa H 2 O ions (charged) § salts, ammonia u large molecules § starches, proteins AP Biology

Membrane fat composition varies § Fat composition affects flexibility u membrane must be fluid & flexible § about as fluid as thick salad oil u % unsaturated fatty acids in phospholipids § keep membrane less viscous § cold-adapted organisms, like winter wheat w increase % in autumn u AP Biology cholesterol in membrane

Diffusion across cell membrane § Cell membrane is the boundary between inside & outside… u separates cell from its environment Can it be an impenetrable boundary? NO! OUT IN food carbohydrates sugars, proteins amino acids lipids salts, O 2, H 2 O AP Biology OUT IN waste ammonia salts CO 2 H 2 O products cell needs materials in & products or waste out