Cell Membrane Maintaining Balance Cells need to maintain

Cell Membrane

Maintaining Balance • Cells need to maintain balance by controlling materials that move in and out of the cell. This balance is called Homeostasis

Structure of the Plasma (Cell) Membrane • All cells are surrounded by a plasma membrane. • Functions like a GATE, controlling what ENTERS and LEAVES the cell. • The cell membrane is semipermeable or selectively permeable.

• A semipermeable membrane only allows certain molecules to pass through.

Plasma (Cell) Membrane • Made of 2 layers of phospholipid. Called a Phospholipid Bilayer or Lipid Bilayer

• A phospholipid consists of – Phosphate Group (Head) sticking Toward the water (hydrophilic- water loving) – 2 Fatty Acids (Tails) nonpolar pointing Away from the water (hydrophobic-water fearing)

• The cell membrane is constantly being formed and broken down in living cells.

Moving with and among the phospholipids are cholesterol, proteins, and carbohydrates. • Cholesterol: Nonpolar lipid that helps to prevent the fatty acid tails from sticking together.

• Proteins: – Found on the surface of the plasma membrane and transmit signals to the inside of the cell. – Embedded in the plasma membrane for structure and support and to move large substances in and out of the cell.

• Carbohydrates – Attached to proteins and helps cells identify chemical signals. – EX: help disease fighting cells recognize and attack a potentially harmful cell

Cell Transport

PASSIVE Transport Kinds of ____ • _________________ Diffusion • __________________ Facilitated Diffusion • Carriers ________________ • Channels ________________

DIFFUSION across a space Happens anytime there is a _____ DIFFERENCE in concentration in one place compared to another Concentration gradient = ____________

DIFFUSION PASSIVE • No energy required = _______ DOWN concentration gradient • Moves _______ from __________ HIGHER to LOWER • Works for any molecules that can pass through the membrane • Example of molecules that move this way in cells: OXYGEN Carbon dioxide ____ & ______

Animatioin from: http: //www. biologycorner. com/resources/diffusion-animated. gif Molecules move FROM _______“where there’s _______” A LOT ____“where there’s _______” to NOT

DIFFUSION across a space Diffusion continues until the concentration equal everywhere is ________ in space Equilibrium = ____________ http: //lhs. lps. org/staff/sputnam/Biology/U 3 Cell/diffusion_1. png

DIFFUSION across a membrane DIFFERENCE Happens anytime there is a _____ in _______ concentration on one side of the membrane compared to the other

CELL EXAMPLE: DIFFUSION automatically moves oxygen from HIGHER concentration (in lungs) to a LOWER concentration (in blood) CO 2 automatically moves from where there is a HIGHER concentration (in blood) to where there is a lower concentration (in lungs) http: //www. le. ac. uk/pa/teach/va/anatomy/case 2/2_2. html

WAY to Cells need a ____ HELP molecules across ____ cell membranes that can’t go across by _______ themselves ______

FACILITATED DIFFUSION membrane proteins to help uses ________ molecules across 2 kinds of proteins help: Carriers Channels _____ & ______ Animations from: http: //bio. winona. edu/berg/ANIMTNS/facdifan. gif http: //www 2. uic. edu/~myilma 1/ionchannel. gif

Facilitated Diffusion with CARRIER PROTEINS Carrier protein grabs a molecule, like glucose, changes shape, and flips across to other side like a revolving door Animation from: http: //bio. winona. edu/berg/ANIMTNS/facdifan. gif http: //www. gobananas. co. uk/edinburgh-stag-party/enquiry/index. htm

FACILITATED DIFFUSION with CHANNELS http: //bio. winona. edu/berg/ANIMTNS/voltgate. htm Membrane proteins create a tunnel through which molecules can pass ions

polar They also allow ____ WATER molecules to get past _____ hydrophobic middle of cell the _____ membrane. http: //www. spps. kvl. dk/news/0507/Lund 4. jpg

The movement of water molecules across a cell membrane is called OSMOSIS _______ http: //student. ccbcmd. edu/~gkaiser/biotutorials/eustruct/channelanim. html

ALL KINDS OF FACILITATED DIFFUSION PASSIVE • No energy required = _______ DOWN • Moves ____ concentration gradient HIGHER to LOWER from ____________ Membrane proteins • __________ help molecules get across membrane

Vocab SOLUTE _______ = substance that is dissolved in a solvent to make a solution SOLVENT = substance in which a _______ solute is dissolved http: //www. makash. ac. il/h_school/hstsb/chem/luach/dissolve. jpg

Use new vocab to make Koolaid powder sugar Solutes = _______& _____ Water Solvent = ______ Koolaid Drink Solution = _______ http: //www. makash. ac. il/h_school/hstsb/chem/luach/dissolve. jpg

Images by Riedell _________ CONCENTRATION = mass of a solute in a given volume of solution MORE molecules there are in a given The _______ volume the ______the concentration GREATER

What if there is a difference in concentration but solute molecules can’t move across a membrane? WATER will move until concentration reaches equilibrium

Solute concentration Lower outside than inside Equal outside and inside Greater outside than inside HYPOTONIC ISOTONIC HYPERTONIC What will happen to an animal cell placed in different solutions?

Remember: Cells try to “maintain stable internal conditions = HOMEOSTASIS __________ http: //bioweb. wku. edu/courses/biol 121/Osmosis. asp So an animal cell in ISOTONIC conditions stays same size Water entering = water leaving Video Choose Blood Isotonic link

Animation from: http: //www. ouhscphysio. org/humanphys/animations/osmosis 3. swf OSMOSIS HYPOTONIC: Concentration outside cell is LESS THAN ________ inside the cell More water enters than leaves cell so cell will __________ swell and possibly burst

Animation from: http: //www. ouhscphysio. org/humanphys/animations/osmosis 4. swf OSMOSIS HYPERTONIC: Concentration outside cell is __________ inside cell GREATER THAN More water leaves cell than enters so cell ______ shrinks

http: //faculty. etsu. edu/currie/images/osmosis 1. jpg

http: //www. stchs. org/science/courses/sbioa/metenergy/bloodcells. gif Animal cells = CYTOLYSIS _____ = CRENATION _____

http: //www. stchs. org/science/courses/sbioa/metenergy/aplantturgor. gif Plant cells CELL WALL keeps _____ plant cells from bursting = PLASMOLYSIS ______

SO WHAT? Bath water is ________ hypotonic compared to you Sitting in the bathtub causes your fingers and toes to wrinkle up when water ____ enters your skin cells by osmosis

Grocery stores spray water on their veggies to “plump them up” http: //www. painetworks. com/photos/gt/gt 0461. JPG

What if cell needs to move a AGAINST the molecule _____ CONCENTRATION GRADIENT? ________ (LOWER HIGHER) Cell example: Want to put MORE glucose into mitochondria when there is already glucose in there Image from: http: //www. biologyclass. net/mitochondria. jpg

ACTIVE Kinds of ____Transport • ____________________ PUMPS • _________________ Sodium-Potassium • ________________ Proton • __________________ Vesicles • Endocytosis ________________ • Exocytosis ________________

SODIUM-POTASSIUM PUMP ACTIVE transport • ______ ATP (requires energy from ______) low concentration • Can move molecules from _____ high to ______ • Special just for Na+ and K + ions membrane proteins called • Uses ____________ to move molecules pumps • Example: nerve cells Na+ is pumped out of cells at same time K + is taken into cells

+ Na and K + Animation from: http: //www. lionden. com/cell_animations. htm PUMP

PROTON PUMP ACTIVE transport • ______ ATP (requires energy from ______) low concentration • Can move molecules from _____ to ____ high • Special just for H+ ions Protein pumps to move molecules • Uses integral ________ Examples: • Lysosomes need acidic conditions for digestion • Photosynthesis/Respiration

PROTON PUMP Moves Protons across membrane H+ ions = ___

ACTIVE TRANSPORT with VESICLES are small membrane sacs that ______ pinch off of cell membranes used by cells for transporting molecules Used for transporting molecules: ENDOCYTOSIS If entering the cell = _______ If exiting the cell = ________ EXOCYTOSIS http: //academic. brooklyn. cuny. edu/biology/bio 4 fv/page/cell-movement. html http: //academic. brooklyn. cuny. edu/biology/bio 4 fv/page/exocy. htm

ENDOCYTOSIS Substances taken into cell ACTIVE transport (requires____) energy • _____ VESICLES • Uses _______ to carry substances low concentration • Can move molecules from _____ to ______ high Examples in cells: – one celled organisms eat this way – white blood cells get rid of bacteria this way

2 KINDS of ENDOCYTOSIS for taking substances into cell If taking in: PINOCYTOSIS fluid or small molecules =_________ PHAGOCYTOSIS large particles or whole cells =_______ Animation from: http: //academic. brooklyn. cuny. edu/biology/bio 4 fv/page/endocytb. htm

ENDOCYTOSIS Animation from: http: //academic. brooklyn. cuny. edu/biology/bio 4 fv/page/cell-movement. html Protist eating another http: //www. accs. net/users/kriel/chapter%20 nine/

PHAGOCYTOSIS White blood cell ______ germs destroying _______

WHITE BLOOD CELL ENGULFING BACTERIA (Phagocytosis) http: //fig. cox. miami. edu/~cmallery/255 ion/fig 14 x 28. jpg

EXOCYTOSIS Substances released outside of cell ACTIVE transport (requires____) energy • _____ VESICLES • Uses _______ to carry substances low concentration • Can move molecules from _____ to ______ high • Examples in cells: – _____ GOLGI release packaged proteins this way

INSULIN being released by pancreas cells using exocytosis http: //fig. cox. miami. edu/~cmallery/255 ion/fig 14 x 26. jpg