A GENDA Standard Cell Membrane and Cell Transport Practice

S TANDARD Students will analyze the nature of relationships between structures and functions in living cells. Explain the role of cell organelles for both prokaryotic and eukaryotic cells, including the cell membrane, in maintaining homeostasis. Explain the impact of water on life processes.

H OMEOSTASIS “Homeo” – similar; the same “Stasis” – stable Homeostasis is the balanced internal condition of cells Also called equilibrium Example: body temperature

C ELL M EMBRANE The protective boundary that separates the cell from its environment. Made up of phospholipids in a double layer Phospholipid bilayer lipid phosphate inside cell outside cell

P HOSPHOLIPIDS Contain 2 fatty acid chains (Made of C, H, and O) and a phosphate group The head is polar and hydrophilic (water loving) The tails are nonpolar and hydrophobic (water fearing)

C ELL M EMBRANE Semi-permeable and Selectively permeable Needs to allow some materials but not all to pass through the membrane Controls what gets in or out; the membrane is selective

C ELL M EMBRANE Fluid Mosaic Model Fluid because individual phospholipids and proteins can move side-to-side within the layer, like it is a liquid Mosaic because of the pattern produced by the scattered protein molecules when the membrane is viewed from above

C ELL M EMBRANE Accessory Proteins Transport proteins allow passage of hydrophilic substances across the membrane Channel proteins are a type of transport protein that have a channel through which certain molecules or ions can pass Carrier proteins are a type of transport protein that binds to molecules and changes shape to carry them across the membrane

C HANNEL P ROTEIN

C ARRIER P ROTEIN

C ELL T RANSPORT Two Types: Passive Transport – does not require energy Active Transport – requires energy

C ELL T RANSPORT Passive transport The cell uses no energy Materials move from high concentration to low concentration 3 types Diffusion Facilitated diffusion Osmosis

D IFFUSION Does not require energy on the part of the cell. Movement of particles from an area of high concentration to low concentration Continues until all molecules are evenly spaced Example: oxygen diffusing into a cell and carbon dioxide diffusing out

F ACILITATED D IFFUSION Does not require energy on the part of the cell. Uses transport proteins to move from areas of high concentration to low concentration Examples: glucose or amino acids moving from blood into a cell

O SMOSIS Requires no energy on the part of the cell Diffusion of water and ONLY water Moves from high concentration to low concentration

O SMOSIS Water is very important to life! Cell survival depends on balancing water uptake and water loss. But the cell doesn’t control water movement through the cell membrane. Three different solutions cells may be exposed to: Hypotonic Hypertonic Isotonic

H YPOTONIC S OLUTION The solution has a higher concentration of water and a lower concentration of solute than inside the cell. Water moves from the solution to the inside of the cell. The cell swells and may eventually burst. hyp o – Swells, envision the cell as an expanding “o”

H YPERTONIC S OLUTION The solution has a lower concentration of water and a higher concentration of solute than inside the cell. Water moves from inside the cell into the solution. The cell shrinks hype r – shrinks; “r” in hyper, “r” in shrink

I SOTONIC S OLUTION The concentration of water and solutes in the solution is equal to the concentration inside the cell. Water moves equally in both directions and the cell remains the same size. iso – equal, no change in the cell’s size

C ELL T RANSPORT Active Transport The cell uses energy Actively moves molecules to where they are needed Movement from an area of low concentration to an area of high concentration – this is hard, requires work! 3 types: Ion pumps Endocytosis Exocytosis

I ON P UMP Requires energy Molecules move through a transport protein from low concentration to high concentration Example: the Sodium-Potassium pump pumps NA + ions out and K + in. This pump is very important in nerve cells to help respond to stimuli and transport impulses

E NDOCYTOSIS Requires energy on the part of the cell. Endo – enter; taking bulky materials into a cell. Phagocytosis – “cell eating” Forms food vacuole and digests food This is how white blood cells eat bacteria

E XOCYTOSIS Requires energy on the part of the cell. Molecules are moved out of the cell by vesicles that fuse with the plasma membrane Exo = exit; forces material out of the cell Examples: hormones or wastes released from cell