Chapter 2: Movement Of Substances🧪

Net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient

Different between concentration between two regions

• Temperature (higher temp, faster diffusion) • SA to vol ratio (larger ratio, higher diffusion) • Concentration gradient (stepper gradient, faster diffusion) • Size/ mass of particles (smaller, diffuse faster) • Diffusion distance (shorter distance, faster diffusion) • Diffusion medium (solid; slowest, liquid; faster, gas; fastest)

Greater SA to volume ratio, faster the rate of diffusion Increased SA to volume ratio in cells function in absorption (eg Root hair cell, epithelial cell)

Time taken for a substance to move from point point to another Shorter diffusion distance, less time needed for substances to travel, increased rate of diffusion

Net movement of ion and polar (water soluble) molecules through cell membranes using specific protein channels or carriers down a concentration gradient (Passive process, only relies on kinetic energy of molecules)

Net movement of water molecules from a region of higher water potential to a region of lower water potential through a ppm

Measure of tendency of water molecules to enter/leave solutions by osmosis Potential of pure water: 0

• Hypotonic: less (solute) • Isotonic: equal • Hypertonic: more Terms are used relative to another solution

Expand/ swell: protected by inelastic cell wall • Cell sap has a lower water potential than solution • Water enters via osmosis through the partially permeable cell membrane • Cell expands and swells. Cell becomes turgid. • Water molecules enter, vacuole size increases and pushes against the cell wall.

Turgidity of cell with water

Pressure by water in vacuole

Cell swells and may burst as there is no cell wall to protect it Water potential is higher than that of the cytoplasm

Same movement of water molecules in both directions No net movement of water molecules in and out of cell

• Cell sap has higher water potential than solution • By osmosis, water molecules leave vacuole and cytoplasm via ppm • Cell decreases in size and becomes flaccid/limp.

Cell loses water and shrinks Spikes appear: crenation Cell becomes dehydrated and eventually dies

Maintains shape word soft tissue: remain firm If not, cell loses turgidity and plant wilts

Energy from respiration is used to move particles of a substance across a membrane, against the concentration gradient: region of lower concentration to region of higher concentration

Bulk transport of materials Carrier protein molecules

Endocytosis and exocytosis: Movement of large molecules (like proteins) in and out of cells

Uptake of materials into cell but inward foldings of cell surface membrane

Sac of membrane are formed that surround a large molecule or even an entire cell from the extracellular environment Membrane pinches off and forms vesicle in cell ATP energy is used to move around cytoplasm Vesicle can fuse with other special vesicles with enzymes to digest its contents Endocytosis may involve uptake of liquids (pinocytosis) or solid particles (phagocytosis)

Materials exported out of the cell via secretory vesicles

Golgi apparatus packages large molecules into secretory vesicles which travel and fuse with cell surface membrane ATP energy is used to move cytoplasm around Exocytosis is important in removal of waste material out of cell and secretion of cellular products (eg digestive enzymes like proteins or hormones like proteins and fats)