Cell Transport PDF

Cell transport: \- transport of substances across membranes: 1\. passive transport (without energy) a\) diffusion b\) osmosis 2\. active transport (with energy) a\) protein pumps b\) vesicles in the cytoplasm (in) - endocytosis: pynocytosis, phagocytosis (out) - exocytosis **1. passive tra...

Cell transport: \- transport of substances across membranes: 1\. passive transport (without energy) a\) diffusion b\) osmosis 2\. active transport (with energy) a\) protein pumps b\) vesicles in the cytoplasm (in) - endocytosis: pynocytosis, phagocytosis (out) - exocytosis **1. passive transport** \- no energy used in the process \- cells need to obtain substances vital in sustaining life a\) diffusion \- passive movement of particles from higher concentration to lower concentration \- solids, liquids, and gases consist of particles: atoms, molecules, ions \- the direction they move in is random \- movement of molecules down the concentration gradient (no need of energy) Diffusion: 1\. simple \- membranes allow some substances to diffuse through but not others \- substances move between the phospholipid molecules in the membrane 2\. faciliated \- substances unable to pass between phospolipids \- channel and carrier proteins = they only allow one type of substance to pass through factors that affect the rate of diffusion: \- surface area: \- the greater the surface the greater the rate of diffusion \- the size of molecules: \- the smaller the molecule, the faster they pass through membranes \- the width of the membrane: \- the thinnier the membrane, the faster the rate OSMOSIS: \- the passive movement of water molecules from a region of lower solute C to a region with a higher solute C solutions of different solute concentration: -\> **isotonic** - the same solute C as the cell´s cytoplasm, e.g. 0,9% of NaCl -\> **hypertonic** - higher number of solute C than the the cytoplasm, ⊙ of sugar or salt \- PLASMOLYSIS: - water is lost, cell membrane begins to leave the cell wall / cytoplasm decreases its volume -\> **hypotonic** - lower number of solute C than the cytoplasm, e.g. distillate water \- water enters the cytoplasm \- plant cell: the membrane is forced against the cell wall \- animal cell: the cell bursts open - PLASMOPTYSIS **2. active transport across membranes - energy is used in this process** = movement of substances across membranes using energy \- a substance called ATP (adenosine triphosphate) supplies the energy a\) protein pumps: \- each pump only transports specific substances \- pumps only work in specific direction - the substance can only enter on 1 side and exit on the other b\) transport of substances by vesicles in the cytoplasm **ENDOCYTOSIS:** \- the substance contacts the cell membrane which indents \- the substance is surrounded by a membrane, forming a vacuole or vesicle \- the fluid inside can contain: a\) solution - pinocytosis b\) larger solids - phagocytosis - when unicellular organism ingest their food **EXOCYTOSIS:** \- vesicles fuse with the cell membrane \- the contents of the vesicle are expelled and the membrane then flattens out again e.g. to remove excess water from the cell of unicellular organisms