(e)+Active+Transport

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**Active Transport** : movement of molecules against its concentration gradient (Low → High) across the a plasma membrane. Forceful transportation → requires __ energy __ (ATP) * ATP : the small energy carrying molecule that is used within cells of ALL living things. Once the energy is used, it becomes ADP. This is recharged back into ATP inside the mitochondria, during respiration.

R easons why cells must use active transport, instead of diffusion :
 * 1) Often a living being requires to uptake molecules that are scarce in their environment
 * 2) Some molecules cannot be diffused → cell uses "cell-eating" process (**Endocytosis**)

P rotein pumps (a.k.a. carrier proteins) : gate for plasma membrane → allows the molecules to move against concentration gradient → facilitates the rate of active transport of large molecules

**Vesicles** : bubble-like membranous sac structure that contains fluid or gas Vesicles act as an indirect connection between the rough ER and Golgi apparatus to transport cellular products through following process :
 * 1) Membrane-bound secretory vesicles bud off from the ER and move to the Golgi apparatus.
 * 2) The membranous components fuse and the contents of the vesicles are delivered for modification within the Golgi apparatus.
 * 3) In turn secretory vesicles from the Golgi can leave the cell via exocytosis at the plasma membrane, where again fusion of membrane component occurs.

Vesicles can form into various things: vacuoles, lysosomes, transport vesicles, and etc... Therefore it also has various functions for the cell. They are involved with Buoyancy control, transport, metabolism, and enzyme storage. __﻿__﻿__21. Define **E//ndocytosis//** & //**Exocytosis**//. Draw a series of diagrams to descrive these processes.__
 * Endocytosis {Endo (with-in), cytosis (cell)}
 * process in which a substances (macromolecules, large particles, small molecules and small cell) gain entry into a cell without passing through the cell membrane. This step subdivided into 3 different types.
 * Pinocytosis (cell drinking)
 * Occurs in almost every single cells continuously
 * Phagocytosis (cell eating)
 * Results in the ingestion of pariculate matter such as bacteria from ECF (Extracellular Fluid)
 * The endosome is large, so it is called //**Phagosome**// or **//Vacuole//**
 * Only occurs in certain specialized cells such as **//Neutrophils//**, //**Macrophages**// and //**Amoeba**//
 * Receptor mediated Endocytosis
 * Some of the integral membrane proteins that a cell displays at its surface
 * To tranferrin on their surface
 * Bind tightly to molecule when it encounters a molecule of transferrin
 * Exocytosis {Exo (outward), cutosis (cell)}
 * Process in which a membrane-enclosed vesicle packaged in the vesicles are secreted from a cell when vesicle membrane fuses with the plasma membrane
 * Restores right amount of plasma membrane
 * //**Secretion**// - any molecules dissolved in the fluid contents of these vesicles are discharged into the extracellular fluid
 * Any integral membrane proteins exposed to the interior surface of the vesicles will now be displated at the cell surface because the vesicles turn inside out as they fuse with the plasma membrane

__22. Distinguish between pinocytosis & Phagocytosis.__
 * Please refer to question 21

__23. what is a contractile vacuole? Explain what it does, why and how it works.__
 * Contractile Vacuole is one of organelle (specialized vacuole of eukaryote cells) from protist cell and often found in freshwater protozoaa such as paramecium and amoeba. It forces water out of the pores to reduce osmotic pressure and prevents the cell from bursting

__24. Make a special not on sodium-potassium pumps, as we meet these lots all through the IB curriculm.__
 * To pump sodium and potassium ions into the cell
 * Active transport mechnism
 * Both sodium and potassium ions are moving from areas of low concentration to areas of high concentration
 * Usage of energy to power sodium-potassium pumps is Breakdown of ATP
 * 1) 3 sodium ions bind to the protein channel and ATP provides the energy to change the shape the shape of the channel that in turn drives the ions through the channel
 * 2) One phosphate group from ATP remains for later job
 * 3) The sodium ions are released on the other side of membrane outside of the cell and the new shape of the channel has a high affinity for potassium ions and two of these ions now bind to the channel
 * 4) The binding again causes a change in the shape of the protein channel and this conformational change releases the phosphate group on the cytoplasm side
 * This release allows the channel to revert to its original shape and as a result, the potassium ions are released inside the cell