Biology; 2.4

ATP is the source of energy for active transport. Explain how ATP releases energy.

- ATP releases energy by bonding of adenosine, diphosphate and phosphate

membrane proteins with their functions:

- Channel/ carrier proteins -> passive transport across the membrane - Protein pumps -> active transport across the membrane - Receptor proteins ->hormone binding and recognition - Enzymes -> used in cell surface reactions - Adhesion proteins -> binding cells together - Neurotransmitter receptors -> communication between cells

Define diffusion.

- Diffusion the passive movement of gas or liquid particles, from a region of high concentration to a region of low concentration.

Distinguish between exocytosis and endocytosis.

- Endocytosis is the process of which the cell takes in a certain substance by surrounding it with its membrane, whereas Exocytosis is the process of which the cell releases a certain substance by carrying it with a vesicle, then pushing it out of the cell as the vesicle merges in with the cell membrane and pushes the substance outwards.

State the functions of these plasma membrane components = Glycoproteins & Cholesterol

- Glycoproteins: Often involved in cell recognition (immunity) and as receptors in cell signaling. - Cholesterol; decreases the fluidity of the membrane

Define macromolecule. Give one example of a macromolecule produced in the cell.

- Macromolecule is a molecule composed of a large number of atoms. Protein is an example, which is made out of amino acids, lipids fatty acids and glycerol.

Define osmosis.

- Osmosis is the passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration.

Explain how osmosis can lead to plasmolysis.

- Plasmolysis is the condition when a plant cell shrinks due to loss of water by osmosis. First, water enters by osmosis, vacuole swells and pushes against cell wall. Second, water loss from cell, vacuole shrinks and cell loses shape.

Define selectively permeable in the context of the plasma membrane.

- Selectively permeable means that are some molecules are able to pass through or not, this is because there is a size limit for molecules to pass into or out the permeable membrane.

how a protein pump is used in active transport of molecules across a plasma membrane. The Na+/K+ pump is an example.

- Sodium potassium pump is an active transport pump that maintains a step concentration gradient. - Sodium is in high concentration outside the cell & low inside - The pump transports three sodium out the cell and two potassium into. 1. Sodium is moved into a higher concentration region outside of the cell using energy 2. Sodium is engulfed and moved out of the cell 3. Same process with potassium, moving it inside to a greater concentrated region 4. Potassium engulfed and moved out of the cell

The process of vesicle transport of a protein molecule through a eukaryote cell. Begin with protein synthesis in the Rough ER and finish with exocytosis though the plasma membrane.

- The nucleus is attached to the Rough ER, while the protein is synthesized in the Rough ER, then is helped by transport vesicles to get to the Golgi Apparatus. They are passed through, become packed, processed and prepared for exocytosis. Then carried by secretory vesicles to the plasma membrane and pushed out the cell.

Explain why the plasma membrane described as a fluid mosaic model.

- The plasma membrane is described as a fluid mosaic model because its made up of a phospholipid bilayer, allowing it easily to bend and move along without breaking or ripping the membrane due to the hydrophobic and hydrophilic poles of the bilayer.

Distinguish between uniport, symport and antiport as different methods of active transport.

- Uniport (a single substance, single direction) - Symport (two substances, same direction) - Antiport (two substances, opposite directions)

Define vesicle.

- Vesicle is a circled shaped membrane bound used to transport substances within a cell, it carriers a certain fluid of substance, and is involved in Exocytosis and Endocytosis.

Describe how the plasma membrane breaks and reforms during exocytosis and endocytosis. How does the fluidity of the membrane allow this?

1. The vesicle approaches the plasma membrane. All membranes are made of the phospholipid bilayer, so share the same properties. 2. The membranes begin to refuse. The fluidity of the plasma membrane - the phospholipid can flow around each other. 3. For a moment, there is a single phospholipid bilayer at the point of contact. 4. The membranes pore opens, allowing the contents to pass through. Through the whole process, there is never an unbroken section of the bilayer.

Define the plasma membrane.

A selectively permeable membrane, which encloses the cell. Also known as a cell membrane. - The plasma membrane is called a Phospholipid bilayer because the structure is composed of TWO layers of phospholipids.

List four ways to maximize the rate of diffusion of a substance across a membrane.

Increase Temperature b. Increase surface area of membrane c. Increase concentration of substance outside the membrane d. Embed more proteins within the membrane

Distinguish between solute, solvent and solution

Solution is a substance made up of the solute and the solvent. The solute is what is being dissolved and the solvent is what the solute is being dissolved into.

Explain how hydrophobic and hydrophilic properties of the phospholipid bilayer allow a membrane to maintain its structure.

The plasma membrane is a phospholipids bilayer structure, where there are two opposite strands of phospholipids. A phospholipid is composed of a hydrophilic phosphate head and two hydrophobic fatty acid tails. The phosphate heads face outwards where they are able to attract water and the hydrophobic tails are in between which repel water. The purpose is it to create a barrier between the internal and external environments of the cell. This creates a barrier to the movement of charged molecules separate the cellular content from the content outside, allowing for the cell to have a higher or lower concentration of molecules.

List six functions of the plasma membrane.

• Hormone binding sites • Immobilized Enzymes • Cell adhesion • Cell to Cell communication • Channels for passive transport • Pumps for active transport