LO topic 2c - d Flashcards
List the roles that cell membranes perform
Function - isolation, regulate molecules and reactions, communication, attachment to cells
Describe the fluid mosaic model of membrane structure, and the chemical components of membranes including the phospholipid bilayer and the various proteins that comprise cell membranes
Molecules in a fluid flow past one another the diagram has 3 layers, inside the cell, phosphate layer with transport proteins and interstitial fluid.
Phospholipids are not bonded together but align in that way due to them being in water
Hydrophobic molecule can readily diffuse
Hydrophilic molecules enter via proteins (enzyme, recognition, transport, receptor, connection)
Describe the process of diffusion and the factors that affect the rate of diffusion through the lipid bilayer. Explain how membrane transporters can increase movement across membranes. This should include a description of facilitated diffusion through channels and aquaporins
Diffusion is the movement from high to low concentrations (down)
Simple diffusion is through the phosphate layer like H20 or 02 or C02. as well as lipid soluble like alcohol, and vitamins
Facilitated diffusion - via transport proteins,ions and polar molecules
Carrier proteins - specific molecules like sugars and small proteins
Channel proteins - pores that open and close
Aquaporions - only water
Define osmosis and discuss the factors that determine the direction of water movement. You should be able to apply this information to predict the direction of movement in different situations.
Diffusion of water across semipermeable membranes reacting to gradients of solutes in its surroundings
Moves from low concentration to high concentration.
Cells in hypertonic solutions shrivel and hypotonic solutions swell and burst.
Define the terms isotonic, hypertonic, and hypotonic
Isotonic - solution with equal concentration water moves to and fro equally
Hypertonic - solution has high concentration of solute
Hypotonic - less concentration of solute
Define turgor pressure and the mechanism used by plants to regulate it
Relates to how much pressure the membrane is punching against the cell wall
Cell absorb water the membrane inflates, causing high turgor pressure on the cell wall
Without water plant lose turgor and wilt
Describe the process of active transport
Expend energy to move substance across the membrane due moving against the gradient
Active transport proteins are referred to as pumps
Molecule enters binding site then ATP binds with the protein and the protein changes shape releasing the molecule onto the other side of the membrane. ATP is released turning into ADP
Explain how large molecules are transported across membranes by vesicle-mediated transport and provide examples of how macromolecules may cross the cell membrane using the mechanisms of endocytosis, pinocytosis, phagocytosis, and exocytosis
Endocytosis - material engulfed from the extracellular environment and transported via vesicles (includes pinocytosis, phagocytosis)
Pinocytosis - done to gather interstitial fluid
Phagocytosis - done to gather food particles
Exocytosis - material is expelled by vesicles fusing into the membrane
Summarise the various types of passive and active transport across membranes, and list the types of substances that are moved by each form of transport
Simple diffusion (passive) water, simple gases and lipid soluble - through bi-layer
Facilitated diffusion (passive) water, ions or water soluble molecule - through proteins
Osmosis (passive) water movement to a high concentration of solute
Active - molecule movement requiring energy (ATP)
Endocytosis (Active) material engulfed from the extracellular environment and transported via vesicles (includes pinocytosis, phagocytosis)
Exocytosis (Active) material is expelled by vesicles fusing into the membrane
List and describe the four types of connections that occur between cells: desmosomes, tight junctions, gap junctions, and plasmodesmata
Adhesive (desmosomes) - protein filament holding cells together via cytoskeletons connecting (in stretching tissues)
Tight - proteins seal cells together (leak proofing like bladder and brain)
Gap - channel proteins connect the insides of adjacent cells (communication like nervous signals and muscle contractions)
Plasmodesmata (plants) - membrane lined channels connecting insides of adjacent cells of molecules can pass.
Define the terms potential energy and kinetic energy and describe their connection to biological systems
Potential - stored energy (batteries, fuel, molecules ATP)
Kinetic - movement and radiant (light, x rays, electrical)
Photosynthesis converts kinetic energy (light) into potential (ATP)
State the first and second laws of thermodynamics; define entropy
First law - energy can neither be created nor destroyed within closed or isolated system (net energy in reaction)
Second law - Energy conversion proceeds from more useful to less useful forms
Entropy - amount of energy gained or lost during a reaction.
Define the terms ‘reactants’ and ‘products’; compare and contrast exergonic and endergonic reactions
Reactants are on the left and products are on the right of the equations
Exergonic reactions (release energy during reaction meaning the products have less energy
Endergonic reactions gain energy from its surroundings meaning the products have more products.
Briefly describe what is meant by activation energy
The minimum amount of energy required for a reaction to occur, this can be lowered using catalysts
Describe the function of biological electron carriers, especially ATP, and their role in coupled reactions
Provides energy for endergonic reactions and are synthesised at the site of exergonic reactions (ATP synthesis).
Coupled reactions are when the products of one reaction are the reactants of another that happens after the first.
