Transport across the membrane Flashcards
passive transport
Movement of substances across a membrane that does not require energy, it the spontaneous process where materials move down the concentration gradient
Simple diffusion
Diffusion is the net movement of particles from a region of high particle concentration to a region of lower particle conc. Occurs because of random kinetic movement of particles, effects were seen when a conc gradient exits until particles are evenly distributed. Particesl continues to move randomly. Passive and down conc. gradient
Equilibrium
2 solutions have the same concentration of solutes and net movement of 0 across semi permeable membrane
Particle theory
Particles making up matter in constant motion, increase temp, increase speed of particles
What can pass (diffusion)
Gases (co2 and o2), small polar molecules (h2o and ethanol), some hydrophobic molecules (benzene)
Facilitated diffusion
Charges particles (na and cl) and large (glucose and aa) cant pass. Must be assisted by transport proteins (carrier and channel).
carrier proteins in facilitated diffusion
Bind to a specific molecule on one side of membrane and change shape then release (glucose transporter protein moves passively depending on conc)
Channel in transport
Inc. aquaporins, for fac diffusion of water and ion channels that open and close in response to a stimulus. Passive. Form a narrow passage through which small ions diffuse rapidly down the gradient. Only specific ions of specific can pass through particular channel
Osmosis
The diffusion of water through a semi-permeable membrane and down a conc gradient. Water is a medium with biochemical processes take place and keep cells in shape, if conc
Osmosis in animals
Water moving in can cause bursts, uni cell organisms like an amoeba that lives in freshwater have important regulatory mechanisms to combat living n hypotonic solutions and can move excess water by forming little pools of water in organs called contractile vacuoles. When stretched to a certain point will contract and expel water. In multi-cell, surrounded by isotonic em until by plasma which is controlled by kidney
Osmosis in plants
Have fluid-filled vacuole and firm but permeable cell wall. Vcule contains a cell sap rich in solutes, a solution of high conc. When hypotonic, water is in the cytosol and into the vacuole. Vacule swells pushing cytoplasm and membrane against the wall, when stretches as much as possible no more enters, and is called turgid. Tugor is important as it supports them, When hot will wilt as water evaporates and the external conc becomes less which vacuoles cell and will become flaccid. If enough water is lost, the membrane pull away from the cell wall called plasmolysis
Active transport
Energy is required to transport from low to high, performed by specific proteins n membranes. Enables cell to maintain reverse conc gradient of substance that cell requires.
Example of active transport
after a meal, nutrients like glucose absorb into the cell lining of the small intestine, if diffusion alone was involved, once conc of glucose in and out of cells became equal, there would be no net movement, and would be excreted
Proteins involved in active transport
Transport proteins are used atp to move molecules and ions up the gradient. As carrier proteins work in only one direction, they act as one-way valves. Without active transport, kidneys can’t reabsorb useful stuff, no muscle contractions, impulses across nerves can happen
Endocytosis
Large molecules such as polysaccharides and proteins in bulk can be transported via endo and exocytosis via vesicle. Active needs the energy to move cases around and change the shape of the cell. Tow types phago and pinocytosis. Macrophages use recognition prin in the membrane of cell the encounter to discriminate between dn engulf bacteria. Fats enter via pinocytosis
