Transport in cells Flashcards
how do particles in liquids and gases move?
what happens due to the particles’ continuous movement in liquids and gases?
continuously
particles will spread themselves evenly throughout a liquid or a gas.
state what is meant by ‘diffusion’:
movement of particles from an area of higher concentration to lower concentration
what is important to state about the movement of particles during diffusion: (2)
particles:
-will move in both directions, but there will be a net movement from high to low concentration
-will end up evenly spread throughout the liquid or gas but will continue to move
describe what is meant by ‘solute’, ‘solvent’ and ‘solution’:
solute: the substance that will be dissolve
solvent: the liquid that the solute will be dissolved in
solution: mixture formed by solute and solvent
what is a concentration gradient?
describe the movement of particles during this process:
-the difference in concentration of a chemical (across a membrane)
-particles will move down a concentration gradient, from a high concentration to a low concentration.
examples of diffusion in biological systems: describe the process in a leaf (2)
palisade and spongy mesophyll
-oxygen moves out of the palisade mesophyll cells by diffusion into spongy mesophyll cells
-carbon dioxide moves into palisade mesophyll cells by diffusion from spongy mesophyll
examples of diffusion in biological systems: describe the process in the lungs (4)
-blood from the body high in carbon dioxide and low in oxygen
-carbon dioxide diffuses from high concentration in blood to low concentration in alveolus
-oxygen diffuses from high concentration in alveolus to low concentration in blood
-blood to the body high in oxygen and low in carbon dioxide
examples of diffusion in biological systems: describe the process in liver cells (3)
-high concentration of urea in liver cells
-low concentration of urea in blood vessel in liver
-urea is filtered from blood by the kidneys
what can the rate of diffusion be affected by? (3)
Concentration gradient,
temperature
Surface area of the cell membrane separating different regions
how does the ‘concentration gradient’ affects the rate of diffusion?
The greater the difference in concentration, the quicker the rate of diffusion
how does temperature affect the rate of diffusion? (2)
The higher the temperature, the more kinetic energy the particles will have,
-so they will move and mix more quickly
how does the ‘Surface area of the cell membrane separating different region’ affect the rate of diffusion?
The greater the surface area, the faster the rate of diffusion
how does diffusion occur in plants?
substances diffuse into and out of the bacterial cell across its surface
how does diffusion occur in multi-cellular organisms?
substances diffuse into the leaves and simple roots over their surface.
how odes a simple organisms need being determined by its volume cause a problem?
As organisms increase in size, their surface area does not increase at the same rate as their volume.
what is osmosis?
diffusion of water molecules, from a region of higher concentration to lower concentration, through a partially permeable membrane.
describes the difference between a dilute solution and a concentrated solution: (2)
-A dilute solution contains a high concentration of water molecules,
-concentrated solution contains a low concentration of water molecules.
what happens when the concentration of water is the same on both sides of the membrane? (2)
the movement of water molecules will be the same in both directions.
-There will be no net movement of water molecules.
what do cells contain? and how will water be transported into and out of the cell?
-dilute solutions of ions, sugars and amino acids.
-since the cell membrane is partially permeable, water will move into and out of cells by osmosis.
describe the process of osmosis in different plant cells: (3)
-Isolated plant cells
-root hair cells
-Leaf cells
-Isolated plant cells placed in a dilute solution or water will take in water by osmosis.
-If the soil is wet or moist then root hair cells will also take up water by osmosis.
-Leaf cells of land plants, unless it is raining or the humidity is high, will have a tendency to lose water.
what do plant cells have outside the cell membrane? what is a feature of it? what does it do to the cell?
-a strong cellulose cell wall.
-fully permeable to all molecules.
-supports the cell and stops it bursting when it gains water by osmosis.
what happens to the cell contents in pure water?
what do fully turgid cells support?
cell contents push against the cell wall and the cell becomes turgid.
-the stems of non-woody plants.
what happens to the cell contents in concentrated solutions?
what does the cell membrane begin to do?
what does the cell become?
cell contents lose water by osmosis and the cells shrink.
The cell membrance starts to pull away from the cell wall.
The cell becomes flaccid.
what happens to the cell membrane in VERY concentrated solutions?
what is this process called?
the cell membrane pulls away from the cell wall completely
-plasmolysis.
