Diffusion and Osmosis Flashcards
What is diffusion?
It’s the movement of a substance from a religion of its high concentration to a region of its low concentration
What kind of a process is diffusion?
Passive - no energy required
Examples of diffusion in humans and plants
Humans - 02 diffuses into the blood in the lungs [c02 diffuses out of]
Plants - Co2 diffuses into the leaf through stomata
What are the membranes in a cell and what do they all have in common?
Cell membrane Mitochondria membrane Chloroplast membrane Nuclear membrane All semi permeable
What is a semi permeable membrane?
It lets some substances in and out
What is osmosis?
It’s the movement of water from a region of high water concentration to a region of low water concentration across a semi permeable membrane
It’s passive
In a solution, if the concentration is high?
The water concentration is low
What occurs in a solution that has a higher concentration?
High concentration = water is low
So water moves out of the cell by osmosis and the cell shrivels up and may die
What occurs with animal cells in a low concentration solution
Low concentration = high water concentration
Water moves into the cell by osmosis
Cell swells up and may burst
What is the problem that can occur in humans
Blood plasma has lower concentration than red blood cells, water moves into the cells from blood and causes cells to burst
What controls the water level in blood plasma
The kidney
Freshwater amoeba
Freshwater has low concentration than amoeba so water move into amoeba causing cells to swell and burst
So they have a contractile vacuole
What is the function of the contractile vacuole?
Collects excess water and realises it
Saltwater amoeba
Do not need contractile vacuole
The concentration of cytoplasm is same as external solution
What is the concentration of amoeba’s cytoplasm
High concentration
What kind of permeability does the cell wall have?
Fully permeable
Plant cells in high concentration solution
Water moves out vacuole and cytoplasm by osmosis which results in cell membrane pulling away from cell wall, cell wall is intact but rest of cell shrivels up = plasmolysed
The plant wilts
Plant cells in a solution with a low concentration
Water moves in to the vacuole and cytoplasm by osmosis.
The vacuole swells up and causing a cell to swell
It is turgid
What is turgor pressure?
It’s the outward pressure of the vacuole and cytoplasm against the cell wall
What is plasmolysis?
It’s the loss of water from the vacuole by osmosis and the pulling away of the cytoplasm from the cell wall
Effects of turgor pressure?
Herbaceous plants reply on turgor pressure for mechanical support
Why do sugary or salt solutions have a low water concentration?
Bacteria/fungi present will lose water by osmosis so the cells will die because they cannot survive without water
Examples of food preservation
Jam is stored in a sugary solution
What is active transport?
The movement of a substance from an area of its low concentration to an area of its high concentration
Requires energy
Demonstrate osmosis
Soften visiking tubing
Knot
Control : one with distilled water
One : sucrose
Eliminate as much air as possible and tie other knot
Record mass using electronic balance
Submerge both in beaker of distilled water
15 mins
Remove and record mass
Mass of sucrose = go up bc water moved in
What happens to a plant when it’s cells lose turgidity
Wilts
If an animal cell were subjected to conditions that result in plant cell becoming turgid, what may happen and why
It would burst - no cell wall
Name location and material involved in an active transport
Nephron
Glucose
In the experiment for osmosis, how did you conclude it had occurred
Increase in mass
From the graph, determine concentration [osmosis experiment]
Where it hits o on graph
Explain how plant cells remain turgid
By being in a higher water solution - Water is taken into vacuole, causing pressure of vacuole and cytoplasm against cell wall. The cell wall prevents it from bursting
Why is diffusion alternatively known as passive transport?
Requires no energy
Osmosis may be described as “a special case of diffusion” explain why?
Movement of war
Requires semi permeable membrane
In the case of a named molecule, give a precise location at which it diffuses in the human body?
Carbon dioxide
It diffuses out of blood in lungs
Water enters the outmost cells of the root by osmosis, what does this tell you about the cell sap of these outermost cells
It has a high solute concentration
