Diffusion
Define diffusion.
The net movement of particles from a region of their higher concentration to a region of their lower concentration (i.e. down a concentration gradient), as a result of their random movement.
Define osmosis.
The net movement of water molecules from a region of higher water potential (lower solute concentration) to a region of lower water potential (higher solute concentration), through a partially permeable membrane.
Define active transport.
The net movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (i.e. against a concentration gradient), using energy from respiration.
List the chemical elements that make up carbohydrates, fats and proteins.
C, H, O, N
Describe the test for starch, including what you use, and what will you see.
iodine
(yellowish-)brown > blue-black
Where does the energy for diffusion come from?
The kinetic energy of random movement of molecules and ions.
Describe the role of water as a solvent in organisms.
In the alimentary canal (digestion), water allows for digestion of food molecules as both the enzymes and food molecules are dissolved in water, allowing them to interact and the molecules to break down.
In the kidneys (excretion), the toxic waste urea and excess ions are filtered from the blood and excreted dissolved in water. This is what forms urine.
Our blood (transport) is responsible for transporting a variety of substances around our body. Many of these are dissolved in the water that forms our blood plasma. Glucose, proteins and hormones are just some examples.
What moves molecules or ions across a membrane during active transport?
protein carriers, protein pumps
Name the monomers of lipids (fats).
fatty acids and glycerol
Describe the test for reducing sugars, including what you use, and what will you see.
Benedict's solution
blue>green>yellow>orange>red
What are some examples of diffusion in organisms?
movement of carbon dioxide and oxygen in leaves,
movement of glucose and other food molecules into and out of cells,
movement of carbon dioxide and oxygen in the alveoli of the lungs
movement of water, glucose, urea in the kidney
How are plants supported?
By the pressure of water inside the cells pressing outwards on the cell wall - turgor pressure.
Using one example, explain the importance of active transport as a process for movement of molecules or ions across membranes.
The concentration of nitrate ions is likely to be higher inside a plant's root hair cells than in the soil surrounding them. Diffusion would cause nitrate ions to move out of the plant. However, active transport allows the plant to take in these vital ions.
Name the monomers of protein. Draw its structure.
Amino acid
[Bonus: name the bond]
Describe the test for proteins, including what you use, and what will you see.
biuret test
blue > purple
Describe the importance of diffusion of gasses and solutes in living organisms.
Many cell processes within living organisms depend on diffusion to deliver or remove dissolved substances, or solutes, and gases through cell membranes.
A plant cell which gains water by osmosis, and has high turgor pressure is described as __(a)_____. It is stiff and helps to support the plant. When a plant cell loses water by osmosis, its cytoplasm and vacuole shrink. Its turgor pressure decreases and it becomes ____(b)____ .The cell becomes less stiff and no longer helps to support the plant. If the plant cell loses a lot of water, the cytoplasm and vacuole may shrink so much that the _____(c)______ pulls away from the cell wall. This is called ____(d)_____, and will probably die.
(a) turgid
(b) flaccid
(c) cytoplasm
(d) plasmolyse
Compare and contrast diffusion, osmosis and active transport in terms of substances transported and requirement of energy from respiration.
substances transported: D - gases and other substances, O - water only, AT - substances in solution
requires energy from respiration: D & O - No, AT - Yes
Name 3 monosaccharides (carbohydrate monomer/micromolecule), 3 disaccarides (carbohydrate dimer), 3 polysaccharides (carbohydrate polymer/macromolecule).
monosaccharides: glucose, galactose, fructose
disaccarides: maltose, lactose, sucrose
polysaccharides: starch, glycogen, cellulose
[Bonus 1: name the bond formed]
[Bonus 2: what is the function of, and difference between starch, glycogen and cellulose.]
Describe the test for fats and oils, including what you use, and what will you see.
ethanol emulsion test
white/milky layer
Name the four factors that influence diffusion. Choose one factor to describe on how it influences diffusion.
Surface area (direct relationship)
temperature (direct relationship)
concentration gradient (direct relationship)
distance (indirect relationship)
Explain the importance of water potential and osmosis in plants and animals.
The water in the soil is often part of a solution that is more dilute than the solution inside the root hair cells. As a result, water enters the root hair cells by osmosis. The water is then pulled through the plant by transpiration.
A red blood cell that gains too much water could swell and burst. This is because it is not protected by a cell wall (unlike plant cells). [Bonus] Body cells can be damaged if they lose or gain too much water by osmosis. To prevent this type of damage, the water concentration of the blood and of the cytoplasm in cells is very closely controlled by the kidneys
Compare and contrast diffusion, osmosis and active transport in terms of membrane requirements, protein carrier requirements, and direction of transport.
membrane requirements: D - No, O & AT - Yes
protein carrier requirements: D & O - No, AT - Yes
direction of transport: D & O - Down, AT - Against
What is the monomer of a DNA molecule? Describe the structure of a DNA molecule.
Structure:
(a) double helix
(b) each strand contains chemicals called bases [Bonus - what is the type of bond linking the bases together in a single strand? EXTRA BONUS - name the bone]
(c) bonds between pairs of bases hold the strands together [Bonus - name the bond]
(d) bases always pair up in the same way, A with T, C with G
Describe the test for Vitamin C, including what you use, and what will you see.
DCPIP
blue > colorless