Cell Transport Flashcards
(37 cards)
What is the function of the cell membrane?
contains the cell and controls what can enter and leave the cell.
What is meant when we state the cell membrane is selectively permeable? (What might it let through/what not?)
Allowing some molecules to move across the membrane through tiny pores but preventing others.
It is freely permeable to small soluble molecules and water but impermeable to large insoluble molecules like starch.
What is the cell membrane composed of ?
(Phospho)lipids and proteins (protein channels)
What is the structure of the cell membrane described as ?
fluid bi-layer of constantly moving (fluid) phospholipid molecules containing a patchy network of protein molecules.
What is the name given to the patchy network of protein molecules composing the cell membrane?
Mosaic pattern
What can be the results of placing beetroot cylinders in 4 different test tubes. A- 10ml water at 25'c B- 10ml acid at 25'c C- 10ml ethanol at 25'c D- 10ml water at 70'c
In test tubes B/C/D = bleeding took place
In test tube A=no bleeding took place
What conclusion can be drawn from placing beetroot cylinders in: A- 10ml water at 25'c B- 10ml acid at 25'c C- 10ml ethanol at 25'c D- 10ml water at 70'c
Since the cell membrane was destroyed by acid and high temperatures this shows that one component of the cell membrane is proteins. Since the cell membrane was also destroyed by ethanol this shows that one component of the cell membrane is lipids.
What is diffusion?
The movement of molecules of a substance from a region of high concentration of that substance to a region of low concentration until the concentrations become equal.
What is the concentration gradient?
difference in concentration between an area of high concentration and an area of low concentration
How do molecules travel during diffusion?
During diffusion, movement of molecules always occurs down a concentration gradient
What kind of process is diffusion?
passive process and does not require energy
What are the 4 examples of useful products that enter the cell by diffusion?
Oxygen
Glucose (dissolved food)
Amino acids (protein production)
Fatty acids
What are the 2 waste products that leave the cell by diffusion?
Carbon Dioxide Water products (e.g. urea)
Name two organs in multi-cellular organisms were diffusion is essential?
Lungs = Oxygen needs to diffuse from air sac into blood and carbon dioxide from bloodstream into air sac.
Small Intestine= diffusion through villi for substances like glucose/amino acids to capillaries and fatty acids to lacteal.
What is meant by a solution being hypotonic? (give an example)
A solution that has a higher water concentration (HYPO-Oh what a lot of water). e.g. pure water is hypotonic to all other solutions.
What is meant by solutions being isotonic? (give examples)
Solutions that have equal water concentrations. e.g. usually include dilute sugar or salt solutions.
What is meant by a solution being hypertonic? (give an example)
A solution that has a lower water concentration. e.g. a concentrated sugar/salt solution
What is osmosis?
Movement of water molecules from an area of high water concentration (HWC) to an area of low water concentration (LWC) through a selectively(semi-) permeable membrane .
How does water travel during osmosis?
down a water concentration gradient.
What is meant by turgid?
firmer
What is meant by flaccid?
softer
What happens when an onion cell is placed into a hypotonic soluton?
Water passes in from the HWC to the LWC and cell swells and becomes turgid.
Describe the appearance of a plant cell placed in a hypotonic solution?
Turgid
Very large vacuole
Cell wall has stretched
What happens when an onion cell is placed into a isotonic solution?
No net gain or loss of water and cell remains unchanged.
