Transport Across Cell Membranes Flashcards
What is the cell membrane composed of?
Lipid and protein.
Is the cell membrane fully permeable or selectively permeable?
Selectively.
A difference in concentration of a substance is a c………… g…………?
Concentration gradient
When a substance does not require additional energy for the movement of its molecules along the concentration gradient from a high concentration to a low concentration, this is called?
Passive transport
Give 2 examples of passive transport.
Diffusion
Osmosis
Describe diffusion.
Diffusion is the movement of substances from a high concentration to a low concentration down a concentration gradient.
Give 3 examples of substances that enter most cells by diffusion?
Oxygen
Glucose
Amino acids
Give 2 examples of substances that leave most cells by diffusion.
Carbon dioxide
Urea
Why is diffusion important to cells?
It helps to provide the cell with raw materials and it helps to remove waste products.
What is Osmosis?
Osmosis is the movement of water from a region of high water concentration to a region of low water concentration through a selectively permeable membrane.
What could happen to an animal cell place in a high concentration of water than what is in its cell.
It could absorb too much water through osmosis and burst.
What could happen to an animal cell that is placed in a lower level of concentration that what is in the cell?
It can lose the water fro, the cell via osmosis and shrink.
Describe the word turgid.
When a plant cell becomes swollen with a full vacuole resulting from water intake due to osmosis.
When a plant cell takes up too much water by osmosis it is called…..
Turgid
When a plant cell is placed in too little water it will lose water via osmosis and become…..
Plasmolysed
Describe the term plasmolysed.
Plasmolysed is the term used to describe a cell in which the vacuole has shrunk due to water loss, causing the cell membrane to pull away from the cell wall.
Describe the term Active Transport.
Active transport is the movement of molecules from a region of low concentration to a region of higher concentration, against the concentration gradient.
What does active transport require to allow membrane proteins to move molecules against the concentration gradient?
Additional energy,
What is a lipid?
Fat or oil with molecules composed of fatty acids and glycerol.
Restricted response questions
Name 2 substances present in cell membranes. (2 marks)
Lipids
Proteins
Give 2 passive processes by which substances pass through membranes.
Diffusion
Osmosis
State the difference between an active and a passive process.
Active processes require energy
Passive ones do not
State on difference between osmosis and diffusion.
Osmosis only involves water and occurs through membranes
Give the meanings of the following terms:
A) turgid
B) plasmolysed
Turgid - plant cells stretched full of water
Plasmolyse - plant cells shrunken
Give an example of a situation in which cells use active transport.
Plant roots taking up irons from their environment
Nerve cells transporting potassium and sodium
State what is meant by a concentration gradient.
The difference in concentration between two areas
Extended response question
Describe the process of diffusion 2 marks
Passive movement of molecules; from a region of high concentration to a region of lower concentration
Describe the role of protein molecules in osmosis and active transport. 2 marks
In osmosis they allow the passage of water molecules through pores; in active transport they act as carriers.
Extended response question
Explain what would happen to a piece of potato tissue placed into a beaker of pure water for 2 hours. 3 marks
Potato would gain water by osmosis; because concentration of water outside greater than inside; cells would swell up; become turgid and no more water would enter.
Extended response question
Explain why immersing a single animal cell in sea water might kill it. 3 marks
Cell would loose waster by osmosis because the water concentration is greater than the outside water concentration; cells would shrink; cell functions would be damaged.
What does ATP stand for?
Adenosine triphosphate - a substance that transfers chemical energy in cells.
What type of ions does a nerve cell have on the inside.
High concentration of potassium ions.
What type of ions does have a nerve cell have on the outside?
High concentration of sodium ions.
What do nerve cells have to pump sodium ions out of the cells and potassium ions in the cells?
Use Sodium - potassium pumps.The energy involved is allowing these pumps to work is called ATP.
