1.2 Transport Across Cell Membranes Flashcards
What is a cell membrane made of?
Phospholipids and proteins
Identify phospholipids and proteins on a diagram of the cell membrane.
See booklet
How permeable is the cell membrane?
Selectively permeable
What does selectively permeable mean?
Membrane has pores that allow small molecules to pass through but not large molecules.
What is passive transport?
The movement of a substance down a concentration gradient and does not require energy.
Give examples of passive transport
Osmosis and diffusion.
What is a concentration gradient?
When different concentrations of substances exist between cells and their environment.
What is diffusion?
Diffusion is the movement of molecules down a concentration gradient from a higher to a lower concentration.
Why does diffusion occur?
It occurs in an experimental procedure by identifying the higher and lower concentrations.
Give examples of substances that diffuse across cell membranes.
Glucose
Carbon dioxide
Oxygen
Amino acids
Why is diffusion important to organisms?
It is the way substances enter and leave cells by movement down a contraction gradient.
What is osmosis?
The diffusion of water (only)
Movement of water molecules from a higher water concentration to a lower water concentration through a selectively permeable membrane.
What happens to animal and plant cells when they are in water?
Animal cells can swell and burst.
Plant cells will become turgid.
What happens to animal and plant cells when placed in strong salt or sugar solutions?
Plant cells become plasmolysed.
Animal cells shrink.
What is active transport?
Active transport is the movement of a substance against a concentration gradient from a lower to higher concentration.
