P1 4.1.3 Transport in cells (will come up) Flashcards
What is diffusion
The movement of particles from an area of higher concentration to and area of lower concentration
What can diffuse through cell membranes
Only very small molecules can diffuse through cell membranes ie oxygen
Examples of diffusion
Gas exchange - Oxygen and carbon dioxide
Waste products - Urea from cells into blood plasma for excretion in the kidney
Factors that affect the rate of diffusion
The concentration gradient
The temperature
The surface area
Why is it useful that a single-celled organism has a large surface area to volume ratio
It allows sufficient transport of molecules into and out of the cell
How is the small intestine adapted for exchanging materials
It contains millions of villi -
They increase the surface area so digested food is absorbed much quicker
Single layer of surface cells - So substances have a short distance to diffuse
A very good blood supply - to assist quick absorption
How are alveoli adapted for gas exchange
They contain millions of alveoli - A really big surface area, very thin walls, good bloody supply, a moist lining for dissolving gases
Process of gas exchange in humans
The alveoli are surrounded by capillaries. There is a higher concentration of oxygen in the air than in the blood, so oxygen diffuses out of the air in the alveoli and into the blood in the capillaries. CO2 diffuses in the opposite direction.
What is active transport
The movement of particles into or out of a cell from an area of lower concentration to an area of higher concentration, across a concentration gradient using energy transferred during respiration
How are gills in fish adapted for exchanging materials
Gill filaments - give a large surface area
Lamellae (in gill filaments) - increase surface area even more
Lots of blood capillaries - speed up diffusion between air and blood
Thin surface layer of cells - shorter diffusion distance
How are leaves on plants adapted for exchanging materials
Flattened shape of leaf - increase the area of the exchange surface
Stomata - carbon dioxide (in), oxygen and water vapour (out) diffuse through them
Walls of cells inside leaf - they form another exchange surface
Air spaces inside leaf - increase the area of the surface so more chance of carbon dioxide getting into cells
How are roots adapted for absorbing water and mineral ions and what is its function
Roots are covered in microscopic hairs - A large surface area
Function - they use active transport to absorb the minerals from a very dilute solution across a concentration gradient. This is for the plants growth. Active transport needs energy from respiration to work
A use of active transport in humans
Taking in glucose from the gut. There is a lower concentration of glucose, nutrients etc in the gut but higher in the blood sometimes so active transport is used. Glucose is used for respiration
Difference between osmosis, active transport and diffusion
Diffusion - movement of particles from an area of higher concentration to an area of lower concentration ( doesn’t require energy)
Active transport - Movement of particles against a concentration gradient, requires energy
Osmosis - Movement of water molecules across a semi permeable membrane from an area of higher water concentration to an area of lower water concentration (doesn’t require energy)
What is osmosis
The movement of water molecules across a partially permeable membrane from an area of high water concentration to an area of lower concentration
