5.3-5.5 - Diffusion, Osmosis, Active Transport Flashcards
Is simple diffusion a passive or active process?
Passive
Is facilitated diffusion a passive or active process ?
Passive
Is osmosis a active or passive process?
Passive
Is active transport a active or passive process?
Active -requires ATP energy
Is bulk transport active or passive process?
(Endocytosis and exocytosis) - active requires ATP energy
What is simple diffusion?
The net overall random movement of particles ( atoms, molecules , ions) from an region of high concentration to an region of lower concentration down a concentration gradient
What is facilitated diffusion?
The passive movement of molecules down a concentration gradient from an area of high to iow concentration across a membrane and involves special carrier and channel proteins in the membrane
What type of proteins enable facilitated diffusion?
• Channel proteins
• carrier proteins
What types of molecules use facilitated diffusion?
•Larger polar molecules eg. Amino acids, glucose or ions such as sodiumions and chloride ions cannot simply diffuse directly through the phospholipid layer of the cell surface membrane
• these substances can only cross the phospholipid bilayer with the help of certain proteins
What are channel proteins?
• water filled pores
• allow charged substances eg. Ions to diffuse through the cell membrane
• diffusion does not occur freely - they’re grated meaning they’re part of the channel protein on the inside surface of the membrane can move and close in order to close or open the pore

Name 5 factors that affect the rate of diffusion
•Temperature
• diffusion distance
• surface area
• size of molecule
• difference in concentration
Explain how a difference in concentration can affect the rate of diffusion
• the more particles there are in one area compared to another the steeper the concentration gradients
• therefore the faster the rate of diffusion
• this is due to more random frequent collisions of the particles
Explain how temperature affects the rate of diffusion
• higher the temperature = more kinetic energy the particles will have
• more frequent collisions between the particles as the particles are moving at higher speeds
• rate of diffusion thus increases
Explain how the surface area of a membrane affects the rate of diffusion
• larger the surface area of the membrane = the more area there is for particles to diffuse across
• rate of diffusion is faster
How does the thickness of the exchange surface/ membrane affects the rate of diffusion?
• thinner the exchange surface = shorter the diffusion pathway for molecules to pass through the membrane
• thus the rate of diffusion increases
What is surface area?
•Refers to the outside area ofan object eg.it is the area around the outside of a cell
• units = Cm^2
What is volume?
•Refers to the amount of space inside of the object eg. It is the space inside the cell
• unit = Cm^3
How are organs specialised to ensure diffusion is efficient?
- Have a large surface area - increases the rate of diffusion
- A membrane that is thin this provides a short diffusion distance
- Animals have an efficient blood supply surrounding the exchange surface
- Large SA: V ratio - there is more surface area relative to the volume inside
What are the adaptations of the intestines?
• many villi - increase the surface area
• single layer of surface cells - very thin walls
• very good blood supply to assist quick absorption
What are the adaptations of the alveoli?
• very thin walls are only one cell thick
• efficient blood supply network of capillaries around the alveoli
• large surface area - allowing fast exchange of gasses
• walls are moist - encouraging gas molecules to easily dissolve
What are the adaptations for gas exchange in fish?
• gills which are made up of many gill filaments -large surface area for gas exchange
• gills are covered in tiny structures called lamellae which increases the surface area
• lamellae are surrounded by blood capillaries- speed up the rate of diffusion
• counter current exchange system
• thin surface layer of cells to provide a short diffusion pathway for gasses
What are the adaptations of the roots of a plant?
• root hair cells - large surface area - absorb more water and mineral ions
• thin - short diffusion pathway for water and mineral ions to travel into the root
What are the adaptations for efficient gas exchange in the leaf?
• leaves absorb carbon dioxide from the atmosphere - release oxygen gas and water vapour in the process of photosynthesis
• leaves are very thin - short diffusion pathway- faster rate of diffusion for gasses
• leaves are broad and flat - larger surface area - more gases can diffuse into and out of the lead
• leaves have tiny pores called stomata- where gases are exchanged
What is water potential?
Measure of the tendency of water molecules to move across a partially permeable membrane
What is water potential measured in?
KPa
What is osmosis?
The net random movement of water molecules from an region of high water potential to a region of iow water potential down a water potential gradient across a partially permeable membrane
What is the water potential of pure water?
Zero
Any solution with a negative water potential has what?
A solute in the solution
Name 3 factors that affect the rate of osmosis
• water potential gradient
• thickness of the exchange surface
• surface area of the exchange surface
How does the water potential gradient affect the rate of osmosis?
• higher the water potential gradient = faster the rate of osmosis
• as osmosis occurs the difference in water potential either side of the membrane decreases = rate of osmosis levels off over time
How does the thickness of the exchange surface affect the rate of osmosis?
Thinner the exchange surface = shorter the pathway of the water molecules have to travel = increases the rate of osmosis
How does the surface area of the exchange surface affect the rate of osmosis?
Greater the surface area of the partially permeable membrane = the more area water molecule have to cross the membrane = increases the rate of osmosis
What is a hypotonic solution?
A solution with more water in it than solute compared to another solution
What is a hypertonic solution?
A solution with more solute In it than water compared to another solution
What is a isotonic solution?
Two solutions/cells that have the same water potential
A hypertonic Solution in a plant cell results it to become…
Plasmolysed
Isotonic solution in plant cells results it to become…
Flaccid
Hypotonic Solution in plant cells leaves the cell to become…
Turgid
Hypertonic solution in an animal cell makes the cell become …
Crenated
Isotonic solution in animal cells makes the cell become…
Normal
Hypotonic solution in animal cells makes the cell become…
Cytolysis
Define active transport
The movement of molecules or ions into or out of a cell from an area of low concentration to an area of high concentration against a concentration gradient across a partially permeable membrane
What are the uses of active transport?
Important in :
• reabsorption of useful molecules and ions into the blood after filtration into the kidney tubules
• the absorption of some products of digestion from the digestive tract
• the loading of sugar from the photosynthesising cells of leaves into the phloem tissue for transport around the plant
• the loading of inorganic ions from the soil into root hairs
How do molecules move via active transport?
- Molecule or ion bonds to receptors on the carrier protein on the outside of the cell
- ATP binds to the carrier protein inside of the cell
- It is hydrolysed to ADP + P with the release of energy
- The phosphate molecule reminds bound to the protein
- This provides the energy required for the carrier protein to change shape
- The molecule or ion is moved to the inside of the cell
- The phosphate is released from the carrier protein and recombines with ADP to form ATP
- Carrier protein returns to its original shape
What is bulk transport?
• form of active transport
• large molecules enzymes and hormones are too large to move through channel or carrier
Bulk transport into cells is called?
Endocytosis
Bulk transport out of cells is called?
Exocytosis
What is endocytosis?
Process by which the cell surface membrane engulfs material forming a small sac around it
What are the two types of endocytosis?
Phagocytosis and pinocytosis
What is phagocytosis?
• bulk intake of solid material by a cell
• cells that specialise in this process are called phagocytes
• the vacuoles formed are called phagocytic vacuoles
• an eg. Is the engulfing of bacteria by phagocytic white blood cells
What is pinocytosis?
•Bulk intake of liquids
• if the vacuole that is formed I’d extremely small the. The process is called micropinocytosis
What is exocytosis?
Process by which materials are removed from or transported out of cells
Now are substances released in exocytosis?
•They are packaged into secretory vesicles formed from the Golgi body
• they fuse with the cell membrane and release their contents outside of the cell
• eg. Secretion of digestive enzymes from pancreatic cells
