Unit 3 Flashcards
What is diffusion
. Net movement of particles from a region of higher concentration to region of lower concentration (down a concentration gradient) -> due to their random motion
Energy for diffusion
Knietic energy of randome movement of molecules and ions
Diffusion in cells
Small molecules can diffuse in and out of cells by diffusion through cell membrane -> allows cells to obtain substances they need (e.g oxygen and nutrients) +get rid of waste products (e.g carbon dioxide)
Factors that affect diffusion: Distance
Shorter distance= faster diffusion (e.g cell membrane is very thin)
Factors that affect diffusion: concentration gradient
Steep concentration gradient= faster diffusion
Factors that affect diffusion: surface area
Larger surface area = faster diffusion
Factors that affect diffusion: temperature
Higher temperature= faster diffusion -> more kinetic energy (molecules move faster and collide more often)
Water as an important solvent: Transport
. Allows soluble molecules to be carried by blood around body + transports soluble mineral ions from the roots to leaves
Water as an important solvent: Digestion
. Digestive enzymes need to be in solution to work properly (water acts as a solvent) + allows products of digestion to dissolve into blood
Water as an important solvent: Excretion
Toxins often dissolved in water
Osmosis
The net movement of water molecules from an area of high water potential gradient (dilute solution) to an area of lower water porential (concentrated solution) through a partially permeable membrane
. Water diffuses through partially permeable membranes (e.g cell membranes) in both directions by osmosis
Osmosis in uptake of water
. Water outside root hair cells usually higher than inside so water diffuses into cells by osmosis
Osmosis in loss of water
. Sea water makes water potential in blood much lower than in cells so water leaves cells by osmosis (can shrivel up + die)
Investigating osmosis using dyalisis tubing
. Dialysis tubing acts like a partially permeable membrane
Investigating osmosis in plant tissues
. If cylinders of potato placed in solution with higher water potential than solution inside potato cells they will draw in water by osmosis + will increase in mass
. If cylinders of potato placed in solution with lower water potential than solution inside potato cells then water will be drawn out by osmosis + will decrease mass
Osmosis in plant cells: plant placed in dilute solution
. Inside cell: lower water potential than outside cell -> water diffuses out by osmosis
. As water enters cell starts to swell up -> water pushes against cell wall developing turgor pressure
Turgid cell:
. Gives plants support through turgor pressure on the cell wall
. Cell wall: prevents cell from bursting
Osmosis in plant cells: plant placed in concentrated solution
. Inside cell: higher water potential than outside cell -> water diffuses out of cell by osmosis
. As water leavess cell, vacuole starts to shrink -> cells no longer firm and becomes flaccid
. Plasmolysed cell: as more water leaves cell cytoplasm shrinks + cell membrane pulls away from cell wall
Osmosis in animals
If animal cell is placed in a solution with high water potential water will move in by osmosis -> if too much water enters there’s nothing stopping the cell from bursting (lack of cell wall)
Active transport
Momevent of particles through a cell membrane from a region of lower concentration to higher concentration (against a concentration gradient) using energy release during respiration
. Active transport uses carrier proteins to move particles across the membrane
Two substances that are small enough to diffuse through cell membrane
Glucose and amino acids
Two substances that are too big to diffuse through cell membrane
Proteins and starch
Active transport in plants
Plants need mineral ions for growth
. Higher concentration of mineral ions inside root-hair cells than in soil -> theough active transport high concentration of magnesium ions is mantained in root-hair cell as minerals move against concentration gradients
