Biology: Chapter 3 Flashcards
Definition of Diffusion
The net movement of particles from a higher concentration region to a lower concentration region (down a concentration gradient), as a result of their random movement.
Name of term for the random movement of particles
Brownian motion
Energy which is used for particles to diffuse and have random motion
Kinetic energy
Definition of Net Movement
Overall/Average movement of particles
Definition of Partially-Permeable Membrane
A cell membrane which can restrict the free movement of molecules
What is the selection of which cells pass the cell membrane and which do not based on?
Size of particle
Functions of Diffusion
- obtain many of their requirement (oxygen/nutrients)
- remove waste products (carbon dioxide & urea)
- carry out gas exchange for respiration
3 Examples of Diffusion in Living Organisms
- photosynthesis (movement of CO2 and O2 in and out of leaf)
- nutrient absorption (digestive products–glucose, amino acid, fatty acid and glycerol–in small intestines pass through blood capillary by diffusion)
- gas exchange (movement of O2 from alveoli into the red blood cell)
Factors that affect a Rate of Diffusion
Surface area to volume ratio
- The bigger a cell/structure is, the smaller its surface area to volume ratio is
- smaller surface area to volume ratio = lower rate of diffusion
- the bigger the structure, the slower the rate of diffusion
Distance between two areas of diffusion
- smaller distance = faster transport
Temperature
- higher temperature = faster movement of molecules (heat energy»_space; kinetic energy)
- higher temperature = faster rate of diffusion
Concentration gradient
- higher concentration gradient between two sides of membrane = faster rate of diffusion
Cells that are adapted for diffusion (that have increased surface area)
- root hair cells in plants (absorb water + mineral ions)
- cell lining the ileum in animals (absorb the products of digestion
Definition of Osmosis
The net movement of water by diffusion from a region of high water potential to low water potential through a partially permeable membrane
What is the concentration is being referred to in osmosis?
Water potential
- diluted solution = high water potential
- concentrated solution = low water potential
Osmosis in animal cells
If an animal cell is placed in pure water:
- inside of the cell is more concentrated that outside of the cell
- water goes in through osmosis
- cell will swell and burst
If an animal cell is placed in a concentrated solution:
- outside of the cell is more concentrated than inside of the cell
- water goes out of the cell by osmosis
- cell will shrink
Osmosis in plant cells
If plant cell is placed in pure water:
- water enters the cell by osmosis
- cytoplasm and vacuole will swell
- strong cell wall will prevent it from bursting
- turgor pressure (water pushing outwards) will keep the cell strong and firm (turgid)
If plant cell is placed in concentrated solution:
- water leaves the cell by osmosis
- cytoplasm and vacuole will shrink
- cell wall will stay in position
- cytoplasm and cell wall pull away from cell wall
- cell becomes soft and floppy (flaccid) after losing turgor pressure
What is the condition of a cell when its cell membrane tears away from cell wall?
Plasmolysed
How is Active Transport is carried out?
Low quantity of molecules
- cells need to take in substances which are only present in small quantities
Carrier protein
- cell membrane pick up molecules from low concentration area
- energy needed to change shape of protein to push molecules through cell membrane
Using ATP
- use energy to move substances across membranes
- energy provided by respiration
3 Examples of Active Transport
- Reabsorption of glucose from glomerular filtrate in blood capillary
- Root hair cells take in mineral ions
- Uptake of glucose in small intestines
How do ions enter cells by active transport?
- Nitrate ion enters carrier protein
- Carrier protein changes shape (requires energy provided by respiration)
- The change of shape of carrier protein pushes nitrate ion into cell
