Ch.3 Movement of Substances In and Out of Cells Flashcards
Define diffusion
The net movement of particles from a region of their higher concentration to a region of their lower concentration, down a concentration gradient, as a result of their random movement.
Energy for diffusion comes
The kinetic energy of random movement of molecules and ions
Diffusion in living organisms #1
Respiratory system
Diffusion in the alveoli
Carbon dioxide out, oxygen in
Diffusion in living organisms #2
Digestive system (small intestine)
In the villus
Dissolved food molecules diffuse from the small intestine into blood
Factors affecting diffusion rate
Concentration gradient, temperature, surface area, distance (CT DS - CT does slay)
Diffusion - concentration gradient
The higher/steeper the concentration gradient, the faster the rate of diffusion.
Eg gas exchange of oxygen and carbon dioxide
Concentration gradient is the difference in concentration between 2 regions
Diffusion - temperature
Higher the temperature, higher the diffusion rate
Heat = kinetic energy, so more collisions hence higher rate of diffusion
Diffusion - surface area
The higher the surface area, the higher the diffusion rate
Diffusion - distance
The shorter the distance, the higher the rate of diffusion
Eg thin walls of alveoli and capillaries
Water
Universal solvent
Roles of water as a universal solvent in humans
TRANSPORT nutrients eg glucose and amino acids in blood, sucrose in phloem
EXCRETION - removal of excretory products eg ammonia, urea
DIGESTION - hydrolysis of large biological molecules into their monomers/subunits eg proteins to amino acids
Define osmosis
The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentration solution), through a partially permeable membrane
Types of solutions - Isotonic
- Same concentration of solutions
- No net movement of water across plasma membrane
- Cells maintain normal shape
Isotonic - RBC and Plant cells
RBC
- Normal
- Won’t change size or shape
PLANT CELL
- Flaccid
- Shrinks, becomes limp
- No net movement of water
Types of solutions - Dilute
Water > solutes
- Higher water potential
- Includes distilled water
Dilute - RBC and Plant cells
RBC
- Haemolysed
- Swells, bursts
- No cell wall to protect it from bursting
- Cytoplasm has a lower water potential than outside solution
- Water enters by osmosis
PLANT CELL
- Turgid
- Expands, swells
- Protected by cell wall
- Supported by turgor pressure exerted by water in the vacuole
- Plant remains upright
Types of solutions - Concentrated
- Water < solutes
Concentrated - RBC and Plant cells
RBC
- Crenated + spikes
- Shrinks and little spikes appear on cell membrane
- Dehydrated and eventually dies
PLANT CELL
- Plasmolysed
- PLASMOLYSIS = Shrinkage of cytoplasm + cell membrane away from the cell wall
- Wilts, eventually dies
Plasmolysis 👍
Shrinkage of cytoplasm and cell membrane away from the cell wall
Turgor
Maintains the shape of soft tissues in plants
Eg changes in the turgor of guard cells cause the opening and closing of the stomata
Active transport
Movement of particles through a cell membrane, from a region of their low concentration to a region of higher concentration, against the concentration gradient of a particle, requiring energy from cellular respiration (ATP)
Why shouldn’t we add too much fertiliser around the roots of plants?
- Thin film of water surrounds soil particles containing dissolved mineral ions, aka soil solution
- Too much fertiliser will cause the soil solution to become very concentrated and water will move out of the roots through osmosis
Protein carriers in active transport
Move molecules or ions across a membrane during active transport
Active transport - root hair cells - adaptations
- Lots of mitochondria which produces energy through cellular respiration
- Large surface area to increase rate of absorption
