Unit 5: Plasma Membranes & Water Flashcards
(45 cards)
What is the state of water that allows chemical reactions to take place?
Liquid state: Water’s liquid state facilitates the dissolution of molecules, enabling various chemical reactions necessary for life.
What is a covalent bond?
What is the link between hydrogen bonds?
Polar covalent bond between hydrogen and **oxygen **results in partial charges within the water molecule, leading to hydrogen bonding between water molecules.
Hydrogen bonds –> dotted line
Oxygen + Hydrogen are bound together in a polar covalent bond
Unequal sharing of electrons → resulting in partial charges
Oxygen has a partially negative charge (delta -)
Hydrogens have a partially positive charge (delta +)
What is cohesion in the context of water molecules?
Attraction between two molecules that are the same
Water molecules sticking together
Cohesion is a result of hydrogen bonding between water molecules
Cohesion in water is due to hydrogen bonding, which is crucial for processes such as transpiration in plants.
What is transpiration?
What is surface tension?
What property of water do we observe?
Hydrogen-bond-based cohesion
Transpiration: Movement of water through a plant due to evaporation from stomata
- Evaporation at leaf stomata pulls the next water molecules upward.
- A continuous column of water rises through xylem tubes, carrying dissolved minerals from roots to leaves. (cohesion)
- Adhesion helps water to stick to the sides of the xylem, aiding in the movement of water against gravity.
Surface tension: The surface of water allows small organisms (e.g., water striders) to live, supports life in aquatic habitats on ponds and streams. (cohesion)
- The surface tension that shapes aquatic ecosystems.
What is adhesion in relation to water?
Capillary action?
Where do we observe this?
Adhesion: Attraction between water molecules and a solid surface
Important for transpiration in plants, capillary action: Adhesion helps water to stick to the sides of the xylem, aiding in the movement of water against gravity.
What are the roles of water as a solvent in biological systems?
- Metabolic importance
- Transport
Metabolic importance
- Chemical reactions needs solvents
- Water is really good at this due to its polarity
- But can only dissolve hydrophilic molecules or things that have a charge e.g. glucose, ions
Transport roles
1) Plants
- Xylem: carries water + dissolved mineral ions travel upward.
- Phloem: carries sucrose, etc, but must be in solution (water)
2) Animals
- Blood transport
- Blood plasma (~90 % water): carries hydrophilic solutes (ions, glucose, amino acids).
*Hydrophobic molecules hitch rides on carriers (e.g., lipoproteins for fats, hemoglobin for O₂) because they are insoluble in water.
Properties of water?
Physical properties as well
- Cohesion
- Adhesion
- Solvent (metabolism, transport)
Physical properties of water:
- Buoyancy
- Viscosity
- Thermal Conductivity
- Specific heat
These are important especially for animals in aquatic habitats
Buoyancy ?
Give examples
Buoyancy (upward force opposing gravity)
Leads to objects being able to float
Less dense objects → float, denser objects → sink
e.g. Duck will float, seal can float
Most aquatic organisms match water’s density;
Some (e.g., fish with swim bladders) actively adjust buoyancy by adding or releasing gas.
Specific heat
Takes a lot of energy to raise or lower water’s temperature, so aquatic habitats stay thermally stable.
Great if you are an aquatic organism
- **Has a moderating effect: ** meaning you can have lots of temperature variation in the air and the temperature of the water won’t change that much (moderates it)
Great for the maintenance of body temperature
- Bodies can produce lot of heat with different metabolic reactions
- Heat energy can enter the water parts of cells (cytoplasm) or water-based fluid (plasma in blood) and that won’t change temperature very much
Ex. African Elephant: big ears, to expose the blood in the ears to the outside air. Exchanges heat with environment, but the blood plasma won’t change temperature drastically
Thermal conductivity? Bad or good?
Why would organisms have adaptations for this?Example?
The ease with which heat passes through a material
Water is a very good conductor of heat (heat can transfer easily through water)
Can be good or bad
Good:
→ Blood plasma (mostly water) efficiently redistributes metabolic heat within bodies.
Bad:
→ Falling into cold water → water takes heat from our body and transports it into water
Organisms must have an adaptation to either take advantage of that or prevent losing too much body heat into that water
- E.g. seal has a lot of fat to not to lose body heat
Viscosity?
Give example?
Water’s resistance to flow
Ex. It helps fish swimming through water: resistance is the fin to help the fish push itself forward
What determines the permeability of a molecule through a cell membrane?
The size of the molecule
- Larger molecules are not as permeable
The charge of the molecule
- Membrane is not permeable to polar/charged molecules (hydrophobic tails of phospholipids, don’t like them and therefore repel anything with a charge or anything polar)
Things that are non polar molecules (ex. Oxygen molecule) can pass through the membrane
→ Things that either aren’t small or aren’t non polar, ex. Glucose needs alternative methods of getting in and out of the cell
Define simple diffusion.
What kind of molecules?
Passive movement of particles from areas of high concentration to low concentration
Diffusion does not require energy and continues until equilibrium is reached.
Some things that can diffuse across membrane:
- Small
- Non polar
Ex. oxygen
Integral proteins?
Integral Proteins
- Transmembrane proteins (from the inside to the outside)
It’s going to be in contact with the polar heads and the nonpolar tails.
→ It will need polar regions and nonpolar regions
Polarity must match whatever is moving through
Ex. if we have glucose (polar), that means the amino acids lining the inner channel must be polar
Ex. ATP synthase, channel proteins, protein pumps
What is a peripheral protein?
Peripheral Proteins
- Only attached to the surface (periphery). Not going to go all the way though like the integral proteins
- Hydrophilic
What is osmosis?
What is an aquaporin?
Osmosis: net movement of water molecules across a semipermeable membrane
- No energy is required(passive)
- Water always flows towards areas of high solute concentration.
Continues until the concentration is equal (equilibrium)
Aquaporin: It is an integral/channel protein, pore to help water move into or out of a cell.
- It aids osmosis
What is facilitated diffusion?
Passive movement through a channel protein from high to low concentration
Facilitated diffusion requires specific channel proteins for molecules that are not small or nonpolar.
What is osmosis?
Net movement of water molecules across a semipermeable membrane
Osmosis occurs towards areas of high solute concentration and does not require energy.
What are aquaporins?
Special channel proteins that facilitate water movement
Aquaporins enhance the efficiency of osmosis, especially in cells with high water transport needs.
What is active transport?
What are pump proteins?
Movement of particles from low concentration to high concentration requiring energy
Pump proteins:
- Protein pumps only move particles one way
- Pumps are specific to each molecules (glucose pump, etc)
The input of energy (ATP) causes the protein to change shape, which moves the particle towards the area of high concentration
What are glycoproteins?
What is glycolipid?
Glycoproteins are proteins embedded in the membrane with carbohydrate chains extending outside
- Glycoproteins are important for cell recognition
Glycolipid: A lipid embedded within those hydrophobic tails with also a carbohydrate sticking on the outside
- Particular to eukaryotic cells
- Used for recognition (in the immune system)
What is the fluid mosaic model of membrane structure?
Model describing the cell membrane as a mosaic of various components that can move
What drives water movement during osmosis?
Difference in solute concentration across a semipermeable membrane
Water moves from less concentrated to more concentrated solutions to achieve equilibrium.
Why is water considered an excellent solvent?
Water is polar
This polarity allows it to dissolve ionic compounds and polar molecules effectively.
