Unit 2 Flashcards
What is the biological medium of earth?
Water
What can water do?
Exist in nature in all 3 physical states
What type of molecule is water?
Polar
Why is water polar?
Because of oxygen (-) on one side and hydrogen (+) on the other side
Why is oxygen negative and hydrogen positive?
Oxygen is more electronegative while hydrogen is less electronegative
Polarity
to have sides
What happens as a result of water being polar?
hydrogen bonding between molecules
Hydrogen Bonds
forces of attraction between water molecules
How are hydrogen bonds represented?
dotted lines
Intermolecular Forces
forces between molecules
What is an example of an intermolecular force?
hydrogen bonds
How do hydrogen bonds happen?
the positive region of one water molecule attracts the negative region of another water molecule
What does the strength of hydrogen bonds do?
it orders molecules into a higher level of structural organization
Intramolecular Forces
exist within a molecule
What is an example of an intramolecular force?
covalent bonds between atoms
What is cohesion?
ability of molecules of the same substance to stick together
Why is water cohesive?
Because of hydrogen bonds between water molecules
What is surface tension?
measure of how difficult it is to stretch or break the surface of a liquid.
What can surface tension do?
allow animals to live on the surface of water and maintain lung structure
What is adhesion?
ability of different types of molecules to stick to each other.
What does the polarity of water molecules allow?
For water to attract to other polar molecules
What is capillary action?
spontaneous movement of liquid through narrow passage (even against gravity)
Why is adhesion stronger?
because adhesion to walls is stronger than cohesive forces between molecules
What is an example of capillary action?
The transport of water upwards in plants from roots to leaves
How does adhesion work with capillary action?
Adhesion of water to walls causes an upwards force on water at edges of narrow passages
How does cohesion work with capillary action?
Cohesion causes surface tension that holds surface of water in tact as it moves up narrow passage
What is a solution?
uniform mixture of two or more substances
What is a solvent?
dissolver in a solution
What is solute?
what is being dissolved
What is an aqueous solution?
A solution in which water is the solvent
Why is water a versatile solvent?
because its fluidity at body temperature allows it to dissolve many solutes
What are some helpful things that water can do as a versatile solvent?
transport materials around organisms and serve as a solvent for chemical reactions in living things
What makes water versatile?
its polarity
What can water dissolve?
polar solutes
Hydration Shell
water molecules around a solute due to the attraction between water and solute particles
What do hydration shells do?
spread out/dissolve solutes in water
Hydrophilic
dissolve in water
Hydrophobic
do not dissolve in water
What do nonpolar solutes do?
dissolve in nonpolar solvents.
What does blood do?
transport polar and nonpolar molecules
What types of polar molecules does blood transport?
glucose, amino acids, sodium chloride, and other salts
What types of nonpolar molecules does blood transport?
cholesterol and fats (transported using lipoproteins)
Why are hydrophobic substances important to biological systems?
forces nonpolar molecules to associate together, shapes molecules with nonpolar regions, forms important interfaces with nonpolar substances
What are water’s 2 thermal properties?
High specific heat capacity and high heat of vaporization
Specific heat capacity
the amount of heat that must be absorbed or lost of 1 g of the substance to change its temperature by 1°C
True or false: Water must absorb large amounts of heat to raise its temperature
true
What does specific heat capacity measure?
How well a substance resists changing its temperature when it absorbs or releases heat
How is hydrogen bonding responsible for water’s high specific heat capacity?
a large amount of hydrogen bonding means that water can absorb a great deal of heat energy before its temperature increases significantly
What is the result of water’s heat specific capacity concerning the environment?
Maintains the fluctuations in temperature in air and water in order to permit life
Heat of vaporization
the quantity of heat a liquid must absorb for 1 g of it to be vaporized
Why does water have a high heat of vaporization?
due to the hydrogen bonds that must be broken for water molecules to vaporize
What des water’s high heat of vaporization lead to?
Evaporative cooling
Evaporative cooling
the cooling of a surface of a liquid that occurs as liquids evaporate
Phospholipid structure
A glycerol that is attached to one phosphate group and two acid tails
Is a phosphate head hydrophobic or hydrophilic?
hydrophilic
Is a fatty acid tail hydrophobic or hydrophilic?
hydrophobic
What do phospholipids form?
bilayers
What direction do phosphate heads face?
outward
What direction do fatty acid tails face?
inward
What does the plasma membrane do? (4 things)
separate contents of the cell, allow selected substances into the cell, support the cell, maintain its shape
What was the evidence for the Davson-Danielli Model?
In electron micrograph images proteins were dark and phospholipids were lights
Davson-Danielli Model
lipid bilayer coated with proteins on both sides (protein lipid sandwich), polar molecules would pass through the membrane through gaps
Fluid Mosaic Model
phospholipid bilayer with proteins imbedded
Singer-Nicolson Fluid Mosaic Model
current understanding of the plasma membrane
Fluid Membrane
fluid (like olive oil) at body temperature
What do most lipids and some proteins do?
drift laterally
Mosaic Membrane
lipids, carbohydrates, and many different types of membrane proteins are associated with either side of the lipid bilayer (form a mosaic)
What are the 2 main membrane protein classifications?
integral and peripheral
Integral protein
span the membrane/embedded in the hydrophobic region of the membrane
Peripheral protein
on the membrane surface
6 classes of membrane proteins with different functions
J - junctions
E - enzymes
T - transports
R - recognition
A - anchorage
T- transductions
Junction/Adhesion Proteins
join cells together (tight junctions and gap junctions)
Tight junctions
seal adjacent cells, precent cell movement and limit passage of particle between cells
Gap junctions
channels that allow passage of particle between cells
Enzymatic proteins
proteins that speed up chemical reactions at the membrane
What are some examples of enzymatic proteins?
-reactants bind to the enzyme and products form
-localizes metabolic pathways
Transport Proteins
channels and pumps move things across the membrane
Channel proteins
move molecules across the membranes without energy
Pumps
move molecules across membranes using energy
Recognition proteins
help cells identify other cells and viruses
Glycoproteins
carbohydrate chain attaches to protein within membrane
Glycolipids (not protein):
carbohydrate chin attached to lipid within membrane
Anchorage Proteins
attachment point for cytoskeleton and extracellular matrix
Cytoskeleton
complex network of interlinking filaments and tubules in the cytoplasm
Extracellular Matrix
mesh of protein fibers and glycoproteins outside of the cell in multicellular organisms
What else do anchorage proteins do?
maintain cell shape and stabilize proteins
Transduction proteins
bind chemical messengers and relay signals to inside cells
hormone receptors
bind hormones and relay signals inside of cells
Cholesterol
a lipid found in membranes, maintains stability of animal cell membrane by regulating fluidity and permeability, also a steroid
Why is cholesterol not present in plants?
the plasma membrane is supported by a cell wall
What is the structure of cholesterol in animal cells?
polar hydroxyl group at the top (attracted to phosphate heads), nonpolar tail at the bottom (attracted to fatty acid tails)
What are cholesterol’s abilities?
reduce the fluidity of the membrane, makes the membrane less permeable, prevents solidification of the membrane at low temperatures
How does cholesterol reduce the fluidity of membranes?
By making the phospholipids pack tightly, cells need to regulate fluidity in order to be able to move
How does cholesterol decrease permeability?
makes the phospholipids pack tightly, membranes need to regulate the permeability of the membrane so substance can move into and out of the cell
How does cholesterol prevent the solidification of the membrane at low temperatures?
it disrupts the regular packing of the phospholipid tails
Concentration
quantity of solute that is dissolved in a given quantity of solvent
Diffusion
passive movement of particles from an area of high concentration to an area of low concentration, tendency for particles to spread out evenly in an available space
Passive
no energy required
How do particles move on the concentration gradient?
Particles move down the concentration gradient when they move from an area of high concentration to low concentration
Passive transport
-when a molecule diffuses down a concentration gradient
-Movement from high to low particle concentration
-No input of energy needed/due to random motion of molecules
Diffusive Equilibrium
when the concentrations of the diffusing substance in the two compartments becomes equal
Simple diffusion (definition and example)
movement of particles directly through plasma membrane which is selectively permeable.
-small, nonpolar molecules (O2 and CO2) move
across by simple diffusion
Facilitated Diffusion
diffusion of a substance across a membrane through a channel or carrier protein
What are the requirements of simple diffusion?
-Solutes move across porous membranes between phospholipids
-solutes move from high to low concentration
-no ATP/energy is involved
-diffusion continues until concentrations are equal
What are the requirements of facilitated diffusion?
-Occurs down concentration gradient (high to low)
-No energy needed
-Proteins only let specific solutes pass through
-Faster than simple diffusion
What is an example of facilitated diffusion?
Voltage-gated potassium channels
What are voltage-gated potassium channels?
-Opens/closes with changes in electrical potential across the membrane
-Protein pore for K+ to cross membrane
What are the requirements for voltage-gated potassium channels?
-channels move K+ across the membrane down a concentration gradient
-K moves through a protein channel
-no ATP (energy)
Where does facilitated diffusion occur?
occurs through channel or carrier proteins
What do protein channels do?
create pores in the membrane
What do carriers do?
bind a solute and then change shape to deliver the solute to the other side.
How does water cross the plasma membrane?
by simple diffusion and facilitated diffusion
Aquaporin
an integral protein that speeds the movement of water molecules
What are the 5 factors that affect diffusion across membranes?
-concentration gradient
-temperature
-surface area
-length of diffusion path
-size of particles
How does the concentration gradient effect diffusion?
↑ gradient, faster diffusion
How does the surface area effect diffusion?
↑ surface area, faster diffusion
How does the length of the diffusion path effect diffusion?
↑ length, slower diffusion
How does the temperature effect diffusion?
↑ temperature, faster diffusion
How do the size of particles effect diffusion? (in the case of them being smaller)
smaller particles, faster diffusion
Osmosis
the movement of water across a membrane
What does the difference in total solute concentration do?
determine the direction of the movement of water
How does water diffuse?
from an area of low solute concentration to high solute concentration until the solution is equally concentrated on both sides of the membrane
True or False: Osmosis is passive transport.
True
Osmoregulation
control of water balance, which is crucial to organisms
Hypotonic extracellular solution
solute concentration is lower outside the cell so the cell gains water
What do animal cells do in a hypotonic solution?
lyse (burst)
What do plant cells do in a hypotonic solution?
become turgid
Isotonic extracellular solution
solute concentration is the same inside and outside
so no net water movement
What do animal cells do in an isotonic solution?
have a constant volume
What do plant cells do in an isotonic solution?
becomes flaccid
Hypertonic extracellular solution
solute concentration is higher outside the cell so the cell loses water
What do animal cells do in a hypertonic solution?
it shrivels
What do plant cells do in a hypertonic solution?
it plazmolyzes
Osmolarity
the concentration of a solution expressed as the total number of solute particles per liter
What medical procedures are isotonic solutions used for?
-fluid introduction to blood system via intravenous drip (rehydration)
-used to rinse wounds, skin abrasions etc.
-keep areas of damaged skin moist, eye drops/wash
Active transport
the movement of solutes across membranes that requires energy (ATP) to move solutes against the
concentration gradient
What is needed for active transport?
protein pumps
What is an example of active transport?
Na+,K+-ATPase Pump
What are the requirements for Na+,K+-ATPase Pumps?
-it’s a protein pump
-it uses energy
-it moves particles against their concentration gradient
What is the solution if particles are too large for proteins or pumps?
Using energy and vesicles for endo and exocytosis
Endocytosis
cells take in molecules or substances from outside of the cell by engulfing them in the cell membrane to form a vesicle.
What are the steps of endocytosis?
-endocytosis occurs when a membrane encloses a target particle
-fluidity of membrane permits movement of membrane
-membrane invaginates to enclose particle
-membrane seals back on itself
-two phospholipid layers enclose particle making vesicle
-vesicle breaks away from membrane/moves into cytoplasm
-changes in membrane shape require energy
Exocytosis
ejection of waste products (excretion) or useful substances (secretion) from the inside of the cell when a vesicle joins with the cell plasma membrane
What are the steps of exocytosis?
-vesicles carry material to plasma membrane
-vesicle fuses with membrane by joining of phospholipid bilayers
-aided by the fluidity of the membrane
-material released/expelled from the cell
-membrane flattens through movement
What is an example of exocytosis?
hormone secretion
What does the fluidity of the membrane allow?
vesicle formation and materials to be taken into cells by endocytosis or released by exocytosis
