Hypertonic solution
A solution in which the concentration of solutes is greater than that of the cell that resides in the solution
Isotonic solution
A solution in which the concentration of solutes is equal to that of the cell which resides in the solution
Hypotonic solution
A solution in which the concentration of solutes is less than that of the cell that resides in the solution
Water diffuses from...
Hypotonic to hypertonic
Osmosis
Diffusion of free water across a selectively permeable membrane
Smaller cells have a higher...
surface area to volume ratio (ex. 12:1)
Smaller cells have a more...
efficient exchange of material with the environment
As cells ________ in volume the relative surface area _________
increase; decreases
Why aren't cells smaller than they already are?
Cells need room for organelles
Amphipathic
Molecules that contain both hydrophilic and hydrophobic properties (phospholipids)
Fluid mosaic model
Model that describes the arrangement and movement of the molecules that make up a cell membrane
At high temperatures, cholesterol _________ cell membrane fluidity
decreases
At low temperatures, cholesterol __________ cell membrane fluidity
increases
Passive transport
Movement of molecules from high to low concentration WITHOUT metabolic energy (ATP)
The inner surface of transport proteins is...
polar to protect polar molecules that come through
Diffusion
Free movement of small, nonpolar molecules from high to low concentration (ex. N2, O2, CO2)
Facilitated diffusion
Movement of larger, polar, and/or charged molecules from high to low concentration through transport proteins; Allows for hydrophilic molecules to pass through membranes (ex. glucose, urea, K⁺, Na⁺, Cl⁻)
Water potential
The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.
Water potential equation
Ψ = Ψs + Ψp
Solute potential equation
Ψs = -iCRT
i in -iCRT is...
ionization constant (ex. sucrose/glucose = 1, sodium chloride = 2)
C in -iCRT is...
molar concentration
R in -iCRT is...
0.0831
T in -iCRT is...
temperature in kelvin (273 + C°)
Solute potential of pure water is...
0
Water moves from _____ _______ solute potential to _____ ________ solute potential
less negative; more negative
Water will move from an area of ______ water potential to an area of ______ water potential
high; low
Proteins designed to help water diffusion
Aquaporins
Unsaturated fatty acid carbon double kinks ______ cell membrane fluidity
increase
Active transport is ______ a concentration gradient
against
Transfer of energy in protein cotransporters
ATP→proton pump→H⁺ ions→cotransporter→sucrose (moved by cotransporter)
Free energy
Ability to do work
Channel proteins
Hydrophilic tunnels in the cell membrane that allow larger, polar, and/or charged molecules to pass through
Carrier proteins
Membrane structures that change shape to move target molecules from one side of the cell membrane to the other
Active transport is ___________ not pushed
performed
There are ____ types of passive transport
2
Osmolarity
Total solute concentration in a solution
Tonicity
The measurement of the relative concentrations of solute between 2 solutions (in and out of cell)
Tonicity can only be in reference to ____ environments
2 (a cell has to be hypo/hyper/isotonic to a solution and vice versa)
Water moves by...
osmosis
Glycoproteins
One or more carb attached to a membrane protein
Glycolipids
Phospholipids with a carb attached (communication)
Free vs. bound ribosomes
Free: float in cytosol and produce proteins for it Bound: attached to the ER, produce proteins that will be a part of the membrane, or enclosed in it
Nucleoid
A non-membrane-bounded region in a prokaryotic cell where the DNA is concentrated
Smooth ER
Lipid synthesis, detoxification, carb metabolism, NO ribosomes on its cytoplasmic surface (liver cells have lots because they host glycolysis and are the site of alcohol detoxification)
Rough ER
Has ribosomes on its cytoplasmic surface
Eurkaryotic ribosomes are built in a structure called the...
nucleolus
Golgi apparatus
Proteins, lipids, and other macromolecules are sent her to be modified by the addition of sugar and other molecules to form glycoproteins
Absence of a particular lysosomal hydrolytic enzyme can lead to...
storage diseases
Tay-Sachs disease
When an enzyme used to digest lipids is absent, leading to excessive accumulation of lipids in th ebrain
Peroxisome
Organelle that contains enzymes that produce hydrogen peroxide as a by-product while performing various functions, such as breakdown of fatty acids and detoxification of alcohol in the liver; also contain an enzyme that converts the toxic hydrogen peroxide by-product of these reactions into water
Cytoskeleton
A network of fibers that provide support, shape, and mobility
Types of cytoskeleton fibers
Microtubules, microfilaments, and intermediate filaments
Microtubules
Constructed from tubulin and help in cell division and are in cilia and flagella
Microfilaments
Constructed from actin and help in muscle contraction
Intermediate filaments
Constructed from keratins (proteins) and help in shape and position of organelles
Plants cells do not have...
centrioles
The surface-area-to-volume ratio affects the ability of a cell to maintain ______________ between its internal and external environment
homeostasis
Plasmolysis
Collapse of a walled cell's cytoplasm when the cell is in a hypertonic solution and water leaves
Endocytosis
Process in which substances are brought into the cells by the enclosure of the substance into a membrane-created vesicle that surrounds the substance and escorts it into the cell (used by immune cells called phagocytes)
Exocytosis
Process in which substances are exported out of the cell when a vesicle escorts the substance to the plasma membrane, causes it to fuse, and ejects the substance outside
Pinocytosis
Process of bringing in droplets of extracellular fluid via tiny vesicles
Phagocytosis
Cell takes in large particles
Types of endocytosis
Phagocytosis, pinocytosis, and receptor-mediated endocytosis
Receptor-mediated endocytosis
Specialized type of pinocytosis that moves specific molecules into a cell due to the budding of specific molecules with the receptor sites on the cell membrane
Organelles in prokaryotes
Cell wall, membrane, ribosomes
Number of _____________________ can be used to measure rate of endocytosis
vesicles in a cell
Sodium-potassium pump (ATPase)
A carrier protein that uses ATP to actively transport 3 Na⁺ ions out of a cell and 2 K⁺ ions into the cell to maintain the membrane potential
If the sodium-potassium pump is shut down...
the sodium and potassium concentration gradients will dissipate, and so will the membrane potential
Membrane potential
An electrical potential difference (voltage) across their cell membrane
Benefits of cell compartmentalization
Minimizes competing reactions, provides a favorable environment for specific reactions, and help protect the cell from potentially hazardous products from certain reactions
Origins of compartmentalization
Prokaryotes formed symbiotic relationships with larger cells (endosymbiosis)