AP Bio Unit 2: Cell Structure and Function

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)