The Cell: Membranes

most life on earth exists as single-celled organisms. true or false?

true

what refers to the most basic unit of structure and function in every organism, including multicellular organisms?

cell

everything that an organism does happens fundamentally at the cellular level. true or false?

true

list 4 structures common to both prokaryotes and eukaryotes.

cytoplasm, plasma membrane, chromosome, ribosomes

what is another term for cytoplasm?

cytosol

what cell structure refers to a gel-like substance composed of water and dissolved chemicals needed for growth?

cytoplasm

what refers to the cell structure that encloses the cytosol/cytoplasm?

plasma membrane

what refers to the cell structure that consists of a large DNA molecule and its associated protein molecules?

chromosome

what cell structure refers to complexes of RNA and protein molecules that function as the site of protein synthesis?

ribosomes

the lipid bilayer of the plasma membrane is less than ____.

5nm

the individual layers of the bilayer cannot be resolved. true or false?

false

what cell structure exhibits selective permeability (allows some substances to cross more easily than others)?

plasma membrane

what cell structure enables cells to maintain unique internal environments from the extracellular environment?

plasma membrane

what cell structure enables organelles to maintain unique internal environments within cells?

plasma membrane

all cells including bacteria, archaea, and eukaryotes have a plasma membrane. true or false?

true

what cell structure captures needed molecules and brings them into the cell?

plasma membrane

what cell structure removes waste from the cell?

plasma membrane

what cell structure communicates with other cells and the environment?

plasma membrane

what cell structure anchors the cell in place?

plasma membrane

biological membranes are a fluid mosaic with man components (lipids, proteins) that move freely within the phospholipid bilayer. true or false?

true

what refers to proteins that enable transport (nutrients, waste), communication with external environment, and attachment to the surroundings [extracellular matrix (ECM), neighboring cells, and surfaces]?

membrane proteins

what refers to proteins that transport, communicate, and attach a cell?

membrane proteins

the plasma membrane of cells are made up of a double layer (bilayer) of ____.

phospholipids

various proteins are embedded within or attached to membranes. true or false?

true

what term refers to having both hydrophobic and hydrophilic parts?

amphipathic

phospholipids are not amphipathic. true or false?

false

in phospholipids, the hydrocarbon tails are ____ while the phosphate heads are ____.

hydrophobic; hydrophilic

in phospholipids, the ____ are hidden from the aqueous surroundings by facing each other in the bilayer while the ____ are exposed to the aqueous surroundings.

tails; heads

membranes are held together by ____ bonds.

noncovalent

the _____ bonds in membranes are weak and allow lipids and some proteins to drift laterally along the membrane.

noncovalent

some ____ move within the membrane because they are driven along the cytoskeleton by motor proteins attached to membrane protein’s cytoplasmic region.

membrane proteins

____ constantly move laterally (side to side) in the plasma membrane.

phospholipids

phospholipids move laterally at about ____ times/sec.

10^7

phospholipids rarely flip to the other layer (leaf) of the membrane about ____ time/month.

1

what type of transport takes place without an input of energy?

passive

what type of transport occurs when molecules move from high to low concentration (down a concentration gradient)?

passive

what type of transport is the movement of a substance that requires an input of energy?

active

what type of transport is necessary to move molecules from a low to high concentration (against a concentration gradient)?

active

what type of transport uses active carrier proteins that change shape as they move their cargo across the membrane?

active

what type of transport requires an energy source like ATP?

active

what type of transport refers to facilitated diffusion?

passive

what type of transport refers to simple diffusion?

passive

what type of transport is when molecules cross the membrane with the help of proteins?

facilitated diffusion

what type of transport is when molecules cross the membrane without the help of proteins?

simple diffusion

what type of transport uses channel proteins and passive carrier proteins?

facilitated diffusion

what refers to proteins that create a channel or hole for molecules to diffuse through?

channel proteins

what refers to proteins that change shape as molecules diffuse through them?

passive carrier proteins

small, non polar molecules such as oxygen and carbon dioxide cannot cross cell membranes without assistance through simple diffusion. true or false?

false

most hydrophobic molecules cannot pass through the cell membrane’s hydrophobic interior. true or false?

false

very large hydrophobic molecules will not pass through the cell membrane very quickly due to their size. true or false?

true

what refers to the diffusion of water molecules across a selectively permeable membrane?

osmosis

osmosis refers to the movement of water molecules. true or false?

true

osmosis refers to the movement of solutes. true or false?

false

the differences in solute concentration drives ____.

osmosis

water always moves from a low solute concentration to a high solute concentration. true or false?

true

what term refers to the degree to which a particular cell can withstand changes in osmotic pressure?

tonicity

____ environments have the same solute concentration as another solution.

isotonic

____ environments have a solution that has a higher solute concentration than another.

hypertonic

____ environments have a lower solute concentration than another.

hypotonic

____ environments can cause cells to be dehydrated and cause crenation (shriveling of the cell).

hypertonic

____ environments can cause cells to expand to the point of lysis.

hypotonic

in cells that lack a cell wall, changes in osmotic pressure can lead to crenation in ____ environments or cell lysis in ____ environments.

hypertonic; hypotonic

for many cells, the cell shape and structure is maintained by the presence of a ____.

cell wall

bacterial cells, plant cells, fungal cells, and some protists (notably algae) cells have cell walls. true or false?

true

the ____ protects the cell from changes in osmotic pressure.

cell wall

cells that possess a cell wall undergo ____ instead of crenation in a hypertonic environment.

plasmolysis

____ provide a hydrophilic passageway for molecules to diffuse across a membrane.

channel proteins

____ alternate between two shapes and the change in their shape captures and releases molecules to help them diffuse across the membrane.

passive carrier proteins

provide an example of a channel protein.

aquaporins

provide an example of a passive carrier protein.

glucose transporters

polar water molecules quickly cross membranes by osmosis through ____.

aquaporins

____ work by allowing glucose to enter beta cells of the pancreas through a carrier protein (GLUT2).

glucose transporters

what refers to an important passive carrier protein that helps maintain blood glucose levels through facilitated diffusion?

GLUT

what kind of transport maintains high internal concentrations of small molecules that are at low external concentrations?

active

what kind of transport maintains low internal concentrations of small molecules that are at high external concentrations?

active

what kind of transport is often called “pumps” because anytime something is pumped across a membrane (energy being used)?

active

____ uses energy (ATP) to pump ions or molecules across the membrane against a concentration gradient.

active carrier proteins

what type of active carrier protein uses the energy of ATP to pump protons (hydrogen ions, H+) across cell membranes?

proton pump