Chapter 5: Biological Membranes

Osmosis

Osmosis

________ is a kind of diffusion in which molecules of water pass through a selectively permeable membrane from a region where water has a higher effective concentration to a region where its effective concentration is lower.

transmembrane proteins

Adhering junctions are formed by cadherins, ________ that cement cells together.

model

According to the fluid mosaic ________, membranes consist of a fluid phospholipid bilayer in which a variety of proteins are embedded.

ATP powered pump

A(n) ________ maintains a concentration gradient.

specific transport proteins

Facilitated diffusion uses ________ to move solutes across a membrane.

metabolic energy

In active transport, the cell expends ________ to move ions or molecules across a membrane against a concentration gradient.

Lipid bilayers

________ are flexible and self- sealing and can fuse with other membranes.

Cells

________ regulate their internal osmotic pressures to prevent shrinking or bursting.

Porins

________ are channel proteins that form relatively large pores through the membrane for passage of water and certain solutes.

Plasmodesmata

________ are channels connecting adjacent plant cells.

Phagocytosis

In ________, the plasma membrane encloses a large particle such as a bacterium, forms a vacuole around it, and moves it into the cell.

Vesicles

The ________ fuse with lysosomes, and their contents are digested and released into the cytosol.

Cotransport

In ________, also called indirect active transport, two solutes are transported at the same time.

Gap junctions

________, composed of the protein connexin, form channels that allow communication between the cytoplasm of adjacent animal cells.

sheet of tissue

Anchoring junctions include desmosomes and adhering junctions; they are found between cells that form a(n) ________.

Channel

________ proteins are transport proteins that form passageways through which water and certain ions travel through the membrane.

Carrier

________ proteins are transport proteins that undergo a series of conformational changes as they bind and transport a specific solute.

Biological membranes

________ are selectively permeable membranes: they allow the passage of some substances but not others.

isotonic solution

A(n) ________ has an equal solute concentration compared with that of another fluid, for example, the fluid within the cell.

Diffusion

________ is the net movement of a substance down its concentration gradient from a region of greater concentration to one of lower concentration.

osmotic pressure

The concentration of dissolved substances (solutes) in a solution determines its ________.

Tight junctions

________ seal membranes of adjacent animal cells together, preventing substances from moving through the spaces between the cells.

Membranes

________ participate in and serve as surfaces for biochemical reactions.

lower solute concentration

When cells are placed in a hypotonic solution, one that has a(n) ________ than the solute concentration of the cell, water enters the cells and causes them to swell.

simple diffusion

In ________ through a biological membrane, solute molecules or ions move directly through the membrane down their concentration gradient.

metabolic energy

The cell expends ________ to carry on exocytosis and endocytosis.

Biological membranes

________ form compartments within eukaryotic cells that allow a variety of separate functions.

Diffusion

________ and osmosis are physical processes that do not require the cell to directly expend metabolic energy.

biological membranes

In almost all ________, the lipids of the bilayer are in a fluid or liquid- crystalline state, which allows the lipid molecules to move rapidly in the plane of the membrane.

The phospholipid molecules are amphipathic

they have hydrophobic and hydrophilic regions

Biological membranes are selectively permeable membranes

they allow the passage of some substances but not others