Bio 181 reading assignment: Membranes

integral protiens are in lipid anchored proteins and intergral membrane protein

1 and 111

which of the following movements of a phospholipid are energetically favorable within the bilayer

lateral movements rotational movements

most phospholipids move freely within a semifluid membrane

laterally along the plane of the membrane in two dimensions

one layer, or half of a phospholipid bilayer is a(n)

leaflet

What is an aquaporin?

water channel protein in a cell

transmembrane proteins

A segment of amino acids is inserted to the phospholipid bilayer

To move a substance through a membrane against a concentration gradient, what is necessary

A transport protein and an energy source

ATP can be used to power which of the following processes?

Active transport

The difference between passive transport and active transport is that active transport requires

An input of energy

Osmosis

Diffusion of water through a selectively permeable membrane from an area of low solute concentration to an area of high solute concentration

Compare simple diffusion and facilitated diffusion.

Facilitated diffusion, but not simple diffusion, requires a transport protein Both simple and facilitated diffusion require concentration gradient

an animal cell is placed in a hypertonic medium. Predict which way water will move

From inside the cell to outside

When channel proteins are _______, it means they can open and close to regulate the movement of ions and molecules across the cell membrane.

Gated

What is the significance of being able to gate a channel protein

Gating a channel protein allows the cell to regulate the movement of solutes

When the concentration of a solute is the higher on one side of membrane than the other, an transmembrane ____ is established

Gradient

Water diffuses through a membrane from a solution that is _______ , Correct Unavailable (lower concentration of dissolved particles) into a solution that is ________ , Correct Unavailable (higher concentration of dissolved particles). Solutions with identical concentrations are said to be_______

Hypotonic Hypertonic Isotonic

Functions os selectively permeable plasma membranes

Maintain a proper supply of essential molecules such as glucose and amino acids remove waste products from within the cell maintain a proper balance of ions within the cell

which of the following statements are consistent with the fluid mosaic model

Many membrane proteins move within the plane of the membrane membranes are mainly composed of proteins and phospholipids phospholipids can move within the plane of the membranes

Explain why the phospholipid bilayers is composed of two leaflets

Membranes must interact with two polar environments, a hydrophilic cytoplasm and a hydrogen extra cellular environment Phospholipids are amphipathic and must interact with polar and nonpolar environments Hydrophobic nonpolar tails can be isolated into a hydrophobic environment between the two leaflets

Diffusion

Movement of a substance from a region where its concentration is high to a region where its concentration is low

facilitated diffusion

Movement of a substance from a region where its concentration is high to a region where its concentration is low through a passageway provided by a transport protein

Active Transport

Movement of a substance from a region where its concentration is low to a region where its concentration is high with the aid of a transport protein and a source of energy

How do transporters differ from channel proteins

Transporters must change conformation to allow solutes to cross the membrane.

animal cell is placed in pure water (which contains no solutes). In what direction will water move?

Water will move into the cell from outside

Two nonpolar tails and one phosphate, polar head

What are phospholipids composed of?

a key similarity between simple and facilitated is that both require

a concentration gradient

The transport of a substance that requires an input of energy is called_____ transport

active

What types of transport require transport proteins

active transport & facilitated

phospholipids have both hydrophobic and hydrophilic components. As such, they are said to be

amphipathic

Why is the phospholipid bilayer an effective to hydrophilic or polar molecules

because of the hydrophobic interior of the bilayer

Unlike transporters, ____________ proteins provide an open passageway all the way across the plasma membrane.

channel

transmembrane proteins called ___ proteins allow ion and hydrophilic molecules to cross the phospholipid bilayer

channel

Transporter proteins bind their solutes in a hydrophilic pocket and then undergo a(n) _____change that switches the exposure of the pocket from one side of the membrane to the other.

conformational

some molecules are known to move laterally in the plane of the membrane. as such, we can say the membrane is

fluid

according to the ____ model, membrane proteins and lipids are able to move relative to one another within the plasma membrane

fluid mosaic

what property of biological membranes describes the ability of individual molecules to move within the membrane

fluidity

What can readily diffuse across the membrane?

gases and small uncharged molecules

Membrane fluidity is increased when

have shorter non polar tails

A sample of cells is places in a salt solution. The cells subsequently shrink and the membrane deforms. Relative to the cells, the salt solution is

hypertonic

In ____ solutions, animal cells will take up water. In extreme cases, the cells can rupture in a process called osmotic lysis

hypotonic

When the concentration of solutes outside the cell is higher than that intra-cellularly, the solution is said to be ______ relative to the inside of the cell.

hypotonic

When the solute concentration is higher inside the cell relative to outside the cell, the outside solution is said to be

hypotonic

What changes in lipid composition would be expected to increase the fluidity of a phospholipid bilayer

incorporating more cholesterol at low temps and more unsaturated fatty acids

biological membranes that are fluid

individual molecules can move within the membrane

A membrane protein that has a portion integrated into the hydrophobic region of the membrane is called ____ membrane protein

integral

When the concentration of molecules on both sides of a membrane is the same, the molecules will

isotonic

how does cholesterol affect the plasma membrane at low temperatures?

it makes the membrane more fluid and prevents freezing

At a high temperature, cholesterol makes a membrane ____ fluid

less

lipid-anchored proteins

lipid molecule that is covalently attached to an amino acid side chain within the protein

What is the plasma membrane made of?

lipids, proteins, and carbohydrates

the cell membrane is referred to as a mosaic because it is a mixture of what types of molecules

lipids, proteins, and carbohydrates

The internal and external environments of a cell are separated by a structure known as the plasma ____

membrane

why is it more appropriate to describe membranes as semifluid

molecules move laterally within the membrane leaflet phospholipids usually move in two dimensions

peripheral membrane proteins

non-covalent associations from with phospholipids or other membrane proteins

Phospholipid bilayers are an effective barrier to many charged or polar solutes because of their _____ interior region

nonpolar, hydrophobic

Small, uncharges molecules pass through the membrane via

passive diffusion

What is the basic structure of the plasma membrane

phospholipid bilayer

what separates the internal contents of a cell from the extracellular environment?

plasma membrane

What are the three molecular components of cellular membranes

proteins, carbohydrates, and phospholipids

What is the movement of a phospholipid that are energetically favorable within the bilayer?

rotational lateral

the fluidity of the plasma membrane can be increased by incorporating fatty acids with ____ tails or by incorporating ____ lipids

shorter unsaturated

The two leaflets of a lipid bilayer are formed because

the polar head groups of phospholipids can interact with the polar interior and exterior of the cell

cellular membranes are described as fluid because

their lipids and proteins can move relative to each other

examples of integral membrane proteins

transmembrane porteins lipid-anchored proteins

what is one way solutes cannot diffuse across the membrane can still gain access to the inside of the cell?

transport proteins

what categories of proteins assists in the movement of molecules and ions across membranes

transporters channels

Proteins that assist in the movement of substances across membranes can be classified into two types based on how they move solutes across a membrane: _______ & ______

transporters and channels