Chapter 5

Which of these is a function of cholesterol in a cells plasma membrane?

regulating membrane fluidity

What is an aquaporin?

A membrane protein that contains a channel for water movement..

Transport proteins allow the movement of ions and small molecules across plasma membranes. Identify the type of transport protein from each example as uniporte, symporter, or antiporter.

A protein moves one \ ce{Ca^2+} out of the cell and three \ce{Na^{+}} into the cell. Antiporter a protein allows glucose to flow into a cell down its concentration gradient. Uniporter a protein moves one\\(/ce{H^{+}}\\) ion and one \\(\ce{K^{+}}\\) ion out of the cell. symporter

Facilitated diffusion is a protein facilitated movement of solutes across a membrane from an area of higher concentration to an area of lower concentration. Which of the terms best describes facilitated diffusions.

Passive transport

Match the description to the appropriate type of transport.

Passive transport. Does not require energy. Move substances down a concentrated gradient. Active transport. Requires energy. Move substances against a concentration gradient.

The sodium - potassium pump, also known as the Na+/K+ ATPase, is shown. the movement of ions through this membrane protein is an example of :

Active Transport

Which example describes an anti-pork mechanism used during active transport in a cell.

Calcium ions going in and sodium ions going out

Classify each of the descriptions as a characteristic of channel proteins, proins, or both.

Channel Protein : Typically requires a stimulusto open and let solutes pass. Has an alpha-helix structure. Porin : Has a beta-barrel protein structure Common in gram-negative bacteria Both : Transports solutes across a membrane by facilitated diffusion

Match each membrane protein to the correct function. Place all answers.

Contains a passage that spans the entire membrane and permits only specific molecules to diffuse across. - Channel protein Contains a carbohydrate chain that allows the body to recognize its own cells. - cell recognition protein. May use energy to move substances across the membrane. - transport protein. Recognizes and binds to Signal molecules leading to a reaction within the cell. - receptor protein. Participates in chemical reactions involved with metabolism. - enzymatic protein. Connect cells together and facilitates communication between them. - Junction protein.

Cell membranes are composed of phospholipids that have head and tail regions. The Phospholipid Head is hydrophobic and spontaneously orients to the inside of the membrane. Which of the phrases best describes the hydrophobic region of a phospholipid?

Has few interactions with water

phospholipids are molecules that have two regions, The Head and the tail, with distinct chemical properties. Classify the descriptions as characteristics of the head or tails of phospholipids.

Heads. Hydro folic phosphate-rich Tails. Does not mix with water non-polar

Cell membranes are composed of phospholipids that have head and tail regions. The Phospholipid Head is hydrophilic and spontaneously orientated towards the environment. Which of the phrases best describes the hydrophilic region of a phospholipid?

Interacts with water

A cell uses many methods to transport cell solutes across the plasma membrane. Classify the descriptions as either simple diffusion, facilitated diffusion, active transport, or bulk transport.

Simple diffusion. movement of solutes out of the cell directly through the plasma membrane. Facilitated diffusion. Movement of solutes out of the cell down their concentration gradient using membrane proteins. active transport. Movement of solutes out of the cell against their concentration gradient using membrane proteins. Bulk transport. movement of contents of Transport vessels out of the cell by Exocytosis.

Membrane proteins are a class of proteins that are embedded within or associated with the plasma membrane of a cell or organelle. Membrane proteins provide a variety of functions necessary for cellular survival. Classify each example as a structural, transport, communication, or recognition protein.

Structural protein : An integral membrane protein attaches to the cytoskeleton of the cell. Transport protein : A potassium pump protein uses ATP to move ions across the plasma membrane against their concentration gradient Communication protein : A membrane receptor protein binds to a hormone sent through the endocrine system Recognition protein : A white blood cell uses membrane glycoproteins to identify a virus capsule

Which choice describes diffusion?

The movement of a substance from a region where it is more concentrated to a region where it is less concentrated, down it's concentration gradient.

Which example describes the use of symport transport across a membrane?

The pumping of iodine and sodium into the thyroid gland

Which conditions would cause diffusion to happen more quickly? would make diffusion have more quickly:

the difference in concentration between two areas is large. Small molecules, rather than very large molecules, are the ones defusing. the solution gets warmer. The molecules are diffusing through a low-density liquid.