Chapter 7 Biology

What is a ligand? What do ligands have to do with receptor-mediated endocytosis?

A ligand is a molecule that binds to a receptor. Ligands mediate receptor-mediate endocytosis.

What is cotransport? Explain how its understanding is used in our treatment of diarrhea.

ATP is used to indirectly provide transport for certain molecules. On molecule is expelled via ATP, and then it returns to the cytoplasm via a cotransporter in addition to a different molecule, that would not be able to do so without the first molecule. It is useful in sugar and sulfate mixes when suffering from diarrhea.

How does CO2, Glucose, H+, O2, and H2O cross the membrane?

CO2 through diffusion, Glucose through carrier proteins, H+ through protein channels, O2 through diffusion, H2O through diffusion and aquaporins.

Pinocytosis

Cell drinking. Examples are the uptake of solutes in fluids.

Phagocytosis

Cell eating. Examples are carbohydrates.

Exocytosis

Cell secretes molecules. Examples are enzymes, such as salivary amylase.

Endocytosis

Cell takes in biological molecules. Examples are ingested bacteria, such as salmonella.

Why don't plant cells burst?

Cell walls.

Distinguish between channel proteins and carrier proteins.

Channel proteins do not change, the just provide a channel. Carrier proteins change shape and hold onto passengers as they change shape.

What are aquaporins?

Channel proteins for water.

What are the two forces that drive the diffusion of ions across the membrane? What is the combination of these forces called?

Chemical force, and electrical force. These forces are called electrochemical forces.

Passive transport

Diffusion across a biological membrane that does not require energy.

Osmosis

Diffusion of water over a semipermeable membrane.

What is facilitated diffusion? Is it active or passive? Cite two examples.

Facilitated diffusion is diffusion along transport proteins. It is passive. Examples are aquaporins and neurotransmitters.

Turgid

Firm.

What is the difference between glycolipids and glycoproteins.

Glycolipids are carbohydrates covalently bound to lipids. In glycoproteins, carbohydrates are covalently bound to proteins

What are two examples of membrane carbohydrates that are important in cell-cell recognition?

Glycolopids, and glycoproteins

Transport proteins

Hydrophilic channel for faster transport.

Cell-cell recognition proteins

Identification between cells.

How does cholesterol affect membrane fluidity?

It acts as a fluid buffer. It makes it more fluid in very cold temperatures, by not allowing the membrane to come in too close. In too warm temperatures it decreases fluidity.

How does decreasing temperature affect membrane fluidity.

It decreases fluidity.

What affect do phospholipids with unsaturated hydrocarbon chains have on the membrane fluidity?

It increases fluidity because of more kinks.

Intercellular joining

Join different cells together.

Hypotonic

Less solute relative to something.

Flaccid

Limp.

Attachment to cytoskeleton and ECM

Maintains cell shape and stabilize cells.

What is meant by membrane fluidity? Describe the movement seen in the fluid membrane.

Membrane is not static. It can shift and move because of unsaturated hydrocarbons. They can move by lateral movement, or by flipping.

Hypertonic

More solute relative to something.

Diffusion

Movement of molecules so that they spread out evenly.

Describe active transport. What type of transport proteins are involved, and what is the role of ATP in the process?

Movement of molecules through proteins, but energy is required. ATP provides energy for this. Example is the sodium potassium pump.

Isotonic

No net movement of water across a membrane. Amounts are equal.

Enzymatic activity proteins

Protein's active site is exposed. Once enzyme activates, it a certain function is performed.

What are integral proteins?

Proteins that penetrate the hydrophobic core.

The large molecules of all living things fall into just four main classes. Name them.

Proteins, lipids, carbohydrates, and nucleic acids

Concentration gradient

Region along which density of a chemical substance decreases.

Who proposed the fluid mosaic model of membrane structure? When? Describe this model.

S.J. Singer and G. Nicolson proposed it in 1972. It is a phospholipid bilayer with proteins embedded.

Signal transduction proteins

Signaling molecules create shape change in proteins, and proteins relay a message.

Receptor-mediated endocytosis

Take up of bulk quantities of sparse items. Cholesterol uptake.

In the 1960s, the Davson-Danieli model of membrane structure was widely accepted. Describe this model and then cite two lines of evidence that were inconsistent with it.

There is a phospholipid bilayer between 2 levels of proteins. The problems were: the model assumed all membranes are identical and also protein placement was illogical.

Explain what is meant when we say a molecule is amphipathic.

There is both a hydrophobic and hydrophilic region.

What are peripheral proteins?

They are not embedded. They are appendages.

What is membrane potential? Which side of the membrane is positive?

Voltage across the membrane. Outside is positive.

Plasmolysis

When plants are in a hypertonic environment and they wilt.

Are transport proteins specific?

Yes, an example is carrier proteins and glucose.