Chapter 7 Biology

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

Proteins, lipids, carbohydrates, and nucleic acids

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

There is both a hydrophobic and hydrophilic region.

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.

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.

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.

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.

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.

What are integral proteins?

Proteins that penetrate the hydrophobic core.

What are peripheral proteins?

They are not embedded. They are appendages.

Transport proteins

Hydrophilic channel for faster transport.

Enzymatic activity proteins

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

Signal transduction proteins

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

Cell-cell recognition proteins

Identification between cells.

Intercellular joining

Join different cells together.

Attachment to cytoskeleton and ECM

Maintains cell shape and stabilize cells.

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

Glycolopids, and glycoproteins

What is the difference between glycolipids and glycoproteins.

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

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.

Are transport proteins specific?

Yes, an example is carrier proteins and glucose.

What are aquaporins?

Channel proteins for water.

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.

Diffusion

Movement of molecules so that they spread out evenly.

Concentration gradient

Region along which density of a chemical substance decreases.

Passive transport

Diffusion across a biological membrane that does not require energy.

Osmosis

Diffusion of water over a semipermeable membrane.

Isotonic

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

Hypertonic

More solute relative to something.

Hypotonic

Less solute relative to something.

Turgid

Firm.

Flaccid

Limp.

Plasmolysis

When plants are in a hypertonic environment and they wilt.

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.

Why don't plant cells burst?

Cell walls.

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.

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

Voltage across the membrane. Outside is positive.

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.

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.

Endocytosis

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

Phagocytosis

Cell eating. Examples are carbohydrates.

Pinocytosis

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

Exocytosis

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

Receptor-mediated endocytosis

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

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.

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