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. |
Chapter 7 Biology
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