Biology chapter 7

What is a phospholipid? What chemical properties of the phospholipid are important to a cell membrane? Why are they called amphipathic.?

A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as a polar, hydrophilic head. Phospholipids form bilayers that function as biological membranes

How do channel and carrier proteins each aid in facilitated diffusion?

Channel proteins have a hydrophobic channel that certain molecules that ions can use as a tunnel. Aquaporins, for facilitated diffusion of water. Carrier proteins bind to molecules and change shape to shuttle them across the membrane.

Describe the differences and similarities between diffusion, passive transport, osmosis, facilitated diffusion and active transport.

Diffusion- one method of movement through the membrane is diffusion. Diffusion is the movement of. Molecules from a region of higher concentration to one of lower concentration. This movement occurs because the molecules are constantly colliding with one another. The net movement of the molecules is away from the region of high concentration to the region of low concentration. Diffusion is a random movement of molecules down the pathway called the concentration gradient . Molecules are said to move down the concentration gradient because they move from a region of higher concentration to a region of lower concentration. A drop of dye placed in a beaker of water illustrates diffusion as the dye molecules spread out and color the water. Osmosis Is the movement of water from a region of lower concentration to one of higher Often occurs across a membrane that is semipermeable. Is let's only certain molecules pass through. Facilitated diffusion Certain proteins in the membrane asset this permitting only certain molecules to pass across the membrane. The proteins encourage movement in the direction that diffusion would normally take place from a region with a higher concentration to a region of lower.

Compare and contrast how hyper and hypo and isotonic solution affect an animal and plant cell.

Hypertonic affects animal cells because a in it results in in crenation where the shape of the cell becomes distorted and wrinkled and water leaves the cell. If it affects plant cells then the water inside the cells are drawn out with osmosis. Causes plant to wilt. Hypotonic cause animal cells to swell and become bloated. They then can burst. It affect plant cells by filling their cells up to full capacity and ,along the, rigid. Isotonic causes no change and cells are at equilibrium.

Identify and explain the various mechanisms that permit bulk transport across the cell membrane?

In exocytosis transport vesicles migrate to the membrane, fuse with it, and release their contents. In endocytosis the cell takes in macromolecules by forming vesicles from the plasma membrane. Three types of this Phagocytosis - cell engulfs a particle in a vacuole Pinocytosis- cell takes in extracellular fluid. Receptor mediated endocytosis- molecules called ligands bond to receptor proteins and cause vestidle formation

What is an electrochemical gradient and why does a cell maintain it? Why is maintaining an electrochemical gradient useful or important to the cell?

It is a combination of chemical force and estricto force (the effect of the membrane potential on the ions movement, moves sodium into cell and potassium out. Cell uses atp to move a substance against concentration.

Describe the process the sodium potassium pump used to actively transport these ions across the cell membrane

It is a type of active transport and generates voltage difference across a membrane. His is created by differences in the distribution of positive and negative ions across a membrane.

What is osmosis? How osmosis is different than discussion? How is it similar? Describe the terms: diffusion, osmosis, concentration gradient, and equilibrium. In what direction does net movement of water occur when a cell is placed in a hypertonic, isotonic, or. Hypotonic solution.

Osmosis is the diffusion of water across a selectively permeable membrane. Diffuses from a region of lower solute to region of higher solute. Diffusion is the movement of molecules of any substance so that they spread out evenly into the available space. Diffusion. Passive transport. High to low. Concentration gradient is the region along which the density of a chemical substance increases or decreases. In isotonic solution the solute concentration is the same as the inside the cell, no net water movement across the plasma membrane. Hypertonic solution: solute concentration is greater than that inside the cell; cell loses water. Hypotonic solution: solute concentration is less than that inside the cell; cell gains water.

How is an integral protein different than a peripheral protein?

Peripheral proteins are under the phospholipid bilayer, while integral proteins are inscribed in the bilayer. Integral proteins pass entirely through the lipid bilayer of the plasma membrane and have domains that go from the outside of the cell to the cytoplasm inside the cell. While peripheral proteins are only on the one side of of the lipid bilayer, either the outside of the cell or the cytoplasmic side inside the cell but not both.

In what ways is the phospholipid bilayer fluid? What is cholesterol and what affect does it have on membranes?

Phospholipids in the plasma membrane can move within the bilayer. As temperature cools, membranes switch from a fluid state to solid state. Cholesterol is a steroid and has a different affect on membrane fluidity. At warm temperatures is restrains the movement of phospholipids. At cool temperatures it maintains fluidity by preventing tight packing.

How are proteins arranged in the cell membrane? What aspect of their structure allows them to be positioned in both hydrophilic and hydrophobic environments?

Proteins are embedded inside the bilayer and loosely connected to the surface. They are able to be in both hydrophobic or Phillic parts.

What's the difference between a saturated and unsaturated lipid? How does this affect bilayer permeability? How deos it affect the membranes fluidity? In what ways is the phospholipid bilayer fluid? What is cholesterol and what affect does it have on a membrane.

Saturated lipids are solid at room temperature, while unsaturated lipids are not. Unsaturated lipids have a least one double bond, which creates a 120 degree kinkin the chain. Saturated lipids have no double bonds. Saturated lipids have all sp3 hydrolized c atoms. Unsaturated lipids have at least two with sp2 or sp hybridization.

Why do cells need to move substances through their membrane?

Selective permeablty allows some substances to cross it more easily than others.

What is meant by selective permeability? What types of solute pass easily across the lipid bilayer? Which cross only to a limited extent? Which cannot cross the lipid bilayer at all? Can such solute ps enter a cell? If so how?

Selectively permeable means, a substance which allows only certain materiales to pass through it, for e.g., a plant cell wall acts as a differently permeable membrane which allow only certain materiales like water pm certain ions etc. To pass through it. Things like glucose can't. Things nonpolar like CO2 can pass. Things like water might have trouble. Larger uncharged polar molecules like glucose can't pass.

What is a plasma membrane? Name and describe the components of a phospholipid layer . How do phospholipids form the bilayer? In what kind of solvent does this occur and why?

The membrane at the boundary of every cell that acts as a selective barrier regulating the cells chemical composition. Phospholipids have 2 ends, the head which is hydrophilic and the tail composed of lipids which is hydropphobic. So phospholipids come together in way where the heads are pointed outside and the tails inside to avoid the contact of the tails with water, thus forming the bilayer.

Describe the functions membranes proteins provide the cell?

They provide transport, enzymatic activity, signal transduction, cell cell recognition, intercellular joining, attachment to the cytoskeleton and extracellular matrix.

What role does Tonicity play in osmoregulation?

Tonicity is the ability of a surrounding solution to cause a cell to gain or lose water. This plays a role in osmoregualtion because it has to do with whether a cell can maintain water balance.