chapter 7

SUMMARY: SODIUM-POTASSIUM PUMP

1. 3 sodium ions come in and attach to the binding sites. 2. ATP is hydrolyzed, a phosphate group binds, and ADP is left behind. 3. The interior side closes and the exterior side opens and the sodium ions are released. 4. The exterior side closes and the interior side opens and 2 potassium ions come in and attach to the binding site. 5. The phosphate group detaches. 6. The protein goes back to the original shape and the potassium ions are released.

concentration gradient

A difference in the concentration of a substance across a distance.

glycolipids

A lipid that has at least one carbohydrate attached to it via a covalent bond. Carbohydrates attached to a lipid.

diffusion

A process that is spontaneous and does not require energy to occur. In this process, substances move into space. This occurs down the concentration gradient.

glycoproteins

A protein that has at least one carbohydrate attached to it via a covalent bond. Carbohydrates attached to a protein.

phagocytosis

A type of endocytosis in which a cell engulfs large particles or whole cells. A cell ingests outside materials and are packaged in the food vacuole.

Pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes. A cell ingests liquids into its vesicles.

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

Active transport is when molecules move from low to high concentrations. This is not moving down the concentration gradient, so it must use energy to function. Carrier proteins are used in active transport. Since active transport requires energy, ATP is the source here.

Peter Agre received the Nobel Prize in 2003 for the discovery of aquaporins. What are they?

Aquaporins are channel proteins that allow the movement of water across the membrane of a cell.

Describe how each of the following can affect membrane fluidity: decreasing temperature

As the temperature decreases, the membrane is fluid until it reaches a point where it becomes solid due to the phospholipids being so close together.

Distinguish between channel proteins and carrier proteins.

Channel proteins have channels and only specific materials can pass through. The transport is passive. Carrier proteins can hold materials and modify in shape to provide transport.

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

Chemical and electrical forces drive the diffusion of ions across the membrane. The combination of these two forces is called the electrochemical gradient.

integrins

Connects the extracellular matrix with the cytoskeleton.

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

Cotransport is when one substance moves down its concentration gradient and the other moves against its concentration gradient. When diarrhea occurs, so much water is released the reabsorption of sodium is not possible, like it normally is, so the levels decrease. To combat this, people drink a salt and glucose combination and sodium-glucose cotransporters are responsible for taking this up.

What is facilitated diffusion? Is it active or passive?

Facilitated diffusion is when molecules move down the concentration gradient and a transmembrane protein is necessary. This type of diffusion is passive, so it does not require energy to occur.

Membrane carbohydrates are important in cell-cell recognition. What are two examples of this?

Glycolipids and Glycoproteins are two examples of membrane carbohydrates that are important in cell-cell recognition.

cell-cell recognition

Glycoproteins are used for identification for other proteins.

turgid

In a plant cell, this describes when the cell becomes firm or bulged and this form is good for plant cells.

passive transport

In passive transport, substances are moved from a high to a low concentration. This process does not require an input of energy to take place. This is a type of simple diffusion.

The currently accepted model of the plasma membrane is the fluid mosaic model. Describe this model.

In this model, there are two layers of phospholipids with proteins embedded within them.

Phospholipids are amphipathic. Explain what this means.

Instead of being strictly hydrophobic or hydrophilic, there are areas in a phospholipid that are hydrophobic, as well as areas that are hydrophilic.

cytoskeleton microfilaments

Make up the cytoskeleton. Protein fibers that help the cell contract and move

attachment to cytoskeleton and ECM

Materials of the cytoskeleton can bind to the membrane proteins.

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

Membrane potential is when there are different charges that occur across the plasma membrane. The side of the membrane that is positive is the exterior.

intercellular joining

Membrane proteins have the ability to link to other membrane proteins and form junctions.

active transport

Molecules are moved from an area of low to high concentration. Since the molecules are moving against their concentration gradient, this process requires energy to occur.

Why does the red blood cell burst when placed in a hypotonic solution, but the plant cell does not?

Plant cells have a cell wall that red blood cells lack. Plant cells are also turgid when they are in a hypotonic solution, which is healthy for them.

exocytosis

Process by which a cell releases large amounts of material. When the vacuole membrane fuses with the cell membrane, contents are released.

Describe how each of the following can affect membrane fluidity: cholesterol

The effect of cholesterol on membrane fluidity varies by temperature. When the temperature is high, cholesterol creates a more fluid membrane because phospholipids cannot move freely. Cholesterol also helps prevent large changes in the fluidity of the membrane that can occur due to temperature variation.

What is the key feature of receptor-mediated endocytosis?

The key feature of receptor-mediated endocytosis is the specific receptor that does the binding.

What is meant by membrane fluidity?

The membranes are not stuck in a specific shape. The lipids and proteins have the ability to move. The membranes can move laterally or flip.

receptor-mediated endocytosis

The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances. This is a type of pinocytosis where the cell is able to take in quantities of substances.

Are the processes you described in question 28 active or passive transport? Explain your response

The processes in question 28 are active processes because all of them require the use of energy by the cell in order to take place and occur.

phospholipid

These are amphipathic and form the bilayers of the plasma membrane.

integral proteins

These have a hydrophobic and hydrophilic area and are located within the membrane. They can penetrate the interior and exterior of the membrane.

transport proteins

These proteins are located along the membrane and provide hydrophilic channels that allow for transport.

peripheral proteins

These proteins are not embedded within the membrane like integral proteins are. They are associated to the surface of the membrane

enzymatic activity

These proteins are within the membrane and can be an enzyme. The active sites and be a pathway.

ECM fibers

They provide a stronger structure by being attached to membrane proteins.

Describe how each of the following can affect membrane fluidity: increasing the number of saturated hydrocarbon tails

This decreases membrane fluidity because they can pack together.

flaccid

This describes when the structure is floppy or limp.

signal transduction

This is the location of the binding site for the chemical messengers.

Describe how each of the following can affect membrane fluidity: phospholipids with unsaturated hydrocarbon chains

This results in a more fluid membrane because phospholipids with unsaturated hydrocarbon chains have kinks that prevent them from packing together tightly enough to solidify the membrane.

cholesterol

This steroid decreases the changes that occur in the membrane, so it can be called a "fluidity buffer."

bulk transport

This type of transport occurs via exocytosis and endocytosis.

plasmolysis

When a cell loses water, it causes the separate from the wall of the cell and usually causes the plant to die.

passive transport

When a molecule diffuses across a membrane. This is a process that does not require energy and they move down the concentration gradient.

hypotonic

When there are less solutes in the solution and it will result in the loss of water from a cell.

hypertonic

When there are more solutes in the solution and will cause the increase of water in a cell.

isotonic

When there is the same solute concentration

osmosis

When water goes from low to high solute concentration areas.

Are transport proteins specific? Cite an example that supports your response.

Yes, they are specific and an example is that the sodium potassium pump works by moving potassium in and sodium out of the cell.

How does the diffusion of one solute affect the diffusion of the second solute?

if the concentration is more then more particles will travel from one side to other side.

endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane. When cells take in substances by forming vesicles.

CO2

via simple diffusion

O2

via simple diffusion

H2O

via simple diffusion and transport proteins

H+

via transport proteins

glucose

via transport proteins