Cell Membrane Movement Types

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Questions and Answers

What is the primary purpose of movement across the cell membrane?

To maintain cell shape

To synthesize proteins

To transport nutrients and oxygen into the cell and waste out of the cell (correct)

To regulate cell division

What are the three main processes involved in the transport of substances across the cell membrane?

Passive transport, active transport, and vesicular transport (correct)

Photosynthesis, respiration, and fermentation

Active transport, passive transport, and mitosis

Meiosis, mitosis, and fertilization

What type of transport does not need energy?

Facilitated diffusion

Vesicular transport

Passive transport (correct)

Active transport

What are the two types of diffusion?

Simple diffusion and facilitated diffusion Signup and view all the answers

What helps in facilitated diffusion?

Carrier proteins of the cell membrane Signup and view all the answers

What is the direction of movement in passive transport?

Downhill Signup and view all the answers

What are the three headings under which diffusion can be discussed?

Simple diffusion through lipid layer, simple diffusion through protein layer, and facilitated diffusion Signup and view all the answers

What is the electronical term for the combination of concentration gradient and electrical gradient?

Electrochemical gradient Signup and view all the answers

What is the primary cause of the transport of atoms or molecules in simple diffusion?

Random movement of molecules Signup and view all the answers

When does the net movement of molecules cease in simple diffusion?

When the concentration of molecules is equal on both sides Signup and view all the answers

What type of substances diffuse rapidly through the lipid bilayer of the cell membrane?

Lipid soluble substances Signup and view all the answers

How do water and other lipid insoluble substances pass through the cell membrane?

Through protein channels Signup and view all the answers

What is the characteristic of protein channels in the cell membrane?

Highly selective to permit only one type of ion Signup and view all the answers

What is the purpose of respiratory gases being transported across the alveolar membrane?

To facilitate simple diffusion Signup and view all the answers

What is the result of the frequency of collision and the probability of striking the cell membrane?

Higher on the side of the membrane with higher concentration Signup and view all the answers

What is the result of the net flux of molecules from areas of high concentration to areas of low concentration?

Diffusional equilibrium Signup and view all the answers

What is the main reason glucose cannot diffuse through the protein channels by simple diffusion?

It has a larger molecular size Signup and view all the answers

What is the term used to describe the type of diffusion that requires the help of carrier proteins?

Facilitated diffusion Signup and view all the answers

What is a characteristic of carrier proteins in facilitated diffusion?

They are highly specific for different molecules Signup and view all the answers

What happens to the rate of diffusion in facilitated diffusion as the concentration of the substance increases?

It increases but reaches a limit Signup and view all the answers

What occurs when two molecules are carried by the same protein in facilitated diffusion?

They compete with each other for transport Signup and view all the answers

What is the major determining factor for the net diffusion?

Cell membrane permeability Signup and view all the answers

How does the thickness of the cell membrane affect diffusion?

Diffusion is inversely proportional to the thickness of the cell membrane Signup and view all the answers

What is the term used to describe the point at which the carrier proteins are fully occupied and the system operates at its maximum capacity?

Saturation point Signup and view all the answers

How does lipid solubility affect diffusion?

Diffusion is directly proportional to lipid solubility Signup and view all the answers

What is true about the specificity of carrier proteins in facilitated diffusion?

They are specific for a particular molecule Signup and view all the answers

What is an example of a substance that crosses the cell membrane by facilitated diffusion?

Glucose Signup and view all the answers

How does temperature affect the rate of diffusion?

Rate of diffusion increases with increase in temperature Signup and view all the answers

How does the size of the molecules affect the rate of simple diffusion?

Rate of simple diffusion is inversely proportional to the size of the molecules Signup and view all the answers

How does the area of the membrane affect the net diffusion?

Net diffusion is directly proportional to the area of the membrane Signup and view all the answers

What is the effect of concentration gradient on simple diffusion?

Simple diffusion is directly proportional to the concentration gradient Signup and view all the answers

What is the effect of electrical potential gradient on diffusion?

Net diffusion occurs from inside to outside due to electrical potential gradient Signup and view all the answers

What is the direction of osmosis?

From high to low solute concentration Signup and view all the answers

What happens to the osmotic pressure when the solute concentration increases?

It increases Signup and view all the answers

What is osmolality?

The concentration of osmotically active particles in a solution Signup and view all the answers

What is the term for a solution that has the same osmotic pressure as the cytoplasm?

Isotonic Signup and view all the answers

What is the term for a solution that is more dilute than the cytoplasm?

Hypotonic Signup and view all the answers

What is the term for a solution that is more concentrated than the cytoplasm?

Hypertonic Signup and view all the answers

What is tonicity?

Describes how an extracellular solution can change the volume of a cell Signup and view all the answers

What is the osmolarity of plasma?

290 mOsm Signup and view all the answers

Study Notes

Movement Across Cell Membrane

The cell membrane plays a crucial role in regulating the movement of substances into and out of the cell, allowing for physiological activities to occur.

Types of Movement

There are three main types of movement across the cell membrane:
- Passive transport
- Active transport
- Vesicular transport

Passive Transport

Passive transport occurs along the concentration gradient or electrical gradient without the need for energy.
It is a downhill movement that does not require energy.
Passive transport mechanisms include:
- Diffusion
- Osmosis

Diffusion

Diffusion is the transport of substances from an area of high concentration to an area of low concentration.
There are three types of diffusion:
- Simple diffusion through lipid layer
- Simple diffusion through protein layer
- Facilitated or carrier-mediated diffusion

Simple Diffusion

Simple diffusion occurs due to the random movement of molecules.
Molecules collide with each other and the cell membrane, resulting in a net flux of molecules from areas of high concentration to areas of low concentration.
Respiratory gases are transported across the alveolar membrane by simple diffusion.
Simple diffusion of lipid-soluble substances through the cell membrane is rapid due to the direct proportional relationship between the rate of diffusion and the solubility of a substance in lipids.
Examples of lipid-soluble substances include oxygen, nitrogen, carbon dioxide, alcohol, steroid hormones, and weak organic acids and bases.

Simple Diffusion of Water and Other Lipid Insoluble Molecules

Water and other lipid insoluble substances can pass through the cell membrane with the help of protein channels.
These channels are highly selective, allowing only specific types of ions to pass through.

Facilitated Diffusion

Facilitated diffusion is the transport of water-soluble substances with the help of carrier proteins.
Carrier proteins have specific binding sites for particular substances.
Examples of substances that cross cell membranes by facilitated diffusion include glucose and most amino acids.

Differences between Simple and Facilitated Diffusion

Specificity: carrier proteins are highly specific for different molecules.
Saturation: facilitated diffusion has a saturation point, where the rate of diffusion increases with the concentration gradient until all binding sites are occupied.
Competition: when two molecules are carried by the same protein, there is competition between the two molecules for transport.

Factors Affecting Net Rate of Diffusion

Cell membrane permeability: the rate of diffusion is directly proportional to the permeability of the cell membrane.
Lipid solubility: the rate of diffusion is directly proportional to the lipid solubility of the substance.
Temperature: the rate of diffusion increases with an increase in temperature.
Size of the molecules: the rate of simple diffusion is inversely proportional to the size of the molecules.
Area of the membrane: the net diffusion of the substance is directly proportional to the total area of the membrane.
Concentration gradient: simple diffusion is directly proportional to the concentration gradient, but facilitated diffusion has limitations beyond a certain level of concentration gradient.
Electrical potential gradient: net diffusion occurs from inside to outside until the concentration gradient created balances the electrical gradient.
Pressure gradient: increased pressure on one side of the membrane causes net movement of molecules from the high-pressure side towards the low-pressure side.

Osmosis

Osmosis is the diffusion of water or other solvent molecules through a semipermeable membrane from a solution containing lower concentration of solutes towards a solution containing higher concentration of solutes.
Osmotic pressure increases with an increase in solute concentration, resulting in greater water flow into the solution.
Examples of osmosis include the movement of water from a sodium chloride solution into a solution containing a higher concentration of solutes.

Osmolarity and Tonicity

Osmolarity: the concentration of osmotically active particles in a solution.
Tonicity: describes how an extracellular solution can change the volume of a cell by affecting osmosis.
A solution can be:
- Isotonic: having the same osmolarity as the cytoplasm.
- Hypotonic: having a lower osmolarity than the cytoplasm.
- Hypertonic: having a higher osmolarity than the cytoplasm.

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Description

This quiz covers the different types of movements across the cell membrane, including their mechanisms and differences. Students will be able to list and describe each type of movement.