Cell Transport

What is diffusion?

The net movement of molecules or ions from a high concentration to a low concentration.

What factors affect the rate of diffusion?

Temperature, concentration gradient, area over which diffusion takes place, and thickness of the exchange surface.

What is Fick's Law?

Rate of diffusion is proportional to (surface area x the difference in concentration) /length of the diffusion path.

What is facilitated diffusion?

Diffusion that involves the presence of protein carriers or channel proteins to allow passive movement of substances across a plasma membrane.

How does facilitated diffusion differ from simple diffusion?

Facilitated diffusion requires specific protein channels, while simple diffusion does not.

Why is facilitated diffusion considered a passive process?

It does not require ATP; the movement is driven by the kinetic energy of the molecules.

What types of substances typically use facilitated diffusion?

Substances such as glucose, amino acids, and ions that cannot pass through the lipid bilayer.

What is osmosis?

The passage of water from a higher water potential to a lower water potential through a partially permeable membrane.

What does water potential represent?

Water potential is represented by the Greek letter psi (ᴪ) and is measured in kilopascals (kPa).

What happens to water potential when solutes are added?

The water potential decreases as solutes are added.

What is the effect of placing animal cells in pure water?

Animal cells may undergo lysis (bursting) due to excess water intake.

What is plasmolysis in plant cells?

Plasmolysis occurs when the vacuole shrinks due to water loss in a hypertonic solution.

What is active transport?

The movement of a substance from a region of low concentration to a region of high concentration, requiring energy.

What are the factors affecting osmosis?

Water potential gradient, thickness of the exchange surface, surface area, number of aquaporins, and temperature.

What is the role of aquaporins in osmosis?

Aquaporins are special proteins that facilitate the passage of water across the cell membrane.

What is the significance of a concentration gradient?

A concentration gradient drives the movement of molecules during diffusion and osmosis.

What is the difference between diffusion and osmosis?

Diffusion involves all types of molecules, while osmosis specifically refers to the movement of water.

What happens to plant cells in a hypotonic solution?

Plant cells become turgid as water enters, but they do not burst due to the cell wall.

What is the effect of temperature on diffusion rates?

Higher temperatures increase the kinetic energy of particles, thus increasing the rate of diffusion.

How do protein channels affect facilitated diffusion?

Protein channels provide specific pathways for certain molecules to cross the membrane, enhancing transport efficiency.

What is the significance of surface area in diffusion?

A larger surface area increases the rate of diffusion by providing more space for molecules to pass through.

What is the role of the plasma membrane in diffusion?

The plasma membrane's composition and the presence of pores determine the permeability and selectivity for diffusing substances.

What happens to an animal cell in a hypertonic solution?

The cell shrinks (crenates) as water leaves the cell.

What is the relationship between diffusion pathway thickness and diffusion rate?

Thinner diffusion pathways increase the rate of diffusion.

What is the outcome of placing cells in isotonic solutions?

There is no net gain or loss of water, maintaining cell size and shape.

What is the main energy source for active transport?

ATP (adenosine triphosphate) from aerobic respiration.

What is a key similarity between active transport and facilitated diffusion?

Both processes require proteins to move substances across the cell membrane.

What is a key difference between active transport and facilitated diffusion?

Active transport requires energy and moves substances from low to high concentration, while facilitated diffusion is passive and moves substances from high to low concentration.

What role do carrier proteins play in active transport?

Carrier proteins bind to specific substances, undergo a shape change, and transport the substance across the membrane.

What factors affect the rate of active transport?

Speed of carrier proteins, number of carrier proteins, rate of respiration, and availability of oxygen and glucose.

What is co-transport?

A mechanism that involves the simultaneous transport of two substances across a membrane, often using the gradient of one substance to drive the transport of another.

How do microvilli aid in absorption in the small intestine?

Microvilli increase the surface area for absorption, facilitating more efficient nutrient uptake.

What is endocytosis?

A bulk transport process where the cell membrane engulfs material to form a vesicle for uptake.

What are the two types of endocytosis?

Phagocytosis (uptake of solids) and pinocytosis (uptake of liquids).

What is exocytosis?

A process where vesicles fuse with the plasma membrane to release their contents outside the cell.

How does the sodium/potassium pump function in active transport?

It actively transports sodium ions out of the cell and potassium ions into the cell, using ATP.

What is the significance of maintaining a concentration gradient in co-transport?

It allows for the efficient uptake of substances like glucose and amino acids by utilizing the sodium ion gradient.

What adaptations do epithelial cells have for absorption in the small intestine?

They have microvilli for increased surface area, numerous mitochondria for ATP production, and many carrier proteins for transport.

What happens during the hydrolysis of ATP in active transport?

ATP is converted to ADP and inorganic phosphate, releasing energy that drives the transport process.

What is the role of respiration in active transport?

Respiration provides the ATP necessary for active transport processes.

How does temperature affect the rate of diffusion?

An increase in temperature raises the kinetic energy of molecules, leading to a faster rate of diffusion.

What is the relationship between surface area and the rate of diffusion?

A larger surface area increases the rate of diffusion by providing more space for molecules to pass through.

What is the effect of a respiratory inhibitor on active transport?

It stops respiration, leading to a lack of ATP and consequently halting active transport processes.

What is the function of the villi in the small intestine?

Villi increase the surface area for absorption and are well-supplied with blood vessels to maintain concentration gradients.

What is the difference between simple diffusion and facilitated diffusion?

Simple diffusion occurs directly through the phospholipid bilayer, while facilitated diffusion requires specific channel or carrier proteins.

What is the role of aquaporins in cellular transport?

Aquaporins are channel proteins that facilitate the rapid transport of water across cell membranes.

What is the significance of the concentration gradient in facilitated diffusion?

It drives the movement of molecules from areas of high concentration to areas of low concentration, allowing for passive transport.

What is the purpose of bulk transport in cells?

Bulk transport allows cells to move large volumes of materials, such as nutrients or waste products, across the membrane.