Unit 5

Question 1

Describe the structure of the cell membrane.

Answer 1

The cell membrane is primarily composed of a phospholipid bilayer, which consists of amphipathic phospholipids with hydrophilic heads and hydrophobic tails.

Question 2

How do phospholipids contribute to the cell membrane’s properties?

Answer 2

Phospholipids are amphipathic, meaning they have both polar (water-loving) and non-polar (water-hating) regions, which allows them to form a bilayer that is essential for membrane structure and function.

Question 3

What role does cholesterol play in the cell membrane?

Answer 3

Cholesterol helps maintain membrane fluidity and prevents phospholipids from packing too closely together.

Question 4

Define integral proteins in the context of the cell membrane.

Answer 4

Integral proteins are embedded throughout the membrane and can span both sides, often functioning as channels or glycoproteins.

Question 5

Explain the difference between integral and peripheral proteins.

Answer 5

Integral proteins are embedded in the membrane, while peripheral proteins protrude from one edge of the membrane or are associated with integral proteins.

Question 6

How do smaller non-polar molecules interact with the cell membrane?

Answer 6

Smaller non-polar molecules can easily travel through the cell membrane due to their compatibility with the hydrophobic interior of the phospholipid bilayer.

Question 7

What is the significance of the amphipathic nature of phospholipids?

Answer 7

The amphipathic nature of phospholipids is crucial for forming the bilayer structure of the cell membrane, allowing for selective permeability and fluidity.

Question 8

Do channel proteins qualify as integral membrane proteins?

Answer 8

Yes, channel proteins are a type of integral membrane protein as they are embedded throughout the membrane and facilitate the transport of substances.

Question 9

What is the function of peripheral proteins in the cell membrane?

Answer 9

Peripheral proteins can interact with the membrane’s surface and may play roles in signaling, maintaining the cell’s shape, or connecting to the cytoskeleton.

Question 10

Describe the composition of the phospholipid bilayer.

Answer 10

The phospholipid bilayer consists of two layers of phospholipids, with hydrophilic heads facing outward towards the extracellular and intracellular environments, and hydrophobic tails facing inward.

Question 11

Describe the role of the lipid bilayer in cell membrane transport.

Answer 11

The lipid bilayer structure is tightly packed with hydrophobic interiors, making the membrane selectively permeable. It allows only certain substances, particularly small non-polar materials, to pass through.

Question 12

How do small non-polar materials cross the cell membrane?

Answer 12

Small non-polar materials, such as fatty acids, can cross the lipid bilayer due to its hydrophobic nature, allowing them to move through without assistance.

Question 13

Define passive transport in the context of cell membranes.

Answer 13

Passive transport is the movement of substances across the cell membrane using their own kinetic energy without the expenditure of chemical energy.

Question 14

What is the driving force behind the movement of molecules across the cell membrane?

Answer 14

The concentration gradient is the driving force that moves small, uncharged molecules across the cell membrane, as they move from areas of higher concentration to areas of lower concentration.

Question 15

Explain the difference between active transport and passive transport.

Answer 15

Active transport requires energy from the hydrolysis of ATP to move substances across the membrane, while passive transport does not require energy and relies on the kinetic energy of the molecules.

Question 16

How does diffusion relate to concentration gradients?

Answer 16

Diffusion refers to the movement of particles down a concentration gradient, where molecules move from areas of higher concentration to areas of lower concentration until evenly distributed.

Question 17

What types of substances typically require assistance to cross the cell membrane?

Answer 17

Water-soluble materials, such as glucose, amino acids, and ions, typically require assistance to cross the membrane because they are repelled by the hydrophobic tails of the phospholipid bilayer.

Question 18

Describe the process that occurs when the concentration of a substance becomes equal on both sides of the membrane.

Answer 18

When the concentration of a substance becomes equal on both sides of the membrane, there will be little movement, resulting in no more net diffusion.

Question 19

What is the significance of the hydrophobic interior of the cell membrane?

Answer 19

The hydrophobic interior of the cell membrane contributes to its selective permeability, allowing only certain substances, particularly small non-polar molecules, to pass through while repelling water-soluble materials.

Question 20

How do ions typically move across the cell membrane?

Answer 20

Ions typically require assistance to cross the cell membrane due to their charge and the hydrophobic nature of the lipid bilayer, often moving through specific channels or transport proteins.

Question 21

Describe the process of cellular respiration.

Answer 21

Cellular respiration is a metabolic process that consumes oxygen (O2) and produces carbon dioxide (CO2), typically occurring in the mitochondria of cells.

Question 22

How does oxygen (O2) move in relation to cells during cellular respiration?

Answer 22

Oxygen generally diffuses into cells because it is more concentrated outside of them.

Question 23

Explain the concept of passive transport.

Answer 23

Passive transport is the movement of substances across a cell membrane without the use of energy, relying on concentration gradients.

Question 24

Define simple diffusion.

Answer 24

Simple diffusion is a form of passive transport where small, non-polar molecules slip between the lipid tails of a cell membrane from an area of higher concentration to an area of lower concentration.

Question 25

What is facilitated diffusion?

Answer 25

Facilitated diffusion is a type of passive transport that allows large polar or ionic molecules to cross the phospholipid bilayer with the help of membrane proteins.

Question 26

How do carrier proteins function in facilitated diffusion?

Answer 26

Carrier-mediated facilitated diffusion involves glucose and other large polar molecules binding to transport proteins, which then change shape to allow the molecules to enter the cell.

Question 27

Describe the role of osmosis in cellular processes.

Answer 27

Osmosis refers to the movement of water across a semipermeable membrane, which can occur through simple diffusion or facilitated diffusion, often following dissolved solutes.

Question 28

What is the significance of concentration gradients in diffusion?

Answer 28

Concentration gradients drive the movement of substances, with molecules moving from areas of higher concentration to areas of lower concentration.

Question 29

Explain the movement of water in osmosis.

Answer 29

In osmosis, water molecules move from areas of lower solute concentration to areas of higher solute concentration, often following dissolved solutes.

Question 30

How do sodium channels facilitate diffusion?

Answer 30

Sodium channels are membrane proteins that form pores, allowing sodium ions to diffuse across the membrane according to their concentration gradient.

Question 31

Describe the role of aquaporins in cellular water transport.

Answer 31

Aquaporins are channel proteins that facilitate the passage of water molecules through the cell membrane, allowing water to move in and out of the cell while preventing the passage of solutes.

Question 32

Define osmotic homeostasis.

Answer 32

Osmotic homeostasis refers to the process of maintaining a stable concentration of solutes and water within the cell and its environment, ensuring that intracellular and extracellular fluids remain similar.

Question 33

How do kidneys contribute to maintaining homeostasis in the body?

Answer 33

The kidneys regulate the balance of water and solutes in the body, helping to maintain an isotonic environment necessary for proper cellular function.

Question 34

Explain the characteristics of a hypertonic solution.

Answer 34

A hypertonic solution has a higher concentration of solutes compared to another solution, causing water to diffuse out of cells, leading to cell shrinkage.

Question 35

What happens to cells in a hypotonic solution?

Answer 35

In a hypotonic solution, which has a lower concentration of solutes, water diffuses into the cells, causing them to swell and potentially burst.

Question 36

Describe the difference between primary and secondary active transport.

Answer 36

Primary active transport directly uses energy from ATP hydrolysis to move substances against their concentration gradient, while secondary active transport uses the energy from the movement of one substance to drive the transport of another.

Question 37

How does active transport differ from passive transport?

Answer 37

Active transport requires energy to move substances across a membrane against their concentration gradient, while passive transport does not require energy and moves substances along their concentration gradient.

Question 38

What is the effect of an isotonic solution on cells?

Answer 38

In an isotonic solution, the concentration of solutes is equal inside and outside the cell, allowing cells to maintain their normal shape and function without net movement of water.

Question 39

Explain the process of osmosis in relation to cell membranes.

Answer 39

Osmosis is the movement of water molecules across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration, aiming to equalize solute concentrations on both sides.

Question 40

Define the term 'solute'.

Answer 40

A solute is a substance that is dissolved in a solvent, forming a solution. In biological contexts, solutes can include ions, sugars, and other molecules.

Question 41

Describe the role of ATP in the concentration gradient of muscle cells.

Answer 41

ATP is used to power pumps that create a concentration gradient by moving ions, such as sodium and potassium, across the cell membrane.

Question 42

How does the sodium-potassium pump function?

Answer 42

The sodium-potassium pump transports sodium out of the cell and potassium into the cell, both against their concentration gradients, which is crucial for maintaining cellular function.

Question 43

Explain the significance of action potential in nerve cells.

Answer 43

Action potential involves the constant pumping of sodium ions out and potassium ions into nerve cells to maintain concentration gradients, allowing these ions to flow across the membrane and change the cell's voltage.

Question 44

Define endocytosis and its process.

Answer 44

Endocytosis is an active transport process where a cell ingests material by enveloping it in a portion of its membrane, which then pinches off to form a vesicle.

Question 45

What is a vesicle in the context of cellular transport?

Answer 45

A vesicle is a membrane-bound portion of the cell membrane that has pinched off, containing materials that can be transported within the cell.

Question 46

Describe phagocytosis and its role in the immune system.

Answer 46

Phagocytosis, or 'cell eating,' is a type of endocytosis where immune cells engulf large particles, such as invading pathogens, to protect the body.

Question 47

What is pinocytosis?

Answer 47

Pinocytosis, or 'cell drinking,' is the process by which a cell takes in fluid containing dissolved substances.

Question 48

Explain receptor-mediated endocytosis.

Answer 48

Receptor-mediated endocytosis is a specific form of endocytosis where the cell membrane contains receptors for certain substances, allowing for targeted uptake.

Question 49

How do red blood cells utilize receptor-mediated endocytosis?

Answer 49

Red blood cells endocytose iron, a component of hemoglobin, using a protein called transferrin to facilitate the process.

Question 50

Define exocytosis and its function in cells.

Answer 50

Exocytosis is the process by which a cell transports materials out of the cell using vesicular transport, where substances are packaged into vesicles that fuse with the cell membrane to release their contents.