Lesson 2.4 - Transport Across Membranes

Question 1

Define Passive Transport

Answer 1

The movement of a substance across a membrane without expending energy.

Question 2

What is the movement of a substance across a membrane without expending energy known as?

Answer 2

Passive Transport

Question 3

Define Dynamic Equilibrium

Answer 3

The state in which continuous action results in balanced conditions.

Question 4

What is the state in which continuous action results in balanced conditions known as?

Answer 4

Dynamic Equilibrium

Question 5

Define Simple Diffusion

Answer 5

The ability of small and non-polar substances to move across a membrane unassisted.

Question 6

What is the ability of small and non-polar substances to move across a membrane unassisted known as?

Answer 6

Simple Diffusion

Question 7

Define Facilitated Diffusion

Answer 7

The facilitated transport of ions and polar molecules through a membrane via protein complexes.

Question 8

What is the facilitated transport of ions and polar molecules through a membrane via protein complexes known as?

Answer 8

Facilitated Diffusion

Question 9

Define Transport Protein

Answer 9

An integral membrane protein that provides a pathway for molecules to cross a membrane.

Question 10

What is an integral membrane protein that provides a pathway for molecules to cross a membrane known as?

Answer 10

Transport Protein

Question 11

Define Channel Protein

Answer 11

A hydrophilic pathway in a membrane that enables water and ions to pass through.

Question 12

What is a hydrophilic pathway in a membrane that enables water and ions to pass through known as?

Answer 12

Channel Protein

Question 13

Define Carrier Protein

Answer 13

A protein that binds to a molecule and transports it across the lipid bilayer.

Question 14

What is a protein that binds to a molecule and transports it across the lipid bilayer known as?

Answer 14

Carrier Protein

Question 15

Define Osmosis

Answer 15

The passive diffusion of water across a membrane.

Question 16

What is the passive diffusion of water across a membrane known as?

Answer 16

Osmosis

Question 17

Define Hypotonic

Answer 17

A solution that has a lower solute concentration than another solution.

Question 18

What is a solution that has a lower solute concentration than another solution known as?

Answer 18

Hypotonic

Question 19

Define Hypertonic

Answer 19

A solution that has a higher solute concentration than another solution.

Question 20

What is a solution that has a higher solute concentration than another solution known as?

Answer 20

Hypertonic

Question 21

Define Isotonic

Answer 21

A solution that has the same solute concentration as another solution.

Question 22

What is a solution that has the same solute concentration as another solution known as?

Answer 22

Isotonic

Question 23

Define Active Transport

Answer 23

The movement of substances across membranes against their concentration gradient using pumps.

Question 24

What is the movement of substances across membranes against their concentration gradient using pumps known as?

Answer 24

Active Transport

Question 25

Define Electrochemical Gradient

Answer 25

The combined effects of a difference in electrical potential energy and a difference in the concentration gradients of ions.

Question 26

What are the combined effects of a difference in electrical potential energy and a difference in the concentration gradients of ions known as?

Answer 26

Electrochemical Gradient

Question 27

Cells and cell organelles must interact with their environment by allowing and controlling the inward and outward movement of molecules and ions through their _____.

Answer 27

Cells and cell organelles must interact with their environment by allowing and controlling the inward and outward movement of molecules and ions through their membrane.

Question 28

Some molecules can pass through a membrane using passive transport (_____ or _____ diffusion), which depends on a _____ gradient.

Answer 28

Some molecules can pass through a membrane using passive transport (simple or facilitated diffusion), which depends on a concentration gradient.

Question 29

Osmosis is the passive diffusion of _____ across a membrane.

Answer 29

Osmosis is the passive diffusion of water across a membrane.

Question 30

Active transport moves a substance against a _____ across a membrane, using a _____. Primary active transport pumps include H⁺, Ca⁺, Na⁺, and K⁺ pumps. Secondary transport pumps occur via symport or antiport.

Answer 30

Active transport moves a substance against a concentration gradient across a membrane, using a pump. Primary active transport pumps include H⁺, Ca⁺, Na⁺, and K⁺ pumps. Secondary transport pumps occur via symport or antiport.

Question 31

Endocytosis moves aggregate molecules _____ the cell. Exocytosis moves protein and wastes _____ the cell.

Answer 31

Endocytosis moves aggregate molecules into the cell. Exocytosis moves protein and wastes out of the cell.

Question 32

Passive transport is the movement of a substance across a membrane without the need to expend _____.

Answer 32

Passive transport is the movement of a substance across a membrane without the need to expend energy.

Question 33

[Passive transport] is driven by _____, which is the movement of substances from an area of high concentration to low concentration.

Answer 33

[Passive transport] is driven by diffusion, which is the movement of substances from an area of high concentration to low concentration.

Question 34

Membranes have selective _____, which means that some molecules can diffuse very rapidly across a membrane while other molecules are unable to transit the membrane without assistance.

Answer 34

Membranes have selective permeability, which means that some molecules can diffuse very rapidly across a membrane while other molecules are unable to transit the membrane without assistance.

Question 35

What two factors does the rate of diffusion in active transport depend on? How do they affect the rate?

Answer 35

Concentration Difference (or Gradient) - The steeper the concentration gradient, the quicker they will diffuse.

Temperature - A higher temperature allows the molecules to move faster, encouraging more movement and increasing the rate of diffusion.

Question 36

Simple diffusion is the ability of small and non-polar substances to move across a membrane _____ and without _____.

Answer 36

Simple diffusion is the ability of small and non-polar substances to move across a membrane unassisted and without energy.

Question 37

[In simple diffusion,] very small _____ molecules (O₂ and CO₂) are readily soluble in the hydrophobic interior and therefore move rapidly from one side to the other. _____ steroid hormones and drugs also cross easily. Small, uncharged molecules (H₂O and glycerol) even though polar, still move quite rapidly. Membranes are impermeable to large molecules and ions.

Answer 37

[In simple diffusion,] very small non-polar molecules (O₂ and CO₂) are readily soluble in the hydrophobic interior and therefore move rapidly from one side to the other. Non-polar steroid hormones and drugs also cross easily. Small, uncharged molecules (H₂O and glycerol) even though polar, still move quite rapidly. Membranes are impermeable to large molecules and ions.

Question 38

_____ diffusion is the _____ transport of ions and polar molecules through a membrane via protein complexes and without energy. [It] still uses the process of diffusion [like in simple diffusion], and is based on a concentration gradient but uses a protein to help substances across the membrane.

Answer 38

Facilitated diffusion is the facilitated transport of ions and polar molecules through a membrane via protein complexes and without energy. [It] still uses the process of diffusion [like in simple diffusion], and is based on a concentration gradient but uses a protein to help substances across the membrane.

Question 39

Channel proteins are _____ membrane proteins that form hydro_____ pathways in the membrane, so substances like H₂O and ions can cross.

Answer 39

Channel proteins are integral membrane proteins that form hydrophilic pathways in the membrane, so substances like H₂​O and ions can cross.

Question 40

Some ion channels are _____, which means that they switch between open, closed, and intermediate states.

Answer 40

Some ion channels are voltage-gated, which means that they switch between open, closed, and intermediate states.

Question 41

Carrier proteins bind to a specific solute (ex. glucose and amino acids) and transport it across the _____ bilayer. When performing the transport step, the carrier protein changes _____, allowing the solute to move from one side of the membrane to the other. Transport proteins are very selective about which solutes they will carry.

Answer 41

Carrier proteins bind to a specific solute (ex. glucose and amino acids) and transport it across the lipid bilayer. When performing the transport step, the carrier protein changes shape, allowing the solute to move from one side of the membrane to the other. Transport proteins are very selective about which solutes they will carry.

Question 42

Osmosis [is] the simple passive diffusion of water across a membrane. Water always diffuses from an area of _____ solute concentration (_____ water concentration) to an area of _____ solute concentration (_____ water concentration).

Answer 42

Osmosis [is] the simple passive diffusion of water across a membrane. Water always diffuses from an area of lower solute concentration (high water concentration) to an area of greater solute concentration (low water concentration).

Question 43

Does the following describe hypotonic, hypertonic, or isotonic conditions?

Solution (surrounding a cell) contains dissolved substances at a lower concentration than they are in the cell.

Answer 43

Hypotonic

Question 44

Does the following describe hypotonic, hypertonic, or isotonic conditions?

Solution (surrounding a cell) contains dissolved substances at a higher concentration than they are in the cell.

Answer 44

Hypertonic

Question 45

Does the following describe hypotonic, hypertonic, or isotonic conditions?

Concentration of water inside and outside cells is equal.

Answer 45

Isotonic

Question 46

Does the following describe hypotonic, hypertonic, or isotonic conditions?

Solution (surrounding a cell) contains a higher concentration of water than in the cell.

Answer 46

Hypotonic

Question 47

Does the following describe hypotonic, hypertonic, or isotonic conditions?

Solution (surrounding a cell) contains a lower concentration of water than in the cell.

Answer 47

Hypertonic

Question 48

Active transport is the movement of substances across membranes _____ their concentration gradient using _____ (energy-dependent process).

Answer 48

Active transport is the movement of substances across membranes against their concentration gradient using pumps (energy-dependent process).

Question 49

_____ active transport moves positively charged ions, such as H⁺, Ca²⁺, Na⁺, and K⁺ across the membrane. The concentration _____ that are established by these active transport pumps underline functions that are absolutely essential for cellular life.

Answer 49

Primary active transport moves positively charged ions, such as H⁺, Ca²⁺, Na⁺, and K⁺ across the membrane. The concentration gradients that are established by these active transport pumps underline functions that are absolutely essential for cellular life.

Question 50

How many Na⁺ ions are pushed out of the cell and how many K⁺ ions are pushed into the cell simultaneously by a sodium-potassium pump?

Answer 50

Three Na⁺ are pushed out of the cell and two K⁺ ions are pushed into the cell simultaneously by a sodium-potassium pump.

Question 51

_____ active transport uses the concentration gradient of an ion, established by a _____ pump, as its energy source.

Answer 51

Secondary active transport uses the concentration gradient of an ion, established by a primary pump, as its energy source.

Question 52

What are the two mechanisms of secondary transport, and how do the differ?

Answer 52

Symport - a solute moves through the membrane channel in the same direction as the driving ion

Antiport - the driving ion moves through the membrane channel in one directioo, providing the energy for active transport of another molecule in the opposite direction

Question 53

Sometimes cells need to move large quantities of materials into or out of their cytoplasm all at once. A process called _____ may accomplish this. As in active transport, all bulk-transport mechanisms use energy in the form of _____.

Answer 53

Sometimes cells need to move large quantities of materials into or out of their cytoplasm all at once. A process called bulk transport may accomplish this. As in active transport, all bulk-transport mechanisms use energy in the form of ATP.

Question 54

Endocytosis is the form of bulk transport used to bring large amounts of material _____ the cell from the extracellular fluid.

Answer 54

Endocytosis is the form of bulk transport used to bring large amounts of material into the cell from the extracellular fluid.

Question 55

What are the three forms of endocytosis?

Answer 55

Phagocytisis, pinocytosis, and receptor-assisted endocytosis.

Question 56

[_____] only occurs in specialized cells, such as a single-celled amoeba or the bacteria eating white blood cells of our immune system (macrophages).

Answer 56

[Phagocytosis] only occurs in specialized cells, such as a single-celled amoeba or the bacteria eating white blood cells of our immune system (macrophages).

Question 57

Phagocytosis begins when a solid particle comes in contact with the plasma membrane of a cell. The cell membrane send out fingerlike projections called _____ that surround and eventually enclose the particle in a vesicle that is within the cell’s cytoplasm. Such a vesicle is called a _____.

Answer 57

Phagocytosis begins when a solid particle comes in contact with the plasma membrane of a cell. The cell membrane send out fingerlike projections called pseudopods that surround and eventually enclose the particle in a vesicle that is within the cell’s cytoplasm. Such a vesicle is called a phagocytotic vesicle.

Question 58

_____ containing digestive enzymes may fuse with the phagocytotic vesicle to digest the particles it contains. Nutrients formed by this digestion process move through the vesicle’s membrane into the cell’s cytoplasm.

Answer 58

Lysosomes containing digestive enzymes may fuse with the phagocytotic vesicle to digest the particles it contains. Nutrients formed by this digestion process move through the vesicle’s membrane into the cell’s cytoplasm.

Question 59

[Pinocytosis] occurs in nearly all cell types. Pinocytosis occurs when a cell’s plasma membrane engulfs a small drop of _____ fluid together with any _____ substances it might contain. This results in the formation of a pinocytotic vesicle.

Answer 59

[Pinocytosis] occurs in nearly all cell types. Pinocytosis occurs when a cell’s plasma membrane engulfs a small drop of extracellular fluid together with any dissolved substances it might contain. This results in the formation of a pinocytotic vesicle.

Question 60

What is the difference between phagocytosis and pinocytosis?

Answer 60

In phagocytosis, the cell takes in large solids. In pinocytosis, the cell takes in small amounts of extracellular fluid with dissolved substances into the cell.

Question 61

[In receptor-mediated endocytosis,] specific molecules attach to membrane _____ that posse a uniquely shape projection or cavity that fits the shape of only one specific molecule.

Answer 61

[In receptor-mediated endocytosis,] specific molecules attach to membrane receptors that posse a uniquely shape projection or cavity that fits the shape of only one specific molecule.

Question 62

Facilitated diffusion is specific. What does this mean?

Answer 62

Facilitated diffusion is specific in that specific transport proteins will carry certain polar or charged molecules but not others.

Question 63

A red blood cell was placed in a beaker of solution. The cell immediately began to swell and finally burst. Explain what happened, referring to the cytosol of the cell and the solution in the beaker.

Answer 63

The cytosol of the cell was hypertonic to the solution in the beaker, which in turn was hypotonic to the cell. When the cell was placed in the beaker, water entered the cell by osmosis until the cell burst.

Question 64

Distilled water is considered hypotonic to body cells. Explain.

Answer 64

Distilled water is hypotonic to body cells as it has a lower concentration of solutes than the cells do.

Question 65

Compare the energy requirements of passive transport, primary active transport, and secondary active transport.

Answer 65

Passive transport requires no energy; active transport requires energy. Primary active transport expends energy directly through ATP hydrolysis. Secondary active transport relies on pre-established ion gradients for energy rather than direct hydrolysis of ATP.

Question 66

What is meant by the term “concentration gradient”?

Answer 66

A concentration gradient is the gradual difference in concentration of a dissolved substance in a solution between regions.

Question 67

Your biology study partner asks you a question about the concentration gradient of water. Is your study partner using the term “concentration gradient” correctly in reference to water? Explain why or why not.

Answer 67

No, “concentration gradient” is not being used correctly as water is usually the solvent, not the solute, and we do not refer to the concentration of the solvent.

Question 68

How do size, polarity, and charge influence the ability of a substance to diffuse across a membrane?

Answer 68

The ability of a substance to diffuse across a membrane is hindered by larger size, polarity, and charge.

Question 69

How does the concentration of a solute on the two sides of a membrane affect passive transport?

Answer 69

The concentration of the solute controls the direction of passive transport. The solute will diffuse across a membrane from the region of high concentration to the region of low concentration.

Question 70

How does the concentration of a solute on the two sides of a membrane affect primary and secondary active transport?

Answer 70

Primary active transport is not dependent on solute concentration and actively works against the solute’s concentration gradient. Secondary active transport utilizes an ion concentration gradient, created by primary active transport processes, to move another solute against its own concentration gradient.

Question 71

The transport of molecules across cellular membranes is important for the proper functioning of cells. Explain the role of transport across cell membranes in the proper functioning of red blood cells.

Answer 71

Red blood cells carry oxygen throughout the body, so the oxygen needs to get into and out of the blood cells.

Question 72

The transport of molecules across cellular membranes is important for the proper functioning of cells. Explain the role of transport across cell membranes in the proper functioning of cells in the gut.

Answer 72

Cells in the gut absorb nutrients to fuel the body, so these solutes and molecules need to move in and out of cells.

Question 73

The transport of molecules across cellular membranes is important for the proper functioning of cells. Explain the role of transport across cell membranes in the proper functioning of the release of hormones.

Answer 73

Hormones are released from cells in glands. Without transport across membranes, the hormones would not be released to help regulate the body.