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IB Biology SL > B1.2 Membrane and membrane transport > Flashcards

B1.2 Membrane and membrane transport Flashcards

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1
Q

What is the basic structure of cell membranes?

A

The basic structure of cell membranes is formed from phospholipid bilayers.

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2
Q

Define amphipathic in relation to phospholipids.

A

Amphipathic means having both hydrophobic and hydrophilic parts, as phospholipids have a hydrophilic phosphate head and hydrophobic hydrocarbon tails.

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3
Q

What is a phospholipid monolayer?

A

A phospholipid monolayer is formed when phospholipids in water orient their hydrophilic phosphate heads towards the water and hydrophobic hydrocarbon tails away from the water.

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4
Q

True or False?

The fatty acid tail of a phospholipid is polar and soluble in water.

A

False.

The fatty acid tail of a phospholipid is nonpolar and insoluble in water (hydrophobic).

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5
Q

What are the two regions of a phospholipid bilayer?

A

The two regions of a phospholipid bilayer are a hydrophobic core and a hydrophilic outer layer.

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6
Q

Why can’t large molecules pass through the phospholipid bilayer?

A

Large molecules cannot pass through the phospholipid bilayer because the hydrophobic region is tightly packed and has low permeability to larger molecules.

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7
Q

Define phospholipid bilayer.

A

A phospholipid bilayer is a two-layered structure composed of phospholipids with their hydrophobic tails facing inwards and hydrophilic heads outwards.

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8
Q

What allows the phospholipid bilayer to form an effective barrier?

A

The phospholipid bilayer forms an effective barrier due to its hydrophobic core and hydrophilic outer layer, which control which molecules can pass through and out of the cell.

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9
Q

True or False?

Polar molecules and ions can easily pass through the hydrophobic tails of the phospholipid structure.

A

False.

Polar molecules and ions cannot pass through the hydrophobic tails of the phospholipid structure due to their hydrophilic nature.

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10
Q

What are the three components of a phospholipid?

A

A phospholipid consists of a molecule of glycerol, two fatty acid tails, and a phosphate group.

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11
Q

What are the two main categories of membrane proteins?

A

The two main categories of membrane proteins are integral proteins and peripheral proteins.

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12
Q

Define integral proteins.

A

Integral proteins are partially hydrophobic (amphipathic) proteins that are embedded in the phospholipid bilayer, either across both layers or just one layer.

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13
Q

What is the difference between channel proteins and carrier proteins?

A

Channel proteins form holes or pores through which molecules can travel, while carrier proteins change shape to transport a substance across the membrane.

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14
Q

True or False?

Membrane proteins have the same content in all cell types.

A

False.

The protein content of membranes can vary depending on the function of the cell.

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15
Q

What is the role of receptor proteins in cell membranes?

A

Receptor proteins bind to specific molecules like peptide hormones, neurotransmitters, or antibodies, generating signals that trigger reactions inside the cell.

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16
Q

Define peripheral proteins.

A

Peripheral proteins are hydrophilic proteins attached to either the surface of integral proteins or to the plasma membrane via a hydrocarbon chain, and can be inside or outside the cell.

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17
Q

What are immobilised enzymes in relation to cell membranes?

A

Immobilised enzymes are integral proteins with the active site exposed on the surface of the membrane, which can be inside or outside the cell.

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18
Q

How do glycoproteins function in cell-to-cell recognition?

A

Glycoproteins act as cell markers or antigens for cell-to-cell recognition, such as the ABO blood group antigens that differ slightly in their carbohydrate chains.

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19
Q

True or False?

Each transport protein can transport multiple types of ions or molecules.

A

False.

Each transport protein is specific to a particular ion or molecule.

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20
Q

What is the main function of the phospholipid bilayer in the plasma membrane?

A

The main function of the phospholipid bilayer in the plasma membrane is to provide a barrier to the movement of some substances into and out of the cell.

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21
Q

What is osmosis?

A

Osmosis is the diffusion of water molecules, from a dilute solution to a solution with a higher solute concentration, across a partially permeable membrane.

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22
Q

What are aquaporins?

A

Aquaporins are channel proteins that allow water to pass through membranes more freely during osmosis.

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23
Q

What is the difference between simple diffusion and facilitated diffusion?

A

Both types of diffusion involve the passive movement of substances from high to low concentration, however simple diffusion does not require a transport protein and facilitated diffusion does require a transport protein.

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24
Q

What are the two types of proteins that enable facilitated diffusion?

A

The two types of proteins that enable facilitated diffusion are channel proteins and carrier proteins.

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25
Q

What types of molecules typically require facilitated diffusion to cross cell membranes?

A

Large molecules, polar molecules, and ions typically require facilitated diffusion to cross cell membranes.

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26
Q

What is the role of gated channel proteins?

A

Gated channel proteins can control the exchange of ions by opening or closing the pore through movement of part of the protein on the inside surface of the membrane.

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27
Q

True or False?

Channel proteins can change shape to transport substances.

A

False.

Carrier proteins change shape to transport substances, while channel proteins have a fixed shape.

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28
Q

What is the difference between channel proteins and carrier proteins?

A

Channel proteins are pores with a fixed shape that allow specific substances to pass through, while carrier proteins can switch between two shapes to transport substances across the membrane.

29
Q

Define active transport.

A

Active transport is the movement of molecules and ions across a cell membrane, from a region of lower concentration to a region of higher concentration, using energy from respiration.

30
Q

True or False?

Active transport requires channel proteins.

A

False.

Active transport requires carrier proteins, not channel proteins.

31
Q

What is a pump protein?

A

A pump protein is a carrier protein that uses energy from adenosine triphosphate (ATP) to transfer specific particles across membranes. This is used in active transport.

32
Q

Define selective permeability.

A

Selective permeability is the ability of the membrane to differentiate between different types of molecules, only allowing some molecules through while blocking others.

33
Q

What are glycoproteins?

A

Glycoproteins are cell membrane proteins that have a carbohydrate chain attached on the extracellular side.

34
Q

Define glycolipids.

A

Glycolipids are lipids with carbohydrate chains attached, located on the outer surface of cell membranes.

35
Q

What is the main function of the carbohydrate chains in glycoproteins and glycolipids?

A

The carbohydrate chains enable glycoproteins and glycolipids to act as receptor molecules, allowing them to bind with substances at the cell surface.True or False?

36
Q

True or False?

Glycoproteins and glycolipids are found on the intracellular side of cell membranes.

A

False.

Glycoproteins and glycolipids are located on the extracellular (outside) side of cell membranes.

37
Q

How do glycoproteins and glycolipids contribute to cell identification?

A

Some glycoproteins and glycolipids act as cell markers or antigens, allowing the immune system to determine whether a cell belongs in the body or is a pathogen.

38
Q

Why are membranes described as ‘fluid’ in the fluid mosaic model?

A

Membranes are described as ‘fluid’ because the phospholipids and proteins can move around within their own layers.

39
Q

What are the four main components of the fluid mosaic model?

A

The four main components of the fluid mosaic model are phospholipids, cholesterol, glycoproteins and glycolipids, and integral and peripheral proteins.

40
Q

True or False?

Membranes only form barriers between the cell and its environment.

A

False.

Membranes form partially permeable barriers between the cell and its environment, between cytoplasm and organelles, and also within organelles.

41
Q

What gives membranes their ‘mosaic’ appearance?

A

The scattered pattern produced by the proteins within the phospholipid bilayer gives membranes their mosaic appearance when viewed from above.

42
Q

How are glycoproteins represented in a diagram of the fluid mosaic model?

A

Glycoproteins are represented with a carbohydrate chain attached on the extracellular side of the membrane.

43
Q

True or False?

Peripheral proteins extend into the hydrophobic region of the membrane.

A

False.

Peripheral proteins do not extend into the hydrophobic region of the membrane.

44
Q

What is the position of cholesterol in the membrane?

A

In the membrane, cholesterol’s OH group is positioned next to the phosphate heads, with the rest positioned next to the tails of the phospholipids.

45
Q

What are the two main components of phospholipid fatty acid chains?

A

The two hydrophobic tails of a phospholipid are made up of fatty acids and the hydrophilic head of a phospholipid is a phosphate group.

46
Q

True or False?

Saturated fatty acids contain one or more double bonds between carbon atoms.

A

False.

Saturated fatty acids have no double bonds and are fully “saturated” with hydrogen atoms.

47
Q

Why do unsaturated fatty acids have lower melting points than saturated fatty acids?

A

Unsaturated fatty acids have lower melting points than saturated fatty acids because unsaturated fatty acids have kinks in their structure from double bonds, preventing them from packing tightly together.

48
Q

Saturated fatty acids have high melting points.

What is the consequence of this property on membrane structure?

A

Saturated fatty acids have higher melting points, which makes membranes stronger at higher temperatures.

49
Q

How does cholesterol contribute to membrane stability at high temperatures?

A

Cholesterol holds fatty acid tails together, increasing membrane stability by preventing excessive fluidity at high temperatures.

50
Q

What role does cholesterol have on membrane structure at lower temperatures?

A

At lower temperatures, cholesterol prevents stiffening of the membrane.

51
Q

Cholesterol helps prevent water-soluble substances from diffusing across the membrane by fitting into the _________‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ between phospholipids.

A

Cholesterol helps prevent water-soluble substances from diffusing across the membrane by fitting into the‎ spaces between phospholipids.

52
Q

Define the term endocytosis.

A

Endocytosis is a process in which cells take in substances from outside of the cell by engulfing them in a vesicle.

53
Q

Define the term exocytosis.

A

Exocytosis is the process of transporting materials from within a cell to the exterior of the cell.

54
Q

True or False?

Endocytosis and exocytosis are passive transport processes that do not require energy.

A

False.

Both endocytosis and exocytosis are forms of active transport and require energy.

55
Q

What is an example of endocytosis, and what does it transport?

A

Phagocytosis is an example of endocytosis that transports solid materials, such as the engulfing of bacteria by phagocytic white blood cells.

56
Q

What is a vesicle?

A

A vesicle is a small, membrane-bound sac within a cell that is filled with liquid. They perform a variety of roles such as transport, storage and communication within the cell.

57
Q

How are vesicles formed?

A

The formation of vesicles is an active process and involves a small region of the plasma membrane being pinched off.

58
Q

What is the role of nicotinic acetylcholine receptors at the neuromuscular junction?

A

Nicotinic acetylcholine receptors open in response to the neurotransmitter acetylcholine, allowing ions (such as Ca²⁺ or Na⁺) to enter, changing the membrane potential and potentially generating an action potential.

59
Q

True or False?

The sodium-potassium pump transports ions down their concentration gradients using ATP.

A

False.

The sodium-potassium pump transports ions against their concentration gradients using ATP.

60
Q

What is indirect active transport in the context of the sodium-dependent glucose co-transporter?

A

Indirect active transport uses the energy from sodium ions moving down their gradient to move glucose against its gradient, without directly using ATP for the glucose transport itself.

61
Q

Which ion channels are examples of voltage-gated channels in neurons?

A

Sodium (Na⁺) and potassium (K⁺) channels are examples of voltage-gated ion channels in neurons.

62
Q

Why are sodium-dependent glucose cotransporters important for glucose absorption in the small intestine?

A

Sodium-dependent glucose cotransporters use the energy from sodium ions moving down their concentration gradient to transport glucose against its concentration gradient.

In the small intestine, this mechanism allows efficient absorption of glucose into the bloodstream.

63
Q

Why are sodium-dependent glucose cotransporters important for glucose absorption in the nephron?

A

In the nephron, sodium-dependent glucose cotransporters enable the reabsorption of glucose from the filtrate back into the blood, preventing glucose loss in urine.

64
Q

What term describes the surface proteins that allow cells to adhere to each other and form tissues?

A

The term describes the surface proteins that allow cells to adhere to each other and form tissue is cell-adhesion molecules (CAMs).

65
Q

What is the role of cell-adhesion molecules (CAMs) in tissue formation?

A

CAMs are proteins on the cell surface that help cells stick to each other, allowing them to form tissues by creating stable cell–cell connections.

66
Q

True or False?

All types of cell–cell junctions use the same cell-adhesion molecules (CAMs).

A

False.

Different types of CAMs are used for different types of cell–cell junctions.

67
Q

Why are cell-adhesion molecules important for multicellular organisms?

A

CAMs enable cells to stick together, allowing them to form organised tissues and structures essential for the complex functions of multicellular organisms.

68
Q

In the context of tissues, what is the primary function of cell–cell junctions mediated by CAMs?

A

Cell-cell junctions provide structural cohesion and communication pathways between cells, ensuring tissue coordination.

IB Biology SL (9 decks)

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