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Grade 12 - SBI4U > Chapter 2 - Review > Flashcards

Chapter 2 - Review Flashcards

1
Q

What is a key difference between eukaryoties and prokaryotes?

  • Eukaryotes do not have a nuclear membrane.
  • Prokaryotes do not have a nuclear membrane.
  • Eukaryotes do not have cell walls.
  • Prokaryotes do not not have cell walls.
A

Prokaryotes do not have a nuclear membrane.

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2
Q

Which term refers to the series of interacting organelles between the nucleus and the plasma membrane?

  • endomembrane system
  • nuclear envelope
  • intermembranal system
  • total functioning unit of the cell
A

Endomembrane System

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3
Q

Which type of cells have mitochondria?

  • eukaryotes
  • prokaryotes
  • cells that perform photosynthesis
  • all cells
A

eukaryotes

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4
Q

Which of the following is NOT a function carried out by a plastid?

  • energy production in animal cells
  • energy production in leaves
  • synthesis and storage of protein molecules
  • synthesis and storage of sugar molecules
A

energy production in animal cells

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5
Q

Which of the following symptoms may be typical of cystic fibrosis?

  • back pain
  • bacterial infections in the lungs
  • weak muscles and bones
  • headaches and dizziness
A

bacterial infections in the lungs

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6
Q

How thick is the lipid bilayer?

  • 0.01 nm
  • 10 nm
  • 1000 nm
  • 1 000 000 nm
A

10 nm

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7
Q

What materials make up a cell membrane?

  • lipids, nucleic acids, and proteins
  • lipid, cholesterols, and proteins
  • lipids, nucleic acids, and cholesterol
  • cholesterol, nucleic acids, and proteins
A

lipids, cholesterols, and proteins

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8
Q

Which form of energy is needed for passive transport to occur?

  • ATP
  • glucose energy
  • ionization energy
  • no energy is requiredno energy is required
A

no energy is required

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9
Q

Which direction do proton pumps move hydrogen ions?

  • from the cytosol to the outside of the cell
  • from the cytosol into the nucleus of the cell
  • from the nucleus into the cytosol of the cell
  • from the outside of the cell into the cytosol
A

from the cytosol to the outside of the cell

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10
Q

Is the following statement true or false?

Nucleoplasm is analogous to cytosol.

A

True

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11
Q

Is the following statement true or false?

Subunits of ribosomes are assembled from proteins and DNA in the cytosol.

A

False

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12
Q

Is the following statement true or false?

Cells that specialize in making and storing enzymes need less rough ER than average.

A

False

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13
Q

Is the following statement true or false?

Mitochondria and chloroplasts have evolved from cells that were engulfed by other cells.

A

True

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14
Q

Is the following statement true or false?

The fluid mosaic model describes how membranes consist of lipid moleculed with embedded proteins.

A

True

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15
Q

Is the following statement true or false?

All primary active transport pumps move negatively charged ions across membranes.

A

False

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16
Q

Is the following statement true or false?

If a semipermeable bag that contains a 2 mol/L sucrose solution is placed in a 10 mol/L sucrose solution, it will shrink.

A

True

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17
Q

Is the following statement true or false?

Secondary active transport pumps use the concentration gradient of an ion, which has been established by a primary pump, as their energy source.

A

True

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18
Q

Is the following statement true or false?

Endocytosis moves proteins and wastes out of the cell.

A

False

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19
Q

Which of the following best descibes the nuclear envelope?

  • protein coat
  • doubled-up lipid bilayer
  • single lipid layer
  • the same as the plasma membrane
A

doubled-up lipid bilayer

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20
Q

Which of the following best describes a nuclear pore?

  • hole through the centriole
  • temporary opening for selective transport
  • passive transport channel
  • cluster of proteins that selectively transport only some materials
A

cluster of proteins that selectively transport only some materials

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21
Q

Which of the following is a function of vesicles?

  • processing water
  • disposing of waste
  • producing toxins
  • isolating carbohydrates
A

disposing of waste

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22
Q

In eukaryotes, which organelle is responsible for making ATP?

  • nucleus
  • Golgi body
  • mitochondrion
  • membrane
A

mitochondrion

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23
Q

Which type of cells do mitochondria resemble?

  • neurons
  • muscle cells
  • bacteria
  • cork cells
A

bacteria

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24
Q

How are peripheral proteins attached to the cytosol side of the cell membrane?

  • by covalent bonds
  • by non-covalent bonds
  • by adhesion
  • by glycosidic bonds
A

by non-covalent bonds

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25
Q

Which of the following is a function of the cytoskeleton?

  • transports materials outside the cell
  • provides energy for the cell
  • aids in cell movement
  • stores materials for the cell
A

aids in cell movement

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26
Q

Which part(s) of a phospholipid is/are hydrophilic?

  • the entire phospholipid molecule
  • the phosphate group and the glycerol head
  • the fatty acid tails
  • the phosphate group only
A

the phosphate group and the glycerol head

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27
Q

What would make a hypertonic solution isotonic?

  • removes water
  • add water
  • removes solutes and water
  • add solutes
A

add water

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28
Q

Which of the following best describes the movement of molecules from an area of high concentration to an area of low concentration?

  • osmosis
  • diffusion
  • passive transport
  • active transport
A

diffusion

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29
Q

Which of the following best describes phagocytosis?

  • a type of endocytosis that takes in large particles
  • a type of endocytosis that takes in fluids
  • a type of exocytosis that removes large particles
  • a type of exocytosis that removes wastes and fluids
A

a type of endocytosis that takes in large particles

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30
Q

Which statement best describes the rate of O2 movement across a cell membrane?

  • It is slow because the O2 molecule needs time to go through the respiration reactions.
  • It is fast because the O2 molecule needs to go through the respiration reactions.
  • It is slow because O2 is a large polar molecules.
  • It is fast because O2 is a small non-polar molecule.
A

It is fast because O2 is a small non-polar molecule.

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31
Q

How does the rate of facilitated transport compare with the rate of simple diffusion for the same substance?

  • Simple diffusion is always the faster method.
  • The rates are approximately equal.
  • Facilitated transport is faster if there are enough transporters.
  • The rate depends on the type of cell, so there is not enough information to compare the rates.
A

Facilitated transport is faster if there are enough transporters.

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32
Q

Why does a cell swell when it is placed in a hypotonic solution?

  • Water diffuses to an area where there is more water.
  • Water diffuses to an areas where the solute concentration is lower.
  • Water diffuses to an area where the solute concentration is higher.
  • The solution must be outside the human body.
A

Water diffuses to an area where the solute concentration is higher.

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33
Q

Is the following statement true or false? If it is false, correct it.

Mitochondria do not have their own DNA.

A

False

Mitochondria have their own DNA.

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34
Q

Is the following statement true or false? If it is false, correct it.

Plants and animals have similar plastids.

A

False

Only plants and some algae have plastids.

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35
Q

Is the following statement true or false? If it is false, correct it.

Mitochondria and chloroplasts probably evolved in a similar way.

A

True

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36
Q

Is the following statement true or false? If it is false, correct it.

Microfilaments help amoebas feed.

A

True

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37
Q

Is the following statement true or false? If it is false, correct it.

The purpose of the cuticle is to give structure to a plant.

A

False

The purpose of the cuticle is to protect the outer surface of leaves and prevent water loss.

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38
Q

Is the following statement true or false? If it is false, correct it.

A cell with a double membrane filled with membrane-bound organelles is a prokaryotic cell.

A

False

A cell with a double membrane filled with membrane-bound organelles is a eukaryotic cell.

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39
Q

Is the following statement true or false? If it is false, correct it.

While plant and animal cells have many of the same organelles, only plant cells have a cell wall, plastids, and a large central vacuole.

A

True

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40
Q

Is the following statement true or false? If it is false, correct it.

Membranes contain steroids that help to maintain their fluidity.

A

False

Membranes contain sterols that help to maintain their fluidity.

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41
Q

Is the following statement true or false? If it is false, correct it.

Integral membrane proteins are positions on top of the lipid layer.

A

False

Integral membrane proteins are embedded into the phospholipid layer.

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42
Q

Is the following statement true or false? If it is false, correct it.

The evolution of more external membranes allowed for more complex processes to develop within cells.

A

False

The evolution of more internal membranes allowed for more complex processes to develop within cells.

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43
Q

Is the following statement true or false? If it is false, correct it.

Voltage-gated channels remain open during the rest phase.

A

False

Voltage-gated channel are closed during the rest phase.

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44
Q

Is the following statement true or false? If it is false, correct it.

Osmosis is defined as the diffusion of water across a membrane.

A

True

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45
Q

Is the following statement true or false? If it is false, correct it.

Simple and facilitated diffusion both depend on a concentration gradient.

A

True

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46
Q

Is the following statement true or false? If it is false, correct it.

Secondary active transport pumps depend on the concentration gradient of an ion established by a primary pump as its source of energy.

A

True

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47
Q

Is the following statement true or false? If it is false, correct it.

Binding by surface receptors takes place in bulk-phase endocytosis.

A

Is the following statement true or false? If it is false, correct it.

No binding by surface receptors takes place in bulk-phase endocytosis.

48
Q

Is the following statement true or false? If it is false, correct it.

Most materials that are ingested by endocytosis do not change in form once they enter the cell.

A

Most materials that are ingested by endocytosis change in form once they enter the cell.

49
Q

Which of the following best describes the cytoskeleton?

  • synthesizes and modifies proteins
  • transports and stores cellular materials
  • produces energy for the cell
  • makes lipids and breaks down fats and carbohydrates
  • sorts and ships proteins and lipids
  • digests and recycles cellular materials
  • inactivates toxins
  • moves the cell and its components
A

moves the cell and its components

50
Q

Which of the following best describes a mitochondrion?

  • synthesizes and modifies proteins
  • transports and stores cellular materials
  • produces energy for the cell
  • makes lipids and breaks down fats and carbohydrates
  • sorts and ships proteins and lipids
  • digests and recycles cellular materials
  • inactivates toxins
  • moves the cell and its components
A

produces energy for the cell

51
Q

Which of the following best describes a lysosome?

  • synthesizes and modifies proteins
  • transports and stores cellular materials
  • produces energy for the cell
  • makes lipids and breaks down fats and carbohydrates
  • sorts and ships proteins and lipids
  • digests and recycles cellular materials
  • inactivates toxins
  • moves the cell and its components
A

digests and recycles cellular materials

52
Q

Which of the following best describes the smooth ER?

  • synthesizes and modifies proteins
  • transports and stores cellular materials
  • produces energy for the cell
  • makes lipids and breaks down fats and carbohydrates
  • sorts and ships proteins and lipids
  • digests and recycles cellular materials
  • inactivates toxins
  • moves the cell and its components
A

makes lipids and breaks down fats and carbohydrates

53
Q

Which of the following best describes the rough ER?

  • synthesizes and modifies proteins
  • transports and stores cellular materials
  • produces energy for the cell
  • makes lipids and breaks down fats and carbohydrates
  • sorts and ships proteins and lipids
  • digests and recycles cellular materials
  • inactivates toxins
  • moves the cell and its components
A

synthesizes and modifies proteins

54
Q

Which of the following best describes a peroxisome?

  • synthesizes and modifies proteins
  • transports and stores cellular materials
  • produces energy for the cell
  • makes lipids and breaks down fats and carbohydrates
  • sorts and ships proteins and lipids
  • digests and recycles cellular materials
  • inactivates toxins
  • moves the cell and its components
A

inactivates toxins

55
Q

Which of the following best describes a vesicle?

  • synthesizes and modifies proteins
  • transports and stores cellular materials
  • produces energy for the cell
  • makes lipids and breaks down fats and carbohydrates
  • sorts and ships proteins and lipids
  • digests and recycles cellular materials
  • inactivates toxins
  • moves the cell and its components
A

transports and stores cellular materials

56
Q

Which of the following best describes the Golgi body?

  • synthesizes and modifies proteins
  • transports and stores cellular materials
  • produces energy for the cell
  • makes lipids and breaks down fats and carbohydrates
  • sorts and ships proteins and lipids
  • digests and recycles cellular materials
  • inactivates toxins
  • moves the cell and its components
A

stores and ships proteins and lipids

57
Q

Which of the following best describes the plasma membrane?

  • are generally found on the cytosol side of the membrane and some are part of the cytoskeleton
  • span the entire membrane bilayer and have regions that are exposed to the aqueous environment
  • responsible for regulating the substances moving in and out of the cell
  • is composed of 18% protein and 82% lipids
A

responsible for regulating the substances moving in and out of the cell

58
Q

Which of the following best describes myelin?

  • are generally found on the cytosol side of the membrane and some are part of the cytoskeleton
  • span the entire membrane bilayer and have regions that are exposed to the aqueous environment
  • responsible for regulating the substances moving in and out of the cell
  • is composed of 18% protein and 82% lipids
A

is composed of 18% protein and 82% lipids

59
Q

Which of the following best describes integral membrane proteins?

  • are generally found on the cytosol side of the membrane and some are part of the cytoskeleton
  • span the entire membrane bilayer and have regions that are exposed to the aqueous environment
  • responsible for regulating the substances moving in and out of the cell
  • is composed of 18% protein and 82% lipids
A

span the entire membrane bilayer and have regions that are exposed to the aqueous environment

60
Q

Which of the following best describes peripheral membrane proteins?

  • are generally found on the cytosol side of the membrane and some are part of the cytoskeleton
  • span the entire membrane bilayer and have regions that are exposed to the aqueous environment
  • responsible for regulating the substances moving in and out of the cell
  • is composed of 18% protein and 82% lipids
A

are generally found on the cytosol side of the membrane and some of the membrane and some are part of the cytoskeleton

61
Q

How do cells with walls interact with each other?

A

A cell that is surrounded by a wall or other secretions is not isolated; it can interact through cell junctions with other cells and with its surroundings. Cells can send and receive ions, molecules, and signals through some junctions. Other junctions help cells recognize and stick to each other and the extracellular matrix.

62
Q

Describe two functions of the nucleus?

A

First, the nucleus keeps the DNA isolated from the metabolic reactions of the cell, away from where it might be damaged. Second, the nucleus has a system of transporters and pumps that regulate the passage of various molecules across the nuclear membrane, allowing certain molecules to access DNA and control the production of RNA and proteins.

63
Q

List some of the functions and products of Golgi bodies.

A

Golgi bodies contain enzymes that modify (attach phosphate groups or sugars, or cleave polypeptide chains) polypeptide chains and lipids that have been delivered from the endoplasmic reticulum. They create membrane proteins, enzymes and other proteins for secretion, which are then packaged and exported in vesicles.

64
Q

Describe the stroma (inside) of a plastid.

A

The stroma is the semi-fluid interior of a plastid, surrounded by two outer membranes. The stroma contains enzymes and the plastid’s DNA. A third highly folded membrane inside the stroma forms a single compartment.

65
Q

Name and describe the structure and functions of the two types of endoplasmic reticulum.

A

The endoplasmic reticulum is a membrane-bound organelle that folds into flattened sacs and tubes. The rough ER has ribosomes attached to its outer surface, while the smooth ER does not. The rough ER is involved in the production and folding of proteins. The smooth ER does not participate in protein production and instead produces most of the cell’s membrane lipids. As well, smooth ER participates in the breakdown of carbohydrates, fatty acids, and some drugs and poisons.

66
Q

Explain the role of chloroplasts and chromoplasts as a tomato ripens

A

Chloroplasts produce sugars through photosynthesis that allow the tomato to grow and mature. As the tomato ripens, green chloroplasts are converted into red chromoplasts: the chloroplasts lose their chlorophyll and orange and red carotenoids become visible, resulting in a red tomato.

67
Q

Which organelles have a membrane?

A

The following organelles have a membrane: nucleus, endoplasmic reticulum, Golgi body, vesicles, mitochondrion, plastids, lysosome, peroxisome, and vacuole.

68
Q

Which two organelles are most likely to pinch off vesicles that contain proteins?

A

The endoplasmic reticulum and Golgi body are the most likely organelles to pinch off vesicles that contain proteins.

69
Q

Identify the organelle that is shown below.

In what type of organism is it found?

What are the dark area in the centre made from: proteins, fluid, membrane, or nucleic acids?

A

The organelle is a chloroplast.

Chloroplasts are found in photosynthetic eukaryotes.

The dark areas in the centre are made from membrane.

70
Q

How does an organized array of microtubules benefit a sperm cell?

A

The pack of microtubules in a sperm make up its tail, which is a type of flagellum. It whips back and forth to help the sperm cell “swim.”

71
Q

Plant cell walls are a type of extracellular matrix that is made mostly of cellulose. Describe the extracellular matrix in fungi and animal bone.

A

The extracellular matrix in fungi is made of chitin. Animal bone is mostly made of collagen, a fibrous protein, and hardened by mineral deposits.

72
Q

List and describe the four functions of membrane proteins.

A

The four functions of membrane proteins are as follows: facilitating the transport of molecules that cannot freely diffuse across the membrane; enzymatic activity like those associated with cellular respiration and photosynthesis; triggering signals of specific molecules, like hormones, by binding of the molecule to the protein and triggering a cascade of events within the cell; and attachment and recognition of cytoskeleton elements, as well as components involved in cell-cell recognition and bonding to the extracellular matrix.

Sorry that one was long and hard.

73
Q

What does A represent on the diagram below?

A

Integral Membrane Proteins

74
Q

What does B represent on the diagram below?

A

Peripheral Membrane Proteins

75
Q

What does C represent on the diagram below?

A

Polar End

76
Q

What does D represent on the diagram below?

A

Non-Polar End

77
Q

What does E represent on the diagram below?

A

Phospholipid Molecule

78
Q

What does F represent on the diagram below?

A

Cytosol

79
Q

What does G represent on the diagram below?

A

Cholesterol (Sterol)

80
Q

Explain why proteins move more slowly than lipid molecules within a plasma membrane.

A

The relatively slow movement of proteins within a plasma membrane is mainly due to their large, ungainly size. The lipid molecules are small and so it is easier for them to spin and flex and trade places with others of their size.

81
Q

Which molecules require facilitated diffusion? Explain why.

A

Metabolic processes require some molecules to enter or exit the cell at a faster rate than they are able to diffuse across the membrane. For example, large polar or charged molecules do not readily undergo simple diffusion. These molecules may require facilitated diffusion. Examples include: water, amino acids, sugar, and ions.

82
Q

Describe the movement of molecules during diffusion, and explain how this applies to diffusion through the cell membrane.

A

When particles diffuse in a space, they move randomly in all directions. In a concentration gradient, the net movement of particles occurs from a region of higher concentration to a region of lower concentration, causing the particles to become evenly distributed in space. In the case of diffusing through the plasma membrane, the particles vibrate and randomly move through the lipid bilayer down the concentration gradient between the cytosol and extracellular fluid created and maintained by the plasma membrane.

83
Q

List the three ways that cells obtain nutrients, as well as the types of nutrients that cells obtain each way.

A

Cells receive ions and small molecules such as sugars and amino acids through passive transport (simple diffusion and facilitated diffusion) or active transport (primary and secondary). They can ingest larger molecules such as proteins by endocytosis (pinocytosis, phagocytosis, and receptor-mediated endocytosis).

84
Q

List the two ways that particles exit the cell.

A

Particles can be pumped out of the cell by active transport or secreted from the cell by exocytosis.

85
Q

Vesicles can fuse with other organelles, or they can form by pinching off from other organelles. Describe examples of these two processes.

A

Sample Answer: Vesicles may form by pinching off from the endoplasmic reticulum. When they pinch off, they carry materials inside them for transport to another location. By fusing with a lysosome, they might receive digestive enzymes to process some cell waste. By fusing with the cell membrane, they would transport a protein to the outside of the cell by exocytosis.

86
Q

Compare and contrast the nuclear envelop with the plasma membrane. What do you think is the key difference?

A

Both of these membranes are made of lipid bilayers and both are selective gatekeepers, letting in certain molecules and keeping out others. However, the nuclear membrane is doubled, with its outer layer being connected to the endoplasmic reticulum. Some students may say that the key difference is location, while others might say the doubling over of the lipid bilayer membrane for the nuclear envelope is the key difference

87
Q

Explain why some cells, such as some pancreas cells that make a greater quntity of enzymes, need more rough ER than other cells.

A

Rough endoplasmic reticulum is where proteins are synthesized, and pancreatic cells synthesize a great deal of enzymes for export.

88
Q

What is an amyloplast?

A

Amyloplasts are unpigmented plastids that store starch.

89
Q

Would you be more likely to find amyloplasts in the leaves or the tubers of a potato? Explain why.

A

Amyloplasts are abundant in cells of tubers because they store starch energy in those locations. When packed with starch, they are dense and may function as gravity-sensing organelles.

90
Q

Membranes are essential for the transport of an enzyme after it is created by a ribosome on the rough ER. Explain why.

A

The ribosome makes the protein and injects it into the rough ER, where it will complete its tertiary folding. The ER will pinch off into a vesicle that will move to fuse with the Golgi apparatus for the finishing touches to be put on the protein. Then it will travel in a vesicle pinched off from the Golgi apparatus to the plasma membrane where it fuses for the exocytosis of the protein.

91
Q

What organelles do you suspect might play a particularly important role in running?

A

Cytoskeleton - muscle contrations

Mitochondria - production of energy

92
Q

What organelles do you suspect might play a particularly important role in sweating?

A

Golgi Body - packaging of cell products and wastes for export

Plasma Membrane - fusion of secretory vesicles (exocytosis)

93
Q

What organelles do you suspect might play a particularly important role in growing hair?

A

Ribosomes - production of hair keratin proteins

94
Q

What organelles do you suspect might play a particularly important role in replacing and repairing cells?

A

Rough ER - production of proteins

Centrioles - organize cytoskeleton elements for cell division

95
Q

What organelles do you suspect might play a particularly important role in passing on information to offspring?

A

Nucleus - stores DNA

Cytoskeleton - involved in seperation of duplicated chromosomes, cell divisions, and gamete mobility (flagellum of sperm cells)

96
Q

What organelles do you suspect might play a particularly important role in digesting dinner?

A

Rough ER - production of digestive enzymes

Golgi Body - modifications to enzymes

Secretory Vesicles - export

97
Q

Explain why the plasma membrane is described as both a fluid and a mosaic.

A

The lipids that make up the plasma membrane’s bilayers are extremely mobile. They spin, vibrate, and change places millions of times per second. The membrane is also fluid in the sense that it can flex, bend, form, and reform. It is even able to open up and then close again. It is called a mosaic because it has many parts imbedded in the lipid—a variety of proteins and carbohydrates that have various functions and that act as recognition sites.

98
Q

Compare the peripheral and integral membrane proteins that are associated with the bilayer membrane of the cell.

A

Peripheral membrane proteins are perched on the surface of the membrane, and do not insert into the core of the membrane. Integral membrane proteins contain hydrophobic regions that allow them to be inserted into, and pass through, the core of the bilayer membrane of a cell.

99
Q

What physical factors might limit the maximum efficiency of cell membranes to perform their functions?

A

Temperature might affect the efficiency of cell membranes. When temperature is low, the fatty acids pack more tightly together and the membrane becomes less permeable. The presence of sterols keeps the membrane more fluid and increases its efficiency. The degree to which the fatty acids in the membranes are unsaturated also increases fluidity and efficiency.

100
Q

Explain why ions such as chlorine, potassium, and sodium, despite being relatively small, cannot diffuse straight through the membrane.

A

The plasma membrane is non-polar on the inside, so ionic particles, which are charged, are not attracted to the nonpolar inner layer of the membrane and don’t pass through. Instead they remain attracted to the highly polar water molecules on either side.

101
Q

What molecule is used to obtain energy for active transport? About how much of the total energy use of a cell is devoted to active transport?

A

Adenosine triphosphate (ATP) is used to obtain energy for active transport. About 25% of the total energy use of a cell is devoted to active transport.

102
Q

Cells need a faster method than diffusion to supply water, amino acids, sugars, and ions. Identify the method they use, and explain how it works.

A

The cell has evolved transport proteins that span the plasma membrane. In facilitated diffusion, molecules that would only slowly diffuse through the membrane can be transported by these proteins at a faster rate based on the concentration gradient. In active transport, molecules can be transported against the concentration gradient when energy is supplied to the transport proteins.

103
Q

Explain the methods of symport and antiport in secondary active transport pumps.

A

In symport transport pumps, the solute moves through the membrane channel in the same direction as the driving ion. In antiport transport pumps, the driving ion moves through the membrane channel in one direction, and this provides energy for the active transport of another molecule in the opposite direction.

104
Q

Describe what happens in a voltage-gated channel as it opens and closes.

A

Voltage-gated ion channels open and close depending on voltage, or a difference in electric potential across the membrane caused by unequal concentrations of positive and negative ions on each side. During resting potential voltage-gated channels are closed. As the voltage increases to a threshold, the electronic environment around the voltage–gated channel causes a conformational change in the channel. This conformational change causes the channel to open and allows certain ions to diffuse through it.

105
Q

Compare the Golgi body and the endoplasmic reticulum, noting any similarities and differences.

A

Proteins are synthesized in the rough endoplasmic reticulum, and completed in the Golgi body. They look similar, except the endoplasmic reticulum may have ribosomes on it and is joined to the nuclear envelope.

106
Q

Compare the plasma membrane and the nuclear membrane, noting any similarities and differences.

A

Both control what goes in and out (of the nucleus, or of the cell). The nuclear membrane does not perform endocytosis and exocytosis, but does have transport “pores.” The nuclear envelope is a double layer, consisting of two lipid bilayers that are folded together, while the plasma membrane consists of a single lipid bilayer.

107
Q

Compare exocytosis and endocytosis, noting any similarities and differences.

A

Exocytosis gets rid of waste and exports cell products such as enzymes, while endocytosis ingests nutrients. Endocytosis can be receptor-mediated, which is more specific. Endocytosis makes the membrane smaller as it pinches off a vesicle, while exocytosis makes it bigger as a vesicle joins the membrane.

108
Q

Compare lysosomes and vacuoles, noting any similarities and differences.

A

Lysosomes contain digestive enzymes and help to chop up the building blocks the cell needs, while vacuoles generally only store particles. Lysosomes are usually smaller than vacuoles. Vacuoles in plant cells can expand to help cells hold their shape.

109
Q

How does receptor-mediated endocytosis differ from regular endocytosis?

A

During receptor-mediated endocytosis the molecules to be ingested are captured by recognition proteins, known as receptors, on the outside of the cell. After enough of the particles are attached, the cell folds inward into a clathrin-coated pit, pinches off into a vesicle, and joins with a lysosome to deliver its cargo of nutrients or building blocks to the cell. This molecular recognition does not occur in regular bulk-phase endocytosis.

110
Q

Would you expect muscle cells or fungal cells to have more mitochondira? Explain your reasoning.

A

The many mitochondria in muscle cells give them plenty of energy to move. Fungus cells only need enough energy for stationary life activities. So, muscle cells are expected to have more mitochondria.

111
Q

Ribosomes do not have a membrane. Explain why the functions of ribosomes do not require a membrane.

A

The ribosomes do not have a membrane and do not need one for their function of assembling polypeptide chains (for proteins). However, they do need to be bathed in a soup that contains the building blocks for their protein. Having no membrane ensures that the ribosome has unimpeded access to these building blocks. Once the polypeptide chain is assembled, however, the ribosome injects it into the endoplasmic reticulum where it can complete its tertiary folding. Then, membrane-bound organelles like the endoplasmic reticulum and pinched-off vesicles help to transport the protein where it needs to go.

112
Q

If vesicles are constantly pinching off to carry proteins to the Golgi apparatus, why does the ER not eventually disapper?

A

The vesicles function in a cyclical manner. There are vesicles that go from the ER to the Golgi bodies and there are also vesicles that go from the Golgi bodies to the ER.

113
Q

Alcohol and many drugs are metabolized in the liver. Explain why people who consume large amounts of these substances would have more smooth ER than a person who does not consume large amounts of these substances.

A

Smooth ER is responsible for detoxification of toxic substances such as drugs and alcohol. The liver is responsible for most of your body’s detoxification processes. Liver cells respond to the constant influx of alcohol and other drugs by synthesizing more smooth ER to try and cope with the increased presence of these toxic substances.

114
Q

Suppose that you accidentally place a freshwater fish in a saltwater tank. What would you expect to happen to the cells in the gills of the fish? Explain.

A

When a freshwater fish is accidentally placed in a saltwater tank, the concentrated salt solution will be hypertonic to the cytosol of the fish gill cells. Therefore, water will flow out of the cells into the surrounding solution by osmosis, and the cells will shrink.

115
Q

Medical personnel use an intravenous saline solution to treat dehydration. Why do you think they use this saltwater solution instead of using pure water?

A

Since pure water contains no solutes, giving it intravenously would make the blood hypotonic. As a result, the red blood cells would swell and burst releasing their hemoglobin into the watery plasma.

116
Q

What would happen if you watered a plant with a saltwater solution?

A

Salt water is a hypertonic solution—having a higher concentration of dissolved particles than the plant cells. Water would flow out of the plant cells into the environment by osmosis causing the plant to shrivel and die.

Grade 12 - SBI4U (28 decks)

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