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IB BIO SL > 1. Cell Biology > Flashcards

1. Cell Biology Flashcards

1
Q

What does cell theory state?

A

Cell are the fundamental building blocks of all living organisms

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2
Q

What are the four common features of cells described by cell theory?

A

1) Every living cell is surrounded my a membrane, which separates the cell contents from everything else outside
2) Cells contain genetic material which stores all of the instructions needed for the cell’s activities
3) Many of these activities are chemical reactions, catalyzed by enzymes produced inside the cell
4) Cells have their own energy release system that powers all of the cell’s activities

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3
Q

What did Robert Hooke do that was so special?

A

Was the first to use the word cell for structures in living organisms- he did this after examining cork cells under a microscope in 1665. He found general trends among cells of various tissues from many living organisms.

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4
Q

What can be placed on temporary mounts to help display cells?

A

Water or stain (often methylene blue stain)

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5
Q

What is the magnification formula?

A

Magnification=size of image / actual size of specimen

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6
Q

What are three atypical examples that bring cell theory into question?

A

1) striated muscle
2) aseptate fungal hyphae
3) giant algae

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7
Q

What are the seven functions of life that unicellular organisms must be able to carry out?

A

1) Nutrition
2) Metabolism
3) Growth
4) Response to environment
5) Excretion of waste
6) Homeostasis
7) Reproduction

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8
Q

What kind of surface area to volume ratio is favourable for a cell and why?

A

Large SA:V Ratio
Larger ratio = Substances can enter cells faster, and waste can be excreted faster
Smaller ratio= cells may overheat because they aren’t losing heat as fast as they are metabolizing it

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9
Q

Name two unicellular organisms

A

Paramecium

Chlamydomonas

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10
Q

Briefly describe Stargardt’s disease

A

A genetic disease that develops in children usually due to a recessive mutation of a gene, which causes the malfunction of a membrane protein used for active transport in retina cells, consequently causing the degeneration of photoreceptive cells in the retina which can progressively worsen eyesight.

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11
Q

How might stem cells be used to treat Stargardt’s disease?

A

Stem cells could be injected into the retina

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12
Q

Describe how stem cells are used for the treatment of a condition other than Stargardt’s disease

A

Removing stem cells from an adult with leukemia (and then freezing the cells to store them) before they undergo chemotherapy allows those stem cells to be injected back in after the chemotherapy treatment so that the body can continue to produce blood cells.

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13
Q

Why was the invention of the electron microscope significant in scientific research?

A

It allowed scientists to view the ultrastructure of cells

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14
Q

What is resolution?

A

Making the seperate parts of an object distinguishable by eye.

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15
Q

What is the maximum resolution of a light microscope?

A

0.2 micrometers

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16
Q

Why is the maximum resolution of a light microscope limited?

A

Because it is limited by the wavelength of light (400-700nm)

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17
Q

What is the maximum resolution of an electron microscope?

A

0.001 micrometers / 1nm

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18
Q

What is the maximum resolution of an unaided human eye?

A

0.1mm / 100micrometers

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19
Q

How do prokaryotes divide?

A

By binary fission

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20
Q

List four advantages to being compartmentalized

A

1) Enzymes and substrates for a particular purpose can be much more concentrated than if they were spread throughout the cytoplasm
2) Substances that could damage the cell can be contained within the membrane of an organelle
3) pH or other conditions necessary for a particular process can be maintained at an ideal level in different parts of the cell
4) Organelles and the contents within them can be moved around the cell

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21
Q

What are the two types of glands and how does their mechanism of release differ?

A

Exocrine glands: secrete product into a duct

Endocrine glands: Secrete product (hormones) directly into the bloodstream

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22
Q

What is the cell type that carries out most photosynthesis in the leaf?

A

Palisade mesophyll

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23
Q

What size of ribosomes do prokaryotes have?

A

70s

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24
Q

What size of ribosomes do eukaryotes have?

A

80s

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25
Q

What does amphipathic mean?

A

Part is hydrophilic and part is hydrophobic

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26
Q

What is the Davson-Danielli model?

A

Proposed that there were layers of protein adjacent to the phospholipid bilayer, on both sides of the membrane

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27
Q

What is the primary function of a cell membrane?

A

To form a barrier through which ions and hydrophilic molecules cannot easily pass.

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28
Q

What are six examples of functions of primary membrane proteins other than the primary function of a cell membrane?

A

Hormone bonding sites/ hormone receptors (eg. insulin receptor)
Active sites for immobilized enzymes on outside of membrane (eg. in small intestine)
Cell adhesion to form tight junctions between groups of cells in tissues and organs.
Cell-to-cell communication (eg. receptors for neurotransmitters at synapses)
Channels for passive transport to allow hydrophilic particles across by facilitated diffusion
Pumps for active transport which use ATP to move particles across the membrane

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29
Q

What are integral proteins?

A

They are hydrophobic on at least part of their surface and are therefore embedded in the hydrocarbon chains in the centre of the membrane. Many are transmembrane.

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30
Q

What are peripheral proteins?

A

Hydrophilic on their surface, so not embedded in membrane. Most are attached to the surface of integral proteins and often this attachment is reversible. Sometimes they have a single hydrocarbon chain attached to them, inserted into the membrane to anchor the protein to the membrane surface.

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31
Q

Describe the structure of cholesterol as it pertains to its position in cell membranes

A

Most of the molecule is hydrophobic so it is attracted to the hydrocarbon tails in the centre of the membrane, but one end of the cholesterol molecule has a hydroxyl (-OH) group which is hydrophilic, and hence attracted to the phosphate heads on the membrane periphery. Cholesterol molecules are thus in between phospholipids in the membrane.

32
Q

What is the role of cholesterol in membranes?

A

It controls the fluidity of animal cell membranes by disrupting the regular packing of hydrocarbon tails of phospholipid molecules. This prevents them crystallizing and behaving as a solid, but also restricts molecular motion and therefore the membrane fluidity. Cholesterol also reduced permeability to hydrophilic particles such as sodium ions and hydrogen ions. Its shape can also help membranes curve into a concave shape which is helpful for the formation of vesicles during endocytosis.

33
Q

Through what process are digestive enzymes released from gland cells?

A

exocytosis

34
Q

What process builds up the concentration for nerve impulses in axons?

A

Active transport carried out by a sodium-potassium pump protein

35
Q

Summarize the six steps of a sodium-potassium pump cycle in an axon

A
  1. Interior of pump is open to axon and three sodium ions enter the pump and attach to their binding sites
  2. ATP transfers a phosphate group from itself to the pump which causes the pump to change shape and its interior closes
  3. The interior of the pump opens to the outside of the axon and the three sodium ions are released
  4. Two potassium ions from the outside can then enter and attach to their binding sites
  5. Binding of potassium causes release of the phosphate group which causes the pump to change shape so that it is again only open to the inside of the axon
  6. The interior of the pump opens to the inside of the axon and the two potassium ions are released. Sodium ions can now enter and bind to the pump again.
36
Q

Via what process do the movements of sodium and potassium ions across the axon membrane during a nerve impulse occur?

A

Facilitated diffusion through sodium and potassium channels

37
Q

Describe size considerations of the pore that allows potassium ions to pass, along with those of the potassium ions

A

The pore is 0.3nm wide at its narrowest.
Potassium ions are slightly smaller than 0.3nm, but when dissolved they are bonded to a shell of water molecules that makes them too large to pass through the pore so the bonds with water must be broken. The potassium instead temporarily bonds with a series of amino acids in the narrowest part of the pore. After passing through the ion can become associated with a shell of water molecules again.

38
Q

Why are the size considerations of the pore in potassium channels important?

A

Other positively charged ions are either too large to fit or too small to form bonds with the amino acids in the narrowest part of the pore so they can’t shed their shell of water molecules

39
Q

How are potassium channels in axons guarded?

A

They are voltage gated

40
Q

Describe the process of the ball and chain mechanism of opening and closing potassium channels

A

If an axon has relatively more positive charges outside than inside, potassium channels are closed.
When there are relatively more positive charges inside, the potassium channels open and potassium ions diffuse through but the channel closes rapidly again. The rapid closing seems to be due to the “ball” which is an extra globular protein attached by a flexible chain of amino acids. The ball fits inside the open pore within milliseconds of its opening and remains there until the channel returns to its original closed state

41
Q

How can osmolarity be estimated?

A

By bathing samples of tissues in hypotonic and hypertonic solutions

42
Q

What are four osmotically active solutions often used in osmosis experiments?

A

Glucose, sodium ions, potassium ions, and chloride ions

43
Q

What is the osmolarity of a solution?

A

The total concentration of osmotically active solutes

44
Q

What are the units for measuring osmolarity and what is the normal level of human tissue

A

osmoles or milliosmoles (mOsm)

Human tissue about 300 mOsm

45
Q

What is an isotonic solution?

A

Has the same osmolarity as a tissue

46
Q

What is a hypertonic solution?

A

Has a higher osmolarity than a tissue

47
Q

What is a solution with a lower osmolarity than a tissue called?

A

hypotonic

48
Q

What kind of osolarity must tissues or organs to be used in medical procedures be bathed in and why?

A

Must be bathed in a solution with the same osmolarity as (iotonic to) the cytoplasm to prevent osmosis.
In a hypertonic solution, water leaves the cells so their cytoplams shrinks in volume but the area of the plasma membrane does not change so it develops indentations.
In a hypotonic solution, cells take in water by osmosis and swell up which may eventually cause them to burst leaving ruptured plasma membranes called red cell ghosts.

49
Q

How can cells be formed?

A

Only by the division of pre-existing cells

50
Q

What is the formation of living organisms from non-living matter called?

A

Spontaneous generation

51
Q

Who preformed the most famous experiments that showed spontaneous generation does not now occur on Earth

A

Louis Pasteur

52
Q

What did Louis Pasteur’s most famous experiment consist of?

A

He placed samples of broth in flasks with long necks (swan-necked) then melted and shaped the necks into a variety of shapes. He then boiled the broth in some of the flasks to kill any organisms present but left other unboiled as controls. Fungi and other organisms soon appeared in the unboiled flasks but not in the boiled ones, even after long periods of time. The broth was in contact with air (it had been suggested air was necessary for spontaneous generation but none occured). He then snapped some of the flasks’ necks to leave a shorter neck and organisms were soon apparent in these flasks and decomposed the broth.

53
Q

How may carbon compounds such as sugars and amino acids arisen from non living material?

A

Methane, hydrogen, and ammonia- thought to be representative of the atmosphere of the early Earth- when zapped with electrical charges simulating lightning can produce amino acids and other carbon compounds needed for life.

54
Q

How may carbon compounds have been assembled into polymers from non living material?

A

A possible site for the origin of the first carbon compounds is around deep-sea vents, which are cracks in the Earth’s surface, characterized by gushing hot water carrying reduced inorganic chemicals such as iron sulphide which represent readily accessible supplies of energy which could be used as a source of energy for the assembly of these carbon compounds into polymers.

55
Q

How might membranes have formed from non living materials?

A

If phospholipids or other amphipathic carbon compounds were among the first carbon compounds, they would have naturally assembled into bilayers which have been shown to readily form vesicles that resemble the plasma membrane of a small cell which could allow different internal chemistry from that of the surroundings to develop.

56
Q

How might a mechanism for inheritance developed out of non living matter?

A

Maybe earlier in evolution RNA was the genetic material because it can store information in the same way as DNA but it is both self-replicating and can itself act as a catalyst.

57
Q

What does endosymbiotic theory state in relation to mitochondria?

A

Mitochondria were once free-living organisms that had developed the process of aerobic cell respiration. Larger prokaryotes that could only respire anaerobically took mitochondra in by endocytosis and allowed them to continue to live in their cytoplasm and they have evolved since.

58
Q

What are four features that suggest mitochondria and chloroplasts (both of which are no longer capable of living independently) evolved from independent prokaryotes.

A

1) they have their own genes, on a circular DNA molecule like that of prokaryotes
2) they have their own 70s ribosomes of a size and shape typical of some prokaryotes
3) they transcribe their DNA and use the mRNA to synthesize some of their won proteins
4) they can only be produced by divison of pre-existing mitochondria and chloroplasts

59
Q

What occurs to mitochondria and chloroplasts in a cell during interphase?

A

The numbers of mitochondria in the cytoplasm increase (in plant cells and algae number of chloroplasts increase).

60
Q

Name the phases of interphase and briefly describe what is occuring

A

G1: cellular components apart from the chromosomes are duplicated
S: cell replicates all the genetic material in the nucleus- chromosomes (some do not progress beyond G1 because they are never going to divide so do no need to prepare for mitosis- these enter G0 phase which may be temporary or permanent)
G2

61
Q

How do chromosomes condense? What helps this happen?

A

By supercoiling. Histones are proteins that are associated with DNA in eukaryote chromosomes and help with supercoiling and enzymes are also involved.

62
Q

What occurs in prophase of mitosis?

A

Chromosomes supercoil,
Nucleolus breaks down
Microtubules grown from structures called microtubule organizing centres (MTOC) to form a spindle-shaped array that links the poles of the cell
At the end of prophase the nuclear membrane breaks down

63
Q

What occurs in metaphase of mitosis?

A

Microtubules continue to grow and attach to the centromeres on each chromosome
The two attachment points on opposite sides of each centromere allow the chromatids of achromosome to attach to microtubules from different poles
Microtubules are put under tention to test whether attachment is correct (happens by shortening the microtubules at the centromere)
If attachment is correct, chromosomes remain on cell equator

64
Q

What occurs in anaphase of mitosis?

A

Each centromere divides which allows pairs of sister chromatids to separate
Spindle microtubules pull them rapidly towards cell poles

65
Q

What occurs in telophase of mitosis?

A

Chromatids have reached the poles and are now called chromosomes.
Chromosomes are pulled into a tight group near the MTOC and a nuclear membrane reforms around them
Chromosomes uncoil
Nucleolus is formed
Usually at this point cell is already dividing and entering interphase again

66
Q

What is the formula for the mitotic index?

A

mitotic index=number of cells in mitosis/total number of cells

67
Q

Outline cytokinesis in animal cells

A

Plasma membrane is pulled inward around equator of the cell to form a clevage furrow by using a ring of actin and myosin (contractile protein). Cleavage furrow reaches the centre and the cell is pinched apart into two daughter cells

68
Q

Outline cytokinesis in plant cells

A

Vesicles are moved to the equator and fuse to form tubular structures across the equator- as more vesicles fuse, the tubular structures merge to form two layers of membrane across the whole of the equator which develop into the plasma membranes of the two daughter cells and are connected to the existing plama membranes at the sides of the cell completing cytoplasm division.

69
Q

How do plant cells build their own cell walls adjacent to the equator after cytokinesis?

A

They bring in pectins and other substances in vesicles and deposit via exocytosis vetween the two new membranes which forms the middle lamella that will link the new cell walls. Both daughter cells then bring cellulose to the equator and depositing it by exocytosis build their own cell walls adjacent to the equator.

70
Q

What do cyclins do?

A

Control the cell cycle

71
Q

How do cyclins do their job?

A

They bind to enzymes called cyclin-dependent kinases which then become active and attache phosphate groups to other proteins in the cell which triggers the other proteins to become active and carry out tasks specific to one of the phases of the cell cycle: unless cyclins reach a threshold concentration, the cell does not progress to the next stage of the cell cycle.

72
Q

What are primary tumors?

A

Benign. A group of cells formed when a tumour cell has been formed and divides repeatedly to form two, then four, then eight cells, etc.

73
Q

What is the movement of cells from a primary tumour to set up secondary tumours in other parts of the body called?

A

Metastasis

74
Q

What are carcinomas?

A

Malignant tumours

75
Q

What are secondary tumours?

A

tumours that became detached and moved elsewhere in the body- they are malignant

IB BIO SL (1 decks)

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