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deca > B2.1 - 2.3 Bio > Flashcards

B2.1 - 2.3 Bio Flashcards

1
Q

What is the plasma membrane made of?

A

Bilayer of phospholipids and other amphipathic molecules form a continuous sheet to control the passage of substances

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2
Q

Phospholipid molecules

A

Phosphate head and two hydrocarbon tails

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3
Q

Are the two hydrocarbon tails hydrophobic or hydrophilic?

A

hydrophobic (scared of water)

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4
Q

Does the membrane core have low permeability or high permeability to all hydrophilic particles?

A

Low

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5
Q

low membrane permeability…

A

makes it possible to maintain differences in concentration (concentration gradients) across a membrane

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6
Q

Examples of hydrophilic particles

A

Ions with positive or negative charge, polar molecules, glucose

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7
Q

Examples of low permeability:

A

large molecules: proteins, starch, glycogen, cellulose
polar molecules: glucose, amino acids
ions: chloride, sodium, potassium, phosphate

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8
Q

Solutes near membrane…

A

might penetrate between the hydrophilic phosphate heads of the phospholipids

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9
Q

Larger the molecule…

A

lower the permeability

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10
Q

Simple Diffusion

A
  • smaller, nonpolar (hydrophobic) molecules
  • concentration gradient is high to low
  • ATP is NOT required
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11
Q

Example of simple diffusion

A

if oxygen concentration inside a cell is reduced from aerobic respiration, oxygen will pass through membrane by passive (simple) diffusion

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12
Q

Polar molecules & simple diffusion?

A

Can diffuse at low rates

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13
Q

Two groups of membrane proteins

A

Integral proteins & peripheral proteins

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14
Q

Integral proteins

A
  • hydrophobic on part of their surface and embedded in hydrocarbon chains in center of membrane
  • may fit in both or one of phospholipid layers
  • some are transmembrane proteins
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15
Q

Transmembrane (subset of integral) proteins

A

they extend across the membrane with hydrophilic parts projecting through the regions of phosphate heads on either side

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16
Q

Peripheral proteins

A
  • Hydrophilic on surface, not embedded in membrane
  • attached to surface of integral proteins
  • some have a single hydrocarbon chain attached to them, to anchor protein to membrane surface
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17
Q

the more active a membrane…

A

the higher its protein content (ie in membranes of chloroplasts and mitochondria, active in photosynthesis and respiration

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18
Q

Osmosis

A

Due to differences in the concentration of substances dissolved in water

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19
Q

How do substances dissolve?

A

By forming intermolecular bonds with water molecules (to restrict movement of water molecules)

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20
Q

Higher solute concentration…

A

lower concentration of water molecules that are free to move

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21
Q

net movement of water

A

lower solute concentration to higher solute concentration

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22
Q

Aquaporins (transport protein)

A

Increase membrane permeability to water (ie kidney cells that reabsorb water, root hair cells that absorb water from soil)

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23
Q

Channel protein

A

Integral transmembrane protein with a pore that connects the cytoplasm to the aqueous solution outside the cell (net movement high to low)

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24
Q

Facilitated diffusion

A

one in which channel proteins are required (passive, no energy)

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25
Q

Pump proteins (active transport)

A
  • use energy so they carry out active transport
  • only move particles across membrane in one direction
  • move against concentration gradient (low to high)
  • ATP is used
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26
Q

Semi permeable membrane

A

allows passage of certain small solutes and is freely permeable to the solvent (ie facilitated diffusion and active transport) (nonexamples: channel and pump proteins, specific to particular particles, simple diffusion: not selective only depends on size and polarity of particles)

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27
Q

controlling movement of molecules:

A

change KE –> manipulate temp –> change concentration gradient –> manipulate concentration –> change SA/V ratio –> manipulate surface area

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28
Q

Glycoproteins

A

conjugated proteins w carbohydrates as non-polypeptide component & component of plasma membrane of cells, protein part embedded in membrane and carb part projecting out into the exterior environment of cell

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29
Q

Glycolipids

A
  • molecules consisting of carbs linked to lipids
  • carb is single monosaccharide or short chain of 2-4 sugar units
  • lipid contains one or two hydrocarbon chains, which natrually fit into hydrophobic core of membranes
  • occur in plasma membrane of all eukaryotic cells, w attached carb projecting outwards into the extracellular environment
  • have a role in cell recognition
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30
Q

glycoproteins and glycolipids

A

form a carbohydrate rich layer on outer face of plasma membrane of animal cells, w an aqueous solution in gaps between carbs (called the glycocalyx)

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31
Q

vesicles

A

small sac of membrane w a droplet of fluid inside, can be used to move materials around cells

32
Q

movement of vesicles

A

protein is synthesized by ribosomes on the rER and accumulates –> vesicles containing the proteins bud off the rER and carry to Golgi apparatus

33
Q

Endocytosis

A
  • small region of membrane is pulled and pinched off
  • use ATP
  • these vesicles contain water and solutes from outside cell
  • often, they contain larger molecules needed by the cell that cannot pass across the plasma membrane
34
Q

exocytosis

A
  • vesicles fuse with a target membrane and disappear
  • transfers all the contents of a vesicles across the membrane
  • if a vesicles fuses w plasma membrane, contents are expelled from cell
  • can also be used to expel waste products
35
Q

example of exocytosis

A

polypeptides that have been processed in the Golgi apparatus are carried to the plasma membrane in vesicles for exocytosis

36
Q

No membrane organelles

A

ribosomes, centrioles, microtubules, proteasomes, nucleoli

37
Q

single membrane organelles

A

vesicles, vacuoles, rER, sER, golgi, lysosome

38
Q

double membrane organelles

A

nuclei, mitochondria, chloroplast, amyloplast, chromoplast

39
Q

Why aren’t cell walls organelles

A

Outside the plasma membrane, so extracellular structures rather than organelles

40
Q

Why isn’t the cytoskeleton an organelle?

A

it consists of narrow protein filaments spread through much of the cell, not discrete enough

41
Q

Why isn’t the cytoplasm n organelle?

A

not a discrete structure

42
Q

Advantage of seperation of nucleus and cytoplasm into seperate compartments?

A

(Eukaryotes): Keeping chromsomes inside nucleus safeguards the DNA

43
Q

Advantages of compartmentalization in cytoplasm of cells

A
  1. Enzymes and substrates can be much more concentrated
  2. Substances that can cause damage to cell can be kept inside membrane of organelle (ie digestive enzymes in lysosome)
  3. Conditions such as pH can be maintained at ideal level
  4. Organelles with their contents can be moved around
  5. Larger area of membrane availible for processes that happen within or across membranes
44
Q

Fertilization

A

fusion of male and female gamete to produce a single cell

45
Q

Zygote

A

an unspecialized cell produced from fertilization

46
Q

Cell divides repeatedly to generate an embryo of many cells

A

zygote -> 2 cell stage -> 4 cell stage -> 16 cell stage -> morula -> blastocyst (inner cell mass make the animal, outer cells give rise to placenta) -> embryo

47
Q

mitosis

A

ensures that cells in an embryo are all genetically identical

48
Q

as embryo grows

A

cells become specialized for specific functions

49
Q

differentation

A

development of cells in different ways to carry out specific functions aka the process by which cells in a multicellular organism become “different” from one another -> specialzied in structure and function

50
Q

gene expression

A

when a certain gene is being used in a cell

51
Q

advantage of differentation

A

division of labor due to cell specialization -> greater efficiency

52
Q

multicellular organisms:

A

have the same genome

53
Q

How cells differentiate into what?

A
  1. chemical signals from nearby cells
  2. physical contact w nearby cells
  3. chemicals inside the cytoplasm
  4. positional information
54
Q

Gradients of signaling chemicals

A

indicate a cell’s position in the embryo and determine which pathway of differentiation it follows (ie gradients of retinoic acid guide differentiation of cells in the development of forelimbs, pancreas, lungs, kidneys)

55
Q

properties of stem cells

A
  1. can divide repeatedly
  2. can remain or differentiate into specific cell type
56
Q

precise location of stem cells within a tissue

A

stem cell niche

57
Q

totipotent stem cells

A

early-stage embryos composed entirely of stem cells, can differentiate into any cell type

58
Q

pluripotent stem cells

A

still capable of differentiating into a range of cell types, but not all
EMBRYONIC STEM CELLS ARE PLURIPOTENT

59
Q

multipotent stem cells

A

adult body, can differentiate into several types of mature cell

60
Q

stem cells:

A
  1. necessary for embryonic development
  2. necessary for repair of adult body - to replace damaged or lost somatic/body cells
  3. gaining more and more importance for therapeutic purposes
61
Q

rate at which substances cross the plasma membrane

A

depends on its surface area

62
Q

If ratio (SA/V) is too small:

A
  1. substances will not enter the cell as quickly as they are required and waste products will accumulate
  2. cells may overheat bc metabolism produces heat faster than it is lost
63
Q

Type I pneumocyte in alveoli

A
  • adapted for diffusion of O2 and CO2
  • little need for mitochondria or other organelles and volume of cytoplasm is very small
  • very thin, distance less, increases rate of gas exchange
64
Q

type II pneumocytes in alveoli

A
  • more numerous (90%), occupy only 5% of SA
  • contain mitochondria, rER, Lysosome
  • large amounts of phospholipids are synthesized in the cytoplasm and stored in lamellar bodies (vesicles containing many layers of phospholipids and some proteins)
  • PRODUCE SURFACTANT
65
Q

why is the alveolus lined by a film of moisture?

A

allows oxygen to dissolve and then diffuse to the blood in the alveolar capillaries

66
Q

surfactant

A

layers of phospholipids and proteins, reduce surface tension so that the alveolus does not collapse on itself

67
Q

why do phospholipids form bilayers in water?

A

shields the hydrophobic tails from the aqueous environment and exposes the hydrophilic heads to the extracellular fluid and cytoplasm

68
Q

Compare the location and timing of initiation of transcription and translation between prokaryotic and eukaryotic cells.

A

Prokaryotic transcription and translation occur simultaneously in the cytoplasm, and regulation occurs at the transcriptional level. Eukaryotic gene expression is regulated during transcription and RNA processing, which take place in the nucleus, and during protein translation, which takes place in the cytoplasm.

69
Q

Outline why post-transcriptional modification of RNA is not possible in prokaryotic cells.

A

Post-transcriptional modifications to DNA are usually unnecessary in prokaryotic organisms due to the lack of introns and exons. Prokaryotic DNA exists as a single continuous strand, so the mRNA transcribed from the DNA is already a complete transcription product, and does not need to be processed further.

70
Q

Outline the benefit of compartmentalization of lysosomes and phagocytic vacuoles in cells.

A

Phagocytic vacuole is specialized to engulf foreign objects, and is then fused with lysosome which contains digestive enzymes to break down the waste. Compartmentalization makes sure the rest of the cell is protected from these potentially dangerous substances.

71
Q

Describe the structure and function of the pores in the nuclear membrane

A

Structure: hole in the nuclear membrane
Function: creates selective passageway which transports big molecules and small, charged molecules between nucleus and cytoplasm
-proteins move into the nucleus
-ribosomes move out of the nucleus
-different types of RNA for protein synthesis move out

72
Q

alveolar epithelum

A

represents a physical barrier that protects from environmental insults by segregating inhaled foreign agents and regulating water and ions transport, thereby contributing to the maintenance of alveolar surface fluid balance.

73
Q

List two examples of cells that are specialized for exchange of materials and have adaptations to increase the SA:V ratio.

A
  1. Intestinal tissue of the digestive tract may form a ruffled structure (villi) to increase the surface area of the inner lining.
  2. Alveoli within the lungs have membranous extensions called microvilli, which function to increase the total membrane surface.
74
Q

List three adaptations of cells that maximize the SA: volume ratio.

A
  1. Long extensions, such as in neurons.
  2. Thin, flattened shape, such as in red blood cells.
  3. Microvilli, such as in small intestine epithelial cells.
75
Q

Describe how the structure of the alveoli increases surface area for gas exchange.

A

They are surrounded by a rich capillary network to increase the capacity for gas exchange with the blood. They are roughly spherical in shape, in order to maximise the available surface area for gas exchange.

76
Q

cholesterol in membrane

A

regulates fluidity -> less fluid at higher temps, more fluid at lower temps

deca (4 decks)

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