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PHA112 > Cell Structure and Cellular Respiration > Flashcards

Cell Structure and Cellular Respiration Flashcards

1
Q

What are stem cells?

A

Undifferentiated biological cells that can differentiate into specialised cells and divide (mitosis) to produce more stem cells.

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2
Q

In a developing embryo, what can stem cells differentiate into?

A

Ectoderm, endoderm and mesoderm (germ layers)

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3
Q

In adults, stem cells act as a repair system for the body alongside what other cells?

A

Progenitor cells.

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4
Q

What is potency?

A

Potency specifies the differentiation potential of a stem cell

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5
Q

What are totipotent stem cells?

A

Stem cells that can differentiate into embryonic and extraembryonic cell types.

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6
Q

How are totipotent stem cells formed?

A

From the fusion of an egg cell and a sperm cell.

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7
Q

What is a pluripotent stem cell?

A

They are the descendants of totipotent cells and can differentiate into nearly all cells, i.e cells that are derived from any of the 3 germ layers

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8
Q

What are multipotent stem cells?

A

Stem cells that can differentiate into a number of cell types, but only those of a closely related family of cells

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9
Q

What are oligopotent stem cells?

A

stem cells that can differentiate into only a few cell types, such as lymphoid or myeloid stem cells.

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10
Q

What are unipotent cells?

A

Cells that can only produce one type, their own, but have the property of self-renewal, which distinguishes them from non-stem cells.

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11
Q

What are some features of prokaryotic cells?

A
  • no nucleus or membrane bound organelles
  • singular, circular chromosomes
  • cell membrane and cell wall (peptidoglycan)
  • contains ribosomes
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12
Q

what’s the difference between bacterial and Archaean cell walls?

A

Archaean cell walls lack peptidoglycan

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13
Q

What is a gram-positive cell?

A

They have a thick mesh-like cell wall made of peptidoglycan which takes up 50-90% of the cell wall, which stains purple

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14
Q

What is a gram-negative cell?

A

have a thinner layer (10% of cell wall), which will stain pink

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15
Q

What are some features of eukaryotic cells?

A
  • Membrane bound nucleus
  • compartmentalise many cellular functions within organelles and the endomembrane system.
  • have a cytoskeleton for support
  • examples include fungi, plant and animal cells and protozoa.
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16
Q

What makes up a plasma membrane?

A
  • phospholipid bilayer
  • cholesterol
  • proteins (internal and peripheral)
  • attached carbohydrates (glycolipids and glycoproteins)
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17
Q

What are the functions of the plasma membrane?

A
  • barrier between inside and outside of cell
  • controls entry and exit of materials
  • receives chemical and mechanical signals
  • transmits signals between intra- and extra- cellular spaces
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18
Q

What are some features of the phospholipids in the plasma membrane?

A
  • phospholipids are amphipathic
  • organised into a bilayer with the non-polar fatty acid chains in the middle
  • the polar regions of the phospholipids are orientated toward the surface of the membrane
  • hydrophobic fatty acid tails
  • hydrophilic phosphate group head
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19
Q

Why are the polar regions of the phospholipids orientated toward the surfaces of the membrane?

A

this is due to their attraction to the polar water molecules in the extracellular fluid and cytosol

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20
Q

What are some features of cholesterol in the plasma membrane? (6)

A

-cholesterol associates with certain classes of plasma membrane phospholipids and proteins, forming organised clusters
-cholesterol molecules are weakly amphipathic.
-the polar -OH group of the cholesterol forms hydrogen bonds with the polar heads of phospholipids and glycolipids
-stiff steroid rings and hydrocarbon tail are nonpolar
-cholesterol has a temperature dependent effects on membrane fluidity
-warm temp=restrains phospholipid movement
cold temp=maintains fluidity by preventing tight packing

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21
Q

What do the clusters of cholesterol, proteins and phospholipids do?

A

they work together to pinch off portions of the plasma membrane to form vesicles that deliver their contents to various intracellular organelles

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22
Q

What are some features of glycolipids in the plasma membrane?

A
  • carbohydrate groups form a polar head and their fatty acid tails are nonpolar
  • glycolipids appear only on the extracellular side of the membrane, making the bilayer asymmetrical
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23
Q

what are some features of integral proteins in the plasma membrane?

A
  • closely associated with the membrane lipids and cannot be extracted from the membrane without disrupting the lipid bilayer
  • they are amphipathic
  • also referred to as transmembrane proteins
  • some form channels where water and ions can cross the membrane, some form channels for chemical signals
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24
Q

What are some features of peripheral membrane proteins in the plasma membrane?

A
  • they are not amphipathic and do not associate with the nonpolar regions of the lipids in the interior surface if the membrane
  • located at the membrane surface where they are bound to polar regions of the integral membrane proteins
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25
Q

What are some features of proteins in the plasma membrane?

A
  • many membrane proteins are glycoproteins (proteins with carbohydrate groups attached to the ends that protrude into the extracellular fluid)
  • the carbohydrate portions of glycolipids and glycoproteins form an extensive sugary coat called the glycocalyx
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26
Q

What is the glycocalyx?

A

acts as a molecular “signature” which allows cells to recognise one another

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27
Q

What are some examples of plasma membrane junctions? (3)

A

desmosomes, tight junctions and gap junctions

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28
Q

What are intergrins?

A

they are transmembrane proteins in the plasma membrane which bind to specific proteins in the extracellular matrix and link them to membrane proteins on adjacent cells

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29
Q

what are desmosomes?

A

they are accumulations of protein known as dense plaques along the cytoplasmic surface of the plasma membrane. they serve as anchoring points for cadherins

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30
Q

what are cadherins?

A

proteins that extend from then cell into the extracellular space where they link up and bind with cadherins from an adjacent cell

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31
Q

what is the function of desmosomes?

A

they hold adjacent cells firmly together in areas that are subject to considerable stretching, such as the skin

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32
Q

when are tight junctions formed?

A

when the extracellular surfaces of two adjacent plasma membranes join together so that no extracellular space remains between them

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33
Q

where are tight junctions located?

A

in a band around the entire circumference of the cell

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34
Q

what are some features of gap junctions?

A
  • consist of protein channels linking the cytosols of adjacent cells
  • connexins from the two membranes join, forming small, protein lined channels linking the two cells
  • their diameter of 1.5nm limits what can pass between the cytosols of the connected cells to small molecules and ions, such as Na+ and K+, and excludes the exchange of large proteins
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35
Q

name 4 functions of cell membranes

A
  • regulate the passage of substances into and out of cells and between organelles and cytosol
  • detect chemical messengers arriving at the cell surface
  • link adjacent cells together by membrane junctions
  • anchor cells to the extracellular matrix
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36
Q

what is cytoplasm and what is its function?

A

fluid portion of cells that suspends the organelles and other components such as ions, proteins, lipids etc. site of many chemical reactions

37
Q

what is the function of the cytoskeleton

A
  • maintains shape of cell
  • position organelles
  • changes cell shape
38
Q

what are some features of the cytoskeleton and what are their functions? (3)

A
  • microfilaments: also known as actin filaments
  • microtubules: both these and microfilaments can be assembled and disassembled rapidly, allowing a cell to alter these components of its cytoskeletal framework
  • intermediate filaments: once assembled are less readily disassembled
39
Q

what is the structure of a centrosome?

A
  • two centrioles arranged perpendicular to each other: composed of microtubules, 9 clusters of 3
  • pericentriolar material: composed of tubulin that grows the mitotic spindle
40
Q

what is the function of a centrosome?

A

moves chromosomes to ends of the cell during cell division

41
Q

what is the function of the cilia and flagella

A

specialised for movement

42
Q

what is the structure of the flagellum

A

single tail like structure on sperm

43
Q

where is the cilia found?

A

in groups in the respiratory system

44
Q

what is the function of ribosomes?

A

-protein synthesis

45
Q

what are some features of the ribosome?

A
  • consists of ribosomal RNA
  • contain large and small subunits
  • can be attached to the ER or free in cytosol
46
Q

what is the structure of the rough endoplasmic reticulum?

A

network of folded membranes studded with ribosomes

47
Q

what is the function of the smooth endoplasmic reticulum? (4)

A
  • lipid synthesis
  • release of glucose in liver cells into bloodstream
  • drug detoxification (especially in liver cells)
  • storage and release of Ca2+ in muscle cells (sarcoplasmic reticulum)
48
Q

what is the structure of the Golgi complex?

A

flattened membrane with bulging edges

49
Q

what are the functions of the Golgi complex?

A

-modify proteins to glycoproteins and lipoproteins that:
.become parts of the plasma membranes
.are stored in lysosomes
.are exported by exocytosis

50
Q

what is the structure of lysosomes?

A
  • spherical or oval surrounded by single membrane

- typical cell may contain several hundred lysosomes

51
Q

what are the functions of lysosomes?

A
  • contain variety of digestive enzymes
  • help in final process of digestion within cells
  • carry out autophagy (destruction of warn out parts of cell) and death of old cells (autolysis)
52
Q

what is tay-sachs?

A

a hereditary disorder where one missing lysosomal enzymes leads to nerve destruction

53
Q

what is the structure of peroxisome?

A

a moderately dense oval bodies enclosed by a single membrane

54
Q

what are the functions of peroxisomes?

A
  • consumes molecular oxygen an undergoes reactions that remove hydrogen from organic molecules including lipids, alcohol and potentially toxic ingested substances
  • it detoxifies and is abundant in liver
55
Q

what is the structure of proteasomes?

A

tiny barrel shaped structure that contain proteases (proteolytic enzymes)

56
Q

what is the function of proteasomes?

A
  • digest unneeded or faulty proteins

- faulty proteins accumulate in brain cells in persons with Parkinson’s or Alzheimer diseases

57
Q

what is the structure of the mitochondria?

A
  • many folded membranes (cristae) and liquid matrix containing enzymes
  • have some DNA, ribosomes (can make proteins)
58
Q

what is the function of the mitochondria?

A

major site of ATP production, O2 utilisation and CO2 formation
-contains enzyme active in Krebs cycle and oxidative phosphorylation

59
Q

what is the structure of the nucleus?

A
  • round structure surrounded by nuclear envelope
  • contains nucleolus: makes ribosomes that pass into cytoplasm through nuclear pores
  • within the nucleus, DNA, in association with proteins, forms a fine network of threads known as chromatin
60
Q

what is the function of cellulose in plants?

A

structure of the cell wall

61
Q

what is the function of glycogen and starch?

A

storage

62
Q

what is catabolism?

A

the breakdown of compounds into simpler molecules

63
Q

why is catabolism useful? (2)

A

it releases energy and provides smaller building blocks

64
Q

what is anabolism?

A

building a more complicated molecule from smaller units (eg amino acids->proteins)

65
Q

what is cellular respiration?

A

the breakdown of glucose in many small steps to make ATP. it involves breaking bonds and moving electrons from one molecule to another

66
Q

what do electrons ‘carry’?

A

energy

67
Q

what is the balanced respiration equation?

A

C6H12O6+6O2–>6CO2+H2O+ATP

68
Q

what does the process of oxidation include? (5)

A
  • adding O
  • removing H
  • loss of electrons
  • releases energy
  • exergonic
69
Q

what does the process of reduction include? (5)

A
  • removing O
  • adding H
  • gain of electrons
  • stores energy
  • endergonic
70
Q

what happens in the redox reaction?

A

glucose is oxidised and oxygen is reduced

71
Q

how do electrons move in biology?

A

they cannot move freely, they move as part of a hydrogen atom

72
Q

what is NAD+?

A

a coenzyme which regulates the activity of the enzyme it is bound to

73
Q

what is NAD+ derived from?

A

the vitamin nicotinic acid/niacin

74
Q

what molecules can NAD+ accept in order to be reduced? and what is it reduced to?

A

it accepts two electrons and two hydrogen atoms to be reduced to NADH

75
Q

what is NADH used for?

A

making ATP in the electron transport chain

76
Q

give an example of NADH production

A

formation of oxaloacetate from maltate in the Krebs cycle

77
Q

what is FAD?

A

a cofactor that binds strongly to an enzyme

78
Q

how is FAD synthesised?

A

from vitamin B2 oe riboflavin

79
Q

how is FAD reduced and what is it reduced to?

A

it accepts two hydrogens and two electrons to be reduced to FADH2

80
Q

how many electrons are transferred per hydrogen

A

two

81
Q

give an example of FADH2 production

A

the formation of fumarate from succinate in the Krebs cycle

82
Q

how does ATP provide energy?

A

the hydrolysis of the high energy phosphate bond

83
Q

why is ATP structurally unstable?

A

due to the repulsion between ionised oxygen atoms which are all in close proximity

84
Q

what are the 4 key stages of the complete oxidation of glucose?

A
  • glycolysis
  • pyruvate oxidation
  • krebs cycle
  • electron transport chain chemiosmosis
85
Q

what occurs during the cori cycle?

A

lactate produced during anaerobic glycolysis is transported to the liver and converted to glucose

86
Q

what does the cori cycle require to occur?

A

ATP

87
Q

where does the glucose that is produced in the cori cycle go?

A

supplied back to the muscle

88
Q

why do cancer cells use a low yield ATP generation system? (3)

A

lactate is thought to promote

  • blood vessel formation
  • metastasis and invasion
  • immune escape
89
Q

where does the oxidation of pyruvate occur?

A

in the mitochondria

PHA112 (10 decks)

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