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Biosci 101 > 02 Cell and Molecular Biology > Flashcards

02 Cell and Molecular Biology Flashcards

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1
Q

Name the 5 characteristics common to all cells

A
  • they arise from pre-existing cells
  • genetic information is stored in DNA in chromosomes
  • proteins are synthesized on ribosomes
  • a selectively permeable plasma membrane encloses every cell
  • sub-cellular components are suspended in a semifluid substance called cytosol
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2
Q

1 mm is how many micrometres μm

A

1000 μm

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3
Q

how many nanometres are there in 1 μm

A

1000

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4
Q

What electron microscopy must be used to view protein and lipid structures?

A

Electron microscopy

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5
Q

What electron microscopy must be used to view most plant and animal cells?

A

Light microscopy

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6
Q

What electron microscopy must be used to view mitochondria?

A

Light microscopy

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7
Q

What electron microscopy must be used to view viruses and ribosomes ?

A

Electron microscopy or super resolution microscopy (light)

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8
Q

What are the three parameters of microscopy?

A

magnification, resolution, contrast

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9
Q

What is magnification?

A

enlargement of an image

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10
Q

What is resolution?

A

a measure of the clarity of an image

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11
Q

What is contrast?

A

the difference in brightness between light and dark areas of an image

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12
Q

What are the two subdivisions of electron microscopy?

A

Scanning electron microscope (SEM)
Transmission electron microscope (TEM)

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13
Q

What is light microscopy used for?

A

used to visualise whole cells and large sub-cellular organelles

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14
Q

What is Electron microscopy used for?

A

Instead of lights, EM’s use electromagnets to focus a beam of light through the specimen (TEM) or onto its surface (SEM)

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15
Q

Describe the difference between TEM and SEM

A

resolution
- TEM, 2nm
- SEM, 10 nm

used for:
- TEM, study internal cell structure eg organelles, proteins, nucleic acids
- SEM, study cell surface and generate 3D images

beam focus:
- TEM focus beam of electrons through the specimen
- SEM focus beam of electrons on surface of specimen

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16
Q

What is the purpose of cell fractionation ?

A

Isolates cell components based on size and density

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17
Q

How can cells be separated using cell fractionation ?

A

blender to break the membrane - forms homogenate - centrifuged

larger organelles will deposit at the bottom at a lower centrifugation force, smaller organelles will require larger centrifugation force to deposit at the bottom

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18
Q

List the 8 components of prokaryotic cells

A
  1. nucleoid - DNA concentrated here but not enclosed by membrane
  2. little or no structure or organelles
  3. ribosomes - synthesise proteins
  4. plasma membrane - encloses cytoplasm
  5. cell wall - rigid structure
  6. glycocalyx - outer coating consisting of a capsule or slime layer
  7. fimbria - attachment to other bacteria
  8. flagella - locomotion
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19
Q

What structures do plant cells have that animal cells lack? Explain their function.

A

cellulose cell wall - protects cell and maintains shape
central vacuole - storage and breakdown of waste products
chloroplasts - photosynthetic organelle

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20
Q

State what the defining feature is of eukaryotic cells

A

have a membrane bound nucleus which contains most of the cell’s DNA

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21
Q

_____ are surface appendages that allow a bacterium to stick to a surface.

A

Fimbria

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22
Q

What is a function of a bacterium’s capsule?

A

protection

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23
Q

Where is a bacterial cell’s DNA found?

A

nucleoid region

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24
Q

Which organelle carries out cellular respiration?

A

mitochondrion

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25
Q

What is the function of mitochondria?

A

Mitochondria convert the chemical energy of organic molecules to chemical energy in the form of ATP.

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26
Q

What is the name given to the double membrane that encloses the nucleus?

A

nuclear envelope

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27
Q

The _____ is composed of DNA and protein.

A

chromatin

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28
Q

Ribosomal subunits are manufactured by the _____.

A

nucleolus

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29
Q

_____ are the sites of protein synthesis.

A

ribosomes

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30
Q

Which organelle manufactures proteins bound for secretion out of the cell?

A

rough endoplasmic reticulum

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31
Q

briefly describe the process of protein synthesis on a rough er ribosome to a golgi.

A

The ribosomes associated with the rough ER synthesize secretory proteins bound for the exterior of the cell. Further processing and packaging occurs in the Golgi apparatus.

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32
Q

Where is calcium stored?

A

smooth endoplasmic reticulum

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33
Q

What roles does the smooth ER have?

A
  • storing calcium
  • role in detoxification and lipid synthesis
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34
Q

What is a hollow rod that shapes and support the cell?

A

microtubules

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35
Q

_____ is/are identical in structure to centrioles.

A

basal bodies

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36
Q

What organelle produces H2O2 as a by-product?

A

peroxisome

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37
Q

What is the role of the central vacuole

A

regulates cytoplasm composition, creates internal pressure and stores cell compounds

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38
Q

What is the function of chloroplasts?

A

makes sugar by converting light energy into chemical energy

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39
Q

What do the photosynthetic reactions do?

A

converting solar energy into chemical energy

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40
Q

Where is rubisco found?

A

stroma (chloroplasts)

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41
Q

Where is photosystem 1 found?

A

internal membrane of mitochondrion and/or chloroplast

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42
Q

Where is isocitrate dehydrogenase found?

A

matrix (mitochondrion)

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43
Q

Where is phosphofructokinase found in the cell?

A

cytoplasm

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44
Q

What is an example of a motor protein? What is its function?

A

actin - move along protein tracks, responsible for moving vesicles and organelles within the cell

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45
Q

What is an integral protein?

A

spans across the membrane (transmembrane)

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46
Q

What components pass through the nuclear pore during normal cellular activity?

A

ribosomal subunits and mRNA

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47
Q

What constitutes the endomembrane system?

A

nucleus, endoplasmic reticulum, golgi apparatus, lysosomes

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48
Q

What is the function of the nucleolus?

A

synthesis of rRNA

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49
Q

What constitutes chromatin?

A

DNA wrapped around 8 histone proteins

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50
Q

What is the nuclear envelope comprised of?

A

2 phospholipid membrane layers

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51
Q

What is the function of the endoplasmic reticulum?

A

smooth ER - synthesis of phospholipids
rough ER - studded with ribosomes for protein synthesis

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52
Q

What structure is continuous with the nuclear envelope?

A

rough ER

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53
Q

Describe the orientation of the Golgi in terms of cis and trans

A

cis closest to rough ER, trans closest to plasma membrane

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54
Q

Explain the process of the Golgi modifying proteins

A
  1. vesicle moves from ER to golgi
  2. Vesicles coalesce to form new cis golgi cisternae
  3. Cisternal maturation, Golgi cisternae move in a cis-to-trans direction
  4. Vesicles form and leave Golgi, carrying specific proteins to other locations or to the plasma membrane for secretion
  5. Vesicles transport specific proteins backwards to newer Golgi cisternae
  6. Vesicles also transport proteins back to ER
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55
Q

Where are lysosomes synthesized?

A

Golgi apparatus

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56
Q

Describe the process of phagocytosis

A
  1. lysosome contains active hydrolytic enzymes
  2. food vacuole fuses with lysosome
  3. hydrolytic enzymes digest food particles
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57
Q

Describe the process of Autophagy

A
  1. Lysosome fuses with vesicle containing damaged organelles
  2. Hydrolytic enzymes digest organelle components
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58
Q

What is the stroma of a chloroplast analogous to?

A

cytosol

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59
Q

What are the three functions of the cytoskeleton?

A

maintain cell shape
facilitates cell movement
facilitates movements of components within the cell

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60
Q

What are the three types of cytoskeletal filaments?

A

microtubules, microfilaments, intermediate filaments

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61
Q

What are microtubules comprised of ? Describe its function.

A

tubulin
- maintains cell shape,
- cell motility (cilia flagella)
- chromosome movements in cell division
- organelle movements

62
Q

What are Microfilaments comprised of ? Describe its function.

A

Actin
- maintain cell shape
- changes in cell shape
- cell motility (pseudopodia)
- cell division

63
Q

What are Intermediate filaments comprised of ? Describe its function.

A

fibrous proteins supercoiled into thicker cables
eg. keratin
- maintain cell shape
- anchorage of nucleus and other organelles
- formation of nuclear lamina

64
Q

What structure provides a network for vesicles to move along inside a cell?

A

microtubules

65
Q

How do microtubules contribute to the function of cilia and flagella?

A

microtubules enable bending of the structure as the motor proteins (dyneins) can walk along the tubule

66
Q

Describe the structure of a basal body in the cilia

A

triplets anchored to a central microtubule by cross linking proteins. Motor proteins on the outer triplet microtubule structures

67
Q

How thick is the phospholipid bilayer?

A

7-8 nm

68
Q

Describe the structure of a phospholipid

A

2 fatty acid tails
glycerol head bound to a phosphate group

69
Q

Where is the ECM found

A

only in animal cells in the extracellular side of membrane

70
Q

What is the ECM analogous to in plant cells?

A

cell wall

71
Q

What is fibronectin

A

protein that links a membrane protein to the ECM

72
Q

How is membrane fluidity maintained?

A
  1. unsaturated phospholipid fatty acid tails - kinks
  2. cholesterol - fluidity buffer, at cold temperatures when fatty acid tails go stiff, it creates space
73
Q

List the 6 examples of membrane protein functions and give an example of each

A
  • enzymatic activity eg. cristae membranes, catalytic activity
  • signal transduction eg. receptor molecule in membrane - signalling cascase
  • cell-cell recognition eg. receptor recognizing other proteins - communication
  • attachment to the cytoskeleton and ECM eg. fibronectin, maintain cell shape
  • intercellular joining (cell junctions) eg. communication, adhering
  • transport eg. diffusion
74
Q

Describe how the synthesis of membrane components occurs and the orientation of these molecules throughout the process.

A
  1. synthesis of phospholipid in the ER - transmembrane protein attached facing into lumen
  2. throughout golgi modification and packaging, orientation remains the same
  3. fuses with the plasma membrane and the transmembrane protein now faces into ECM (if orientation was the other way around in ER, protein would face the incorrect way in PM - cant function)
75
Q

List the cell junctions in animal tissues

A

tight junctions
desmosomes
gap junctions

76
Q

State the cell junctions in plant cells

A

plasmodesmata

77
Q

Describe the composition of tight junctions

A

claudins and occludins - prevent fluid from moving across a layer of cells

78
Q

Describe the composition of desmosomes

A

intermediate filaments, keratin
linking protein, cadherin
provides adhesion between cells

79
Q

Describe the composition of Gap junctions

A

6 connexins, ions, AA from one cell to another
cytoplasm of two cells continuous

80
Q

What are plasmodesmata analogous to? Where can they be found?

A

gap junctions between the cell walls of plant cells

81
Q

How do membranes regulate molecular traffic? Give examples

A

passive transport - diffusion, facilitated diffusion
active transport - Na/K pump

82
Q

Describe what is meant by passive transport

A

molecules move passively from high to low concentrations
spontaneous

83
Q

Explain diffusion

A

small, non-polar molecules like oxygen and CO2 and lipids are hydrophobic and can easily diffuse through the cell membrane

84
Q

Explain facilitated diffusion

A

Polar molecules like water ions and glucose are hydrophilic and require TRANSPORT PROTEINS to diffuse through the membrane

85
Q

What is osmosis

A

diffusion of water across membrane

86
Q

What are the two mechanisms for facilitated diffusion

A

a channel protein and a carrier protein

87
Q

Describe what is meant by active membrane transport

A

molecules move across membrane against concentration gradient
usually require energy in the form of ATP
all carrier proteins

88
Q

Describe the benefits of membrane transport proteins

A

provide selectivity
can increase rate of transport
continuously recycled
BUT
rate of transport limited by number of proteins

89
Q

Describe the mechanism of the NA/K pump

A
  1. 3 Na+ bind to carrier protein
  2. carrier protein is phosphorylated - binding of phosphorus induces shape change of Na+ binding site = decreased affinity and Na+ released into extracellular fluid
  3. 2 K+ bind causing dephosphorylation
  4. Change in shape of K+ binding site and higher affinity again for Na+
90
Q

How are large molecules transported?

A

exocytosis and endocytosis.

91
Q

Name the three types of endocytosis

A

phagocytosis “cell eating” - fuse with lysosome
pinocytosis “cell drinking” - not selective, vesicles form
receptor mediated endocytosis - highly selective, ligand binding, cluster, cell enveloped them, vesicle

92
Q

What is the highest energy form of adenosine?

A

Adenosine triphosphate (ATP) is the high-energy form of adenosine because it contains the most phosphate groups (three).

93
Q

Which part of the adenosine triphosphate molecule is released when it is hydrolyzed to provide energy for biological reactions?

A

The γ -phosphate is the primary phosphate group on the ATP molecule that is hydrolyzed when energy is needed to drive anabolic reactions. Located the farthest from the ribose sugar, it has a higher energy than either the α - or β -phosphate.

94
Q

What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?

A

hydrolysis

95
Q

“Conservation of energy” refers to the fact that _____.

A

energy cannot be created or destroyed but can be converted from one form to another

96
Q

Chemical energy is a form of _____ energy.

A

potential

97
Q

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?

A

cellular respiration

98
Q

What are the by products of cellular respiration

A

heat, carbon dioxide and water

99
Q

Which of these cell junctions form a barrier to the passage of materials?

A

tight junctions

100
Q

The primary role of _____ is to bind animal cells together.

A

desmosomes

101
Q

_____ aid in the coordination of the activities of adjacent animal cells.

A

gap junctions

102
Q

When molecules move down their concentration gradient, they move from where they are ____ to where they are ___.
Diffusion across a biological membrane is called _____

A

more concentrated, less concentrated, passive transport

103
Q

Facilitated diffusion is a type of _______.

A

passive transport

104
Q

Endocytosis moves materials _____ a cell via _____.

A

into, membranous vesicles

105
Q

You can recognize the process of pinocytosis when _____.

A

the cell is engulfing extracellular fluid

106
Q

A white blood cell engulfing a bacterium is an example of _____.

A

phagocytosis

107
Q

___ structure is achieved when a protein folds into a compact, three-dimensional shape stabilized by interactions between side-chain R groups of amino acids.

A

tertiary

108
Q

___ structure is the result of two or more protein subunits assembling to form a larger, biologically active protein complex.

A

quaternary

109
Q

___ structure is the sequence of amino acids in a protein.

A

primary

110
Q

___ structure describes the alpha-helices and beta-sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain.

A

secondary

111
Q

Proteins are polymers of _____.

A

amino acids

112
Q

What type of bond joins the monomers in a protein’s primary structure?

A

peptide

113
Q

The secondary structure of a protein results from _____ between repetitive regions of the backbone.

A

hydrogen bonds

114
Q

Tertiary structure is NOT directly dependent on _____.

A

peptide bonds

115
Q

When two amino acid monomers are positioned so that the carboxyl group of one is adjacent to the amino group of the other, they can be joined through a ___ reaction. This reaction forms a(n) ___ bond.

A

dehydration, peptide

116
Q

When would you use a space filling model?

A

If you wanted to show the 3-dimensional shape of a protein, including all of the atoms composing it

117
Q

When would you use a simplified diagram

A

If you wanted to show the general shape of a protein, along with some important functional details such as folds and coils

118
Q

When would you use a ribbon model

A

If you wanted to show the 3-dimensional shape of a protein, including the backbone structure, folds, and coils

119
Q

When would you use a simple shape diagram?

A

If you wanted to show a generalized protein in which the focus is on the protein’s function rather than its structure

120
Q

When would you use a wireframe model?

A

If you wanted to show the 3-dimensional shape of a protein by showing the amino acid side chains and their interactions

121
Q

What could happen if a mutation in a gene caused a hydrophobic amino acid in a polypeptide to be replaced by a hydrophilic amino acid?

A

The new amino acid would not form the same interactions with hydrophobic R groups, and the protein’s shape would likely be affected.

122
Q

What is the name of the central carbon in an amino acid?

A

𝛼 carbon

123
Q

List the 4 components of an amino acid

A

carboxyl, amino, R group and hydrogen

124
Q

What form is the amino acid in at pH 7

A

ionised state (NH3 + and COOH-)

125
Q

State the three classes of amino acids

A

Nonpolar - hydrophobic
Polar - hydrophilic
Electrically charges - hydrophilic

126
Q

How are amino acids joined together?

A

Peptide bonds - carboxyl group to amino group, remove H2O

127
Q

What constitutes a peptide bond?

A

O=C-N-H

128
Q

What type of reaction forms a peptide bond?

A

dehydration

129
Q

Are peptide bonds formed simultaneously?

A

No - one at a time

130
Q

What constitutes the repetitive backbone?

A

everything but R group

131
Q

What does the R group determine?

A

sequence/properties determines folding and function

132
Q

Where is mRNA produced?

A

nucleus

133
Q

What happens to mRNA once it is made it in the nucleus?

A

Leaves the nucleus through a nuclear pore to the cytoplasm

134
Q

What happens to the mRNA in the cytoplasm?

A

it attaches to a ribosome and is translated into a protein

135
Q

How often does hydrogen bonding occur between amino acids in the secondary alpha helix structure?

A

every 4 amino acids

136
Q

Where is the N and C terminus found respectively in an alpha helical membrane protien?

A

N-terminus in extracellular fluid
C-terminus in cytoplasmic side

137
Q

How do beta pleated sheets form hydrogen bonds?

A

between the O and H of neighbouring polypeptide backbones

138
Q

What types of side chain interactions are there?

A

weak interactions
- hydrogen
- ionic bond
- hydrophobic interactions and van der waals
- disulfide bridges (only bw cysteine)

139
Q

Give an example of a quaternary protein

A

collagen - ECM fibres, 3 coiled, identical

140
Q

Give an example of a quaternary protein

A

collagen - ECM fibres, 3 coiled, identical

141
Q

What is the function of a chaperone?

A

assist the folding of proteins
- protects polypeptide from degradation
- polypeptide folds spontaneously into proteins

check correct folding
- refold
- mark for destruction

142
Q

Explain how a chaperone functions

A
  1. unfolded polypeptide enters the cylinder from one end
  2. cap attaches causing cylinder to change shape in a way that it creates a hydrophilic environment for the folding polypeptide
  3. cap comes off and the properly folded protein is released
143
Q

Explain what is meant by denaturation of a protein

A

destruction of the 2°, 3° and 4° structure (3D shape)

144
Q

What factors cause a protein to denature?

A

heat, pH, reducing agents, organic solvents, detergents

145
Q

how does pH affect denaturation?

A

changes ionisation patterns of R groups

146
Q

how does heat affect denaturation?

A

break weak bonds

147
Q

how do reducing agents affect denaturation?

A

reduce S-S bonds to SH

148
Q

how do organic solvents affect denaturation?

A

disturb hydrophobic and hydrophilic interactions

149
Q

how do detergents affect denaturation?

A

disrupt hydrophobic interactions

150
Q

What is meant by the hydrolysis of a polypeptide?

A

addition of H2O to break the polypeptide bond

151
Q

What is a key difference between denaturation oand hydrolysis?

A

denaturation is the loss of 3D structure (2, 3, 4)
hydrolysis breaks the 1 structure

Biosci 101 (3 decks)

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