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MSE study Flashcards

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1
Q

Describe cell theory

A

Explains the relationship between life and properties of the cell.
- All organisms consist of one or more cells
- The cell is the basic unit of all organisms
- All cells come from pre-existing, living cells

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2
Q

What are the common structures in all cells?

A

The plasma membrane, cytoplasm, DNA, and ribosomes

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3
Q

What are the common functions of cells?

A

Duplicate DNA, use DNA and RNA to make proteins, handle energy transfer, regulate exchange of materials

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4
Q

What are the limiting factors that determine the size of cells?

A

Diffusion rate of molecules, maintaining concentrations of substances in the cell, surface area to volume ratio

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5
Q

How do you calculate total surface area?

A

Length x width x number of sides x number of cells

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6
Q

How do you calculate total volume?

A

Length x width x height x number of cells

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7
Q

What are the differences between eukaryotic cells and prokaryotic cells?

A

Prokaryotes are unicellular; their genetic information is not contained in a nucleus but concentrated in a nucleoid region. Lacks membrane-bound organelles. E.g. Bacteria and archaea
Eukaryotes are multicellular, have genetic information contained in a nucleus, and have membrane-bound organelles.
e.g. Plants, animals and yeast

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8
Q

What is the usual size of a prokaryote cell?

A

1-5 μm

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9
Q

What is the size of a eukaryotic cell?

A

10-100 μm

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10
Q

How does each cell type divide?

A

Prokaryotic cells: Binary fission
Eukaryotic cells: Mitosis, meiosis, and cytokinesis

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11
Q

What are the common cell structures in prokaryotes and eukaryotes?

A

Plasma membrane
Cytoplasm (cytoplasm + organelles)
Ribosomes

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12
Q

What is the structure of the plasma membrane?

A

Lipid bilayer with proteins
Phospholipids have polar heads and twin non-polar tails
8-10nm thickness

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13
Q

What are the functions of the plasma membrane?

A
  1. Define boundaries of the cell and any internal compartments (e.g. mitochondria)
  2. Serves as sites for biochemical functions (e.g., electron transport in mitochondria)
  3. Transports solutes in and out of the cell (selective permeability)
  4. Detect and transmit electrical and chemical signals
  5. Provide mechanisms for cell-to-cell contact, adhesion and communication
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14
Q

What is cytosol?

A

Semi-fluid part of the cell
Site where many chemical reactions take place (e.g., glycolysis)

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15
Q

What is cytoplasm?

A

Majority of the internal volume of the cell
Comprises of cytosol, organelles and cytoskeletal fibers

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16
Q

What is the structure and function of ribosomes?

A

Not membrane-bound organelles made up of RNAs and proteins. Consist of two subunits (small and large)
Can be free or grouped (as part of rough ER)
Function: protein synthesis

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17
Q

What are the differences between plant and animal cells?

A

Plant: cell wall, chloroplasts, large vacuole, glyoxysome, no centrosome.
Animal: No cell wall, no chloroplasts, small temporary vacuole, normal peroxisome, centrosomes

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18
Q

What is the structure and function of the nucleus?

A

Double membrane-bound organelle, covered by nuclear envelope.
Contains chromatin (DNA and proteins) that act as an information centre
Nuclear pores form channels to transport molecules such as RNAs, proteins and ions
Contains the nucleolus: Site of ribosome component synthesis

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19
Q

What is the structure and function of the cytoskeleton?

A

3D array of interlaced proteinaceous structures
Internal framework for shape of cell
Organelle/cell movement, contractility
Permits cell division
Influences water distribution

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20
Q

What is the structure and function of the mitochondria?

A

Double membrane, outer membrane and an inner membrane with folds (cristae) encloses matrix (semifluid)
Function: Generation of energy (ATP; aerobic respiration)

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21
Q

What is the structure of the endoplasmic reticulum?

A

Single membrane-bound organelle with lumen inside. A network of tunnels usually attached to nuclear envelope
Two types, Smooth ER and Rough ER

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22
Q

What is the function of the rough endoplasmic reticulum?

A

Protein synthesis and processing

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23
Q

What is the function of smooth endoplasmic reticulum?

A

Lipid/steroid synthesis
Carbohydrate metabolism
Detoxifying drugs, alcohol and poisons.
Storing and release of calcium ions

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24
Q

What is the structure and function of the Golgi complex?

A

AKA dictyosome / Golgi Apparatus
“processing centre” of cell
Single membrane-bound sacs called cisternae
Functions: Forms vesicles (packages of secretory proteins and lipids), Synthesis of complex polysaccharides

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25
What is the structure and function of lysosomes?
Single membrane bound vesicle produced from Golgi complex Functions - Stores enzymes (e.g., lysozyme, hydrolase) - Destroys/lyses material in vesicles - Breakdown macromolecules (e.g. proteins) - Recycles cell contents (e.g. aging organelles)
26
What is the structure and function of peroxisomes?
Single membrane bound vesicle with a crystalline core (the core contains catalase) Packages and destroys hydrogen peroxide safely with catalase. Catalase breaks down hydrogen peroxide into water and oxygen. Protects cell from damaging reactive oxygen species (ROS)
27
What are centrosomes?
Organelles that consist of two centrioles. In charge of organising microtubules and are involved in cell division.
28
What is a vacuole for?
Temporary storage or transport
29
What is cilium?
And appendage on the cell surface capable of movement.
30
What is the structure and function of the cell wall?
Provides structural support Made up of cellulose microfibrils in a matrix of polysaccharides and proteins so it is flexible and extensible Cell walls are connected by plasmodesmata (openings) which are membrane-lined and allows for water and small solutes to pass.
31
What is the structure and function of chloroplasts?
Inner and outer membrane The third membrane system consists of granum which are stacks of flattened sacs called Thylakoids Tubular membranes: Stroma thylakoids that connect sacs together Functions: Site of photosynthesis, produce sugars and organic compounds
32
What is the structure and function of a vacuole in a plant cell?
Single membrane bound organelle Temporary storage and transport Phagocytosis Storage and intracellular digestion Maintain turgor pressure so it doesn't explode from water. Store nutrients and water
33
What is the structure and function of a glyoxysome?
-Specialised peroxisomes - Crystalline core contains the enzyme catalase Germination: has enzymes that can convert fat into carbohydrates - Involved in photorespiration
34
What is the basic structure of an amino acid?
α carbon Hydrogen atom Carboxyl group (carboxylic acid): (-COO-) Amino group (Amine): -NH3+ R group
35
how many amino acids are there?
20
36
How are R groups classified?
Non-polar (or hydrophobic) Polar (or hydrophilic) Neutral Negatively charged Positively charged
37
What are non polar amino acids?
The R group mostly contains hydrocarbon group e.g. CH3 May also have N or S atoms R groups that only have carbon and hydrogen are always nonpolar, and hydrophobic Benzene rings are also non-polar
38
What are polar, uncharged amino acids?
Polar: R group contain either a hydroxyl group (OH), sulfhydryl group (SH) or amide group (CONH2) Neutral: R group does not have a charge, but may contain a highly electronegative atom such as O, N, or S
39
What are charged amino acids?
Negatively charged: R groups contain a negatively charged acid Positively charged: R groups contain a positively charged base (e.g. -NH3+)
40
What is the stereoisometric form of amino acids found in proteins?
L-amino acids
41
What are peptide bonds?
Strong covalent bonds that link amino acids together between the C from (carboxyl group) COO- and the N from (amine) NH3+
42
What happens in a condensation reaction to create peptide bonds?
One oxygen from the carboxyl group is removed and two hydrogens from the amino group to create water and the carbon and nitrogen form a covalent bond.
43
What are hydrogen bonds?
Donors (e.g., Amine or hydroxyl group of amino acid) have H atoms linked to a more electronegative atom of an acceptor (e.g., carbonyl and sulfhydryl groups of amino acids) Weak, non-covalent bond
44
What is the N-terminus and C-terminus?
The N-terminus is the starting end of the peptide that has the amine group and the C-terminus is the end with the carboxyl group
45
What are disulphide bonds?
Form between sulphur atoms of two cysteine amino acid residue by covalent bonding Strong covalent bond Through oxidation: removal of hydrogen atoms
46
What are ionic bonds?
R groups can have positive or negative charges non-covalent bonds The ionic bond is weak inside an aqueous solution Electrostatic interactions between R groups +ve bind to –ve (attract) Similar charge (repel) Too high/ low pH value affects ionic bonds results in denaturation of proteins
47
What are Van der Waals interactions?
Transient attraction of two non-polar molecules Typically weak and only effective if the molecules are close.
48
what are hydrophobic interactions?
Tendency of hydrophobic molecules excluded from water interaction They hate water so much that they interact with each other
49
What are the four protein structures?
Primary, secondary, tertiary and quaternary.
50
What is the primary structure?
A linear sequence of amino acids in polypeptide chains, linked by peptide bonds Sequence determines the higher order of structures
51
What is the secondary structure?
Backbone of a polypeptide formed by the linear sequence folding upon itself Structure is stabilised by Hydrogen bonds that are either intermolecular (Between CO and NH groups of amino acids of two different polypeptides) Intramolecular (Between CO and NH groups of amino acids of the same polypeptide) They form ɑ helix or β sheets
52
What is an alpha helix?
Spiral in shape, coils around itself. CO groups bind to the NH group of the peptide, binding 4 amino acids downstream Makes the structure stretchable (because of the coil) Most amino acids can be inside the helix but some amino acids disrupt α helix (Helix breaker) Proline lacks H needed for H bonding, it is attached to the R group instead
53
What is a beta sheet?
Sheet-like conformation They form when two parts of a polypeptide chain lie side by side Stabilised by hydrogen bonds
54
What are motifs?
Combinations of α helices and β sheets Connected via looped regions of varying length (random coils)
55
What is the tertiary structure?
Higher order of folding Polypeptide chain folded back on itself to form a condensed structure Depends on the interaction between the side chains Stabilised by - Disulphide bonds - Hydrogen bonds - Ionic bonds - van der Waals interaction - Hydrophobic interaction The two main classes are fibrous proteins and globular proteins
56
What are the differences between fibrous and globular proteins?
Fibrous proteins are extended and filamentous with a repetitive amino acid sequence. Only a small fraction is present in cells with structural functions such as hair keratins. Globular proteins are compact and have different amino acid sequences. They make up most of the proteins in cells, they are functional such as enzymes.
57
What is the quaternary structure
Links between multiple polypeptides Held together by the same bonds of tertiary structure Example: Haemoglobin Multimeric protein = tetramer = 4 polypeptides
58
What are the functions of proteins?
Enzymes (majority) Structural Motility Transport Signalling/hormonal Receptor Defensive Storage
59
What is the function of enzymatic proteins?
Selective acceleration of chemical reactions
60
what is the function of defensive proteins?
protect against disease
61
What is the function of storage proteins?
Storage of amino acids
62
What is the function of transport proteins?
transport of substance. e.g. integral proteins in cell membrane
63
What is the function of hormonal proteins?
Coordination of an orgnanisms actvities
64
what is the function of receptor proteins?
Response of cell to chemical stimuli
65
What is the function of contractile and motor proteins?
Movement. e.g. myosin and actin
66
What is he function of structural proteins?
Support, e.g. keratin
67
How does pH affect proteins?
Affects proteins by changing the protonation state of the charged residues
68
What is the isoelectric point (pI)?
pH at which proteins are at zero nett charge Positive and negative charges are balanced Proteins are least soluble in this state because they would rather interact with each other than water.
69
What happens if you put a neutral amino acid in an acidic environment?
Acidic environment = low pH = increases H+ The hydrogen ions will attach to the negative side of the amino acid creating an overall positive amino acid.
70
What happens if you put an amino acid in a basic/alkaline environment?
High pH = Decease H+ The environment will steal hydrogen ions from the amino acid, creating an overall negatively charged molecule.
71
What bonds are affected by changes in pH?
Ionic and hydrogen bonds are affected by the change in pH because of the hydrogen changes and because of the charge changes.
72
What is electrophoresis?
A method of separating proteins based on charge. Separates mixture of proteins in a gel matrix with voltage Cathode (-) and anode (+) ends of gel Opposite charges attract Protein mix will separate based on charge and rate proportional to size of charge
73
What is chromatography?
Separation of molecules suspended in a phase (liquid solution) Due to molecules having different properties (e.g., charges, affinity to certain molecules, polarity)
74
What is Ion exchange chromatography
Beads traps/slows down flowing proteins of opposite charge Proteins of same charge flow through Collected in fractions to purify proteins To get the proteins retained in the column, change buffer (different pH and salt concentration)
75
What is Gel filtration?
Beads slow down small proteins by adding more pathways for them to go through Larger protein travel faster ("excluded") through resin and elute first Collected in fractions to purify proteins
76
What is separation based on solubility: Isoelectric point precipitation
Separated based on solubility difference in water Charge of protein attracts water forming hydrating shell and solubilises Putting proteins in solutions with different pH, each protein will precipitate at its pI
77
What is solubility Ammonium sulphate precipitation?
(NH4)2SO4 strips away hydration shell Water will mix with the ammonium sulphate instead of the protein Decrease solubility allowing proteins to precipitate Different proteins precipitate at different concentrations of ammonium sulphate
78
What is protein denaturation?
Structures must be maintained for biological function Agents may cause loss of structures (2°, 3° and/or 4°) by disrupting bonds Loss of structure + function = denaturation
79
What are factors that cause denaturation?
Organic solvents, detergents, pH extremes, Heat.
80
How do organic solvents cause denaturation?
Disrupt H bonds (2°, 3°, 4°)
81
How do detergents cause denaturation?
disrupt hydrophobic bonds (3°, 4°)
82
How do pH extremes cause denaturation?
disrupt H bonds (2°, 3°, 4°) and ionic (electrostatic) bonds (3°, 4°)
83
How does heat cause denaturation?
increase kinetic energy and disrupt all non-covalent bonds (2°, 3°, 4°)
84
What are the 6 enzyme classes?
Oxidoreductase, hydrolase, ligase, lyase, transferase, isomerase
85
What does oxidoreductase do and what is an example?
Catalyse redox reactions (transfer of H, O or e-) Glyceraldehyde-4-phosphate dehydrogenase.
86
What does a transferase do?
Transfer a function group from one molecule to another. Hexokinase
87
What does hydrolase do?
Hydrolyse (break bonds) in the presence of water. Glucose-6-phosphatase.
88
What does lyase do?
Remove or add groups to a molecule (breaks bonds, electron rearrangement) Pyruvate decarboxylase
89
What does an isomerase do?
Rearrange functional groups in a molecule (isomers) Phosphoglucoisomerase
90
What does a ligase do?
Join molecules pyruvate carboxylase
91
What are the three properties of enzymes?
They are catalysts, so they speed up reactions. They are stable, meaning they retain structural conformation during reactions. They are specific which means they only catalyse a single reaction or closely related reactions.
92
What is the equilibrium constant?
a measure of directionality in a reversible reaction. a reaction will strive towards the equilibrium constant.
93
What is the equation for the equilibrium constant?
Keq = Substrate concentration of the product / substrate concentration of the reactant. If the ratio is less than 0.5 the reaction will proceed to the right, if it is 0.5 the reaction will stop moving in either direction
94
What is activation energy?
Energy needed to react with each other to form products Need to reach transition state Stage where reactants have free energy higher than initial reactants
95
What are the two ways to reach transition state?
Adding catalyst to lower EA Increasing temperature
96
How do enzymes act as catalysts?
Lowers activation energy requirement Makes a conducing environment for the reaction to happen Forms transient, reversible complexes with substrate, facilitates interaction and stabilise the intermediate transition state Substrate binding occurs at active site of an enzyme Changes the rate at which Keq is achieved
97
What factors effect enzymes as a catalyst?
[S], temperature, [E], and pH
98
How does enzyme concentration affect enzymes?
As [E] increases, reaction velocity increases as Positive linear relationship When [S] is in excess
99
How doe substrate concentration affect reaction rate?
As [S] increases, reaction velocity increases until a certain point where all the enzymes are saturated and the rate can't increase anymore
100
What is Km?
(Michaelis constant): [S] where reaction velocity is half of max velocity
101
What does the Km tell us about the binding affinity?
Tells us about the binding affinity of enzyme to substrate Km has an inverse relationship with the binding affinity of an enzyme for its substrate High Km = low affinity for substrate to enzyme
102
How does temperature affect reaction rate?
At low temperature, enzyme is inactive As temperature increases, reaction velocity increases Kinetic energy increases the collision rate Extreme temperature denatures proteins
103
How does pH affect reaction rate?
Most enzymes active within a pH range of about 3-4 units Extreme pH denature enzymes Amino and carboxyl groups affected leading to disruption in electrostatic bonds Hydrogen and ionic bonds affected by pH Diminished enzyme activity Enzymes are sensitive to pH changes, one that works in the stomach (acidic), won't work in the intestines (alkaline)
104

BIO152 (2 decks)

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