topic 2 - molecular biology & SL Cellular Respiration, Photosynthesis Flashcards
(139 cards)
1
Q
What is Metabolism?
A
describes the totality of chemical processes that occur within a living organism in order to maintain life
OR
web of all enzyme-catalysed reactions that occur within a particular cell or organism
2
Q
What is molecular biology?
A
explains the biological processes in terms of the chemical substances (molecules) involved
3
Q
What are biological processes?
A
processes regulated by enzymes
expression is controlled by DNA (gene activation)
4
Q
What are organic compounds?
A
molecules that contain carbon and are found in living things (exception: carbonates and oxides of carbon)
5
Q
What is the importance of carbon atoms?
A
form the basis of organic life due to their capacity to form 4 covalent bonds = allows a diversity of stable compounds to exist
6
Q
What are the four main groups of organic compounds in cells?
A
Carbohydrates, lipids, proteins and nucleic acids
7
Q
What are carbohydrates?
A
monomer: monosaccharides (can exist as a ring or 3D configurations)
polymer: polysaccharide
8
Q
What makes lipids different from the other main groups of organic compounds in cells?
A
carbohydrates, proteins and nucleic acids = made up of recurring subunits
lipids are NOT (may contain triglycerides)
9
Q
What are proteins?
A
monomer: amino acid
polymer: polypeptide
10
Q
What are nucleic acids?
A
monomer: nucleotide
polymer: DNA/RNA
11
Q
What is anabolism? Give an example.
A
- synthesis of complex molecules from simpler ones (water is produced = condensation)
ex: photosynthesis
12
Q
What is catabolism? Give an example.
A
breakdown of complex molecules –> simple molecules (water is consumed = hydrolysis reaction)
example: cellular respiration
13
Q
What is Vitalism? and How as it falsified? Use urea as an example.
A
Vitalism: doctrine that organic molecules could ONLY be synthesized by living systems (living organisms were said to possess a “vital force” that was required to manufacture organic molecules)
Falsification of Vitalism:
In 1828, Frederick Woehler artificially synthesized an organic molecule
heated ammonium cyanate (inorganic salt) produced urea (organic) under laboratoty conditions
14
Q
What is the structure of water?
A
- made up of two hydrogen atoms covalently bonded to an O atom
15
Q
Describe the polarity of water.
A
- Oxygen atom has a higher electronegativity and attracts the shared electrons more strongly = gives it the polarity
- dipolarity allows water to form polar associations with other polar/ionic molecules (thus, can have bonds with other water molecules)
16
Q
H-bonds and dipolarity gives water its properties. Describe its cohesive and adhesive properties.
A
Cohesion: formation of h-bonds with other water molecules (like molecules stick tgth)
- RESULTS: high surface tension (can resist low level of external forces)
- allow small organisms to move on its surface (ex: Basilisk lizard)
Adhesion: formation of polar associations with charged molecules (unlike molecules stick tgth)
- RESULTS: potential capillary action (transpiration stream in plants –> water moves up xylem)
17
Q
H-bonds and dipolarity gives water its properties. Describe its solvent properties.
A
- has capacity to dissolve a large number of substances (ionic/polar) –> important for metabolic reactions & necessary transport medium
- large quantities of water molecules sufficiently weaken forces & form dispersive hydration shells
18
Q
Hydrophilic v.s. Hydrophobic
A
Hydrophilic: CAN dissolve in water
(ex: glucose, amino acids, sodium chloride, oxygen)
Hydrophobic: CANNOT dissolve in water
(ex: lipids: fats and cholesterol)
19
Q
H-bonds and dipolarity gives water its properties. Describe its thermal properties.
A
- has capacity to absorb large amounts of heat energy before undergoing a state change
- high specific heat capacity
- effective coolant (evaporation of sweat requires absorption of heat)
20
Q
H-bonds and dipolarity gives water its properties. Describe its transparent properties.
A
- allow light to pass through it (important for photosynthesis and vision)
21
Q
H-bonds and dipolarity gives water its properties. Describe its density properties.
A
- water expands when frozen = becomes less dense
- explains why ice floats and oceans underneath don’t automatically freeze
22
Q
What is the difference between water and methane?
A
- differ in thermal properties due to polarity of water and capacity to form intermolecular h-bonds
- water: polar = form intermolecular h-bonds (oxygen has higher electronegativity)
- methane: non-polar = only form weak dispersion forces between its molecules (carbon has lower electronegativity)
Thus, Water has a higher: MP/BP, specific heat capacity, heat of vaporisation and heat of fusion)
23
Q
Describe the Water Cycle.
A
Evaporation - water is converted to vapour by the sun and transferred from the Earth’s surface to the atmosphere
Transpiration - water vapour is released by plants and soil into the atmosphere
Condensation - water vapour is transformed into liquid water droplets in the air (creating clouds and fog)
Precipitation - water vapour in the atmosphere condenses into rain or snow returns to the Earth
Infiltration - flow of water from the ground surface into the soil
Runoff - variety of ways water moves along the ground
Subsurface flow - flow of water underground (will eventually drain into oceans or return to the surface via springs)
24
Q
What are monosaccharides?
A
- monomer of a carbohydrate
- primary function as an energy source
- covalently joined by glycosidic linkages by condensation reactions to form polymers (disaccharides or polysaccharides for easier transportation)
25
The carbohydrate formed depends on the monosaccharide subunits used and the bonding arrangement between them.
TRUE or FALSE?
TRUE
26
What are the 3 uses of polysaccharides for cell functions?
1. short term energy storage (ex: glycogen, starch)
2. structural components (ex: cellulose)
3. recognition/receptors (ex: glycoproteins)
27
What are the three types of polysaccharides?
1. cellulose
2. starch
3. glycogen
28
Describe the structure and significance of cellulose.
- linear made of B-glucose subunits that are bound in 1-4 arrangement
- component of plant cell wall
29
Describe the structure and significance of starch.
- alpha-glucose subunits
2 forms:
1. Amylose: linear (helical) & bound in 1-4 arrangements
2. Amylopectin: branched & bound in 1-4 AND 1-6 arrangements
30
Describe the structure and significance of glycogen.
- branched, alpha-glucose subunits
| - similar to amylopectin BUT w/ more frequent 1-6 bonding
31
Carbohydrates and lipids are both used as energy storage molecules and are the same in all aspects.
TRUE or FALSE
FALSE
| Yes, they are both used as energy storage, however they differ in certain key aspects
32
Which key aspects does carbohydrates and lipids differ in terms of energy storage?
(THINK: SODAS)
Storage: lipids used for long term storage, carbs is for short term
Osmotic pressure (osmolality): lipids easier to store, but less effect; carbs have more effect
Digestion: lipids harder to digest; carbs easier to digest = easier to use
ATP yield: lipids 2x larger = store more energy per gram; carbs smaller
Solubility: lipids insoluble = harder to transport; carbs soluble
33
How do you calculate BMI?
BMI = mass in kg/ (height in m)^2
34
Are lipids polar or non-polar organic molecules?
NP
35
What are the cellular functions that lipids serve?
THINK: SHIPS
1. Storage of energy (triglycerides --> adipose tissues)
2. Hormonal roles (steroids)
3. Insulation (thermal)
4. Protection of organs (phospholipid bilayer)
5. Structural roles (cholesterol --> animal cell membrane)
36
Describe the structure of a triglycerides and why they are used for energy storage.
- composed of a glycerol molecule linked to 3 fatty acids chains via condensation
- used for long-term energy storage
37
Describe the two types of fatty acids. Give an example for each.
Saturated Fatty Acids: no double bond, generally solid @ rm temp. (ex: animal fat)
Unsaturated Fatty Acids: YES double bond, generally liquid @ rm temp. (ex: plant oils)
38
Describe the structure of a fatty acid.
hydrocarbon + carboxylic group
39
What are the two distinct configurations of unsaturated fatty acids?
Cis and Trans Isomer
40
What is a Cis Isomer?
- H atoms on the SAME side
- doubled bond creates bend
- loosely packed = usually liquid
- occur in nature
- GOOD for health
41
What is trans isomer?
- H atoms on DIFFERENT side
- no bend = linear
- tightly packed = solid
- occurs in processed food
- BAD for health
42
What are some of the health risks of lipids?
Fats and cholesterol cannot dissolve in the blood and so are packaged with proteins (as lipoproteins) for transport
• Low density lipoproteins (LDLs) transport cholesterol
from the liver to the rest of the body (bad for health)
• High density lipoproteins (HDLs) scavenge excess
cholesterol and return it to the liver for disposal (good)
Fatty acids can influence the levels of lipoproteins:
• Cis fats raise levels of HDL (⬇ blood cholesterol)
• Saturated fats raise levels of LDL (⬆︎︎ blood cholesterol)
• Trans fats raise levels of LDL and lower levels of HDL
High levels of blood cholesterol can cause atherosclerosis and lead to health issues like coronary heart disease (CHD)
43
How are lipids absorbed in the digestive system?
- Bile salts, secreted from the gall bladder, emulsify these fat globules and break them up into smaller droplets
- Hydrolytic enzymes called lipases then digest the fats into their component parts
44
How are lipids absorbed into epithelial cells of the intestinal lining?
- combined to form triglycerides
- triglycerides are combined with proteins inside the Golgi apparatus to form chylomicrons
- Chylomicrons are released from the epithelial cells and are transported via the lacteals to the liver
45
While in the liver, chylomicrons may be modified to form a variety of lipoproteins. What are these two varieties and how do their absorptions differ?
- Low density lipoproteins will transport lipids via the bloodstream to cells
- High density lipoproteins will scavenge excess lipids from the bloodstream and tissues and return them to the liver
46
What is the monomer of a protein called?
amino acid
47
Briefly describe the formation of a polypeptide chain.
- via condensation reactions, amino acids are covalently joined
- a peptide bond is formed
- occurs at the ribosome
48
What does the sequence of amino acids encode?
genes :)
49
Describe the primary structure of a protein.
- determines the order of amino acid sequence (i.e. how it will fold)
- formed by covalent peptide bonds
50
Describe the secondary structure of a protein.
- fold into repeated patterns by h-bonds b/w amine and carboxyl grps
(1) Alpha-helix:
- amino acid sequence in a coil/spiral arrangement
(2) B-pleated sheet:
- amino acid sequence in directionally-oriented staggered strand conformation
51
Describe the tertiary structure of a protein
- 3D arrangement determined by interactions b/w variable side chains
52
Describe the quaternary structure of a protein.
multiple polypeptides or inorganic prosthetic grps
53
What is an example of a quaternary structure of a protein?
Haemoglobin
- 4 polypeptide chains (2 alpha chains and 2 beta chains)
- composed of iron-containing haeme groups (prosthetic groups responsible for binding oxygen)
54
What are the main, general functions of proteins within a cell?
SHITS ME
* Structure (collagen, spider silk)
* Hormonal (insulin, glucagon)
* Immunity (immunoglobulins)
* Transport (haemoglobin)
* Sensation (rhodopsin)
* Movement (actin, myosin)
* Enzymatic (Rubisco, catalase)
55
What is proteome?
- The totality of all proteins that are expressed within a cell, tissue or organism at a certain time
- unique for each person, since protein expression patterns are influence by a genome
56
What is denaturation?
a structural change in a protein that results in the loss (usually permanent) of its biological properties
folded protein --> unfolded (denatured)
57
What causes denaturation to occur?
Temperature (heat may break structural bonds)
| • pH (alters protein charge ➡︎ changes solubility & shape)
58
Importance of the following protein function: Structure. Give an example.
Collagen: A component of the connective tissue of animals (most abundant protein in mammals)
OR
Spider silk: A fiber spun by spiders and used to make webs (by weight, is stronger than kevlar and steel)
59
Importance of the following protein function: Hormones. Give an example.
Insulin: Protein produced by the pancreas and triggers a reduction in blood glucose levels
OR
Glucagon: Protein produced by the pancreas that triggers an increase in blood glucose levels
60
Importance of the following protein function: Immunity. Give an example.
Immunoglobulins: Antibodies produced by plasma cells that are capable of targeting specific antigens
61
Importance of the following protein function: Transport. Give an example.
Haemoglobin: A protein found in red blood cells that is responsible for the transport of oxygen
OR
Cytochrome: A group of proteins located in the mitochondria and involved in the electron transport chain
62
Importance of the following protein function: Sensation. Give an example.
Rhodopsin: A pigment in the photoreceptor cells of the retina that is responsible for the detection of light
63
Importance of the following protein function: Movement. Give an example.
Actin: Thin filaments involved in the contraction of muscle fibres
OR
Myosin: Thick filaments involved in the contraction of muscle fibres
64
Importance of the following protein function: Enzymes. Give an example.
Rubisco: An enzyme involved in the light independent stage of photosynthesis
65
What are fibrous proteins?
composed of long and narrow strands and have a structural role (they are something)
66
What are globular proteins?
have a more compact and rounded shape and have functional roles (they do something)
67
What is the difference between fibrous and globular proteins?
Think: SPADES
SHAPE
F: long and narrow
G: round/spherical
PURPOSE
F: structural
G: functional
ACID SEQUENCE
F: repetitive
G: irregular
DURABILITITY
F: less sensitive to pH, temperature and etc. changes
G: more sensitive to pH, temperature and etc. changes
EXAMPLES
F: collagen, myosin, fibrin, actin, keratin. elastin
G: enzymes, haemoglobin, insulin, immunoglobulin
SOLUBILITY
F: insoluble
G: soluble
68
What is an enzyme?
- biological catalyst
- globular protein that speeds up the rate of a chemical equation by lowering the activation energy
- can be re-usedNOT consumed
69
What molecule(s) does the enzyme react with?
substrate
70
What does the substrate bind to?
Active suite: complementary region on enzyme's surface
71
Describe the Lock and Key Model.
Enzyme and substrate complement each other precisely in terms of both their shape and chemical properties
The active site and the substrate will share specificity
72
Describe the Induced Fit model.
Active site is not a rigid fit for the substrate and changes its conformation to better accommodate the substrate
This stresses the substrate bonds and induces catalysis
73
How does temperature affect enzyme activity? What would the graph look like?
- Increases enzyme activity (more kinetic energy = more collisions)
- Enzyme activity peaks at an optimal temperature
- Higher temperatures decrease activity (causes denaturation)
Graph: skewed to the left, spread out
74
How does pH affect enzyme activity? How would the graph be presented?
* Enzyme activity is highest at an optimal pH range
* Activity decreases outside of this range (due to denaturation)
Graph: highest peak is relatively in the middle, narrow
75
How does substrate concentration affect enzyme activity? How would the graph look like?
- increases enzyme activity (more particles = more collisions)
- @ a certain point, activity plateaus (saturation of active sites)
Graph: sharply increases and then plateaus
76
True or False
| The rate of enzyme catalysis can be increased by increasing the frequency of enzyme-substrate collisions
TRUE!
| this is molecular motion of enzyme kinetics
77
True or false?
The rate of enzyme catalysis is decreased by denaturation
TRUE
78
Why are Immobilized enzymes often used in industrial practices?
- fixed to a static surface to prevent enzyme loss = improves separation of product and purity of yield
79
Describe one application for immobilized enzymes.
Production of Lactose-free milk (includes associated dairy products):
- Lactase (enzyme) digests lactose into glucose / galactose
- Lactase is purified from yeast or bacteria
• Lactase is bound to an inert surface (e.g. alginate beads)
• Milk is repeatedly passed the immobilized enzyme to become lactose free
80
What are the advantages of lactose-free dairy products?
- provide a course of dairy for lactose-intolerant ppl
- increases sweetness of milk (less need for sweeteners)
- reduces crystallization and production times for cheese
81
What is the monomer of a nucleic acid called?
nucleotide
82
What is a nucleotide composed of?
* A pentose sugar
* A phosphate group
* A nitrogenous base
83
What are the nitrogenous bases? How do they pair up?
Adenine pairs with Thymine (in DNA) or Uracil (in RNA) --> 2 h-bonds
Guanine pairs with Cytosine --> 3 h-bonds
84
True or False?
Nucleotides are linked together into a single strand via condensation reactions (between a 3’-phosphate and a 5’-hydroxyl group of adjacent nucleotides)
FALSE
Nucleotides are linked together into a single strand via condensation reactions (between a 5’-phosphate and a 3’-hydroxyl group of adjacent nucleotides)
85
True or False?
The polynucleotide arrangement results in the formation of a sugar-phosphate backbone that is covalently linked together by phosphodiester bonds
True
86
Describe the DNA structure of a polynucleotide.
Two complementary strands line up in opposite directions (anti-parallel) with the bases facing inwards and connected by hydrogen bonds (G ≡ C and A = T)
The double stranded molecule then twists in order to adopt a more stable energy configuration – a double helix
87
Describe the RNA structure of a polynucleotide.
The polynucleotide chain remains single stranded, but may fold upon itself to form double stranded motifs (e.g. the cloverleaf shape of a tRNA molecule)
88
Compare the structural difference between DNA and RNA
DNA
- sugar = deoxyribose
- has Thymine
- double stranded (forms double helix)
RNA
- sugar = ribose
0 has Uracil
single stranded
89
How did Crick and Watson elucidation of structure of DNA in 1953 using model making?
Using data from previous scientific experiments (plus trial and error), Watson and Crick developed a DNA model that demonstrated:
- a double helix structure composed of antiparallel DNA strands
- internally facing bases w/ complementary pairing
90
What is messenger RNA (mRNA)?
- a transcript copy of a gene which encodes a specific polypepetide
91
What is transfer RNA (tRNA)?
carries the polypeptide subunits (amino acids) to the ribosome (the organelle responsible for synthesis)
92
What is Ribosomal RNA (rRNA)?
a primary component of the ribosome and is responsible for its catalytic activity
93
Why is the DNA replication process described as semi-conservative?
one strand is from an original template molecule and one strand is newly synthesised
This occurs because each base will only pair with its complementary partner and thus ensure the sequence is conserved
94
What is the role of Helicase in DNA replication?
Unwinds and separates the double stranded DNA
Breaks the hydrogen bonds between the base pairs
95
What is the DNA Polymerase III in DNA replication?
Free nucleotides line up opposite complementary partners
DNA Pol III covalently joins the free nucleotides together
96
How did Meselson and Stahl's results obtain support for the theory of semi-conservative replication of DNA?
Prior to this experiment, three hypotheses had been proposed for the method of replication of DNA:
Conservative Model – An entirely new molecule is synthesised from a DNA template (which remains unaltered)
Semi-Conservative Model – Each new molecule consists of one newly synthesised strand and one template strand
Dispersive Model – New molecules are made of segments of new and old DNA
They incorporated radioactive nitrogen isotopes into DNA
• Templates were prepared with heavier 15N
• New sequences were replicated with lighter 14N
The DNA was then separated via centrifugation in order to determine its composition of radioisotopes
• 1st division: DNA had 15N and 14N (i.e. mixed)
• 2nd division: DNA is mixed or has 14N only
RESULTS:
- After one division, DNA molecules were found to contain a mix of 15N and 14N, disproving the conservative model
- After two divisions, some molecules of DNA were found to consist solely of 14N, disproving the dispersive model
97
What is PCR (polymerase chain reaction)?
an artificial method of DNA replication that is used to rapidly copy sequences
98
True or False?
| a standard PCR sequence of 30 cycles creates over 1 billion copies (2^30)
True
| - each reaction doubles the amount of DNA
99
Describe the repeating steps of PCR that occur in a thermal cycler.
1. Denaturation: DNA heated to separate strands
2. Annealing primers attach to ends of a target sequence
3. Elongation: Taq polymerase (a heat-tolerant polymerase) copies strands
- extends the nucleotide chain from primers thsu primers are used to select the sequence to be copied
100
Briefly describe Transcription and the process.
Transcription is the synthesis of mRNA copied from the DNA base sequence by RNA polymerase
occurs within the nucleus of a cell
Process:
RNA polymerase binds to a promoter and unwinds DNA
• It breaks the H bonds between complementary bases
Nucleoside triphosphates bind to complementary bases
• In RNA, uracil pairs with adenine instead of thymine
RNA polymerase covalently joins the nucleotides together
• The two extra phosphates are released (provides energy)
Transcription occurs in a 5’ → 3’ direction (antisense strand)
• At the terminator site, RNA polymerase is detached and the RNA sequence is released (and the DNA rewinds)
101
What is the role of RNA polymerase in transcription?
- separates the DNA strands (breaks h-bonds b/w base pairs) --> ribonucleoside triphosphates pair up
- covalently joins free complementary RNA nucleotides together through the removal of additional phosphate groups (release of ATP) --> RNA polymerase detaches and double helix reforms
102
What happens after transcription?
RNA is released to the cytoplasm (for translation) and the DNA remains within the nucleus and reforms a double helix
103
Briefly define Translation.
Translation is the process of polypeptide synthesis by the ribosome
104
Briefly describe the process of translation
• Messenger RNA (mRNA) is transported to the ribosome
Initiation (component assembly)
• The small ribosomal subunit binds to mRNA and moves
in a 5’ → 3’ direction to the START codon (AUG)
• The complementary tRNA molecule binds to the
START codon via its anticodon
• ThelargesubunitalignsitselftothetRNAmoleculeat
its P-site and forms a complex with the small subunit
Elongation / Translocation (polypeptide synthesis)
• A tRNA molecule pairs with the next codon (via A-site)
• The ribosome covalently attaches the amino acid in the
P-site to the amino acid in the A-site (via peptide bond)
• The ribosome moves along one codon position and the
deacylated tRNA molecule is released (from the E-site)
• The elongation and translocation processes continue
along the mRNA coding sequence in a 5’ → 3’ direction
Termination (component disassembly)
• When a ribosome reaches a STOP codon, a polypeptide
is released and the ribosome disassembles into subunits
Helpful way to memorize:
A cell is like a restaurant – differentiated cell types are like restaurants specialising in different cuisines
The DNA is the set of instructions for the cell – like a cook book is the set of instructions for a restaurant
A single DNA instruction is a gene – this is akin to a single recipe in a cook book
Transcription is the process of making an RNA copy of a gene – RNA polymerase is like a photocopy machine
The mRNA transcript (i.e. photocopied recipe) is transported to the ribosome – which functions as the cook
The ribosome reads the mRNA one codon at a time – as a cook would read the recipe one step at a time
Each codon corresponds to an amino acid – just like each step in a recipe refers to a specific ingredient
The amino acids are brought to the ribosome by tRNA – these tRNA molecules are like kitchen hands
The ribosome joins the amino acids together to make a polypeptide – just like a cook mixes ingredients to make food
105
What is the genetic code?
The genetic code is the set of rules by which information encoded in mRNA sequences is converted into a polypeptide sequence
106
What are codons?
triplets of bases which correspond to a particular amino acid
107
What is the significance of codons?
Its order determines the amino acid sequence for a protein
AUG --> start codon
UAA, UAG, UGA --> stop codon
108
What are the two key features of the genetic code?
1. Universality: all organisms use the same genetic code --> allow gene transfer b/w species
Ex: production of human insulin
2. Degeneracy: multiple codons may code for the same amino acid
109
What is a gene?
A gene is a sequence of DNA that encodes a polypeptide sequence
1 gene = 1 polypeptide (proteins may have multiple polypeptides)
110
What are some exceptions to the relationship of gene -> protein?
* Genes may be alternatively spliced (one gene = many polypeptides)
* Genes encoding tRNA or rRNA are transcribed but not translated
* Genes may be mutated to alter the original polypeptide product
111
Describe an example of universality.
Production of human insulin in bacteria for mass production
- The gene responsible for insulin production is extracted from a human cell
- It is spliced into a plasmid vector (for autonomous replication and expression) before being inserted into a bacterial cell
- The transgenic bacteria (E. coli) are then selected and cultured in a fermentation tank (to increase bacterial numbers)
- The bacteria now produce human insulin, which is harvested, purified and packaged for human use (i.e. by diabetics)
112
The strand that is NOT transcribed is called the antisense strand and is complementary to the RNA sequence
True or False
False
| The strand that IS transcribed is called the antisense strand and is complementary to the RNA sequence
113
The strand that is not transcribed is called the sense strand and is identical to the RNA sequence (with T instead of U)
True or False
True :)
114
Briefly explain the overall molecular biology of the flow of genetic information within a cell.
DNA → RNA → Protein
- DNA codes for RNA via the process of transcription (occurs within the nucleus)
- RNA codes for protein via the process of translation (occurs at the ribosomes)
Exception:
retroviruses could copy DNA from an RNA sequence (reverse transcription)
115
What is cell respiration?
Cell respiration is the controlled release of energy from organic compounds to produce ATP
main organic compounds used are carbohydrates (i.e. glucose), but lipids or proteins may also be used
116
What is ATP?
ATP (adenosine triphosphate) is a molecule that functions as an immediate source of energy when hydrolysed (to form ADP)
Different organic compounds will have distinct breakdown pathways and so have varied ATP yields
117
Briefly describe glycolysis.
Cell respiration begins with the break down of glucose via a process called glycolysis (occurs in the cytosol)
• Glucose is broken down into pyruvate (×2)
• There is a small ATP yield (net gain = 2 ATP)
• Requires the reduction of NAD+ (to form NADH)
118
Pyruvate (from glycolysis) will follow one of two pathways. Identify these two pathways and describe them
Anaerobic Respiration
• Occurs in the cytosol and does NOT require oxygen
• Results in a small energy yield (2 ATP from glycolysis)
• Forms lactic acid (animals) or ethanol and CO2 (plants / yeast)
• Also known as fermentation and is reversible
• Stages: Glycolysis, Link Rxn, Krebs Cycle, Electron Transport Chain
Aerobic respiration
• Occurs in the mitochondria and REQUIRES oxygen
• Results in a large energy yield (approx. 36 ATP per glucose)
• Forms CO2 and H2O
• uses hydrogen carriers to make ATP (oxidative phosphorylation)
• Stages: Glycolysis, Fermentation
119
What is Fermentation?
Fermentation is a reversible anaerobic process that allows ATP production to continue in the absence of oxygen
Fermentation restores NAD+ stocks (needed in glycolysis) to ensure a continued production of ATP (by glycolysis)
120
What does fermentation produce in animals? How is this significant?
Fermentation in animals produces lactic acid, and is used to maximise muscle contractions when oxygen is limited • This reaction can be reversed when oxygen is restored
121
What does fermentation produce in plants? How is this significant?
Fermentation in plants and yeast produce ethanol and CO2 gas which can be used in baking (leavening dough)
• Also for the production of alcohol, yogurts and cheese
122
What is a respirometry?
A respirometer determines an organism’s respiration rate by measuring either carbon dioxide production or oxygen uptake
Commonly used for invertebrates or germinating seeds
123
Describe a simple example of a respirometer.
A simple respirometer may involve the use of a manometer (pressure change moves the water)
- an organism is sealed in a container w/ a CO2 absorbant
- oxygen uptake creates a pressure change which displaces the fluid in the manometer (allowing for quantitation) --> this is measured
124
Factors which may affect respiration rates?
temperature, hydration, light (plants), age and activity levels
An increase in carbon dioxide levels will indicate an increase in respiration (CO2 is a product of aerobic respiration)
A decrease in oxygen levels will indicate an increase in respiration (O2 is a requirement for aerobic respiration)
125
Lactate production in humans when anaerobic respiration is used to maximise the power of muscle contractions
True or False? Explain why.
TRUE
Muscle contractions require the expenditure of high amounts of energy and thus require high levels of ATP
When exercising at high intensity, the cells’ energy demands will exceed what the available levels of O2 can supply aerobically
Hence the body will begin breaking down glucose anaerobically to maximise ATP production
This will result in an increase in the production of lactic acid, which leads to muscle fatigue
When the individual stops exercising, oxygen levels will increase and lactate will be converted back to pyruvate
Although carbohydrates, lipids and proteins can all be consumed as energy sources, only carbohydrates will typically undergo anaerobic respiration
126
Briefly describe Photosynthesis.
Photosynthesis involves the use of light energy to synthesise organic compounds from inorganic molecules
6CO2 + 12H2O --> (light, chlorophyll) C6H12O6 (glucose) + 6O2 + 6H2O
127
How are photosynthesis and cell respiration connected?
Photosynthetic organisms use the light energy from the sun to create chemical energy (ATP)
This chemical energy can either be used directly by the organism or used to synthesise organic compounds (e.g. glucose)
Animals then consume these organic compounds as food and release the stored energy via cell respiration
Photosynthesis (anabolic synthesis of organic compounds) is essentially the reverse of cell respiration (catabolic breakdown)
128
True of False
Visible light has a range of wavelengths (approx. 400-700 nm) with violet the shortest wavelength and red the longest
True
129
What is the significance of pigments?
are required for the conversion of light energy into chemical energy in photosynthetic organisms
130
What is the purpose of chlorophyll as the main photosynthetic pigment?
Chlorophyll absorbs red light and blue light most effectively and reflects green light more than other colours
131
What is the purpose of an absorption spectrum?
indicates the wavelengths of light absorbed by each photosynthetic pigment (e.g. chlorophyll)
132
What is the purpose of an action spectrum?
indicates the overall rate of photosynthetic activity at each wavelength of light
133
Describe the Stages of Photosynthesis
Photosynthesis is a two step process:
(1) Light Dependent Reactions
Light energy is converted into chemical energy
• Light is absorbed by chlorophyll to produce ATP
• The photolysis (light energy --> water) of water forms oxygen and hydrogen
(2) Light Independent Reactions
Carbon compounds are made from the chemical energy • ATP and hydrogen are fixed with carbon dioxide
• Thisresultsintheformationoforganicmolecules
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What are the possible limiting factors of photosynthesis?
* Temperature(influencesphotosyntheticenzymes)
* Light intensity (required for chlorophyll photoactivation)
* Carbon dioxide concentrations (CO2 is a core substrate)
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What is Chromatography? How does it work?
Chromatography is an experimental technique by which mixtures can be separated (Separation of photosynthetic pigments by chromatograph)
How?
• Pigments are dissolved in fluid
• The fluid is passed through a static material
• Pigments are separated according to size
Results?
A retardation factor (Rf value) is calculated:
Rf = distance of pigment ÷ distance of solvent
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How has the Earth's oceans changed due to photosynthesis?
Approximately 2.3 billion years ago, photosynthetic organisms began to saturate the environment with oxygen
Earth’s oceans initially had high levels of dissolved iron (released from the crust by underwater volcanic vents)
When iron reacts with oxygen gas it undergoes a chemical reaction to form an insoluble precipitate (iron oxide)
When the iron in the ocean was completely consumed, oxygen gas started accumulating in the atmospher
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How has the Earth's atmosphere changed due to photosynthesis?
Approximately 2.3 billion years ago, photosynthetic organisms began to saturate the environment with oxygen
For the first 2 billion years after the Earth was formed, its atmosphere was anoxic (oxygen-free)
The current concentration of oxygen gas within the atmosphere is approximately 20%
138
How has the Earth's rock deposition changed due to photosynthesis?
Approximately 2.3 billion years ago, photosynthetic organisms began to saturate the environment with oxygen
The reaction between dissolved iron and oxygen gas created oceanic deposits called banded iron formations (BIFs)
These deposits are not commonly found in oceanic sedimentary rock younger than 1.8 billion years old
This likely reflects the time when oxygen levels caused the near complete consumption of dissolved iron levels
As BIF deposition slowed in oceans, iron rich layers started to form on land due to the rise in atmospheric O2 levels
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How might biological life be changed due to photosynthesis?
Approximately 2.3 billion years ago, photosynthetic organisms began to saturate the environment with oxygen
Free oxygen is toxic to obligate anaerobes and an increase in O2 levels may have wiped out many of these species
Conversely, rising O2 levels was a critical determinant to the evolution of aerobically respiring organisms
