biological molecules Flashcards
(169 cards)
1
Q
what are the four key elements that make up most biological molecules
A
- carbon (C)
- hydrogen (H)
- oxygen (O)
- nitrogen (N)
2
Q
what are two additional elements that play important roles in cell biochemistry?
A
- phosphorus and sulfur
3
Q
name 4 other biologival elements and their functions
A
- sodium (Na) -nerve impulse transmission, kidney function
- potassium (k) - nerve impulse transmission, stomotal opening
- calcium (Ca) - muscle contraction, nerve impulse transmission
- iron (Fe)- oxygen transport (in haemogobin)
4
Q
what is a covelant bond
A
when two atoms share a pair of electrons
5
Q
how many bonds can these form
- carbon
- nitrogen
- oxygen
- hydrogen
A
- carbon- 4
- nitrogen- 3
- oxygen- 2
-hygrogen-1
6
Q
why is life referred to as carbon based
A
because carbonbcan form four bonds, making it the backbone of most biological molecules
7
Q
what is an ion
A
an atom or molecule where the total number of electrons is NOT equal to the total number of protons
8
Q
what is the difference between a cation and an anion
A
cation is a positively charged electron (loses electrons)
anion is negative charged ion (gains)
9
Q
what is an ionic bond
A
when one atom donates an electron abnd the other receives it, creating oppositely charged ions that are held together by electrostatic attraction
10
Q
whart are the functions of key cations in biological system
A
- calcium ions (Ca2+) - nerve impulses transmission, muscle contraction
- sodium ions (Na+) - nerve impulse transmittion, stomatal opening
- hydrogen ions (H+) - catalysis of reactions, pH determination
- ammonium ions (NH₄⁺): production of nuitrate ions by bacteria
11
Q
what are the functions of key anions in biological systems
A
- nitrate ions (NO₃⁻) - nitrogen supply to plants for amino acid and protein formation
- hydrogen carbonate ions (HCO₃⁻): maintenance of blood pH
- chloride ions (Cl-) - balances the positive charge of sodium and potassium ions in cells
- phosphate ions (PO₄³⁻) cell membrane, nucleic acid, and ATP formation + bone formation
- hydroxide ions (OH-) - catalysis of reactions, pH determination
12
Q
what elements are found in carbohydrates and in what ration
A
carbon, oxygen, hydrogen in the ratio Cₓ(H₂O)ᵧ.
13
Q
what elemets are found in lipids
A
carbon, hygrogen and oxygen
14
Q
what elements are found in proteins
A
carbon, hydrogen, oxygen, nitrogen, sulfur
15
Q
what elements are found in nucleic acids
A
carbon, hydrogen, oxygen, nitrogen, and phosphorus
16
Q
whats a polymer
A
a long chain molecule made up of repeating units called monomers
17
Q
what are the monomers of carbohydrates and proteins
A
- carbohyderates : sugars (saccharides)
- proteins: amino acids
18
Q
what causes hydrogen bonding between water molecules
A
- water is polar
- the oxygen atom has a greater share of electrons, making it slightly negative
- while hydrogens are slightly positive
- this creates regions of positive and negative, allowingf water molecules to attract eachother and form hydrogen bonds
19
Q
are hydrogen bonds strong or weak
A
indiviudually, hydrogen bonds are weak but they occur in high numbers, making them significant inb determining waters properties
20
Q
what is the difference between cohesion and adhesion
A
cohesion: water moolecules stick to each other due to hydrogen bonding
adhesion: when water molecules stick to other surfaces (e.g water on your skin)
21
Q
why does water have a high boiing point
A
due to the large number of hydorgen bonds, which require a lot of energy to break
22
Q
why is ice less dense than liquid water
A
when water freezes, hydrogen bonds fix the molecules in a rigid open structure, creating more space between them.
this makes ice less dense than liquid water, allowing it to float
23
Q
what is surface tension and why is it important
A
- surface tension occurs because water molecules are more cohesive to eachother than air
- this creates a ‘skin’ on the surface strong enough to support small insects like pond skaters
24
Q
why is water a good solvent
A
- its polar, allowing it to disolve many solutes, including amino acids, proteins and nucleic acids
- this makes it a medium for chemical reactions and a transporter of dissolved compounds into and out of cells
25
how does water act as a transport medium in living organisms
- cohesion allows water molecules to stick together during transport
- adhesion causes water molecules to stick to polar surfaces, enabling capillary action (e.g water rising in plant xylem against gravity)
26
how does water act as a coolant
- water buffers temp changes during chemical reactions by absorbing large amounts of energy to break hydrogen bonds
- this helps maintain a stable environment for enzymes, which function best within a narrow temperature range (optimum)
27
why is water’s stability vital for aquatic life
- water has high SHC, making it resistant to temperature changes, providing a constant environment for aquatic life
- when ice forms on the surface of ponds and lakes, it insulates the water below, preventing the entire habitat from freezing
28
how does surface tension benefit certain organisms
surface tension allows small insects, like pond skaters to move across the waters surface without sinking
29
what are the three types of carbohydrates
- monosaccharides: simple sugar unit (e.g glucose, fructose, ribose)
-disaccharides: two monosaccharides linked (e.g lactose, sucrose, maltose)
- polysaccharides: many monosaccharides linked (e.g starch, glycogen cellulose)
30
what is the chemical formula of glucose
C₆H₁₂O₆.
31
what is glucose and its two structural forms
- glucose is a hexose monosaccharides (6 carbons)
two forms:
- alpha glucose: hydroxyl group (OH) on carbon 1 points down
- beta glucose: OH group on carbon 1 points up
32
why is glucose soluble in water
it is polar, allowing it to form hydrogen bonds with water, making to soluble to the cytosol of cells
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what happens during a condensation reaction
Two monosaccharides join by a glycosidic bond and a water molecule is removed
E.g two alpha glucose molecules form maltose via a 1’4 glycosidic bond
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What happened during hydrolysis
A water molecule is added, breaking the glycosidic bond and
This releases monosaccharides, providing glucose for respiration
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What disaccharides are formed by these monosaccharides
Glucose + glucose = maltose
Glucose + fructose = sucrose
Glucose + galactose = lactose
36
What is starch and what are its two forms
Starch is a plant energy storage polysaccharide made up of alpha glucose molecules
It’s two forms:
amylose
1’4 glycosidic bonds only
Coils into a helix (compact and less soluble)
Amylopectin
1’4 and 1’8 glycosidic bonds
Branched structure (branching every 25 subunits)
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What is glycogen and how is it different from starch
Glycogen is the animal and fungal equivalent of starch
It has more branches than amylopectin making it;
- more compact (better for mobile animals)
- faster glucose release due to more free ends
38
What is cellulose made up of
- beta glucose monomers linked by a 1’4 glycosidic bond and
- alternate beta glucose molecules are flipped upside down forming a straight chain
39
How is cellulose used in plants
- Cellulose chains form hydrogen bonds, creating micro fibrils
- microfibrils bundle into macrofibrils, forming strong insoluble fibres that provide structural support in plant cell walls
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Why is cellulose important for human diet
It is indigestible by humans and provides fibre, aiding digestion
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What is a reducing sugar
A sugar that can donate electrons to reduce another molecule
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What chemical is used in Benedict’s test
Benedict’s reagent/ alkaline copper III sulfate
43
Describe the tests for Benedict’s test
1. Place the sample in a boiling tube (grind/blend if solid)
2. Add an equal volume of Benedict’s reagent
3. Heat the mixture gently in a boiling water bath for 5 mins
44
What colour change indicates a positive result for reducing sugars
- blue = no reducing sugar
- green/yellow = low concentration
- orange = medium concentration
- red = high concentration (Cu²⁺ ions reduced to Cu⁺).
45
Why does Benedict’s reagent turn red with reducing sugars
Reducing sugars donate electrons
Reducing blue Cu²⁺ ions to red Cu⁺ ions
Forming a brick red precipitate
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What is a non reducing sugar
A sugar that cannot donate electrons (e.g sucrose)
47
How do you test for non reducing sugars
1. Perform the Benedict’s test - if no colour change, continue with the next steps
2. Boil the sample with dilute HCl (hydrolyses the sugar into monosaccharides)
3. Neutralise with sodium hydrogen carbonate
4. Perform Benedict’s test again - positive result if reducing sugar is know prevent
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What chemical is used in the iodine test
Iodine dissolved in potassium iodide solution
49
What indicates a positive test for starch
Yellow/brown into blue/black
No colour change indicates starch is absent
50
What do reagent strips test for
The presence of reducing sugars, most commonly glucose
51
What is the advantage of using reagent strips
- fast and easy detection
- the concentration of sugar can be determined using a colour coded chart
- useful for diabetes management
52
What does a colorimeter measure
The absorbance or transmission of light through a coloured solution
53
why is colorimetry used in Benedict’s test
To quantitatively measure the concentration of reducing sugar
54
What are the steps for using a colorimeter
1. Select the correct filter (e.g red filter for Benedict’s test)
2. Calibrate with distilled water (zero the machine)
3. Perform Benedict’s test on glucose of known concentrations
4. Filter the solutions to remove the precipitate
5. Measure the % transmission of each solution
6. Plot the calibration curve using data
7. Test the unknown solution and use the graph to estimate its glucose concentration
55
How do you calculate % absorbance from % transmission
Absorbance = 100 - transmission
56
What is a biosensor
A device that uses biological components to detect the presence or concentration ofg
molecules
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What are the 3 components of a biosensor
1. Molecular recognition: a protein (enzyme/antibody) or ssDNA binds to the target molecule
2. Transduction: this interaction triggers a change in pH or produces an electrical signal
3. Signal processing: the signal is processed and displayed as a colour change or digital reading
58
How could biosensors help in diabetes management
- biosensors detect glucose in blood
- provides a quantitative result
- helps diabetics monitor and manage their blood sugar levels accurately
59
Is a canary in a coal mine, a biosensor
Yes because the birds biological response (distress or death) indicates the presence of toxic gases
Disadvantage:
- unreliable as canaries have different sensitivities to gas
- inhumane at it endangers the birds Life
60
What makes lipids insoluble in water
They are non polar molecules so do not interact with water molecules
61
What is the difference between fats and oils
Fats: solid at room temp (saturated lipids)
Oils: liquids at room temp (unsaturated lipids)
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Why are lipids considered macromolecules
They are large complex molecules put not polymers as they are not made of repeating units
63
What is the structure of a triglyceride
1 glycerol molecule + 3 fatty acids
Formed through esterification
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What is esterification
A condensation reaction forming ester bonds between glycerol and fatty acids Formed through
it producers 3 water molecules
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How are are triglycerides broken down?
By hydrolysis (addition of water)
3 water molecules are needed to break the Ester bonds between glycerol
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What is an un sature d fatty acid
- Contains no double bonds between carbon atoms
- molecules can pack closely together so are solid at room temperature (fats)
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What is an unsaturated fatty acid
- contains one or more double bonds between carbon atoms
- the double bonds causes the chain to kink, making it harder for molecules to pack closely together so is liquid at room temp (oils)
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What are mono saturated and poly saturated fats
- monosaturated: one double bond
- Poly saturated: two or more double bonds
69
How are phospholipids different from triglycerides
One fatty acids chain is replaced by a phosphate group
Contains hydrogen, carbon and phosphorous
70
What is the structure of a phospholipid
Hydrophilic head- phosphate group
Hydrophobic tails - fatty acids
71
What structures do phospholipids form in water
- micelles: spherical structures with hydrophobic tails inside
- bilayers: double layered sheets with tails facing inwards and heads facing outwards — forms cell membrane
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What are sterols
Steroid alcohols , complex lipids with a 4 carbon ring and a hydroxyl group
Cholesterol is the most common sterol
73
What role does cholesterol play in the cell membranes
Stabilises the membraned by interacting with phospholipids
Prevents the membrane from becoming too fluid at high temperatures and too rigid at low temperatures
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What are the 8 biological roles of lipids
1. Membraned formation - hydrophobic barriers
2. Hormone production - steroid hormones
3. Electrical insulation - e.g myelin sheath around neurons
4. Waterproofing - e.g plant leaves, bird feathers
5. Energy storage -long term energy reserve
6. Thermal insulation - prevents eat loss (e.g penguins)
7. Cushioning - protects vital organs
8. Buoyancy - help aquatic animals float
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What is the emulsion test used for
To detect the presence of lipids
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Describe the steps of the emulsion test used
1. Mix the sample with ethanol (lipids dissolve in ethanol)
2. Add water and shake
Positive test = white emulations forms on surface
Negative test = the solution remains clear
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Why does the emulsion test work
Lipids are insoluble in water but soluble in ethanol
When mixed with water, lipids precipitate out forming a white emulsion
78
Why are unsaturated fats considered healthier than saturated fats
- unsaturated fats reduce LDL (bad cholesterol) levels
- saturated fats increase LDL levels - linked to coronary heart disease
- however evidence linking saturated fats to heart disease is inconclusive
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What are trans fats and why are they unhealthy
- formed during hydrogenation of vegetable oils
- unsaturated fats become partially saturated, making them solid
- trans fats increase LDL and lower HDL (old cholesterol) - increasing heart disease risk
80
How is margarine made from vegetable oil
- vegetable oils arte hydrogenated to remove double bonds, making them solid
- this process creates trans fats as a byproduct
- modern spreads avoid trans fats by using mono and poly saturated oils
81
What is food synergy
The combined effect of multiple nutrients is greater than the effect of individual nutrients
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What are the four elements found in all proteins
Carbon, hydrogen, oxygen and nitrogen
83
What is the general structure of an amino acid
Carbon atom (C)
Amine group (NH₂)
Carboxyl group (COOH)
Hydrogen atom (H)
Variable R-group (side chain)
84
What are the three categories of amino acids based on dietary needs
- non essential: synthesised by the body
- essential: obtained from food
- conditionally essential: only needed by infants/growing children
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How is a peptide bond formed
- through a condensation reaction
- where the hydroxyl group (OH) from the carbonyl group of ones amino acid combines with the hydrogen group pf the amine group of another
- water is removed
- a peptide bond forms between the carbon and nitrogen
86
What enzyme catalyses peptide bound formation in ribosomes
Peptidyl transferase
87
What is the primary structure of a protein
The sequcning of am,into acids joined by peptide bonds, directed by dna
88
How does the primary structure influence the final shape of the protein
The sequence determines folding, affecting the final shape and function
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What bonds are involved in the primary structure
Only peptide bonds
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What’s the secondary structure of a protein
The folding or coiling of the polypeptide chain due to hydrogen bonding between the backbone groups (not R groups)
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What are the two main secondary structures
Alpha helix: coiled structures with hydrogen bonds parallel to the helix
Beta pleated sheets: polypeptide chains running parallel, joined by hydrogen bonds, forming a sheet like shape
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Which type of bond stabilises the secondary structure
Hydrogen bonds
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What is the tertiary structure of a protein
The 3D folding of the polypeptide chain, including sections of the secondary structure
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What R group interactions stabilise the tertiary structure
1. Hydrophobic/hydrophilic interactions: weak interactions between polar and non polar R groups
2. Hydrogen bonds: weak, between polar R groups
3. Ionic bonding: between oppositely charged R groups
4. Disulphide bridges: covenant bonds between sulfúreo atoms in cysteine
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What is the quaternary structure of a protein
The association of two or more polypeptides (subunits) into a functional protein
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What bonds and interactions are involved in quaternary structures `
The same with tertiary (hydrogen bonds, hydrophobic, hydrophilic interactions, ionic bonds, disulphide bridges)
BUT between subunits rather than within a single polypeptide
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Give an example of a protein with a quaternary structure
Haemoglobin
- made of 4 subunits: 2 alpha and 2 beta chains
- contains prosthetic haem groups with iron that binds oxygen
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What are globular protein
- compact, spherical and water soluble
- formed when proteins fold to keep hydrophobic R groups on the inside and hydrophilic ones on the outside
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Why is the solubility of globulars proteins important
It allows them to dissolve in blood and bodily fluids, enabling transport and chemical reactions
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Give examples of globular proteins
Insulin : hormone regulating blood glucose
Catalase : enzyme that breaks down hydrogen peroxide
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What are fibrous proteins
- long, insoluble and strong
- contain many hydrophobic R groups
- Have a repetitive amino acid sequence, making them tightly structured
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Give three examples of fibrous proteins and their functions
1. Keratin: High sulfur content = disulphide bridges= strength and inflexibility
2. Elastin: elastic fibres in lungs and blood vessels. Provides flexibility
3. Collagen: connective tissue in skin, tendons and ligaments. Provides tensile strength
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What is thin layer chromatography used for
To separate and identify amino acids in a mixture
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What are the two phases in TLC
1. Stationary: thin layer of silica gel or another adhesive material
2. Mobile phase: organic solvent (e.g hexane, water, acetic acid, butanol)
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What determines how far an animo acid travels in TLC
- Affinity for the stationary phase (hydrogen bonding with silica)
- solubility in the mobile phase
- more soluble amino acids travel further
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Why are gloves worn and the plate handles by the edges
To prevent contamination by skin cells
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Why is the jar sealed during the experiment
To prevent solvent evaporation, ensuring consistent conditions
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What is the purpose of the biuret test
To detect the presence of proteins by identifying peptide bonds
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What are the steps por the biuret test
1. Add 3 cm^3 of Sample to the test tube
2. Add equal volume of 10% sodium hydroxide
3. Add a few drops of 1% copper sulfate
4. Mix and leave to stand for 5 mins
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What colour change indicates the presence of a protein
Purple/ lilac : due to peptide blonds forming violet complexes with copper ions
Blue: no protein present
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Why doesn’t the biuret test quantify the amount of protein
It only indicates the presence/absence, not concentration
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What is a prosthetic groups
A non protein component permanently attached to a protein
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What type of protein contains prosthetic groups
Conjugated proteins
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Give an example of a conjugated protein
Haemoglobin with iron containing haem groups
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What are the three components of a nucleotide
1. Pentose sugar (5 carbon sugar)
2. Phosphate group (negatively charged)
3. Nitrogenous base ( A, T, G, C)
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What type of sugar is found in DNA and RNA
RNA= ribose
DNA= deoxyribose (one fewer oxygen atom than ribose)
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What are the two main categories of nitrogenous bases
1. Pyrimidines: smaller, single ring bases (thymine, cytosine, uracil)
2. Purines: larger, double ring bases (adenine + guanine)
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How are nucleotides joined to form a polynucleotide
- condensation reactions
- a phosphodiester bond forms
- between the phosphate group at the 5’ end of one carbon of a nucleotide
- and the hydroxyl group at the 3’ end of the carbon of the adjacent nucleotide
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What are the four DNA bases and their complementary pairs
1. Adenine and thymine joined by 2 hydrogen bonds
2. Cytosine and guanine joined by 3 hydrogen bonds
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What is the structure of DNA?
- double helix: two polynucleotide strands twisted into a spiral
- anti parallel strands : one strand runs 5’-3’ but the other 3’-5’ \
- sugar phosphate backbone: with bases projecting inwards
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What maintains the stability of the DNA double helix
- hydrogen bonding between complementary base pairs
- base pairing riles maintain a constant distance between the sugar phosphate backbones
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What is complementary base pairing
- purine always pairs with pyrimidine
- this maintains a consistent distance between the two DNA strands
- ensures equal amounts of complementary bases (A-T, G-C)
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Why is complementary base pairing important
- ensure accurate replication of genetic information
- allows for efficient transcription into mRNA
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What are the key differences between RNA and DNA
1. Sugar; dna contains deoxyribose, rna contains ribose
2. Bases: dna uses thymine, rna uses uracil
3. Strand: dna is double stranded, rna is single stranded
3. Size: dna is larger than rna
4. Function: dna is for the long term storage of gentic information, rna is for temporary copies of gentic information
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what are the roles of RNA in the cell
1. mRNA - transfers gentic information from dna to ribosomes
2. tRNA - carries amino acids for protein synthesis
3. rRNA - component of ribosomes aiding in translation
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What is the purpose of dna extraction
To isolate and purify DNA from plant cells
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What are the steps in DNA extraction
1. Grind the sample (using a mortar and pestle) - breaks down cell walls
2. Mix with detergent -breaks down the cell membrane, releasing cell contents
3. Add salt - disrupts hydrogen bonds between dna and water molecules
4. Add protease enzyme - breaks down proteins associated with dna
6. Add ethanol (alcohol) - precipitates the dna out of solute
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Why does dna precipitate in ethanol
- dna is insoluble in alcohol
- it appears as white strands between the aqueous layer and ethanol
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Why is it important to keep the temperature low during dna extraction
To prevent the degradation of the dna by enzymes
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How are polynucleotides broken down
- by hydrolysis reactions
- water breaks down the phosphodiester bonds
- which releases individual nucleotides
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What is a polynucleotide
A long chain of nucleotides linked by a phosphodiester bond
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What is the sugar phosphate backbone
The repeating chain of sugars and phosphates that form the structural framework of rna and dna
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What is a phosphodiester bond
A covenant bond between the phosphate group of one nucleotide and the hydroxyl group of another
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What does anti parallel mean in dna structure
The two DNA strands run in opposite directions:
• One strand → 5’ → 3’
• The other strand → 3’ → 5’
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Why is dna ideal for storing genetic information
- stable double helix structure protects genetic code
- complementary base pairing ensures accurate replication
- long molecule stores large amounts of information
- hydrogen bonds allow the strands to separarte easily for replication and transcription
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How is the dna sequence bases linked to protein synthesis
- the sequence of bases carriers the genetic code
- this code is transcribed into mRNA and translated into proteins
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Why do cells divide in mitosis
To produce more cells needed for growth or repair
The daughter cells produced are genetically identical to each other and the parent cell
Their dna has identical base sequencing
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What is the process of dna replication called
Semi conservative replication
Where each new dna molecule consists of one old strand and one new strand
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What are the steps of semi conservative replication
1. DNA helicase unwinds the double helix and breaks the hydrogen bonds allow
2. Free dna nucleotides pair with complementary bases
3. Dna polymerase forms phosphodiester bonds between adjacent nucleotides
4. Two identical dna molecules are produced with each with one original and one new strand
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What is the role of dna helicase in replication
DNA helicase unwinds the double helix and catalyses the breaking of hydrogen bonds between complementary base pairs
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What does dna polymerase do
It catalyses the formation of phosphodiester bonds between free nucleotides, synthesising the new dna strand
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What is continuous replication
The leading strand (unzipped from the 3’ end) is replicated continuously as dna unwinds, since dna polymerase moves in the same direction
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What is discontinuous replication
The lagging strand (unzipped from the 5’ end) is replicated in short Okazaki fragments because DNA polymerase moves in the opposite direction
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What enzyme joins Okazaki fragments
DNA ligase joined them into a continuous strand
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What is the genetic code
The genetic code is the sequence of DNA bases that determines the sequence of amino acids in a protein
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What is a codon
A codon is a triplet of 3 bases on mRNA that codes for one amino acid
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Why is the genetic code described as universal
The same codon codes for the same amino acids in across all species
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What does it mean that the genetic code is degenerate
Multiple variations of codons can code for the same amino acids
E.g GGU, GGC, GGA, GGG all code for glycine
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What are start and stop codons
Start codons: signals the start of protein synthesis ( AUG, coding for methionine)
Stop codons: signals the end of translation and does not code for any amino acid
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What is transciption
The process where the evens dna sequence is copied into mRNA
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What’s enzyme catalyses transcription
RNA polymerase
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What are the steps of transcription
1. DNA helicase unwinds and unzips the double helix
2. One strand (the antisense strand) acts as a template
3. Free RNA nucleotides base pair with complementary bases on the template strand
4. RNA polymerase catalyses the formation of phosphodiester bonds between rna nucleotides
5. mRNA detaches and leaves the nucleus through the nuclear pore
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What base is used in RNA instead of thymine
Uracil
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What is translation
The process where mRNA is decoded by a ribosome to produce a polypeptide (protein)
156
What are the temps of translation
1. mRNA binds to the small subunit of the ribosome
2. A tRNA molecule with a complementary anticodon binds to the start codon on the mRNA, carrying the corresponding amino acid
3. The ribosome catalyses the formation of peptide bonds between the amino acids
4. The process continues until a stop codon is reached
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What is the role of tRNA in translation
- it carries a specific amino acid
- it has an anticodon that pairs with a complementary codon on mRNA
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What enzyme catalyses peptide bonds between the formation during translation
Peptidyl transferase, which is part of the ribosome rRNA
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What is a mutation
A random spontaneous change in the DNA’s base sequence during replication
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How do replication errors occur
When complementary bases do not match correctly
Causing base substitutions, insertions or deletions
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What are the 3 main types of activity that cells require energy for
1. Synthesis: e.g large molecules like proteins
2. Transport- e.g pumping ions or molecules across cell membranes by active transport
3. Movement - e.g protein figures in muscle cells causing muscle contraction
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What is the universal currency in all living cells
Adenosine triphosphate (ATP)
163
What is the structure of an ATP molecule
- Adenine ( nitrogenous base)
- ribose (pentose sugar)
- 3 phosphate groups
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How is the structure of ATP similar to the structure of DNA and RNA nucleotides
- ATP contains adenine, like nucleotides in DNA/RNA
- ATP is a ribose sugar like RNA
- ATP has three phosphate groups instead of one
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How does ATP release energy
- ATP is hydrolysed into adenosine diphosphate (ADP) and an inorganic phosphate (pi)
- this releases energy for cellular processes
- it is a hydrolysis reaction, using a water molecule
- it is catalysed by atp hydrolase
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Why is ATP not a good long term energy store
- the phosphate bonds in ATP are unstable
- fats and carbohydrates are better for long term energy storage
- ATP is more suited as an immediate energy source
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What process reforms atp from ADP
Phosphorylation.
ADP + Pi = ATP (+water)
This is a condensation reaction
Catalysed by ATP synthase
During respiration and photosynthesis
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What are the key properties of ATP that make it suitable for energy transfer
1. small: moves easily into, out of and within cells
2. Water soluble: suited for aqueous environments where reactions occur
3. Inorganic phosphate can be used to phosphorylase other compounds, making them more reactive
4. Intermediate energy bonds: releases enough energy for cellular reactions but not too much to avoid heat wastage
5. Releases energy in small quantities: preventing energy waste
6. Easily regenerated: quickly reformed by ADP
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