unit 1 Biological molecules Flashcards
( coursebook imformation) (104 cards)
1
Q
What is covalent bonding ?
A
- atoms that share a pair of electrons in their outer shells. As a result the outer shell of both atoms is filled and a more stable compound (molecule) is frormed
2
Q
what is ionic bonding ?
A
- Ions with opposite charges attarct one another. This electrostatic attraction is known as an ionic bond.
3
Q
what is hydrogen bondong ?
A
The electrons within a molecules are not evenly distributed but tend to spend more time at one position. this region is more elctronegatively charged than the rest molecule.
a molecule within a uneven distribution of charge is said to be polarised(polar molecule)
4
Q
what are monomers and polymers ?
the importance of these n example
A
- long chains of monomers sub- unit are called polymers
- the monomers are based on carbons
- “polythene” and “polyesters” = are industrially produced
- ” polysaccharides “ “ polypeptides” “ polynucleotide” are made naturally by living organisms
5
Q
what are the example of monomers ?
A
- monossaccharides
- amino acids
- nucleotides
6
Q
what are examples eg polymers
A
- polysaccharides
- polypeptides
- polynucleotides
7
Q
Carbohydrates:
- the basic monomer
- a pair of monomer
- combined monomer
A
- the basic monomerunit is sugar ( sccharide) therefore the monomer is called ( monosaaccharide )
- a pair of monosaccharides can be form a disaccharide
- Monosaccharides can also be combined in much larger numbers to be polysaccharides
8
Q
what is monosaccharides ? and examples
A
- monosaccharides are sweet-tasting
- soluble substance
*general formula = Ch2O
eg. glucose , galatose and frutose
9
Q
structure of glucose
A
- glucose is hexose (6-carbons) sugar
- Formula of = C6HY12O6
10
Q
what are the two isomers of glucose and the structure.
A
- Isomers alpha-glucose : has H on top and OH bottom
- Isomer beta-glucose : Oh on top and H on bottom
11
Q
What are reducing sugar and give examples :
reduction ?
A
- Monoscaccarides and disaccharides are reducing sugar
- reduction is chemical reaction involving the gain of electrons or hydrogen
- a reguding sugar is therefore a sugar that can donate electrons (or reduce) another chemical.
12
Q
how is the reducing sugar test carried out ?
A
- Add 2cm^3 of the food sample to be tested to a test tube ( if the sample is not already in liquid form = first grind it up in water)
- add an equal volume of benedict’s reagent
- heat the mixture in a genetly boiling water bath for five miniutes
13
Q
what do you observe in the reducing sugar experiment?
A
if a reducing sugar is present an orange- brown colour is formed
14
Q
why does benedict’s reagent turn red when heated with a reducing sugar ?
A
Benedicts reagent is an alkaline solution of copper(II) sulfate. when a reducing sugar is heated with bebedict’s reagent it forms an insoluble red precipitate of copper(I) oxide
15
Q
suggest other way than comparing colour changes, in which different concentration of reducing sugar could be estimated.
A
Dry precipitate in each sample and weigh it.
the heavier the precipitate the more reducing sugar is present.
16
Q
why is it not possible to distinguish between very concentrated samples, even when their concentrations are different ?
A
once all the copper (ii) sulfate has been reduced to copper(i) oxide, further amounts of reducing sugar cannot make a difference.
17
Q
what pairs of monosaccharides form a disaccharide?
A
- Glucose + glucose = maltose ( the formation of a 1-4 glycosidic bond between two alpha glucose molecules in order to form a molecule of maltose)
- Glucose + frutose = sucrose
- Glucose + galatose = lactose
18
Q
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How are monosaccharides join ?
- bond used - the processs
A
- when monosaccharides join, a water is removed and the reaction therefore is called condensation reaction.
- the bond formed is called glycosidic bond
19
Q
how are monosaccharide released ?
A
- When water is added to a disaccharide under suitable conditions, it breaks the glycosidic bond releasing the constituent monosaccharides.
- the reaction is called hydrolysis which is the addition of water that cause breakdown
20
Q
how is disaccharides formed?
what are they ?
A
- two monosaccharides can join together in a condensation reaction to form a disaccharide. in this process a molecule of water is produced
- some disaccharides are reducing sugar
21
Q
what is the test for non-reducing sugars that do not change colours when heated?
A
- The benedict test
- which has to be hydrolysed into its monosachharide components by hydrolysed
22
Q
What is the process of non-reducing sugar ?
A
- 2cm3 of foood sample (must be in liquid form) is added to 2cm3 of benedict’s reagent. this is then placed in a water bath for 5 mins to gently warm
- if the colour does not change from ** blue** to ** brick red** then a reducing sugar is not present
- another 2cm3 of the same food sample is then taken and 2cm3 of diluted hydrochloric acid is added. the test tube is then placed in a water bath for 5 mins. (the dilute HCL will hydrolyse the disacchrides and polysacchrides into their consitutent monosacchrides)
- the solution can now be retested by adding 2cm3 of benedict reagent to solution and placing in water bath for 5 mins
- if a non reducing sugar is present in the orginal sample then a colour change from the blue benedict’s reagent to ** brick red (orange-brown)** will be observed
23
Q
what is the chemical test for starch is ?
A
- iodine/potassium iodide
- solution turns blue/black is colour from orange-brown then starch is present
24
Q
how are polysacchrides formed ?
A
It is formed from many gluose units joined together
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what are the two examples of polysaccharides and what glucoes were used ?
1. Glycogen and starch which are both formed by the condensation of alpha glucose
2. cellulose formed by condensation of beta glucose
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what is starch and what is the importance of starch ?
* startch is a polysacchride that is found in many parts of a plant in rhe form of small grains
* large amount of starch occur in seeds and storage organs such as potato tubers
* forms an important component of food and is the major energy source in most diets
* only found in plants
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how is startch formed?
startch is made up of chains of alpha glucose monosaccharides lined by glycosidic bonds that are formed by condensation reactions
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what is the structure of unbranched chains ?
the unbranched chain is wound into a tight coil that makes the molecule very compact so alot of it can
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why is startch being insoluble an advantage ?
1. it is insoluble and therefore doesn't affect water potential so water is not drawn into cells by osmosis
2. being large and insoluble it does not diffuse out of cells
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what happenes when startch are branched ?
the branched form has many ends, each of which can be acted on by enzymes stimultaneously meaning that glucose monomers are released very rapidly
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what happenes when stratch is hydrolysed ?
when hydrolysed it forms alpha glucose which is both easily transported and readily used in respiration
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importance of glycogen :
1. glycogen is found in animals and bacteria but never in plant cells
2. similar to stratch but has sjorter chains and is more highly branched
3. in animals it is stored as samll granules mainly in the muscles and the liver
4. the mass of carbohydrate that is stored is relatively small bc fat is main storage molecule in animals
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why does glycogen's structure suits for storage ?
1. it is insoluble and therefore does not tend to draw water into the cells by osmosis
2. being insoluble, it does not diffuse out of the cells
3. it is compact, so alot of it can be stored in a small space
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why is being highly branched an advantage to glycogen ?
it is more highly branched than starch and so has more ends that can be acted on simultaneously by enzymes. theremore more rapidly broekn down to form glucose monomer, which are used in respiration.
**this is important** to animals which have hugher metabolic rate and therefore respiratory rate than plants because they are more active.
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how is cellulose formed ?
it is made of monomers of beta glucose rather than alpha glucose
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structure of cellulose
1. instead of being coioled like starch, cellulose has straight unbranched chains
2. these run parallel to one another, allowing hydrogen bonds to form cross-linkages between adjacent chains
3. the hydrogen bon strengthens the cellulose
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what happenes when cellulose molecule are together
when the cellulose molecules are grouped together it forms microfibrils which in turn are arranaged in parallel groups called fibres
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what are the importance of cellulose
1. the cellulose major component of plant walls and provides rigidity to the plant cell
2. the cellulose cell wall also prevenst the cell from bursting as water enters it by osmosis
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how does cellulose prevent cells from bursting?
* it does this by exerting an inward pressure that stops any further influx of water as a result living plant cell are turgid and psh against one another, making non-woody parts of the plant semi-rigid. this is especially important in maintaining stems andleaves in a turgid state so they can provide the maximum surface are of photosynthesis
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what are the characteristics of lipids?
1. they contain carbon, hydrogen and oxygen
2. the proportion of oxygen to carbon and hydrogen is smaller than carbohydrates
3. they are insoluble in water
4. they are soluble in organic solvents as alcohols and acetone
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what are the roles of lipids?
1. souce of energy - when oxidised, lipids provide more than twice the energy as the same mass of carbohydrate and release valuable water
2. waterproofing - lipids are insoluble in water and therefore useful as waterproofing.
3. insulation - fats are slow conductors of heat and when stored beneath the body surface help to retain body heat.
4. protection - fat is often stored around delicate organs such as kidney
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what is the role of phospolipids?
* phospholipids contribute to the flexibility of membranes and the transfer of lipid-soluble substances across them
40
what is the structure of triglycerides?
* they have three fatty acids combined wirh glycero.
* eavh fatty acid forms an ester bond with glycerol in a condensation reaction
* hydrolysis of triglyceride therefore produces glyverol and three fatty acids
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what is amylose
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what is amylopectin
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what are saturated ?
when there is no double bonds between carbon atoms
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what is mono saturated ?
when there is one double bond between csrbon atoms
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what is polysaturated? disadvantage and eg
when more than one double bond between carbon atoms.
the double bond causes the molecule to bend. they cannont therefore pack together so closley making the liquid at room temperature.
eg oils
46
a hydrophilic head ?
which interacts with water but not with fat.
(it is attracted to it )
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a hydrophobic tail ?
which orients itself away from water but mixes readily with fat.
water-hating
48
explain the porpoties of phospholipids:
phospholipids are polar molecules
* this means having a hydrophilic phosphate head and a hydrophobic tail of two fatty acid
* phospholipids form a bilayer within cell-surface membranes
* a hydrophobic barrier is formed between the inside and outside of a cell
49
advantage of hydrophilic phosphate
phospholipid molecules help to hold at surface of the cells-surface membrane
50
how is glycolipids formed and why is it important:
* the phospholipids structure allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane
* the glycolipids are important in cell recognitions
51
What is the test for lipids ?
The emulsion test
1. 2cm3 of sample added to 5cm3 of ethanol
2. shake the tube to disolve
3. milky-white emulsion = presence of lipid
4. ( as a control ) make sure to repeat the process using water instead of the sample = remain clear
52
whay does it turn cloudy colour
-due to the lipid in sample being finely dispersed in the water to form emulsion. light passing through this emulsion is refracted as it passes from oil droplets to water droplets making it appear cloudy.
53
how are protein formed?
* when **amino acid** join together to form polypeptide and the **polypeptide** is joined to form proteins.
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four different chemical groups that the amino acid attached to
1. amino group = NH3
2. carboxyl group = COOH
3. hydrogen atom = H
4. R = range of chemical group
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how is dipeptide formed?
* amono acid combine to form a dipeptide by the condensation reation.
* they are linked by the peptide bond
* the peptide bond of the dipeptide bond is broken by hydrolysis to give its amino acid
*
56
what is the primary structure ?
a protein that contains the initial sequence of amino acids and will therefore determine the proteins funtion in the end.
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what is the secondary structure b?
- is the shape that the long polypeptide chain to be twisted into a 3D shape, such as coil known as a spiral alpha-helix
- also forms beta pleated sheet
- the hydrogen in -NH has slightly postive charge while the oxygen in C=O has a slightly negative charge as result to weak hygrogen bonds can form the alpha helicas and beta pleated sheets
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what is the tertiary structure ?
the structure is due to the bending an twisting of plypeptide helix into compact structure.
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what are the types of bond in tertiary structure?
Disulfide bridges
- between sulfur of amino acid (cysteine)
-are strong and not easily broken
ionic bond
-between carboxyl and amino groups that are not involved in the peptide bond
-easily broken by ph and are weaker than disulfide bridges
hygrogen bonds
-numerous
-easily broken
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what is quaternary structures ?
-aroses from combination of a number of different peptide chans and associated non-protein
-heamogobin
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test for proteins
-Biuret test
-add an equal volume of sodium hydroxide (NaOH) to the test tube at room temperature
-add drops of diluted copper(ii) sulfate solution and mix gently
**-purple** = presence of peptide bond = protein
***-blue -*** negative result
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what is globular proteins?
-when proteins such as enzymes are compact
-the pieces of tring are fewer and rolled into a ball
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what is fibrous proteins ?
-when protein such as keratin are long and this can be used to form fibres.
-many pieces of string are twisted together into a rope
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what are enzymes ?
* they are globular proteins whose shape is determined by the primary sequence of amino acids
* act as catalysts
* without enzymes reactions would proceed too slowly to sustain life
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how does enzyme increase the rate of reaction ?
-enzymes work by lowering this activation energy which allows enzymes to take places in lower temperature than normal
-this enables metabolic process to occur rapidly
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what is active site?
* area of the enzymes that is made up of only a few amino acids and forms a small depression in the overall enzyme
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what are substrate ?
* the molecule that the enzymes acts upon
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what is the induced fit model?
* enzymes are specific to substarets they bind to = only one type of substrate fits into the active site of the enzyme
* when the enzyme substrate bind they form and enzyme substrate complex
* the enzyme is flexible and can mould itself around the substrate
* enzyme is altered so that the active sire of enzyme fits around the substrate
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what is the lock key model?
* each key has a specific shape that fits and operates only a single lock
* a substrate will only fit the active site of only particular enzyme
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limitation if the lock and key model ?
the enzyme (lock) is considered to be rigid structure
71
how is the enzyme catalysed reactions measured?
we usually measure its time course, how long it takes for a particular event to run its course.
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what are the two most frequently measured in the enzyme catalysed reaction ?
1. the formation of the products of the reaction
2. the disappearance of the substrate ( the reduction in concentration of starch when jts acted upin by amylase )
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effect of temperature on enzyme action
1. a rise in temperature increases the kenetic energy of molecules.
2. as a result the molecules move around more rapidly and collide with each other more often.
3. there are more effective collisions resulting in more enzyme-substrate complexes being formed and so the rate of reaction increases
74
what happen when temperature rises beyound the optimum temperature ?
1. when the temperature rises it also begins to cause the hydrogen and other bonds in the enzyme molecule to break
2. enzyme abd active site to change shape
3. the substrate wont be able to fit into the active site
4. which slows down the rate of reaction
5. the enzyme does not function again
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what is denaturation?
* is a permanent change, the enzyme does not function again
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effect of the PH on enzyme action and what it measures
* the ph of a solution is a measure of the hydrogen ion concentration
* can be calculated using ph = -log[H+]
* the enzymes shape can be effected by ph as it can disrupt the bonds in tertiary structure of the enzyme
* like temp enzymes work at different optimum pH's
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effect of enzyme controlle by enzyme concentration
* the rate of reaction increases as enzyme concentration increases as there are more active sites for substartes to bind to
* however, increasing the enzyme concentration beyound a certain point has no effect on rate of reaction as there are more actie sitesthan substrate si substrate concentration becomes the limiting factors
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effect of substarte concentration
* rate of reaction increases as more enzyme-substrate complexes are formed
* beyound certain point the rate of reaction no longer increass as enzyme concentration becomes the limiting factor
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whats is competitive reversible inhibitors and how does the concentration effect:
1. it is an inhibitor that worh by "competing" with the substrate for the active site on the enzyme they have a similar shape to the substrate molecule
2. increase = rate of reaction will decrease as the active sites are temporarily blocked
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what is noncompetitive reversible inhibitors and how does that effect enzymes
1. they bind to a site on the enzyme that is not the active site which changes the 3D tertiary structure of the enzymes
2. increase= rate of reaction decreases as the subsreate cannot form the product
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structure of DNA
1. DNA holds genetic information
2. DNA nucleotide are deoxyribose sugar, a phosphate group and one of the nitrogen containing ogranic bases adenine, cytosine, guanine or thmine
3. has a double helix structure
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Structure of RNA
* transfers the genetic information from DNA to ribosomes for protein synthesis
* ribosomes are formed of ribosomal RNA and proteins
* both deoxyribonucleic and ribonucleic acid are polymers of nucleotides
* Nucleotide are ribose sugar, a phosphate group and one of the nitrogen containing organic bases adenine, cytosine, guanine or uracil
* short polynucleotide
83
how is dinucleotide and polynucleotides formed ?
* nucleotides join together by phosphodiester bonds formed in condensation reactions..
* the result is a dinucleotide, which join to form polynucleotides
* this bond forms between the deoxyribose sugar of one nucleotide and the phosphate group of another
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what is a double helix DNA
* when composed of two polynucleotide joined together by a hydrogen bonds between complementary bases
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what are the base pairing
1. adenine = Thymine
2. guanine = cytosine
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why is DNA a stable molecule
1. the (phosphodiester backbone) protects the more chemically reactive nitrigen containing organic bases inside the double helix
2. hydrogen bond form brdges between the phosphodiester uprights = higher proportion of C-G pairings makes DNA more stable
87
steps for DNA replication
| ( semi conservation replication )
1. an enzyme ** DNA helicase ** causes the two **strands of DNA to seperate** breaking the hydrogen bonds between the complementary bases
2. one of the strands is used as the template and complementary base pairing occurs between the **template strand and free nuclotides **
3. once activated nucleotides are bound the enzyme DNA polymerase joins them together by forming phosphodiester bonds
4. results = two identical strands of DNA are formed
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what is a semi conservative replication ?
* DNA ensures genetic continuity between generations of cells meaning that genetic information is passed one from one generation from the next
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what is the process of energy release?
* energy released when ATP is hydrolysed to form ADP and a phosphate molecule
* this process is catalysed by ATP hydrolase
* energy comes from bond between phosphate molecules
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what is the property of phospate that causes energy release
* the phospate molecules bonds are very unstable and this have a low activation energy
* the breaking of these is quick and releases a considerable amount of energy
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what is inorganic phosphate used for
* can be used to phosphorylate other compounds as result making them more reactive
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how is ATP produced in photosynthesis and respiration
the inorganic phosphate can be used to phosphorylate other compounds in respiration and phososynthesis
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properties of ATP
1. ATP is an immediate source of energy and is more desirable to used than glucose as ATP can be broken down in a single step to release a manageable quanity of energy
2. ATP isnt stored in large quanities as it can be reformed from ADP in seconds
3. metabolic process, movement, etc
94
explain how water is polar molecule
* due to the unever distribution of charge within the molecules the oxygen atoms attrcts electrons a bit more strongly than the hydrogen atoms
* the uneven sharing of electrons gives the water molecule a slightly negative charge near its oxygen atom
* slight positve charge near its hydrogen atoms
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properties of water and explain
1. metabolite= metabolic reactions such as condensation and hydrolysis which are used to forming an breaking chemical bonds
2. solvent = allowing gases to readily diffuse as well as enzymes and waste products
3. high heat specific capacity = water molecules stick together + hydrogen bond meaning that alot of energy is required to break these bonds
96
how does water act as a buffer
high heat specific capacity: water molecules stick togetehr with hydrogen bonds meaning that a lot of energy is required to break these bonds
- helps to minimise temp in living things = acts as a buffer
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how does water have large latent heat of vaporisation ( properties )
* hydrogen bonding means that it requires a lot of energy to evaporate 1 gram of water.
* large LHV = evaporation of water provides a cooling effect with little water loss ( sweating )
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how is strong cohesion effective
- strong cohesion between molecles enables effective transport of water in tube like the xylem
- the strong cohesion support column of water as a result of strong cohesion the surface tension at the water-air boundary is high
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where does inorganic ions occur
- in cytoplasm and body fluid of organisms ( high con or low con)
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what are the essential ions and their use ?
1) hydrogen ions = determine the pH of substances such as blood (the higher the con of hydrogen = lower ph)
2) iron ions = component of heamoglobin (oxygen carrying ) in red blood cells
3) sodium ions = involved in co - transport of glucose and amino acids
4) sodium ions = co trnasport of glucose and amino acids
5) phosphate ions = component of DNA and ATP
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