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Biology/Business/IT > Topic 1: Biological Molecules > Flashcards

Topic 1: Biological Molecules Flashcards

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1
Q

What are some examples of monomers?

A

Some examples include amino acids, Monosacchirides, and nucleotides

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2
Q

What is a condensation reaction?

A

A condensation reaction is a reaction where two molecules join together with the formation of a chemical bond and involves the elimination of a molecule of water

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3
Q

What is a hydrolysis reaction?

A

A Hydrolysis reaction breaks a chemical bond between two molecules and involves the use of a water molecule

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4
Q

What ratio are hydrogen and oxygen atoms present in carbohydrates?

A

2:1
H:O

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5
Q

What/how are carbohydrates classified as?

A

Carbohydrates can be classified as:
-Monosaccharides
-Disaccharides
[Both are small,soluble molecules that are easy to transport and sweet tasting]
-Polysaccharides

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6
Q

What are monosaccharides and what are some of their uses?

What are 3 common examples of monosaccharides?

A

–>They are the basic molecular units (monomers) of carbohydrates

–>They are basic sugars (give a positive
Benedict’s result of a layer of brick red precipitate)

–>They are mainly used in respiration to provide energy

–>They are used in growth during the formation of larger carbohydrates

–>They include: Glucose
Fructose
and Galactose [all isomers of each other]

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7
Q

What are the isomers of Glucose?

A

1)Alpha Glucose
2)Beta Glucose

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8
Q

How are Disaccharides formed?

A

A disaccharide is formed when two monosaccharides are joined together by a glycosidic bond formed in a condensation reaction

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9
Q

What are 3 examples of disaccharides and how are they formed?

A

1) glucose + glucose –> maltose + water

2) glucose + fructose –> sucrose + water

3) glucose + galactose –> lactose + water

[C6H12O6 + C6H12O6–> C12H22O11 + H2O]

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10
Q

What is a quantitative benedict’s test?

A

a quantitative benedicts test produces a colour whose intensity depends in the concentration of reducing sugar in a solution.

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11
Q

How do you do a Quantitative benedict’s test?

A

1) perform benedicts test on reducing sugar solutions of known concentrations

2)Use a colorimeter to measure the absorbance of each known solutions

3)Plot a graph of known concentration (on X-axis) against absorbance value (on Y-axis) –> this is called a calibration curve

4)add a line of best fit

5)Repeat benedicts test with the unknown sample (keeping all the control variables the same)

6)Use the absorbance value of the unknown to read off the calibration curve to find its concentration

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12
Q

How do you test for a non-reducing sugar e.g. Sucrose?

A

1)Take a small sample and heat it to 95 C with benedicts solution to confirm a negative result

2)Hydrolise another sample by heating it to 95 C with dilute acid e.g HCL

3)when cooled, neutralise the acid with an alkali

4)Add the same concentration of benedicts solution and heat in a 95 C water bath

5) A positive brick red coloured precipitate indicates a non reducing sugar (sucrose) was present

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13
Q

What are the 3 polysaccharides/polymers of glucose and how are they formed?

A

They are:
-Cellulose
-Starch
-Glycogen

and they are formed by the joining of glucose molecules during condensation reactions.

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14
Q

How are Glycogen and Starch formed?

A

Glycogen and Starch are formed by the condensation of Alpha glucose

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15
Q

How is Cellulose formed?

A

Cellulose is formed by the condensation of Beta Glucose

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16
Q

What are some properties of Polysaccharides?

A

-They do not taste sweet

-They are relatively insoluble in water

-They are non-reducing sugars (give a negative result in the benedict’s test)

-They function as storage (Starch and Glycogen) or structural molecules (cellulose)

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17
Q

What is Starch?

A

The storage carbohydrate found in plants,consisting of long,branched chains of alpha glucose molecules linked together by glycosidic bonds as a result of condensation reactions.

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18
Q

Where is starch stored?

A

Starch is stored in starch grains in the cytoplasm of plant cells

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19
Q

How is Starch ideally suited to its function as a storage compound?

A

-Large,so it cannot cross the cell-surface membrane and leave the cell

-Insoluble,so therefore is osmotically inactive (i.e does not draw water into a cell via osmosis which could lead to cell damage)

-The molecule has a helical shape, forming a compact store

-It is branched so glucose is easily released for respiration

(More branched= faster hydrolysis)

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20
Q

what is glycogen?

A

Glycogen is the storage compound found in the cytoplasm of cells.

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21
Q

how is glycogen formed?

A

Glycogen is formed by the condensation of Alpha glucose

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22
Q

Where is glyocgen stored?

A

In mammals it is stored in large amounts in liver and muscle tissues.

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23
Q

How is glycogen suited to its function as a storage compound?

A

-Insoluble and therefore osmotically inactive

-It has a similar structure to starch but with more branches (free ends) which means it can be hydrolysed more rapidly to release glucose for respiration.

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24
Q

What is cellulose?

A

Cellulose is a polymer of Beta glucose molecules joined together by glycosidic bonds (formed in condensation reactions) to produce long,straight chains of Beta glucose molecules

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25
Q

Where is cellulose found?

A

Cellulose is found in the cell wall of plants,which provide rigidity and shape to the cell,preventing the plant cell from bursting (osmolysis)

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26
Q

describe 2 properties of cellulose

A

-in cellulose, every other Beta glucose monomer is inverted.

-in cellulose hydroxyl (OH) groups project from either side of the Beta glucose chain and form hydrogen bonds with the OH groups of other adjacent chains, producing a three-dimensional structure known as a microfibril (which provides strength)

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27
Q

describe properties of the hydrogen bonds

A

The hydrogen bonds are weak individually but strong collectively

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28
Q

What elements do lipids contain?

A

Lipids contain the elements carbon,hydrogen and oxygen

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29
Q

What is a distinct fact about lipids?

A

Lipids are insoluble in water but soluble in a range of organic solvents e.g alcohol

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30
Q

What are the 2 types of lipids you need to know about?

A

1)Triglycerides
2)Phospholipids

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31
Q

What are Triglycerides?

A

-Triglyceride molecules have 3 fatty acids joined to one glycerol molecule.

-Joined in 3 condensation reactions,with the loss of 3 water molecules and forming 3 ester bonds.

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32
Q

What is the formula for glycerol?

A

C3H8O3

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33
Q

What is the general formula of a fatty acid?

A

The general formula for a fatty acid is R-COOH

(the R represents a long hydrocarbon chain and COOH is a carboxylic acid group)

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34
Q

What is the difference between saturated and unsaturated fatty acids?

A

Saturated=No double bonds between the carbon atoms

Unsaturated=One or more double bonds between the carbon atoms

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35
Q

How can lipids be Hydrolysed?

A

Lipids can be hydrolysed by:
-Heating with an acid or alkali
-using the enzyme lipase at its optimum temperature and PH

36
Q

What are some properties of triglycerides?

A

-They possess a high proportion of carbon-hydrogen bonds so that they release twice as much energy as carbohydrates during respiration

-Have a high ratio of hydrogen to oxygen atoms,releasing water when respired (metabolic water) (important for organisms in dry deserts)

-Are non-polar molecules (have no electrical charge) and thus, —-insoluble in water ( so are ideal storage compounds as they are osmotically inactive)

37
Q

What are Phospholipids?

A

Phospholipids are lipids containing a phosphate group.

38
Q

What does a phosphate group usually replace?

A

In the commonest type of phospholipid,a phosphate group replaces one of the fatty acid molecules.

39
Q

What are some properties of Phospholipids?

A

-A phospholipid molecule consists of one glycerol,two fatty acids and a phosphate group joined by a condensation reaction (which forms ester bonds)

-The phospholipid molecule has a polar Hydrophillic head (attracts water) containing the phosphate group, and a non-polar Hydrophobic tail (repels water) consisting of the long fatty acid chains

NOTE: the Phosphate head conducts electricity

40
Q

How do Phospholipids place themselves inside water?

A

The head points downwards (towards the water) and the tail points upwards (away from the water).

41
Q

What is the structure of phospholipids inside a cell membrane

A

They form a bilayer (two layers) of phospholipids due to the hydrophobic tails being repelled by water.

42
Q

What is the emulsion test for lipids?

A

The emulsion test is a test that is used to detect Lipids in a sample:

1) A small amount of sample is placed in a test tube with ethanol (alcohol)

2)Shake the mixture so the fat dissolves

3)Add to water in another test tube and mix the contents

4)A white emulsion of fat droplets indicates a lipid is present

43
Q

Give 3 similarities in the structure of phospholipids and triglycerides

A

-Both are insoluble in water

-Both contain Glycerol

-Both contain Ester Bonds

-Both contain C,H and O (but phospholipids also contain ‘P’)

44
Q

Give 2 differences in the structure of phospholipids and triglycerides

A

-Triglycerides have 3 fatty acids (phospholipids have 2 + a phosphate group)

-Triglycerides are hydrophobic/non-polar and phospholipids have hydrophillic and hydrophobic regions

45
Q

How is an ester bond formed in both Triglycerides and Phospholipids?

A

A condensation reaction between glycerol and fatty acid (R-COOH) forms an ester bond

46
Q

What elements do proteins contain?

A

Proteins contain carbon, hydrogen,oxygen,nitrogen and sometimes sulfur

47
Q

What are some key facts about amino acids?

A

-All amino acids contain an amine group (NH2) and a carboxylic acid group (COOH) but differ in their carbon-containing side group ‘R’

-Amino acids are joined together by peptide bonds (-CONH-) formed by condensation reactions

-Two amino acids join together in a condensation reaction to form a dipeptide

-Many amino acids join together in a chain form a polypeptide

-A protein may consist of one or more polypeptides

48
Q

How can proteins be hydrolysed?

A

Proteins can be hydrolysed by heating with acid or by using enzymes (proteases)

49
Q

What is the primary structure of Proteins?

A

Refers to the sequence of the amino acids in the polypeptide chain (determines the specific shape of the protein)

50
Q

What is the secondary structure of Proteins?

A

Represents the folding or coiling of the polypeptide chain as a result of hydrogen bonding between amino acids

(secondary structures include the alpha helix and beta pleated sheet)

51
Q

What is the tertiary structure of proteins?

A

-Formed by further folding and coiling of the secondary structure due to hydrogen bonds, ionic bonds and disulfide bonds (formed between the R group of amino acids which determine the sequence of amino acids in the primary structure)

-They are specific and unique

-The tertiary structure of an enzyme determines the shape of its active site and its precise function

52
Q

-What is the quaternary structure of proteins?

-What is Denaturation in proteins?

A

-When proteins consist of more than one polypeptide chain (held together by ionic bonds,hydrogen bonds and sometimes disulfide bonds)

-Denaturation is an alteration in the tertiary structure of a protein. (this loss of the 3D shape of the protein is often irreversible and the protein is no longer functional)

53
Q

What are enzymes?

A

-Enzymes are biological catalysts regulating biological processes in living organisms.

54
Q

What determines the specific function of an enzyme?

A

The protein nature and tertiary structure determine the specific function of an enzyme.

55
Q

What do enzymes do?

A

Enzymes catalyse a
wide range of intracellular and extracellular reactions.

56
Q

What determines enzyme specificity and therefore the shape of the active site of the enzyme?

A

The tertiary structure

57
Q

How do enzymes increase the rate of reaction?

A

Enzymes increase the rate of a reaction by Lowering the activation energy (the energy required for chemical reactions to take place)

58
Q

What are the 2 theories behind the shape of the active site of an enzyme?

A

-Initially, the shape was thought to be fixed or rigid (Lock and Key model) but that model has now been replaced by the (Induced Fit Model)

(Molecules complementary to the the active site will bind to it to form an Enzyme-substrate complex.

59
Q

What is the ‘Induced Fit Model’ ?

A

-The induced fit model suggests that the active site of an enzyme can slightly change shape as it is flexible, only the presence of the correct substrate induces (causes) the change in the shape of the active site.

60
Q

What are the factors which affect the rate of enzyme reactions?

A

1 ) Substrate concentration–> increasing the substrate concentration will increase the rate of reaction as collisions between substrate and enzyme molecules are more likely
(However the rate of reaction then levels out as all the active sites get occupied (saturated) by the substrate molecules)

2 ) Enzyme concentration–> When the concentration of substrate is in excess (i.e. all the active sites are saturated) then an increase in enzyme concentration increases the rate of reaction.

3 ) Temperature–> Enzymes are less effective at lower temperatures as the reactant molecules have less kinetic energy.an increase in temperature provides the molecules with more kinetic energy which results in more collisions between the active site of enzymes and substrate molecules, therefore more enzyme substrate complexes are formed. (as the optimum temperature is reached)
-however if the temperature goes past the optimum then the tertiary structure will denature as the hydrogen and ionic bonds are broken.

4 ) PH–> Enzymes have an optimum PH at which the rate of reaction is at a maximum
Very different PHs from the optimum cause denaturation.

61
Q

What are enzyme inhibitors?

A

Enzyme inhibitors are chemicals which slow down the rate of enzyme catalysed reactions

62
Q

What is a competitive inhibitor?

A

-An inhibitor which has a similar structure to the substrate molecule and competes with it for attachment to the active site.

–>Therefore the rate of reaction is reduced as the substrate cannot bind to the active site of the enzyme, however this competitive inhibition can be reduced by the addition of more substrate as it will outcompete the inhibitor molecules for attachment to the active site.

63
Q

What is a non-competitive inhibitor?

A

-An inhibitor which is not similar in structure to the substrate.

–>It combines at a position other than the active site to form an enzyme/inhibitor complex, altering the tertiary structure (and shape of the active site) of the enzyme so therefore the substrate cannot attach as it is no longer complimentary.

-(The degree of inhibition is completely dependent on the amount of inhibitor present) + (a high concentration of substrate will not reduce non-competitive inhibition)

64
Q

What is DNA and RNA?

A

DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid) are both nucleic acids and both are polymers of monomers called nucleotides.
:
–>DNA holds genetic information
–>RNA transfers genetic information from DNA to the ribosomes.

65
Q

What is the structure of DNA and who discovered it?

A

Watson and Crick discovered the structure of DNA: it consists of 2 polynucleotide strands joined together by hydrogen bonding to form a double helix structure.

66
Q

What does each nucleotide consist of?

A

Each nucleotide consists of:
1) The pentose sugar (deoxyribose)
2) a phosphate group
3) one of four nitrogen-containing bases ( Adenine/Thymine/Cytosine/Guanine)

67
Q

How are nucleotides joined together?

A

The nucleotides within each strand are joined together by phosphodiester bonds formed in condensation reactions.

(The sugar and phosphate group form the backbone of the polynucleotide strands whilst the bases are oriented towards the centre of the helix to protect them from reacting with other chemicals)

{The bases on one of the strands have a complementary base pairing with the other strand}
–> AT
CG

68
Q

How are the bases joined together?

A

The bases are joined together by Hydrogen bonds (which are individually weak but are strong collectively) which maintain a stable structure.

{The DNA is then further coiled to produce a super helix, providing a compact store of genetic information}

69
Q

What are the functions of DNA?

A

1) Genes are sections of DNA which contain coded information as a specific sequence of bases, these genes code for polypeptides that determine the nature and development of organisms

2) Self replicate (mitosis and meiosis)

3) Alterations in its base sequence (mutations) occur providing genetic diversity (variation) and via natural selection, the basis for evolution.

70
Q

How is each structure of DNA adapted to its function?

A

1) Sugar-Phosphate backbone–> Gives strength

2) Helix–> Gives compact shape and Protects sequence of bases

3) Double-stranded –> Each strand serves as a template in replication
-Protects sequence of bases
-Makes molecules more stable

4) Large molecule–> Large amounts of information can be stored

5) Many Hydrogen Bonds–> -Gives stability
-individual hydrogen bonds are weak allowing the helix to unzip easily for replication.

6) Sequence of bases–> Codes for specific sequence of amino acids in a polypeptide

7) Complementary base pairing–> Enables information to be replicated accurately

71
Q

What are each of the structures of DNA?

A

1) Sugar-Phosphate backbone

2) Sequence of bases

72
Q

What is RNA and what is its structure?

A

-RNA is a relatively short polynucleotide and its structure is made up of: -Pentose sugar (Ribose instead of Deoxyribose)
-The organic base Uracil replaces Thymine (the 3 other bases are the same except for Thymine)
-mRNA and tRNA are single stranded in comparison to double stranded in DNA

73
Q

When does DNA replication occur?

A

-DNA replication occurs during the process of cell division and has an important role in the growth and reproduction of organisms.

74
Q

What are the steps in (Semi Conservative) DNA replication?

A

1) The enzyme DNA helicase breaks the hydrogen bonds and separates the two polynucleotide strands
( Each of the strands act as a template for the formation of two new complimentary strands)

2) Individual DNA nucleotides align and attach by hydrogen bonding to the exposed bases of each template strand according to specific complementary base pairing ( Adenine pairs with Thymine and Cytosine pairs with Guanine)

3) The DNA nucleotides in each new strand are joined together by phosphodiester bonds in condensation reactions catalysed by the enzyme DNA polymerase

(The 2 DNA molecules are identical to each other and to the original DNA)

{Each newly formed DNA molecule contains one of the original polynucleotide strands and a new strand, hence the term semi-conservative replication}

75
Q

who showed that replication is semi-conservative?

A

Meselson and Stahl

76
Q

How did Meselson and Stahl show that replication is semi-conservative?

A

1) They grew bacterium E.coli on a medium in which the normal isotope 14N was replaced with the heavy isotope 15N

2) the cells were allowed to divide until it was certain that 15N had been incorporated into the entire DNA

3) They were then transferred to a medium containing only the normal isotope 14N and allowed to divide

4) Samples of the bacteria were taken after each division and the DNA was extracted and spun in a centrifuge.–> DNA containing the heavy isotope 15N is slightly heavier than DNA containing the normal isotope 14N

77
Q

What is ATP and what is it made up of?

A

ATP (Adenosine triphosphate) is used as the immediate energy source by cells for biological processes.

{It is formed from a molecule of ribose, adenine and 3 other phosphate groups}

78
Q

How is ATP used?

A

ATP is continuously hydrolysed to release energy and then resynthesised.

79
Q

How is ATP hydrolysed?

A

-ATP is hydrolysed into ADP (Adenosine Diphosphate) and an inorganic phosphate group (Pi) is catalysed by the enzyme ATP hydrolase.

80
Q

What happens after the hydrolysis of ATP?

A

–>The energy released during the hydrolysis of ATP can be coupled to energy requiring reactions within cells (e.g. protein synthesis)

–>The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds, often making them more reactive (e.g. glucose is phosphorylated during respiration to form glucose phosphate, making it more reactive.

81
Q

How is ATP resynthesised?

A

-ATP is resynthesised by the condensation of ADP and Pi (inorganic phosphate).This reaction is catalysed by the enzyme ATP synthase during photosynthesis, or during respiration.
(It is the energy released from respiration or photosynthesis that enables the resynthesis of ATP)

82
Q

What is Water?

A

-Water is the most abundant compound on Earth and makes up 60 to 95% of all living organisms.
(It consists of 2 hydrogen atoms covalently bonded to 1 oxygen molecule)

83
Q

What is responsible for the properties of water?

A

Weak hydrogen bonds between the water molecules.

84
Q

What are all the different roles of Water?

A

1) Metabolic Rate–> Water is a metabolite in many metabolic reactions including:
–>Condensation and hydrolysis reactions
–>required for photosynthesis
–>a metabolic product of respiration ( important for organisms living in dry conditions)

2) Solvent–> Water is a solvent and is used:
–>To transport nutrients e.g. glucose in blood, and sucrose in phloem of plants
–>To remove excretory products e.g. urea, ammonia.
–>as a medium in which metabolic reactions can occur.

3) Temperature regulation–>

-Water has a relatively high heat capacity (it can absorb a large amount of heat energy before rising in temperature) due to the energy being absorbed by hydrogen bonds:
–>It minimises the increase in temperature within cells
–>helps prevent dangerous fluctuations in temperature in aquatic habitats

-Water also has a relatively large latent heat of vaporisation (as energy is required to break the hydrogen bonds) , providing a coolinh effect with the loss of water through evaporation:
–>Helps some animals to maintain a constant body temperature through sweating
–>Has a cooling effect in plants via transpiration.

4) Support–> -Internal Support:
–>Strong Cohesive forces between water molecules due to hydrogen bonding support water columns in the tube like transport cells (e.g. xylem) of plants, allowing transport from roots to leaves.
–>Provides support in non-woody plants via turgor pressure (as it is not easily compressed) e.g. hydrostatic skeleton in earthworms.

–> -External Support:
–>Strong Cohesive forces between water molecules due to hydrogen bonding produce surface tension where water meets air, which enables insects to walk on the surface of water or be suspended at the surface
–>Water provides buoyancy for aquatic organisms e.g. whales

85
Q

What are inorganic ions and where do they occur?

A

-Inorganic ions are charged particles (ions) that do not contain carbon-hydrogen bonds, making them “inorganic”.

-Inorganic ions occur in solutions in the cytoplasm and bodily fluids of organisms (some in high concentrations and others in very low concentrations)

86
Q

What are the roles of these inorganic ions?:
-Sodium
-Iron
-Hydrogen
-Phosphate

A

1) Sodium–> Co-transport of glucose and amino acids across cell membranes

2) Iron–> Component of haemoglobin which transports oxygen.

3) Hydrogen–> important in determining pH and thus affecting protein structure and enzyme activity

4) Phosphate–> important as a structural component of DNA, RNA and ATP.

Biology/Business/IT (8 decks)

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