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A Level Biology Revision > Biological Molecules- Joseph Felton > Flashcards

Biological Molecules- Joseph Felton Flashcards

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1
Q

What is the difference between a monomer and a polymer?

A

Monomer is a small single molecule, can be linked together to form polymer, polymer is a larger molecule made of many monomers.

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2
Q

What is a condensation reaction?

A

joining two monomers together, removal of water, chemical bond formed.

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3
Q

What is a hydrolysis reaction?

A

separation of a polymer into constituent monomers, addition of water, chemical bond broken.

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4
Q

Monosaccharides?

A

Alpha and beta Glucose, galactose, fructose.

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5
Q

What Monosaccharides are used to make lactose, maltose and sucrose?

A

Lactose=Glucose+Galactose
Sucrose=Glucose+Fructose
Maltose=A Glucose+A Glucose

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6
Q

How are glycosidic bonds formed?

A

Condensation reaction, removal of water, Monosaccharides form polymers. glycosidic bond formed between two monomers.

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7
Q

How does polymerisation result in the formation of a polysaccharide?

A

Many condensation reactions, lots of glycosidic bonds created between Monosaccharides, removal of water. Monosaccharides linked together to form starch or glycogen.

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8
Q

How do you carry out the test for reducing sugars?

A

Benedict’s test, 2cm3 of sample, equal volume of Benedict’s reagent, heat mixture in gently boiling water bath for 5 minutes, orange- brown shows reducing sugar.

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9
Q

How do you carry out the test for non-reducing sugars?

A

Add 2cm3 of food sample to 2cm3 of dilute hydrochloric acid, add sodium hydrogen carbonate to neutralise acid, re-test solution by gently heating it with 2cm3 of Benedict’s reagent for 5 minutes, orange shows reducing sugar present.

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10
Q

How do you carry out the test for starch?

A

The iodine test, place 2cm3 of sample into a test tube, add two drops of iodine solution, presence of starch shown by blue colouration.

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11
Q

Explain how the glycosidic bonds in starch and glycogen influence its structure and relate this to their functions and properties?

A

Starch has many branches which can be acted on simultaneously by enzymes, starch is also compact, large and insoluble, Glycogen is more highly branched than starch allowing a more rapid breakdown by enzymes. Glycogen is also compact, large and insoluble.

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12
Q

Explain how the glycosidic bonds in cellulose influence its structure and relate this to its function and properties?

A

Beta glucose forms glycosidic bonds which creates straight, unbranched chains, chains linked by hydrogen bonds, microfibrils form fibrils which all add to collective strength.

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13
Q

What is a lipid?

A

group of substances that contain hydrogen, carbon and oxygen, they are insoluble, main group is called triglycerides (fats and oils)

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14
Q

What are the roles of lipids?

A

Source of energy, waterproofing, insulation and protection.

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15
Q

Describe the structure of triglycerides?

A

3 fatty acids and a glycerol

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16
Q

How do triglycerides form fatty acids and a glycerol and recall what an ester bond is?

A

Hydrolysis reaction, ester bond broken between fatty acids and glycerol, addition of water.

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17
Q

Recognise saturated and unsaturated fatty acids?

A

Saturated have no double bonds, mono-unsaturated and poly-unsaturated have carbon double bonds and have a kink in the chain.

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18
Q

How is the structure of triglycerides related to their structure?

A

Triglycerides are non-polar and are insoluble, low mass to energy ratio making them good storage molecules.

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19
Q

Describe the structure of phospholipids?

A

2 fatty acids, a phosphate and a glycerol.

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20
Q

Explain the properties of phospholipids related to their structure?

A

Being polar molecules they form a bilayer within an aqueous environment. Phospholipid structure allows them to form glycolipids when combined with carbohydrates.

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21
Q

Compare the different properties of triglycerides and phospholipids?

A

Phospholipids only have 2 fatty acids and a phosphate whereas triglycerides have 3 fatty acids. Phospholipids have a hydrophilic head and hydrophobic tail.

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22
Q

Describe the test for lipids?

A

Emulsion test, 2cm3 of sample tested with 5cm3 of ethanol, shake thoroughly to dissolve sample, add 5cm3 of water and shake gently, cloudy white colour shows presence of lipid.

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23
Q

Recall and describe the general structure of an amino acid?

A

Amino group -NH2
Carboxyl group -COOH
Hydrogen atom -H
R group

24
Q

Explain how dipeptides form polypeptides through condensation of amino acids?

A

Condensation reaction, removal of water, formation of peptide bond. amino acids combined with dipeptide to form a polypeptide polymer.

25
Q

Explain the relationship between primary, secondary, tertiary and quaternary structure and protein function?

A

Primary polypeptide structure consists of highly specific sequence of amino acids linked by peptide bonds. Primary structure determines structure secondary helix. primary structure influences the placement of bonds in the tertiary structure. number of polypeptide chains in the quaternary structure influences the type of prosthetic group and functionality.

26
Q

Explain the role of hydrogen bonds, ionic bonds and disulphides bridges in the tertiary protein structure?

A

Hydrogen bonds are numerous but are easily broken, ionic bonds are stronger than hydrogen bonds but are easily broken by pH changes, disulphides bridges are fairly strong and not easily broken.

27
Q

Describe the test for proteins?

A

The Biuret test, detects peptide bonds, place sample in tube with an equal volume of sodium hydroxide, add a few drops of dilute copper sulphate, purple colour shows presence of peptide bonds.

28
Q

Explain the variety of functions proteins have and why they are so important to the body?

A

Globular proteins carry out metabolic functions, enzymes catalyse reactions whereas insulin controls blood glucose levels. Fibrous proteins have structural functions, collagen found in tendons that hold muscle to bone and keratin in hair.

29
Q

Describe enzymes as catalysts that lower the activation energy of reactions?

A

Enzymes are globular proteins that catalyse the rate of reactions by lowering the activation energy needed to start the reaction, one way this is achieved is by lowering the body temperature for some chemical reactions to occur faster.

30
Q

Explain and describe the lock and key theory and induced fit model of enzyme action?

A

The lock and key theory suggests enzyme structure is rigid and non-flexible, and that substrate fits in active site exactly. Induced fit model suggests presence of substrate distorts amino acid bonds within active site moulding itself around the substrate, also suggests enzymes are flexible.

31
Q

Evaluate the strengths of the induced fit model against the lock and key model?

A

Scientists observed other molecules attaching to other sites than the active site suggesting enzyme structure is flexible in presence of substrate.

32
Q

Use knowledge of tertiary structure to explain enzyme specificity and the formation of enzyme-substrate complexes?

A

Amino acid sequence in polypeptide chains highly specific, affects placement of bonds in tertiary structure, affects active site specificity, will only respond to substrates with a complementary shape to the active site to form enzyme-substrate complexes.

33
Q

Explain how temperature affects enzyme action?

A

A rise in temperature increases kinetic energy of molecules resulting in more enzyme substrate collisions. Rate of reaction increases, as temperature increases to extreme levels hydrogen bonds break in enzyme causing it to denature.

34
Q

Explain how pH affects rate of enzyme action?

A

An increase of decrease in pH alters the charges on the amino acids that make up the active site, this changes its shape preventing enzyme-substrate complexes from being formed.

35
Q

Explain how enzyme concentration affects enzyme action?

A

Low enzyme concentration means the rate of reaction is decreased as there are too many substrates to be converted. Intermediate enzyme concentration means rate of reaction has reached its max as all substrates occupy an active site.

36
Q

Explain how substrate concentration affects rate of enzyme action?

A

Low substrate concentration means the rate of reaction is only half its maximum because there are too few substrates present for the active sites. Intermediate substrate concentration means the rate of reaction is at maximum because all active sites are occupied.

37
Q

Explain the significance of DNA to organisms as it carries an organisms genetic information?

A

The genetic information of an organism is stored within DNA and is transferred through generations of offspring.

38
Q

Explain that DNA is a polymer of nucleotides formed by condensation, with phosphodiester bonds between nucleotides?

A

A polynucleotide consists of many nucleotides joined together through condensation reactions and the removal of water. Between each nucleotide is a phosphodiester bond created by condensation reactions.

39
Q

Describe how each nucleotide is formed from a deoxyribose, a nitrogen-containing organic base and a phosphate group?

A

Deoxyribose sugar, organic base and the phosphate group joined together through the removal of water in a condensation reaction to produce a single nucleotide.

40
Q

Describe the structure of DNA as a double helix, held together by hydrogen bonds between complementary bases?

A

DNA consists of two polynucleotide chains twisted to form a helix structure, between each complementary base hydrogen bonds form to link the two chains together.

41
Q

Explain the role of RNA in transferring genetic information as a component of ribosome?

A

During protein synthesis mRNA transfers genetic information from DNA to the ribosomes during transcription, tRNA then transfers amino acids to the mRNA strand attached to the ribosome in translation.

42
Q

Explain the structure of RNA, an identify structural components of an RNA nucleotide from diagrams?

A

Short polynucleotide chains, ribose sugar, uracil base instead of thymine.

43
Q

Compare and contrast the similarities and differences between DNA and RNA?

A

RNA transfers genetic information whereas DNA stores the genetic information. DNA has a Deoxyribose sugar whereas RNA is a ribose sugar. Both DNA and RNA made out of nucleotides.

44
Q

Describe process of DNA semi-conservative replication, including role of enzymes?

A

DNA helicase breaks hydrogen bonds, strand separates, free nucleotides join to their complementary bases, DNA polymerase joins these nucleotides via condensation reactions and the formation of phosphodiester bonds.

45
Q

Explain the significance of DNA replication and evaluate the work of scientists in validating the Watson-Crick model of DNA replication?

A

The experiment showed that the bacteria underwent semi-conservative replication as both isotopes of nitrogen were found in both DNA strands.

46
Q

Recall and describe the structure of ATP?

A

Adenosine organic base, ribose sugar, 3 phosphates.

47
Q

Explain how the hydrolysis of ATP to ADP and Pi is catalysed by the enzyme ATP hydrolase, and can be used to phosphorylate compounds or provide energy to energy requiring cellular reactions?

A

ATP is hydrolysed to ADP and Pi during a hydrolysis reaction catalysed by ATP hydrolase, use of water to break chemical bond. this hydrolysis produces enough energy for metabolic processes, movement and active transport.

48
Q

Explain how ATP is resynthesized from ADP and Pi by the enzyme ATP synthase, during photosynthesis or respiration?

A

Reversible reaction, ATP synthase removes water via condensation reaction, Pi bonded to ADP to form ATP. Occurs in plant and animal cells during oxidative phosphorylation.

49
Q

Recall and describe the property of water as a metabolite?

A

Water is used to break down many complex molecules via hydrolysis, chemical reactions take place in an aqueous medium.

50
Q

Recall and describe the property of water as a solvent?

A

water readily dissolves other substances like oxygen and carbon dioxide, wastes such as ammonia and urea.

51
Q

Recall and describe the property of water as having a high heat capacity?

A

Water molecules stick together meaning more heat is needed to separate them, hydrogen bonding means water has a high heat capacity.

52
Q

Recall and describe the property of water as having a large latent heat vaporisation?

A

Hydrogen bonding means a lot of heat energy is required to evaporate 1 gram of water. Heat in mammals is used to evaporate sweat.

53
Q

Recall and describe the property of water as having strong cohesion between molecules?

A

Tendency for water molecules to stick together known as cohesion, water has large cohesive properties, allows it to be pulled through tube such as xylem.

54
Q

Describe and explain the properties of water linked to the polar nature of the molecule?

A

Oxygen atom has slightly negative charge whilst hydrogen atoms has slightly positive. This means the molecule is dipolar.

55
Q

Explain the significance of these properties to living organisms and processes?

A

Evaporation for cooling animals and temperature control, transparency allows aquatic plants to photosynthesise.

56
Q

Explain what is meant by the term inorganic ions and where they occur in the body?

A

They occur in the cytoplasm of cells and body fluids, involved in a range of functions, phosphate in ATP.

57
Q

Explain the specific role of hydrogen, iron, sodium and phosphate ions in the body?

A

IRON-found in haemoglobin involved in oxygen transport
SODIUM-involved in transport of glucose and amino acids across plasma membranes.
PHOSPHATE- storing energy in ATP molecules.
HYDROGEN-maintain pH in blood for enzyme functionality.

A Level Biology Revision (10 decks)

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