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Biology > B1 - Biological Molecules > Flashcards

B1 - Biological Molecules Flashcards

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1
Q

What is the difference between monomers and polymers?

A

Monomers are smaller units from which larger molecules are made
Polymers are molecules that are made from a large number of monomers joined together in a chain

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2
Q

What is a condensation reaction?

A

A reaction that releases water when monomers combine together by covalent bonds.

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3
Q

What is hydrolysis?

A

Hydrolysis is when water is used to break covalent bonds

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4
Q

What is the difference between reducing and non-reducing sugars?

A

Reducing sugar scan donate electrons whereas non-reducing sugars cannot donate electrons

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5
Q

What are examples of monosaccharides?

A

Glucose, fructose and galactose

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6
Q

What are examples of disaccharides?

A

Sucrose, lactose and maltose

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7
Q

What is an isomer?

A

Molecules with the same chemical formula but a different structure

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8
Q

What is the difference between an α-glucose and a ß-glucose?

A

α has the OH below the ring but ß has the OH above the ring

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9
Q

What is a glycosidic bond and how do they form?

A

Covalent bond between sugars between 2 hydroxyl (-OH) groups. It is a condensation reaction

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10
Q

Which 2 monosaccharides form maltose?

A

2 α-glucose

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11
Q

Which 2 monosaccharides form sucrose?

A

α-glucose and a fructose

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12
Q

Which 2 monosaccharides form lactose?

A

α-glucose and galactose

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13
Q

What are polysaccharides?

A

Macromolecules formed by many monosaccharides joined by glycosidic bonds to form a chain. E.g. starch, glycogen

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14
Q

What are glycogen and starch formed from?

A

α-glucose

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15
Q

What is starch?

A

The storage polysaccharide in plants

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16
Q

What is the structure of starch?

A

Amylose - unbranched helix chain which is stabilised by H-bonds, 1,4 glycosidic bonds
Amylopectin - branched structure with terminal glucose molecules for easy access, 1,4 and 1,6 glycosidic bonds (the different bonds create the branches)

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17
Q

What is glycogen?

A

Storage polysaccharide of animals and fungi

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18
Q

What is the structure of glycogen?

A

Very branched (more than amylopectin) so there are many terminal glucose molecules, 1,4 and 1,6 glycosidic bonds.

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19
Q

What is cellulose?

A

It is a structural polysaccharide, that is the main component of cell walls

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20
Q

What is the structure of cellulose?

A

long chain of ß-glucose with every other ß-glucose inverted, creating many H-bonds, providing strength, 1,4 glycosidic bonds

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21
Q

What is the benedict’s test for reducing sugars

A
  1. Add benedict’s solution to the solution being tested
  2. Heat sample in a water bath for 5 minutes
  3. If reducing sugars are present there will be a colour change from blue to brick-red
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22
Q

What is the benedict’s test for non reducing sugars?

A
  1. Add dilute HCl to hydrolyse glycosidic bonds
  2. Neutralise with sodium hydrocarbonate
  3. Add benedict’s solution to the solution being tested
  4. Heat sample in a water bath for 5 minutes
  5. If reducing sugars are present there will be a colour change from blue to brick-red
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23
Q

What is the test for starch?

A
  1. Add a couple of drops of iodine solution to the sample
  2. If starch is present solution will turn blue/ black from orange
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24
Q

What are the 2 groups of lipids?

A

Phospholipids and triglycerides

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25
Q

How are triglycerides formed?

A

They are formed by esterification, which is when ester bonds form between a hydroxyl (-OH) group on a glycerol and a carboxyl group (-COOH) on a fatty acid

26
Q

What is the difference between saturated and unsaturated fats?

A

Saturated fats have no C=C bonds
Unsaturated fats have C=C bonds

27
Q

What are the 2 monomers in triglycerides?

A

Fatty acids and glycerol

28
Q

What 2 groups do fatty acids have?

A

A methyl group (-CH3) and a carboxyl group (-COOH)

29
Q

What functions do triglycerides have?

A

Buoyancy
Protection
Insulation
Energy storage

30
Q

What is the structure of phospholipids?

A

A glycerol, 2 hydrophobic and non-polar fatty acids and a hydrophilic polar phosphate ion

31
Q

What do phospholipids form in the presence of water?

A

Monolayers or bilayers
The hydrophobic fatty acid tails are in the middle creating a hydrophobic core
The hydrophilic phosphate head in on the cell lining

32
Q

What is the function of phospholipids?

A

Building block of cell membranes, they act as a barrier to water soluble molecules + control the substances that enter and leave the cell
Saturated fatty acids = less fluid
Unsaturated fatty acids = more fluid
Phospholipids control orientation of proteins in cell membrane

33
Q

What is the emulsion test for lipids?

A
  1. Grind up food sample and add to test tube
  2. Add ethanol and water to test tube and shake
    If lipids are present a milky emulsion will form
34
Q

What are proteins?

A

Polymers made from monomers of amino acids
The sequence type and number of amino acids within a protein determines its shape and function

35
Q

What is the general structure of an amino acid?

A

NH2 + CRH + COOH
R = variable side chain

36
Q

What is a peptide bond?

A

Covalent bond between the amine group (-NH2) of 1 amino acid and the carboxyl group (-COOH) on another. Water is released as it is a condensation reaction

37
Q

What is the difference between a dipeptide and a polypeptide?

A

Dipeptide is formed by the condensation of 2 amino acids
Polypeptide is formed by the condensation of many amino acids

38
Q

What are the 4 bonds present in proteins?

A

H-bonds
Hydrophobic interactions
Ionic bonds
Disulphide bridges
(Increasing in strength down)

39
Q

What is the primary form of a protein?

A

Sequence of amino acids bonded by covalent peptide bonds

40
Q

What is the secondary structure of a protein?

A

H-bonds between amino acids form on:
α-helix on every 4th peptide bond
ß-pleated sheet with H-bonds between parallel parts of a polypeptide chain

41
Q

What is the tertiary structure of a protein?

A

More conformational changes (folding) with bonds including H-bonds, weak hydrophobic interactions, ionic bonds and disulphide bridges

42
Q

What is the quaternary structure of a protein?

A

More than 1 polypeptide chain creating a macromolecule. Each polypeptide chain is a subunit (each tertiary structure) Subunits are bonded by disulphide bridges

43
Q

What is the difference between globular and fibrous proteins?

A

Globular are circular but fibrous are long strands
Globular have irregular and a wide range of R-groups nut fibrous is repetitive with a limited range of R-groups
Globular are functional but fibrous are structural
Globular are soluble (polar), fibrous are insoluble (non-polar)

44
Q

What is the structure of haemoglobin?

A

Quaternary structure with 4 subunits that are held together by disulphide bonds.
Each unit has a prosthetic haem group. It is a globular protein

45
Q

What is the structure of collagen?

A

It is a fibrous protein. It contains 3 polypeptide chains, each being a helix shape and containing hydrophobic amino acids. the chains are held together by H-bonds, forming a triple helix (tropocolagen)
Covalent cross links also form between multiple triple helices, forming collagen fibrils
Many fibrils are then arranged together to form collagen fibres
In vertebrates, collagen is an important component of connective tissue - tendons, cartilage, ligaments, bones, teeth, etc

46
Q

What are enzymes?

A

Enzymes are biological catalysts, they speed up the rate of chemical reactions without being used up, they lower the activation energy required. Enzymes are also globular proteins, containing an active site, which the substrate binds to. They can be intracellular or extracellular

47
Q

What is special about the active site?

A

The active site of an enzyme has a specific shape to fit a specific substrate - they are complementary. The complementary shape is determined by the tertiary structure of protein that makes up the enzyme

48
Q

What is it called when the enzyme and substrate are together?

A

Enzyme-substrate complex

49
Q

What is a catabolic reaction?

A

Involves the breakdown of complex molecules into simpler products

50
Q

What is an anabolic reaction?

A

Involves the building of complex molecules from simpler ones

51
Q

How do enzymes lower activation?

A

Bond-breaking and forming occur more readily so activation energy is lowered

52
Q

What is the difference between the lock and key theory and the induced fit hypothesis?

A

Lock and key - enzymes are highly specific and fixed structures
Induced fit - active site can do conformational changes, changing the tertiary structure and change shape slightly as substrate enters enzyme

53
Q

How was the induced-fit hypothesis proved?

A

X-ray diffraction techniques allow for 3D pictures of molecules to be formed
This technique was used to produce pictures of enzymes before and after it binds to a substate
The images confirmed that the active site of the enzyme changed shape after the substrate bound

54
Q

What happens to an enzyme if the temperature is too high?

A

Bonds holding the enzyme molecules together start to break
Tertiary structure of the protein changes
Active site becomes damaged → substrate cannot bind → enzyme becomes denatured

55
Q

How does pH affect enzymes?

A

Too acidic or alkaline solutions can cause hydrogen & ionic bonds to break
Shape of the active site changes → enzyme-substrate complexes form less easily - enzyme denatures

56
Q

How does enzyme concentration affect enzymes?

A

Higher the enzyme conc. → greater number of active sites available → greater likelihood of enzyme-substrate complex formation = higher RoR
This relationship is linear until the amount of substrate becomes the limiting factor

57
Q

How does substrate concentration affect enzymes?

A

Greater the substrate concentration → greater likelihood of enzyme-substrate complex formation → higher the rate of reaction
RoR plateaus when all active sites are saturated

58
Q

What are 2 types of enzyme inhibitors?

A

Competitive inhibitors have a similar shape to substrate molecules → compete with the substrate for the active site
Non-competitive inhibitors bind to the enzyme at an alternative site → alters the shape of the active site → prevents the substrate from binding to it

59
Q

Are competitive or non-competitive inhibitors more efficient?

A

Competitive inhibitors - increasing substrate concentration can increase the rate of reaction again
Non-competitive inhibitors - increasing substrate concentration cannot increase the rate of reaction again
So non-competitive are more efficient

60
Q

How do inhibitors work in metabolism?

A

The end-product will also be an inhibitor for the first enzyme meaning that the chain to form the end product will be stopped. This stops excess formation of products.

Biology (17 decks)

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