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Biology > Topic 1 : Biological Molecules > Flashcards

Topic 1 : Biological Molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Explain how all living things have a similar biochemical basis

A

Living things are all mostly made up of only 4 kinds of organic polymers. These being carbohydrates, lipids, proteins and nucleic acid. This would mean that they all have a similar biochemical basis if they are all made up of the same few molecules

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2
Q

What is a monomer?

A

Small units which form a larger molecule

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3
Q

What is a polymer?

A

Large, complex molecules made up of large chains of monomers

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4
Q

Examples of monomers

A

Monosaccharides, glycerol, fatty acids, amino acids, nucleotides

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5
Q

Examples of polymers

A

Polysaccharides (starch, cellulose), Proteins

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6
Q

What is a hydrolysis reaction?

A

A reaction that breaks a chemical bond between two molecules, involving the addition of a water molecule

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7
Q

What is a condensation reaction?

A

Bonding of two monomers to form polymers in which water is a product.

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8
Q

Describe how larger carbohydrates are made from monosaccharide monomers

A

A condensation reaction occurs where monosaccharide monomers are joined together by covalent bonds known as glyosidic linkages.

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9
Q

Elements carbohydrates are made up of

A

C, H, O

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10
Q

List some common monosaccharides

A

Glucose
Galactose
Fructose

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11
Q

What is glucose?

A

A hexose sugar - a monosaccharide with six carbon atoms per molecule

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12
Q

What are the two isotopes of sugar?

A
  • Alpha glucose and beta glucose
  • The hydroxyl (-OH) group is reversed
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13
Q

What is maltose?

A

A disaccharide of two alpha glucose molecules

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14
Q

What is sucrose?

A

A disaccharide formed by the condensation of alpha glucose and fructose

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15
Q

What is lactose?

A

A disaccharide formed by the condensation of an alpha glucose molecule and a galactose molecule

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16
Q

How are glycogen and starch formed?

A

By the condensation of alpha glucose

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17
Q

How is cellulose formed?

A

By the condensation of beta glucose

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18
Q

What is the function of starch?

A

Storage in plants

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19
Q

How would you test for starch?

A

2cm^2 of starch solution into test tube
Add 2 drops of iodine solution and shake/stir
Presence of starch indicated with a blue/black colour

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20
Q

What makes starch good for storage?

A

-Insoluble in water so doesn’t affect water potential so it doesn’t cause water to enter cells by osmosis, making them swell and burst.
-Compact so easily stored in smaller space

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21
Q

What makes starch good for giving plants energy?

A

Branched ends allowing for more enzyme action and releasing energy to plant cells

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22
Q

Describe how the structure of glycogen relates to its structure

A

Highly branched ends allowing for rapid enzyme action - quick release of energy in animals.
Compact molecule

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23
Q

Describe how the function of cellulose relates to its structure

A

Straight, unbranched chains running parallel allows for lots of hydrogen bonds forming cross bridges to strengthen cellulose making it a valuable structural material

24
Q

Describe the biochemical test for reducing sugars

A
  • 2cm^2 of food sample to a test tube
  • Add equal volume of benedict’s reagent
  • heat the mixture in boiling water bath
  • If colour changes from blue to orange/red then a reducing sugar is present
25
Q

Describe the biochemical test for non-reducing sugars

A

Prepare the sample
Add HCL and boil for 1 minute
Add sodium hydrogen carbonate to neutralise
Add benedict’s reagent
Heat
if colour changes from blue to orange/red this shows there is NO reducing sugar

26
Q

What are the roles of lipids

A
  • energy source
  • waterproofing (waxy cuticle)
  • Insulation (slow conductors of heat)
  • Protection (stored around delicate organs)
27
Q

What is an unsaturated and saturated R group

A

Unsaturated = double bonds between carbon atoms
Saturated = no double bonds between carbon atoms

28
Q

Explain how triglycerides are formed

A

Condensation reactions between one glycerol and 3 fatty acids, which form ester bonds.

29
Q

How are phospholipids formed

A

One of the fatty acids is replaced with a phosphate-containing group.

30
Q

How is the structure of phospholipids related to their properties

A
  • The fatty acids creates a hydrophilic head, the phosphate group creates a hydrophilic tail
  • In an aqueous environment, phospholipids form a bilayer within cell-surface membranes
  • Structure allows them to form glycolipids with carbs within the cell-surface membrane, these glycolipids are important in cell recognition
31
Q

How is the structure of triglycerides related to their properties

A
  • Large, insoluble molecules that do not affect osmosis in cells or their water potential
32
Q

How does a polypeptide form?

A

Many amino acids join together by condensation polymerisation. They form peptide bonds in condensation reactions. lots of polymerisation between amino acids causes large chain sequences to be formed = a polypeptide

33
Q

Describe the primary structure of a protein

A

Sequence of amino acids in a polypeptide chain held together by peptide bonds

34
Q

Describe the secondary structure of a protein

A

When the chain begins to pleat and coil due to hydrogen bonding

35
Q

Describe the tertiary structure of a protein

A

Further bending and twisting of the chain as the R groups of each amino acid form di sulphide bridges, hydrogen and ionic bonds with each other

36
Q

Describe the quaternary structure of a protein

A

Bonding, twisting, shaping and compacting of more than one polypeptide chains, eg haemoglobin.

37
Q

How do you test for lipids

A

Emulsion test:
- Add 2cm^3 of sample to test tube
- Add 5cm^3 of ethanol to the test tube
- Shake thoroughly to dissolve lipid
- Add 5cm^3 of water and shake gently
- Cloudy white emulsion if lipids are present

38
Q

Explain fibrous proteins and explain the properties of collagen and why they are useful.

A
  • Proteins which play structural roles
  • Collagen forms long chains which run parallel to each other
  • Chains are linked by hydrogen cross bridges
  • Tightly wound polypeptide strands with cross bridges allow for a strong flexible structure useful in tendons
39
Q

Describe the test for proteins

A

Biuret test - test for peptide bonds
- 2cm^2 of solution to test tube
- Add equal volume of sodium hydroxide solution
- Add a few drops of biuret reagent
- Purple if protein is present
- Blue if protein is absent

40
Q

How does an enzyme’s structure relate to its function?

A
  • Bonds within the enzyme hold its tertiary shape, thus the shape of the active site. This unique active site will only be complementary to the substrate it needs to hydrolyse, thus creating more e/s complexes
41
Q

How do you calculate the rate of change at a given time

A
  • Draw tangent and find gradient (change in x / change in y)
42
Q

How does the temperature affect the rate of an enzyme controlled reaction?

A
  • higher temp –> more kinetic energy, so more successful collisions per second therefore more e/s complexes (higher rate of reaction)
  • When the temp is too high, the active site of the enzyme will denature as bonds will be broken and the tertiary structure (thus shape) will alter. No longer making the active site complementary, therefore less e/s complexes
43
Q

How does the pH affect the rate of an enzyme controlled reaction?

A

Change in pH alters the charges in amino acids that make up the active site of the enzyme. If charges change, tertiary structure of the active site changes therefore less e/s complexes are made (lower rate of reaction)

44
Q

How does the substrate concentration affect the rate of an enzyme controlled reaction?

A

More substrates, higher chance of successful collisions therefore more e/s complexes per second (higher rate of reaction). Graph will plateau when the amount of substrates is more than the enzymes can cope with

45
Q

How do inhibitors affect the rate of an enzyme controlled reaction?

A

Competitive - occupies active site of enzyme so an e/s complex cant be made, the more competitive inhibitors the less complexes and therefore the lower rate of reaction
Non-competitive - Occupies other site of an enzyme, changing the shape of the active site so it is no longer complementary to the substrate, so les e/s complexes.

46
Q

What are DNA and RNA and what are their functions?

A

DNA is the storage molecule of the genetic code in the nucleus
RNA are the sections of DNA extracted to be replicated, a template for protein production

47
Q

What is phosphodiester bond and how is it formed?

A
  • Formed by a condensation reaction between a deoxyribose sugar and a phosphate group in newly bound adjacent nucleotides.
48
Q

Compare and contrast the components of DNA and RNA

A

DNA - Deoxyribose sugar
RNA - Ribose sugar

DNA - Thymine
RNA - Uracil

49
Q

Compare and contrast the structure of DNA and RNA

A

RNA- Short chained, single handed template
DNA - Longer chained, double stranded, helical molecule

50
Q

How is the structure of DNA related to its function?

A
  • Tightly coiled and helical yet very large and is therefore compact but can store more information in a smaller space
  • Nucleotides are bonded by hydrogen bonds and therefore easily broken allowing for transcription/replication to occur.
  • Base pairing so DNA can be replicated and transfer info as mRNA
51
Q

Describe the semi-conservative method of DNA replication

A

1 - DNA helicase breaks the hydrogen bonds between base pairs. Separating the 2 strands
2 - Free floating nucleotides bond to their complementary base pair
3 - Once fre4e nucleotides are bound, phosphodiester bonds form between deoxyribose sugar and phosphate group of adjacent nucleotides
4 - Once all nucleotides are bound and bonded together, you are left with two identical molecules of DNA, with one strand of original material and one strand new material

52
Q

Describe how a single molecule of adenosine triphosphate is a nucleotide derivative

A

ATP structure is a nucleotide with an adenine base and three phosphate groups.

53
Q

How is ATP converted to ADP, and what enzyme catalyses it?

A

Hydrolysis reaction between second and third phosphate group. Catalysed by ATP hydrolase. Low activation energy required for this reaction so is easily hydrolysed.

54
Q

Why is ATP suitable for its function?

A

Bond between the 2nd and 3rd phosphate group is easily hydrolysed
- Is an immediate energy source
- Releases much less energy than from a glucose molecule so is therefore more manageable.

55
Q

How is a water molecule dipolar?

A
  • Oxygen region has slight negative charge
  • Hydrogen region has slight positive charge
56
Q

What are the properties that are important in water?

A
  • High SHC - more energy required to separate water molecules therefore a higher boiling point, allowing it to act as a temperature buffer making aquatic environments stable
    -High latent heat of vaporisation - Lots of energy is required to heat 1g of water, lots of body heat used to evaporate water off skin making sweating effective at cooling the body
  • Cohesion and surface tension - Tendency of the molecules to stick together due to hydrogen bonding allows water to be pulled up through a tube (xylem)
  • Water is a solvent - Readily dissolves substances such as co2, o2, wastes such as urea and enzymes

Biology (7 decks)

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