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Biological Molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What are the 4 major categories of biological molecules?

A
  1. Carbohydrates
  2. Proteins
  3. Lipids
  4. Nucleic acids
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2
Q

What are the monosaccharides that form maltose, sucrose and lactose?

A

Maltose: Glucose+glucose
Sucrose: Glucose+fructose
Galactose: Glucose+galactose

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3
Q

Describe

The structure of starch, glycogen and cellulose and where they are found

A

Starch: Long chain of glucose, linear structure; moderately branched. Found in plants.

Glycogen: Highly branched structure; found in animal liver and muscle cells

Celluose: Long chain of glucose; linear structure, but bonded in a ‘z’ appearance unlike starch; unbranched. Found in plants

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4
Q

What is the purpose of polysaccharides?

A

For storage

  1. Large size –> cannot leave cell membrane
  2. Cannot dissolve
  3. Compact –> saves space compared to individual molecules
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5
Q

What is the element composition of carbohydrates?

A

Carbon, hydrogen and oxygen

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6
Q

How do monosaccharides combine to form more complex carbohydrates?

A

Through condensation reactions, where two simple molecules are joined together to form a large molecule with the removal of one molecule of water. Monosaccharides are combined with a glycosidic bond

——OH HO———

————O————- +H2O
Glycosidic bond

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7
Q

How do complex carbohydrates break down into monosaccharides?

A

Glycosidic bonds can be broken through hydrolysis, where a water molecule is needed to break up a complex molecule into simpler molecules.

———-O———- +H2O
———OH HO——–

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8
Q

Define

A condensation reaction

A

A condensation reaction is a chemical reaction in which two simple molecules are joined together to form a larger molecule with the removal of one molecule of water.

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9
Q

Define

A hydrolytic reaction

A

A chemical reaction in which a water molecule is needed to break up a complex molecules into simpler molecules

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10
Q

What is the elemental composition of proteins?

A

Carbon, hydrogen, oxygen, nitrogen and sometimes sulfur

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11
Q

What are the different groups in an amino acid? (Structure of an amino acid)

A
  1. Carboxylic group (COOH)
  2. Amino group (NH2)
  3. Side chain (R)
  4. Hydrogen atom

There is also a carbon atom in the centre that connects these groups

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12
Q

Describe

How amino acids join together to form long chains

A

They join during condensation reactions to form proteins by means of peptide bonds.

C—-OH H—-N
Carboxylic group Amino group

C—-N +H2O

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13
Q

What are proteins in the primary structure and what bonds are present?

A

This structure refers to the linear sequence of amino acids.
Peptide bonds are present (C—N)

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14
Q

What are proteins in the secondary structure and what bonds are present?

A

The secondary structure refers to patterns contained within the amino acid chains. When combinations of amino acids join together in the chain, there is a tendency for parts of the chain to fold and form helixes and pleated sheets. The bonds present are peptide bonds (C—-N) and hydrogen bonds (OH IIIII O—; same as those in chemistry).

Hydrogen bonds are sensitive to heat

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15
Q

What are proteins in the tertiary structure and what bonds are present?

A

It refers to the protein’s overall geometric/ 3D shape found in structural or functional proteins. Bonds present are peptide bonds (C—-N), hydrogen bonds (OH IIIIIII O), disulfide bridges (S—S) and ionic bonds (NH4+ —– O)

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16
Q

What are proteins in the quaternary structure and what bonds are present?

A

When a protein is made of more than one polypeptide, it has a quaternary structure.

Eg: collagen, antibodies, haemoglobin

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17
Q

Compare the energy yield of carbohydrates and lipids

A

Lipids yield more than twice as much energy than carbohydrates, though energy is released faster in carbohydrates than lipids

18
Q

What is the elemental composition of lipids?

A

Carbon, hydrogen and oxygen

19
Q

What makes up a lipid molecule?

A

One molecule of gylcerol and three fatty acid chains

20
Q

What makes up nucleic acids?

A

A long chain of repeated sub-units known as nucleotides

21
Q

What is the structure of nucleotides?

A

A nitrogeneous base, a deoxyribose sugar and a phosphate group

22
Q

What nitrogenous bases are present in DNA?

A

Adenine, cytosine, guanine, thymine

23
Q

What nitrogenous bases are present in RNA?

A

Adenine, cytosine, guanine, uracil

24
Q

In DNA, what nitrogenous base pairs are formed with hydrogen bonds?

A

Adenine + thymine, cytosine + guanine

25
Q

What is the purpose of the Benedict’s test?

A

To determine the presence of reducing sugars

26
Q

Which sugars are reducing sugars?

A

All monosaccharides, and some disaccharides (sucrose etc.)

27
Q

What are the possible results of the Benedict’s test?

A

Blue: Reducing sugars are absent
Green: Trace amounts of reducing sugars
Yellow + orange/orange-red: Moderate amount of reducing sugars
Brick-red precipitate: High amounts of reducing sugars

28
Q

What is the procedure for Benedict’s test (provided reducing sugars are present)?

A
  1. Add solution to test tube
  2. Add equal volume of Benedict’s solution and shake gently
  3. Place in boiling water bath for 2-5 mins
29
Q

What is the procedure for Benedict’s test (provided non-reducing sugars are present)?

A
  1. Add solution to test tube
  2. Add half the volume of HCL to test tube
  3. Boil for one minute
  4. Neutralise carefully with hydrogen carbonate
  5. Add equal volume of Benedict’s solution (as solution at first) and shake gently
  6. Place in boiling water bath for 2-5 mins
30
Q

What is the purpose of the iodine test?

A

To test for the presence of starch

31
Q
A
32
Q

What are the possible observations for the iodine test?

A
  1. Remains yellow brown –> starch is absent
  2. Turns blue-black –> starch is present
33
Q

What is the purpose of the ethanol emulsion test?

A

Tests for the presence of lipids

34
Q

What are the possible obsevations for the ethanol emulsion test?

A
  1. Mixture remains colourless –> lipids are absent
  2. Cloudly white emulsion –> lipids are present
35
Q

What is the procedure for ethanol emulsion tests?

A
  1. Add the fat or oil to the test tube
  2. Add an equal amount of absolute ethanol
  3. Shake vigourously
  4. Add equal amount of cold water
36
Q

What is the purpose of the biuret test?

A

Tests for the presence of proteins

37
Q

What are the possible observations of the biuret test?

A
  1. Pale blue –> Proteins are absent
  2. Pink –> Shorter polypeptides are present
  3. Violet –> Proteins are present
38
Q

What is the procedure for the biuret test?

A
  1. Add protein solution
  2. Add equal volume of 5% sodium/potassium hydroxide solution
  3. Add copper sulfate solution dropwise
39
Q

What level of structure of proteins do ribosomes synthesise?

A

Primary structure

40
Q

What is an isomer and give an example

A

Isomer are polyatomic molecules with identical molecular formulas, but distinct arrangement of atoms. An example is glucose, fructose and galactose, all of which are C6H12O6.

Biology (10 decks)

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