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Biology > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

What are Monomers and Polymers?

A

Monomers are small units which join together to form larger molecules.
Polymers are molecules made from many monomers joined together.

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2
Q

Give examples of monomers and polymers:

A

Monomers: monosaccharides like glucose, amino acids, nucleotides,
Polymers: DNA, RNA

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3
Q

What reaction joins monomers?

A

Condensation reaction where a water molecule is eliminated.
(Converse: Hydrolysis reaction where a water molecule is added).

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4
Q

What is a carbohydrate?

A

Molecule that only consists of carbon, hydrogen and oxygen, they are long chains of sugar units called saccharides.

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5
Q

What is the result of combining many monosaccharides?

A

A Polysaccharide, which is joined together with a glycosidic bond formed from a condensation reaction.

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6
Q

What are the main features of a Monosaccharide?

A
  • sweet tasting
  • soluble
  • only contain C, H, O atoms
  • General formula (CH2)N where n = 3-7
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7
Q

What are the three hexose monosaccharides?

A
  • Glucose
  • Fructose
  • Galactose
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8
Q

What are the two Pentose monosaccharides and their formula?

A
  • Ribose
  • Deoxyribose
    C6H1206
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9
Q

What are the two isomers of glucose?

A

Alpha-Glucose
Beta-Glucose

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10
Q

What is the importance of monosaccharides?

A
  • Source of energy (glucose)
  • Able to be transported in solution in animals (glucose in blood)
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11
Q

What is a disaccharide?

A

Two monosaccharides joined together in a condensation reaction resulting in a glycosidic bond where a water molecule is removed

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12
Q

Glucose + Glucose =

A

Maltose

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13
Q

Glucose + Fructose =

A

Sucrose

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14
Q

Glucose + galactose =

A

Lactose

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15
Q

What happens to disaccharides in the presence of water?

A

They are hydrolysed into monomers, this reaction can be catalysed by specific enzymes

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16
Q

What are the properties of polysaccharides?

A
  • very large
  • insoluble
  • suitable for for storage
  • or structural support (cellulose) in plants
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17
Q

Examples of polysaccharides?

A
  • starch
  • cellulose
  • glycogen
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18
Q

What is starch?

A

Stores energy in plants, mixture of two polysaccharides Amylose and Amylopectin.

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19
Q

What is Amylose?

A

An unbranched chain of alpha glucose joined by 1:4 glycosidic bonds
It is coiled which makes it very compact = good for storing energy.
OH groups form hydrogen bonds to hold the helix in place

20
Q

What is Amylopectin?

A

It is branched and made up of both 1:4 and 1:6 glycosidic bonds.
Many side branches means they can be acted upon simultaneously by many enzymes to release energy.

21
Q

What is starch’s structure especially suited for?

A

Insoluble - does not affect water potential and water is not drawn into the cell by osmosis
Large and insoluble so it doesn’t diffuse out of cells
Compact - a lot can be stored in a small space

22
Q

What is glycogen and how its structure is suited to its role?

A

Insoluble
Compact
More highly branched than starch, more energy released important for animals as they have a higher metabolic and respiratory rate.

23
Q

What’s is cellulose? And what Is its properties?

A

Made from beta glucose
Cellulose is straight, unbranched, running parallel to one another, allowing hydrogen bonds to form cross links between chains. The overall combined strength is high.
Cellulose molecules form microfibrils providing rigidity to the plant cell.

24
Q

What is the test for reducing and non-reducing sugars?

A

Reducing sugars:
- all monosaccharides and some disaccharides are reducing.
- add Benedict’s reagent
- heat the mixture gently in a water bath
- brick red precipitate is formed if positive result

Non-Reducing:
- add dilute hydrochloric acid
- add sodium hydrogen carbonate
- add Benedict’s reagent again
- brick red precipitate

25
Q

What is the test for starch?

A

Add iodine/potassium iodide.
If solution turns blue/black starch is present

26
Q

What are lipids?

A

Lipids are biological molecules made up of Caron, oxygen and hydrogen molecules which are only soluble in organic solvents like alcohols.
Main types of lipids are triglycerides and phospholipids.

27
Q

What are triglycerides?

A

They are lipids made up of one molecule of glycerol and three fatty acids joined together by ester bonds in a condensation reaction.
Unsaturated - double C-C bonds - plants
Saturated- no double C-C bonds - animal fat

28
Q

How is triglycerides structure related to their properties?

A

High ratio of energy storing carbon-hydrogen bonds to carbon atoms which make them an excellent energy store.
Low mass to energy ratio so they are a good storage molecule.
Large and non-polar molecules makes them insoluble, therefore storage doesn’t affect water potential of cells.
High ratio of hydrogen-oxygen atoms meaning they release water when oxidised = good source of water for organisms that live in a dry environment.

29
Q

What are phospholipids?

A

Where one of the fatty acids in a triglyceride is replaced with a phosphate group.
Hydrophilic heads
Hydrophobic tails
Polar molecule

30
Q

How are phospholipids structure related to their function?

A

In aqueous environments being polar means a bilayer can be formed.
Their structure allows them to form glycolipids with carbohydrates on the cell surface membrane for cell recognition.

31
Q

Test for lipids?

A

The Emulsion test:
- grease free test tube add sample and ethanol
- shake thoroughly
- add water and shake again
- positive result = cloudy-white precipitate is formed
(Control - test water and final result should be clear)

32
Q

What are proteins?

A

Made form Amino Acids (AA), which contain an amino group (NH2), a carboxylic acid group (-COOH) and a variable R group.
20 types of amino acids determined by their R group.
They join together with peptide bonds formed in condensation reactions.
Dipeptide contains two AAs and a Poly peptide contains 3 or more.

33
Q

What are the structures of proteins?

A

The structure is determined by the order and number of AAs and the bonding and shape of the protein:
- Primary structure = initial sequence of amino acids
- Secondary structure = EITHER Beta pleated sheet or Alpha helix formed by weak hydrogen bonds caused by the slight positive charge of the hydrogen in the -NH and the slight negative charge in the oxygen in -C=O.
- Tertiary structure = the 3D shape caused by the three types of bonds: Disulphide bridges (between sulphur and cysteine, strong and hard to break), Ionic bonds (carboxyl and amino acids, weaker and easily broken by pH), Hydrogen bonds (numerous and easily broken).
Globular proteins - compact e.g. enzymes
Fibrous proteins - long and can form fibres e.g. keratin

34
Q

What is the test for proteins?

A

The Biuret test, to test for the peptide bonds:
- add sodium hydroxide
- add very dilute copper sulphate solution and mix
- positive result = purple colour

35
Q

What are enzymes?

A

They increase rate of reaction by lowering activation energy of the reaction it is catalysing.
The active site is an area made up of only a few AAs and forms a depression in the enzyme. Enzymes are complementary to the substrate and will form enzyme-substrate complexes - lock and key.
Induced fit model - active site changes shape to fit the substrate.

36
Q

what are the factors affecting the rate of enzyme activity?

A
  • Temperature = rate of reaction (ROR) increases to the optimum temperature as the kinetic energy of the enzymes increase. Beyond nth optimum temp the enzymes active site changes shape due to the tertiary structure changing and the enzyme denatures.
  • pH = same as temp
  • Enzyme concentration = ROR increase as enzyme concentration increases up to a certain point where there are more enzymes than substrates, so substrate becomes limiting factor.
  • Substrate concentration = ROR increases as substrate concentration increase until enzymes become the limiting factor.
  • Competitive inhibitors = ROR decreases as concentration of competitive inhibitors increases as active sites are blocked.
  • Non-Competitive inhibitors = ROR decreases as the concentration of non-competitive inhibitors increases as the active site is altered.
37
Q

What is the structure of DNA?

A

DNA nucleotides consist of deoxyribose sugar, a phosphate group and one nitrogen containing base A, T, C, G.
Carries genetic information, it is also a polymer of nucleotides.
Nucleotides join together by phosphodiester bonds formed in condensation reactions.
DNA is a double helix composed of two polynucleotides joined together by hydrogen bonds.
Phosphodiester backbone
Three hydrogen bonds between G and C and two between A and T.

38
Q

What is the structure of RNA?

A

RNA nucleotides consist of a ribose sugar, a phosphate group and one of the nitrogen containing bases A, U, C, G.
RNA transfers the info from DNA to ribosomes for protein synthesis.
RNA is a relatively short polynucleotide chain.

39
Q

What is DNA replication?

A

Semi-conservative replication of DNA ensures genetic continuity between generations of the cells meaning that genetic information can be passed from one to the next.
The steps :
1. DNA helicase causes the strands to unzip, breaking the hydrogen bonds between the bases.
2. One strand is used as the template and there is complimentary base paring occurs between the strand and free nucleotides.
3. DNA polymerase joins them together by forming phosphodiester bonds, resulting in two identical strands of DNA.

40
Q

What is ATP?

A

Adenosine triphosphate consists of ribose, adenine and three phosphate groups.
- Energy is released when ATP is hydrolysed to from ADP and a phosphate molecule. This process is catalyse by ATP hydrolyse
- Inorganic phosphate can be used to phosphorylate other compounds.
- Condensation of ADP and inorganic phosphate is catalysed by ATP synthase produces ATP during photosynthesis and respiration.

41
Q

What are the properties of ATP?

A
  • It is an immediate source of energy.
  • ATP isn’t stored and can be reformed from ADP in seconds.
  • Metabolic processes, movement, active transport, secretion and activation of molecules.
42
Q

What is water?

A

It is a polar molecule, a metabolite, a solvent, has a high specific heat capacity, large latent heat of vaporisation and a strong cohesive.

43
Q

What are the properties of water?

A
  • Polar Molecule = due to uneven distribution of charge, allows many water molecules to stick together.
  • Metabolite = in condensation and hydrolysis.
  • Solvent = things can dissolve in it.
  • High SHC = minimises temp fluctuations so it acts as a buffer.
  • Large LHV provides a cooling effect.
  • Strong cohesion = supports columns of water so the surface tension at the water-air boundary is high.
44
Q

What are inorganic ions?

A

They occur in solution in the cytoplasm and body fluid of organisms.

45
Q

What are some of the essential inorganic ions?

A

Hydrogen ions = determine the pH (the higher the concentration of hydrogen ions the lower the pH.
Iron ions = component of haemoglobin.
Sodium ions = involved in co-transport of glucose and amino acids.
Phosphate ions = component of DNA and ATP.

Biology (3 decks)

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