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Biology > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

Where are the OH group in the alpha glucose?

A

-They’re both at the bottom

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2
Q

Where are the OH group in beta glucose?

A

-One at the top and other at the bottom.

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3
Q

What does two alpha glucose forms?

A

Maltose

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4
Q

Three types of monomer found in biological molecules-

A

Monosaccharides, amino acids, nucleotide.

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5
Q

Explain the hydrolysis process.

A

-Disaccharides/polysaccharides can be broken down by a chemical reaction called hydrolysis.
-It breaks the chemical bonds by using water molecule.
-Produces monomers.

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6
Q

The bonding in secondary structure vs tertiary structure-

A

-Both contain hydrogen bonding
-Tertiary structure also contains ionic bonds and disulfide bridges

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7
Q

Haemoglobin is the oxygen carrying molecule in red blood cells.
At low pH, haemoglobin’s ability to bind oxygen is reduced.
Suggest why?

A

-A low pH interferes with the bonds in the haemoglobin molecule.
-Causing it to change its shape, so it can no longer bind to oxygen.

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8
Q

What bond forms between the amino acids?

A

Peptide bond.

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9
Q

What test is used to identify starch?

A

-Iodine test
-If starch is present, brown-orange colour.
-If not, blue-black colour

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10
Q

What test is used to identify reducing sugars?

A

-Reducing sugars include all monosaccharides and some disaccharides.
-You add Benedict’s reagent (blue) to a sample and heat it in a water bath that is brough to boil.
-If the test is positive, it’ll form a coloured precipitate.

blue->green-> yellow-> orange-> brick red

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11
Q

What test is used to identify non-reducing sugars?

A

-Even the result for reducing sugar test is negative, there can be non-reducing sugars.
-First, break down into monosaccharides by heating with dilute hydrochloric acid.
-Then, neutralise with sodium hydrogencarbonate.
-Carry out the Benedict’s test
-

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12
Q

Glucose+ fructose= ?

A

Sucrose

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13
Q

Glucose+ galactose=?

A

Lactose

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14
Q

What is a product of a condensation reaction?

A

Water

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15
Q

What are the three polysaccharides for carbohydrates?

A

-Cellulose
-Starch
-Glycogen

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16
Q

Starch is a mixture of two alpha glucose ………. and ……….

A

-amylose
-Amylopectin

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17
Q

Describe amylose-

A

-A long, unbranched chain of a-glucose
-The angles of the glycosidic bonds, give it a coiled structure.
-Makes it compact, good for storage- can fit more in to a small place.

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18
Q

Describe amylopectin-

A

-A long, branched chain
-Side branches allow the enzymes get at the glycosidic bonds easily.
-Glucose released quickly.

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19
Q

Glycogen-

A

-Main energy storage material in animals
-Similar structure to amylopectin but has more side branches
-Glucose can be released quickly.
-Very compact molecule

20
Q

Cellulose-

A

-Major component of cell walls in plants
-Long, unbranched chains of beta glucose
-When beta glucose molecules bond, they form straight cellulose chains linked together by hydrogen bonds to form strong fibres called microfibrils.
-Strong fibres mean that cellulose provides a structural support for cells.

21
Q

Describe how triglycerides are formed?

A

-When three fatty acids join to a glycerol molecule
-through ester bonds.
-In a series of three condensation reaction.

22
Q

Saturated vs unsaturated fatty acids

A

-Saturated fatty acids don’t have any double bonds between their carbon atom
-Unsaturated fatty acids have at least one double bond

23
Q

Phospholipids structure-

A

-Found in cell membranes
-Similar to triglycerides except one of the fatty acid is replaced with a phosphate group.
-Phosphate group is hydrophilic (attracts water)

24
Q

The function of triglycerides tails-

A

They are hydrophobic- repel water- makes it insoluble in water

25
Q

How the structure of triglycerides relate to their function?

A

-Used as energy store molecule.
-Long hydrocarbon tails contains lots of chemical energy/insoluble, so they don’t affect the water potential of the cell and cause water to enter the cell by osmosis.
-Triglycerides clump together as insoluble droplets in the cells because the fatty acid tails are hydrophobic. The tails face inwards, shielding themselves from water with their glycerol heads. This means that they can be stored in cells as a source of energy without affecting the water potential.

26
Q

How the structure of phospholipids relate to their function?

A

-Make up the bilayer of the cell membranes
-Heads are hydrophilic and tails are hydrophobic, so they form a double layer with their heads facing out towards the water
-The centre of the bilayer is hydrophobic, water soluble substances can’t easily pass through it- membrane acts as a barrier

27
Q

Describe the emulsion test-

A

-Its a test for lipids.
-Shake the test substance with ethanol for a minute so it dissolves, then pour the solution into water.
-Any lipid will show up as milky emulsion

28
Q

How are proteins formed?

A

Made up of one or more polypeptides (formed when more than two amino acids join together)

29
Q

What happens in the secondary structure of proteins?

A

-Hydrogen bonds form
-Makes it coil into an alpha helix or fold into a beta pleated sheet

30
Q

What happens in the tertiary structure?

A

-Final 3-D structure for proteins made from a single polypeptide chain.
-Hydrogen bonds, ionic bonds and disulfide bridges form

31
Q

Describe the biuret test-

A

-A test for proteins
-Test solution needs to be alkaline- add sodium hydroxide solution
-Then add some copper (II) sulfate solution
-Purple= protein is present
-If it stays blue no protein is present

32
Q

Structure and function of enzymes-

A

-Roughly spherical due to the tight folding of the polypeptide chains
-Soluble and have roles in metabolism (some help to break down large food molecules) (some help to synthesise large molecules)
-Speed up chemical reactions by acting as biological catalysts.
-Lower the activation energy of a reaction.

33
Q

Structure and function of antibodies-

A

-Involved in the immune response
-Made up of two light and two heavy polypeptide chain

34
Q

Structure and function of transport proteins-

A

-Present in cell membranes
-Channel proteins contain hydrophilic and hydrophobic amino acids, which cause the protein to fold up and form a channel
-Transport molecules and ions across membranes

35
Q

Structure and function of structural proteins-

A

-Physically strong
-Consist of long polypeptide chains lying parallel to each other with cross-links between them.
-Include keratin and collagen

36
Q

Factors affecting enzyme activity-

A

-Temperature- increases the rate of reaction, more kinetic energy, molecules move faster, more likely to collide, energy of these collisions also increases, each collision is more likely to result in a reaction.

-pH- Above and below the optimum pH, the H+ and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds.

-Enzyme concentration- affects the rate of reaction
Increasing the concentration of enzymes, increases the rate of reaction. However, if the amount of substrate is limited, adding more enzyme won’t have any affects.

-Substrate concentration- affects the rate of reaction to a point
The higher the substrate concentration, the faster the reaction. Only true up to a ‘saturation’ point. All active sites are used, increase in conc of substrate wont have any effect.

37
Q

What is competitive inhibition?

A

-Competitive inhibitor have a similar shape to substrate molecules
-They compete with the substrate molecules to bind to the active site, but no reaction takes place.
-They block the active site, so no substrate can fit in.

38
Q

What is non-competitive inhibition?

A

-Bind to the enzyme away from its active site.
-Causing active site to change shape so the substrate can no longer bind to it.
-They don’t ‘compete’ with the substrate because they are different shapes.
-Increasing the concentration of substrate wont make any difference to the reaction rate.

39
Q

PRACTICAL- Measure the rate of an enzyme-controlled reaction-
-How fast the product is made
-How fast the substrate is broken down

A

How fast the product is made-
-Catalase catalyses the breakdown of hydrogen peroxide into water and oxygen. We can measure how fast the product is made by measuring the volume of oxygen produced.
-The oxygen released displaces the water from the measuring cylinder.
1-Set up boiling tubes containing the same volume and concentration of hydrogen peroxide. To keep the pH constant add equal volumes of a suitable buffer solution to each tube.
2-Set up the rest of the apparatus
3- Put each boiling tube in a water bath set to a different temperatures along with another tube containing catalase..
4-Use a pipette to add the same volume and concentration of catalase to each tube. Then quickly attach the bung and delivery tube.
5-Record how much oxygen is released in the first minute
6-Repeat it at each temperature three times. Then find the average vol of oxygen produced
7- Calculate the average rate of reaction.

40
Q

What is RNA?

A

-Similar in structure to DNA.
-Transfer genetic information from the DNA to ribosomes (synthesis protein)- ribosomes read the RNA to make polypeptides in a process called translation.

41
Q

What is a nucleotide made from?

A

-A pentose sugar
-A nitrogen containing organic base
-A phosphate group

42
Q

How does nucleotides join together to form polynucleotides?

A

-Join up by condensation reaction between the phosphate group of one nucleotide and sugar of another.
-Forms a phosphodiester bond
-Chain of sugars and phosphates is known as the sugar-phosphate backbone.

43
Q

How does DNA made?

A

-made of two polynucleotide chains in a double helix structure
-Two DNA polynucleotide strands join together by hydrogen boning between the bases (A-T C-G)
-Two hydrogen bonds form between A and T
-Three hydrogen bonds from between C and G
-Two antiparallel polynucleotide strands twist to form the DNA double helix.

44
Q

Describe semi conservative replication-

A

1) -The enzyme DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide DNA strands.
-Makes the helix unwind to form two single strands
2) -Each original single strand acts as a template for a new strand.
-Complementary base pairing means that free-floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand.
3) - Condensation reaction joins the nucleotides together- catalysed by the enzyme DNA polymerase.
-Hydrogen bonds form between the bases
4) -Each new DNA contains one original strand and one new strand.

45
Q

What are the properties of water?

A

-Metabolite
-High latent heat of vaporisation (requires a lot of energy to break the hydrogen bonds between water molecules, useful for living organisms, they can use water loss through evaporation to cool down)
-Buffer changes in temperature (Hydrogen binds between the water molecules can absorb a lot of energy, high specific heat capacity, useful for living organisms because water doesn’t experience rapid temperature changes. Makes it good habitat, temp is more stable under water, helping them to maintain a constant internal body temperature)
-Good solvent (a lot of metabolic reactions are ionic, the ions will get surrounded by water molecules)
-Strong cohesion between water molecules (Very cohesive because they’re polar, helps water to flow, high surface tension when it comes into contact with air)

46
Q
A

Biology (12 decks)

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