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Chapter 3 Flashcards

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1
Q

WHEN ARE COVALENT BONDS FORMED?

A

Occur when electrons are shared to allow the atom to gain a full outer shell becoming a stable ion.

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2
Q

DEFINE A CONDENSATION REACTION

A

Two molecules join with the removal of water.

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3
Q

DEFINE A HYDROLYSIS REACTION

A

Two molecules split with the addition of water (usually addition of two OH)

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4
Q

WHAT IS POLYMERISATION

A

Monomers join together to form a big polymer.

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5
Q

PROPERTIES OF WATER -
LIQUID
STATE THREE BENEFITS OF THIS.

A

Water is a liquid. This means that water can:
○ Provide habitats for living things.
○ Medium for chemical reactions
○ Effective transport medium

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6
Q

PROPERTIES OF WATER - DENSITY

A

The density provides an ideal habitat for living. If water was less dense, aquatic organisms find it hard to float. When most liquids get colder they get denser. But not water. Below 4 degrees, the hydrogen bonds start to push out. This makes ice less dense than water.
○ In winter when ice freezes it floats, providing an insulating layer underneath.
○ A stable environment for aquatic organisms.

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7
Q

PROPERTIES OF WATER - GOOD SOLVENT

A
  • Water is a good solvent because it id polar.
  • Molecules and ions can react in water.
  • Solutes can be transported whilst dissolved in water.
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8
Q

PROPERTIES OF WATER - COHESION AND SURFACE TENSION

A

hydrogen bonding pulls water molecules together. This creates a layer on the surface of water upon which small insects can walk.
○ Allows columns of water to be pulled up xylem
○ Insects like pond skaters can walk on water

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9
Q

PROPERTIES OF WATER - HIGH SPECIFIC HEAT CAPACITY

A

As water molecules are held together very strongly the forces required to break are high, therefore high specific heat capacity. This makes water quite stable in that it doesn’t vaporise spontaneously.
○ Living things need a stable temperature for enzyme controlled reactions
○ Stable environment for aquatic organisms.

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10
Q

PROPERTIES OF WATER - HIGH LATENT HEAT OF VAPORISATION

A

Hydrogen bonds require a large amount of energy to overcome to make the water into vapour. This energy can be taken from the body thus cooling the organism.
○ E.g. Sweat - Evaporated water sucks heat energy from the skin cooling it down.

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11
Q

PROPERTIES OF WATER - REACTANT

A

Water is also a reactant in reactions such as photosynthesis.
○ Digestion
○ Synthesis of large molecules

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12
Q

DEFINE CARBOHYDRATES AND IDENTIFY THREE USES

A 
Basically hydrated carbons meaning each carbon has two hydrogens and one oxygen. 
The uses of carbs are three:
	- Source of energy
	- Store of energy
	- Structural units
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13
Q

EXPLAIN THE STRUCTURE AND USE OF MONOSACCHARIDES

A 
Simplest carb
		• Important source of energy
		• They are sugars which taste sweet
		• Soluble in water
		• They have a backbone of single bonded carbon atoms some are aliphatic and some are alicyclic
		• E.g. alpha glucose
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14
Q

EXPLAIN THE STRUCUTRE AND USE OF DISACCHARIDES

A

Sweet and soluble
• E.g. maltose, sucrose and lactose.
Made by two monosaccharides joining together forming glycosidic bonds. (two hydroxyl groups line up and a water is removed - condensation reaction)
They are broken back into monosaccharides by hydrolysis reactions (adding water which breaks the glycosidic bond)

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15
Q

WHAT ARE POLYSACCHARIDES. EXPLAIN IN TERMS OF GLUCOSE.

A

These are polymers of monosaccharides. Made of thousands of monosaccharides joined together.
Glucose is a source of energy because it’s used to make ATP. But if you join loads of glucoses together you get a store of energy - Glycogen.

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16
Q

WHAT IS GLYCOGEN AND WHAT PROPERTIES DOES IT HAVE TO MAKE IT A GOOD ENERGY STORE?

A

Energy storage in animals. Has 1-4 glycosidic bonds but more 1-6 bonds than amylopectin. Doesnt coil as much and is more branched. But very compact.

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17
Q

WHAT IS STARCH?

A

Energy storage in plants.

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18
Q

WHAT IS AMYLOSE? DESCRIBE ITS STRUCTURE.

A

Unbranched chain of alpha glucose. Has 1-4 glycosidic bonds. It coils into a spiral and has H bonds. Hydroxyl groups on carbon 2 are on the inside of the coil making it not water soluble.

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19
Q

DESCRIBE THES STRUCTURE OF AMYLOPECTIN

A

Branched, therefore more compact. Has 1-4 glycosidic bonds that are broken down by amylase. Also has 1-6 glycosidic bonds resulting in branching. Also coils into spirals but has branches as well.

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20
Q

IDENTIFY THE USE OF CARBOHYDRATES AS STRCTURAL UNITS

A

Mainly forms cell walls

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21
Q

WHAT IS CELLULOSE?
IDENTIFY THREE PROPERTIES.
DESCRIBE THE STRUCUTRE.
HOW IS IT ADAPTED TO ITS ROLE (MICROFIBRILS)?

A
  • Forms cell walls in plants.
  • Tough, insoluble and fibrous.
  • Made of long chains of beta glucose. Beta-glucose has the OH’s on opposite sides of the plain, each alternate glucose will twist around so that the hydrogen bonds can form. This will form a straight line of glucoses. This adds to the strength of the structure.
  • Several hundred of these form a microfibril whihc then forms a microfibril. The microfibrils are embedded in pectin’s to form the wall.
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22
Q

DESCRIBE FIVE PROPERTIES OF CELLULOSE CELL WALLS

A
  • Very high tensile strength due to glycosidic bonds and hydrogen bonds.
  • Microfibrils run in all directions criss-crossing to increase strength.
  • Difficult to digest.
  • Because plants do not have a skeleton each cell need to do its job to support the whole structure by turgidity of cells.
  • There are spaced between my fibrils to allow water and mineral ions to pass - permeable.
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23
Q

WHAT ARE BACTERIAL CELL WALLS MADE OF?

DESCRIBE ITS STRUCUTRE.

A

Made of peptidoglycan. These are made from long polysaccharide chains that lie in parallel, cross linked by short peptide chains.

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24
Q

DESCRIBE LIPIDS. WHAT ARE THE THREE TYPE OF LIPIDS?

A

Contain large amounts of carbon and hydrogen and smaller amounts of oxygen. Insoluble, not polar but dissolve in alcohols. There are three types all of which are macromolecules:
TRIGLYCERIDES
PHOSPHOLIPIDS
STEROIDS

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25
Q

DESCRIBE THE TWO COMPONENTS OF TRIGLYCERIDES AND HOW THEY ARE BONDED.

A

Made of glycerol and fatty acids.
• GLYCEROL: an alcohol with three OH groups.
• FATTY ACIDS: these have a carboxyl group (-COOH) attached to a hydrocarbon tail. The hydroxyl group can disassociate into H+ and COO, this makes it an acid. The chains can be saturated or unsaturated. Unsaturated double bods provide kinks in the structure making it more fluid.
ESTER BONDS join the two together. A -COOH and a -OH join to release a H2O.

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26
Q

DESCRIBE THE FIVE FUNCTIONS OF TRIGLYCERIDES.

A

ENERGY SOURCE: triglycerides are broken down to release energy and generate ATP. First the ester bond is hydrolysed then both glycerol and fatty acids are broken down to CO2 and water.
ENERGY STORE: insoluble so can be stored without affecting water potential.
INSULATION: acts as a heat insulator. Lipids line nerve cells and are electrical conductors.
BUOYANCY: because fat is less dense than water, it can help mammals float.
PROTECTION: fat around delicate organs act as a shock absorber.

27
Q

DESCRIBE PHOSPHOLIPIDS.

A

Has the same structure as triglycerides but one fatty acid chain is replaced by a phosphate. The head is hydrophilic and the tail is hydrophobic.

28
Q

DESCRIBE THE STRUCTUR OF PHOSPHOLIPID BILAYER AND EXPLAIN HOW IT RELATES TO THE FUNCTION.

A

Two layers of phospholipids, each with the heads facing out and tails facing in. This gives it stability and makes it waterproof. It is also partially permeable.

29
Q

HOW DOES CHOLESTROL CONTRIBUTE TO THE PHOSPHOLIPID BILAYER.

A

Made of four carbon-based rings. Small hydrophobic molecules. Cholesterol is small and hydrophobic, it sits in between the phospholipids to regulate fluidity.
Steroid hormones are made of testosterone, oestrogen, and vitamin D.

30
Q

DEFINE AMINO ACID.
WHAT MAKES THEM GOOD ENZYMES?
WHAT IS THIER USE IN THE BILAYER?
DESCRIBE THE STRUCTURE OF AMINO ACIDS.

A

Large polymers made of long chains of amino acids.

  • Structural importance: muscles
  • Tendency to adopt specific shapes makes them good enzymes
  • Present in membranes which help to transport substances.
  • Proteins are made of carboxylic acid on one side and a amine on the other side. They all have a specific Are-group in the middle.
31
Q

DESCRIBE HOW A PEPTIDE BOND IS FORMED BETWEEN AMINO ACIDS.

A

Amino acids are joined by peptide bonds. This involves a condensation reaction. The OH from the carboxyl combines with the H from the amine. This forms a peptide bond and water is released. Adding water breaks the bond by hydrolysis.

32
Q

EXPLAIN THE PRIMARY STRUCTURE OF PROTEINS.

A

This is the sequence of amino acids that make up the protein chain. The length of the chain and position of each determines the protein chain.

33
Q

EXPLAIN THE SECONDARY STRUCTURE OF PROTEINS.

A

The chain of amino acids can twist into shapes called secondary structures by hydrogen bonds. There are many which makes both the following structures very strong.

  • Alpha helix
  • Beta Pleated sheet
34
Q

EXPLAIN THE TERTIARY STRUCTURE OF PROTEINS.

A

When these two start to coil and wind around each other a very specific tertiary structure is formed.

35
Q

EXPLAIN THE QUATERNARY STRUCTURE OF PROTEINS.

A

multiple polypeptide chains joined together to make a complex protein.

36
Q

DESCRIBE THE THREE TYPES OF PROTEIN BONDING

A
  • HYDROGEN BOND: forms between hydrogen atoms w a slight positive charge and other atoms with a slight negative charge, usually OH and H.
  • IONIC BOND: forms between carboxyl groups and amino groups and others too.
  • DISULPHIDE BRIDGES: forms between two R-groups of cysteine, because cysteine contains sulphur
37
Q

WHAT ARE FIBROUS PROTEINS

A

Have regular, repetitive sequence of amino acids. Insoluble. This enables fibres to form.

38
Q

DESCRIE THE USES OF THE FIBROUS PROTEIN COLLAGEN. WHERE IS IT FOUND?

A

Provides mechanical strength:
• In artery walls it prevents the walls from bursting under the pressure.
• Tendons are also made of collagen and connect muscle to bones.
• Bones are made of collagen then re-in forced with calcium phosphate.
• Cartilage and connective tissue

39
Q

DESCRIE THE USES OF THE FIBROUS PROTEIN KERATIN. WHERE IS IT FOUND?

A 
Rich in cysteine so has lots of disulphide bridges. This makes them very strong. Found in most places where the body parts are hard and strong. 
		• Nails
		• Hair
		• Claws
		• Hoofs
		• scales
40
Q

DESCRIE THE USES OF THE FIBROUS PROTEIN ELASTIN. WHERE IS IT FOUND?

A 
Has cross links and coils to make it very strong. Found wherever living things need to stretch. 
	• Skin can stretch around bones
	• Lungs can inflate
	• Bladder can expand to hold urine. 
        • Blood vessels can stretch
41
Q

WHAT ARE GLOBULAR PROTEINS

A

Tend to roll up almost into spheres with hydrophobics on the inside and hydrophilic on the inside

42
Q

DESCRIBE THE STRUCTURE AND FUNCTION OF HAEMOGLOBIN (GLOBULAR)

A

The quaternary structure is made of four polypeptide chains, to alpha-globin and two beta-globin. Each chain has a prosthetic group of an iron ion. This is a conjugated protein because of the attached haem group. Oxygen binds to this and can be transported around the body in the blood.

43
Q

DESCRIBE THE STRUCTURE AND FUNCTION OF INSULIN (GLOBULAR)

A

Made of two polypeptide chains. A chain begins with alpha glucose and B chain ends in beta glucose. Both chains fold together. Insulin binds to glycoprotein receptors on the outside of muscle and fat cells to increase their uptake of glucose.

44
Q

DESCRIBE THE STRUCTURE AND FUNCTION OF PEPSIN (GLOBULAR)

A

Digests proteins in the stomach. It has a very simple shape so remains relatively unaffected by the low pH in the stomach.

45
Q

WHAT DO QUALITATIVE TESTS TEST FOR?

A

Test for presence of the substance.

46
Q

HOW DO YOU TEST FOR CARBOHYDRATES (STARCH)?

A
  • STARCH: add iodine solution. If starch is present it will change from yellow-brown to blue-black. This happens when the iodine forms an ion which slips into the amylose helix.
47
Q

HOW DO YOU TEST FOR REDUCING SUGARS?`

A

All monosaccharides and disaccharides. Heat with benedict’s solution, colour changes from blue to green to yellow to orange-red. Precipitate forms from copper ions. The concentration of the sugar is proportional to the intensity of the red.

48
Q

HOW DO YOU TEST FOR NON-REDUCING SUGARS?

A

First the bond has to be hydrolysed to free up the reducing sugars. To do this boil it with hydrochloric acid, this will hydrolyse the sucrose into glucose and fructose. Cool then add sodium hydrogen carbonate to neutralise.

49
Q

HOW DO YOU TEST FOR LIPIDS?

A

Mix the sample with ethanol. Filter. A cloudy white emulsion will form.

50
Q

HOW DO YOU TEST FOR PROTEIN?

A

Use the biuret test. If protein is present the colour changes from blue to lilac. Biuret solution comprises of sedum hydroxide and copper sulfate. It tests for the presence of peptide bonds.

51
Q

WHAT IS A QUANTITATIVE TEST?

A

Tests how much of the thing there is

52
Q

QUANTITATIVE TEST FOR REDUCING SUGARS.

A

To test for concentration of reducing sugars using colorimetry. Centrifuge the solution to separate the precipitate and any excess benedict’s solution. Using a pipette place the sample into a cuvette. You may use a filter to increase accuracy. If there is more sugar present there will be more precipitate and copper ions will decrease because more copper oxide is formed.
Transmission will be higher if more sugar is present.

53
Q 
CHROMATOGRAPHY
EXPLAIN THE PHASES.
EXPLAIN THE FIVE STEPS.
HOW DOES IT WORK TO SEPERATE SOLUTIONS?
WHAT DYES ARE USED IF COMPONENTS CANNOT BE SEEN?
A

Separates a mixture into its constituents.

  • STATIONARY PHASE: chromatography paper.
  • MOBILE PHASE: solvent. E.g. water of ethanol
    1) Draw a pencil line at the bottom of the paper
    2) Add the dye
    3) Place the paper in the solvent so that the bottom (under the pencil line) is submerged.
    4) The mobile phase will move up the stationary phase.
    5) Divide the distance travelled up the mobile phase by the solvent, divided by the distance travelled by the dye.

As the solvent moves up the paper, the solution will travel with it. The different components travel at different speeds.
The speed depends on solubility. More OH groups will form more bonds with the paper making it move slower. So a highly polar solvent will be adsorbed, a non-polar solvent will more quicker.

If the components cannot be seen:

- ULTRAVIOLET LIGHT: most of the plate will glow except certain spots where the solute has travelled to. 
- NINHYDRIN: allows amino acids to be seen. It will bind to the amino acids to make them visible. 
- IODINE: allow to dry, place in an enclosed space with a few iodine crystals. The iodine forms a gas, which then binds to the molecules.
54
Q

WHAT IS DNA?

A

Present in all living organisms. Codes for genes.

55
Q

DESCRIBE THE STRUCTURE OF NUCLEOTIDES.

EXPLAIN DIFFERENCE BETWEEN RNA AND DNA.

A

They are pentose sugars with a nitrogenous base. It also has a phosphate group linked to either the C5 or C3. they form the monomers of nucleic acids DNA and RNA.
- In RNA the nucleotide pentose sugar is ribose.
- In DNA the nucleotide pentose sugar is deoxyribose.
When the nucleotide contains phosphates it becomes phosphorylated.

56
Q

DESCRIBE THE STRUCTURE AND BONDING OF DNA.
WHAT ARE PURINES AND PYRAMIDINES?
DESCRIBE THE SUGAR-PHOSPHATE BACKBONE.

A

A polymer made of repeating monomeric units - nucleotides. A molecule of DNA consists of two polynucleotide strands. The two strands run in opposite strands. Each DNA nucleotide consists of a phosphate group, deoxyribose and of four bases:

PURINE:
	- Adenine
	- Guanine
PYRIMIDINE: 
	- Thymine
	- Cytosine

There is a phosphodiester bond between the deoxyribose and the phosphate group.
The two anti-parallel strands are joined by hydrogen bonds. Adenine pairs with thymine by two hydrogen bonds. Guanine always pair with cytosine by three hydrogen bonds.
A purine binds with a pyrimidine, it then coils around an imaginary axis.

SUGAR-PHOSPHATE BACKBONE: this is the backbone of the ladder. The opposite direction is caused by where the C5 and C3 are. In both they are on opposite ends.

57
Q

DESCRIBE THE DIFFERENCE IN DNA ORGANISATION IN EUKARYOTES OR PORKAYOTES.

A
  • EUKARYOTIC: in the nucleus. Each large molecule of DNA is wound tight around histone proteins into chromosomes.
  • PROKARYOTIC: DNA in a loop in the cytoplasm. Not enclosed in nucleus.
58
Q

EXPLAIN THE THREE STEPS OF DNA REPLICATION

A

SEMI-CONSERVATIVE REPLICATION:

- DNA unwinds.
- DNA unzips by DNA helicase resulting in two single strands with exposed bases. 
- Free nucleotides bind to exposed bases following the complimentary base rule. This is catalysed by DNA polymerase. It uses each strand as a template. The leading strand is synthesised continuously whereas the lagging strand is in fragments that are later joined on.  
- This produces two DNA molecules
59
Q

EXPLAIN THE DIFFERENCE IN DNA AND RNA

A

RNA is structurally different from DNA:

- The sugar is ribose
- Uracil replaces thymine
- The polynucleotide chain is usually single stranded and shorter
60
Q

EXPLAIN THE THREE TYPES OF RNA: mRNA, tRNA, rRNA/

A
  • mRNA - messenger RNA (this is created when the original strand of DNA is transcribed)
  • tRNA - transfer RNA (strand of RNA folded so that three bases -the anticodon are at the end)
  • rRNA - ribosomal RNA (this makes up part of the ribosome, maintains structural stability and plays a biochemical role in catalysing the reaction)
61
Q

HOW DOES DNA CODE FOR POLYPEPTIDES?

A

Each chromosome has specific lengths of DNA called genes. Each gene has a sequence of DNA base triplets that determines the amino acid sequence of a polypeptide. This code needs to be used for protein synthesis. The whole chromosome cannot be taken out, only a small bit that needs to be used is transcribed (copied) into a length of RNA and transported out of the nucleus into ribosomes. Here the base triplets are called codons.

62
Q

DESCIRIBE THE THREE CHARECTARISTICS OF DNA:

    • UNIVERSAL
    • DEGENRATE
    • NON-OVERLAPPING
A
  • UNIVERSAL: In almost all living organisms the same sequence of DNA cods for the same protein.
  • DEGENERATE: for all amino acids there is more than one base triplet. This reduces the chance of mutation.
  • NON-OVERLAPPING: the chain is read from one fixed point in groups of three. If a base is added or deleted it causes a frame shift - every single base shifts along too.
63
Q

DESCRIBE THE FIVE STAGES OF TRANSCRIPTION.

A

The process by which a gene is transcribed into a length of mRNA.
• Gene unwinds and unzips
• Hydrogen bonds between complimentary bases breaks
• Enzyme RNA polymerase catalyses the formation of temporary bonds hydrogen bonds between RNA nucleotides and unpaired bases
• A length of RNA that is complimentary to the template strand of the genes is produced. It is a copy of the coding (original strand)
• mRNA passes out of the nucleus through the nuclear envelope and attaches to a ribosome.

64
Q

DESCIRIBE THE FIVE STEPS OF TRANSLATION

A

• tRNA is made in the nucleolus and passed out of the nucleus.
• mRNA binds to specific site on the small subunit of ribosome. Ribosome holds mRNA in positions as it is translated into a sequence of amino acids.
• tRNA which is a strand of RNA bent so that the anticodon - three bases - are at one end. This anticodon will bind to a complimentary codon on the mRNA following normal base pairing rules.
• The tRNA carries a amino acid. As the tRNA bind to the mRNA the proteins also join together. This forms the primary structure of the protein that the mRNA codes for.
• Amino acids are added one at a time, polypeptide chain grows as this occurs.
After the amino acid has joined, the tRNA is released and the mRNA moves along.

Biology AS OCR (11 decks)

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