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A Level Biology OCR A > 2.1.2 > Flashcards

2.1.2 Flashcards

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1
Q

Which elements do Carbohydrates contain?

A

C,H,O

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2
Q

Which elements do Lipids contain?

A

C,H,O

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3
Q

Which elements do Proteins contain?

A

C,H,O,N,S

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4
Q

Which elements do Nucleic Acids contain?

A

C,H,O,N,P

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5
Q

What are the bond numbers for Nitrogen, Oxygen, Carbon and Hydrogen?

A

N-3
O-2
C-4
H-1

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6
Q

A negative ion is a _______?

A

anion

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7
Q

A positive ion is a _______?

A

cation

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8
Q

Formula of the Sodium Ion and its use?

A

Used in nerve impulse transmission
Kidney Function
Na(+)

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9
Q

Formula of the Hydrogen Carbonate Ion and its use?

A

Maintains blood pH

HCO3(-)

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10
Q

Formula of the Pottasium Ion and its use?

A

Used in nerve impulse transmission
Opening of stomata
K(+)

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11
Q

Formula of the Hydroxide Ion and its use?

A

ph determination
Catalyses reactions
OH(-)

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12
Q

Formula of the Calcium Ion and its use?

A

Used in nerve impulse transmission
Muscle contraction
Ca(2+)

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13
Q

Formula of the Phosphate Ion and its use?

A

Cell membrane formation
ATP and Nucleic Acid formation
Bone formation
PO4(3-)

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14
Q

Formula of the Ammonium Ion and its use?

A

Production of nitrate ions by bacteria

NH4(+)

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15
Q

Formula of the Nitrate Ion and its use?

A

Nitogen supply to plants for amino acid and protein formation.
NO3(-)

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16
Q

Formula of the Chloride Ion and its use?

A

Balances out the postive charges of the sodium and pottasium in cells
Cl(-)

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17
Q

Formula of the Hydrogen Ion and its use?

A

pH determination
Catalyses reactions
H(+)

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18
Q

What biological molecules are neccessery for life?

A

Carbohdrates, Lipids, Proteins, Nucleic Acids

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19
Q

Water bonding?

A

Two hydrogens covalently bonded to one oxygen

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20
Q

Why is water a polar molecule?

A

The hydrogens and oxygen share electrons but oxygen has the larger share of the electrons so is slightly negative(delta -) and hydrogen therefore is slightly positive(delta+)

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21
Q

Why do hydrogen bonds form?

How to draw hydrogen bonds?

A

The slightly negative oxygen attracts a slightly positive hydrogen, this forms a relatively weak hydrogen bonds.
Drawn as a broken up line from oxygen to adjacent hydrogen with deltas and charges on respective elements.

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22
Q

Properties of hydrogen bonds(single bond not many)?

A

Relatively weak, can break and reform as the molecule moves.

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23
Q

Properties of hydrogen bonds in water?

A

Many bonds therefore strong and need lots of energy to break them apart

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24
Q

Why is water liquid at room tempreture?

Why is this beneficial?

A

Similarly massed molecules are gas whereas water is a liquid at room tempreture. This is because of the many hydrogen bonds in water.
This means water habitats dont just evaporate.

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25
Q

Why is water a solvent?
Why is this beneficial?
What structures do cells have to accomodate this feature of water?
How does water act to be a solvent?

A

Water is a polar molecule therefore contains both positive and negative parts, this makes it good for attracting solute.
This can help transport nutrients in and out of cells in xylem and blood.
Prokaryotes have the cytosol (made up mainly of water)
Eukaryotes have the cytoplasm (where chemical reactions take place)
It forms a layer around the ion, then breaks the ion from the compound.

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26
Q

What is waters beneficial property when it is solid?
Why is this not usual?
How does waters structure allow this?
Why is this beneficial?

A

Water is less dense as a solid than as a liquid.
Solids are usually more dense than liquids due to their fixed compact structure.
When water freezes it forms a crsytal lattice, leaving gaps, and is less dense than it was as liquid.
This means that when water in lakes freezes, the ice rises to the top due to its lower density), this acts a insulating layer preventing the water below from freezig and maintaining the habitat for many animals.

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27
Q

How does cohesion affect the movement of water?

A

Water molecules are attracted to each other so move as one mass.

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28
Q

What does adhesion in water result in?

A

Water is attracted to other materials.

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29
Q

How does adhesion and cohesion in water help plants?

A

It means capilary action can take place, this is when water moves up a narrow tube against gravity, tgis can only happen because water has the properties of adhesion and cohesion.

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30
Q

How does adhesion and cohesion help create surface tension?

Example of an insect that benefits from surface tension?

A

The water molecules are more strongly cohesive to each other rather than the air
Water Skater.

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31
Q

What property of water leads to water being a coolant?

Why is it usefull?

A

Water has a high specific heat capacity, this means that it takes lots of energy (due to the many hydrogen bonds) to heat it up. This means it can be usefull as a heat buffer in chemical reactions and for enzymes it can prevent denaturing and effectiveness (due to their narrow tempreture ranges).

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32
Q

What three properties allow water to be a suitable home?

A

Water has a high specific latent heat of vaporisation, this results in it not evaporating easily and maintaing habitats.
Water also requires lots of energy to heat up so remains at a constant tempreture.
When water freezes it forms a crsytal lattice, leaving gaps, and is less dense than it was as liquid.
This means that when water in lakes freezes, the ice rises to the top due to its lower density), this acts a insulating layer preventing the water below from freezig and maintaining the habitat for many animals.

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33
Q

What element is life on earth based on?

A

Carbon.

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34
Q

Carbon often forms ______ ________ or __________ of elements.

A

long chains,

backbones

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35
Q

What is an organic molecule?

A

A molecule built around carbon.

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36
Q

What is the monomer in carbohydrates(saccharides)?

A

simple sugars (monosaccharides)

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37
Q

What is the polymer in carbohydrates(saccharides)?

A

comlplex carbohydrates (polysaccharides)

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38
Q

Carbohdrates can be used for?

A

energy sources or structural materials

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39
Q

What is the general formula for carbohdrates?

A

Cx(H20)x

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40
Q

What are the three main groups of carbohydrates, examples of them and the general formula of monosaccharides?

A
  • monosaccharides, simple sugars, Cn(H2O)n n=3-7, eg. glucose galactose fructose ribose deoxyribose
  • disaccharides, double sugars(two monosaccharides joined), eg. lactose maltose sucrose
  • polysaccharides, large molecules, starch glycogen cellulose, formed from many monosaccharides
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41
Q

What is the formula for a hexose monosaccharide?

A

C6H1206

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42
Q

Glucose is a _________ monosaccharide?

A

hexose

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43
Q

Monosaccharides are __________ tasting and soluble/insoluble.

A

sweet tasting,

soluble

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44
Q

What is the structure of glucose?

A

ring structure

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45
Q

What are the isomers of glucose and what is the difference beetween them?

A

Alpha and Beta,

Alpha has the hydroxyl group on the first carbon is at the bottom wheras the beta has the hydroxyl at the top.

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46
Q

Which glucose can plants or animals use?

A

alpha-animals and plants, beta-just plants

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47
Q

Glucose molecules are soluble/insoluble and ______.

A

soluble and polar.

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48
Q

Why is glucose soluble?

A

Because the hydroxyl groups will for hydrogen bonds with water molecules.

49
Q

Why is the solubility of glucose important?

A

It means glucose can be transported into the cytosol or cells and glucose is crucial for cells.

50
Q

Hexose monosaccharides (other than glucose)?

A
  • fructose, more soluble than glucose and sweeter tasting, main sugar in plants,ring structure
  • galactose, not as soluble as as glucose so not as sweet, important for proction of glycolipids and glycoproteins, ring structure
51
Q

Pentose monosaccharides?

A

Ribose-present in RNA nucleotides, ring structure

Deoxyribose-present in DNA nucleotides, ring structure

52
Q

What is the bond beetween saccharides callled?

What is the chemical reaction that leads to di and poly saccharides?

A

glycosidic bond

condensation reaction

53
Q

monosaccharide=monosaccharide=disaccharide
glucose+glucose=
glucose+fructose=
glucose+galactose=

A
  • maltose+water
  • sucrose+water
  • lactose+water
54
Q

In condensation reactions:
The two __________ ________, which are side by side interact(react) to form a ________ bond, leaving behind one ________ and formng _________.

A

hydroxyl groups,
glycosidic,
oxygen,
water

55
Q

In a disaccharide of alpha glucose what are the glycosidic bonds called?

A

1-4

56
Q

Hydrolisis is?

A

add water to add back the hydroxyl groups and break the disaccharide.

57
Q

A polysacharide is a ________?

A

long chain of monosaccharides.

58
Q

Examples of polysaccharides?

A

starch(in plants), glycogen(in animals)

59
Q

Where is glycogen stored?

A

in liver and muscle cells.

60
Q

What are starch polysaccharides made up of?

A

amylose and amylopectin.

61
Q

Amylose structure

A

alpha glucose joined by 1-4 glycosidic bonds,
straight(not branched) due to only 1-4 glycosidic bonds,
helix structure,
hydrogen bonds help stabilise it

62
Q

Amylopectin structure

A

alpha glucose joined together with 1-4 and 1-6 glycosidic bonds,
branched(not straight) due to 1-4 and 1-6 glycosidic bonds every 25 units,
helix structure.

63
Q

How does the structue of amylose and amylopectin help it function?

A

due to helix structure it is compact,
they are big molecules so are insoluble so wont affect the waterr potential of cells and wont cause osmosis and celll lysis.

64
Q

Where is starch stored?

A

In chloroplasts and specialised storage organs.

65
Q

Why is a more branched molecule usefull for storage/energy?

Why do animals need more branched molecules?

A

more branches=quicker access,

they require quicker access to energy for movement

66
Q

Glycogen structure?

A

Polymer of alpha glucose and a similar structure to amylopectin,
More branched than amylopectin so quicker access
Compact, insoluble-due to the removal of hydroxyl groups during condensation and branched

67
Q

Why is the strucuture of glycogen ideal?

A

Insoluble-doesnt affect water potential, more branched-more ends so quicker access(removal/addition of glucose) for movement in animals, compact-more can be stored.

68
Q

Glucose made by photosynthesis is stored as?

A

starch

69
Q

What process turns glycogen/starch back to energy?

A

Hydrolysis reaction, add water back and seperates di/poly saccharides.

70
Q

Cellulose is made of alpha/beta glucose?

A

beta glucose

71
Q

What do the chains of cellulose contain?

A

many hydrogen bonds

72
Q

How do the beta glucoses form cellulose?

A

The beta glucose have to alternatively flip so that the hydroxyl groups can interact a have a condensation reaction, as a oxygen has to be left behind in a condensation reaction.

73
Q

Why is cellulose strong?

Why is this important?

A

Many hydrogen bonds beetween chains if cellulose which require lots of energy to break,
This allows cells to reach turgidity.

74
Q

Chains of cellulose build up to form:

A

cellulose chains join to form microfibrils.These microfibrils lay parrallel to form macrofibrils and these macrofibrils make up the cellulose fibres.This structure provides enormous stregnth.

75
Q

What does the arrangement of macrofibrils lead to?

A

A mesh like structure which allows water to enter through the cell walls of plants.

76
Q

Properties of cellulose and why they are important?

A

High tensilen stregnth, due to fibres and hydrogen bonds

-Insoluble, so dont break as they are needed for cell wall in plants.

77
Q

Why can cellulose not be a helix shape or branched?

A

The way in which the beta glucose have to alternatively flipped.

78
Q

What is reduction?

A

The gain of electrons

79
Q

Which carbohydrates can be reduced?

A

all monosaccharides and some disaccharides(maltose and lactose)

80
Q

How do you carry out the benedicts test for reducing sugars?

A
  1. Place the sample in the boiling tube, if its not a liquid grind it or blend it in water.
  2. Add an equal amount of benedicts reagent(alkaline solution of copper(II) sulfate).
  3. Heat the mixture in a water bath for 5 mins.
81
Q

What will the results be for the benedicts test for reducing sugars?

A

Reducing sugars will react to the copper ions in the benedicts. This results in the additon of electrons to the Cu(2+) ion, which are blue. These now become Cu+ ions which are red. If the solution produces a brick red precipitate it is a positive result. Green-low conc, Yellow-medium conc, Red-high conc.

82
Q

Why is there a seperate test for non-reducing sugars?

A

Non-Reducing sugars will not reduce Cu ions in benedicts so no colour change is seen and a negative test is produced.

83
Q

What is the test for non-reducing sugars?

Why is ______ added in addition to benedicts?

A

We add HCl to the sample and boil it, we then carry out the benedicts test.
HCl is added so that the disaccharide is hydrolised and becomes two monosaccharides as the hydroxil groups are added back.

84
Q

What is the iodine test for starch?

A

Add iodine dissolved in pottasium iodide solution to the sample,
If the sample goes from brown/yellow to purple/black, it is a positive result and starch is present, if the solution remains brown/yellow it is a negative result, and no starch is present.

85
Q

How is a re-agent strip used?

What is the advantage of this?

A

You can use a manufactered reagent strip by simply dipping it into the sample to test for the presence of a reducing sugar,
a colour chart can be used to give you a rough concentration.

86
Q

How do biosensors work?

A

Use a biological molecule to determine the preesence of a molecule such as glucose,
A protein(enzyme or antibody) or single strand of DNA is immobilised to the surface and will interact/bind with the molecule being investigated,
the interaction willl cause a change in the transducer and the transducer will produce a response eg. dye release, electrical signal,
This will then produce a qualitative or quantitative response eg. reading on a screen or colour.

87
Q

Qualitative?

A

Qualitative data is descriptive information about characteristics that are difficult to express numerically.

88
Q

Quantitative?

A

Quantitative data is numerical information that can be measured or counted.

89
Q

Semi-Quantitative?

A

Numerical ranges instead of exact values.

90
Q

What elements do lipids contain?

A

C,H,O

91
Q

What are lipids commonly known as?

Which of these types is liquid and which are solid at room temperature?

A

Fats and oils.

Fats are solid at room temperature, oils are liquids at room temperature.

92
Q

Are lipids made of repeating units?

A

No, they do not consist of monomers instead they are known as large molecules called macro molecules.

93
Q

Are lipids polar?
Why?/Why not?
Are lipids soluble?

A

Lipids are non polar because the electrons are evenly distributed within them. This results in lipids having no positive or negative regions, so they are not soluble in water. This is why oil and water do not mix.

94
Q

What are triglycerides made of?
What groups are its components from?
Why do these components join to form triglycerides?
What is the bond between them called and what type of reaction called?

A

Three fatty acids and glycerol,
Fatty acids are carboxylic acids and are part of the carboxyl group (COOH) with a hydrocarbon chain attached and glycerol is in the alcohol group,
Both glycerol and fatty acids have OH groups, glycerol having three, these interact, forming ester bonds and water through a type of condensation reaction called esterification.

95
Q

How is esterification reversed?

A

Hydrolysis reaction, add water back to reverse the process.

96
Q

Saturated means?

A

No double binds between carbon atoms, because the maximum number of bonds is reached.

97
Q

Unsaturated means?

A

Double bonds present, the maximum number of bonds is not reached.

98
Q

Double carbon bonds is called?

A

monounsaturated-one double bond

polyunsaturated-two or more double bonds

99
Q

How do double bonds affect the shape of a molecule?>

How does this affect the state are room temperature?

A

Double bonds cause a kink in the molecule, this means that it is not as tightly packed, causing it to be a liquid.
Unsaturated are liquid(oils)
Saturated are solids(fats)

100
Q

Where are saturated fatty acids usually found?

A

Animal lipids, solid at room temperature.

101
Q

Where are unsaturated triglycerides found?

A

Unsaturated triglycerides are usually found as oils in plants.

102
Q

Which are more healthy, saturated triglycerides and fats or unsaturated triglycerides?
What is the unhealthy one linked to?
Why can the healthy one also be bad?

A

Unsaturated triglycerides are more healthy,
Some evidence links saturated to coronary heart disease however this evidence is inconclusive,
Any type of fat in excess leads to obesity which affects the heart.

103
Q

How are the elements of phospholipids different to triglycerides?
What elements do they contain?

A

One of the fatty acids is replaced by a phosphate group,

C,H,O,P,

104
Q

Where are phosphate ions found?
Are they charged and why/why not?
What properties does this lead to?

A

In the cytoplasm of every cell,
negatively charged because there are extra electrons,
soluble in water.

105
Q

Describe a phospholipid’s structure?

A

Has a charged, hydophillic end which is the head and has a non-polar hydrophobic end which is the tail.

106
Q

What properties do the tails and heads lead to?

A

Hydrophobic tail is repelled by water as it is non polar but mixes readily with fats. Hydrophillic tails are attracted by water as they are charged.

107
Q

As a result of their dual hydrophobic/hydrophilic structure, how do phospholipids behave?

A
  • They form a layer on the top of water, with their hydrophobic tails sticking out and their hydrophillic heads in the water. This is why they are surfactants or surface active agents.
  • They also form structures based on a two layered formation (bi layer). Their hydrophobic tails point inwards and their hydrophillic heads points inwards, protecting the tails from the water. Due to this bi layer, they are important for cell membrane formation. They can separate the aqueous environments outside the cell from the aqueous environment inside the cell.
108
Q

What does the bi layer structure in cell membranes help achieve?

A

Helps achieve compartmentalization. The organelles can be separated from each other and the cytoplasm allowing individual function.

109
Q

What are sterols?

A

Sterols, also known as steroid alcohol, are lipids However they are not lipids or fats.They are composed of four carbon rings with a hydroxyl group. They are complex alcohol molecules.They have dual hydrophobic/hydrophillic characteristics, the OH being polar, so hydrophillic and the rest being hydrophobic.

110
Q

What is cholesterol?

A

A sterol that is manufactured in the liver or the intestines.

111
Q

What is cholesterol important for?

A

Its important in the formation of the cell membrane and becomes positioned in the hydrophobic side of the bi layer. In the membrane it gives stability by regulating the fluidity, if the temperature goes too low, the membrane goes solid, if it gets too high the molecules are pushed too far away in the membrane leading to a leak. Cholesterol regulates the temperature.
Vitamin D, Bile and steroid hormones are also manufactured using cholesterol.

112
Q

What are the roles of lipids?

A

-Due to their non-polar nature:
Can form membranes with a hydrophobic barrier
Used in hormone production
Insulation for electrical impulse transmission
-lipids, in particular triglycerides, have an important role in long term energy storage
-thermal insulation to reduce heat loss eg,penguins
-cushioning for vital organs
-buoyancy for aquatic animals eg,whales

113
Q

What is the test for the identification of lipids?

A 
Emulsion test
1.Add ethanol to the sample
2.Add water and shake
3.Positive test(lipid will appear as a white emulsion and rise, as hydrophobic elements repel water and lipids are denser than water)
negative test(nothing happens).
114
Q

Why does health advice always change?

A

Due to how the media portrays new findings. The validity and research has not always been evaluated and the science is hard to explain to the public who may not have a scientific background.
Scientific knowledge also always changes, this can be due to new technology.
It can also be difficult to isolate the effect of one nutrient as nutrients often work together, called synergy.
People could also lie when carrying out studies, subjects may not disclose a certain food they ate.
Surveys with small numbers of people can also be inaccurate.

115
Q

What is the polymer in peptides and the monomer?

What do proteins consist of?

A

polymer-peptide
monomer-amino acids
One or more polypeptides arranged as macro molecules.

116
Q

What elements do proteins contain?

A

C, H, O, N (and some contain S)

117
Q

Describe the structure of amino acids?

A

All amino acids have the same basic structure, amine group(NH2) and carboxyl group(COOH), the R group is what determines the amino acid.

118
Q

How many commonly found amino acids are there in our cells and how many are essential,conditionally essential and non-essential?

A

20 commonly found
5 non-essential(our body can make them from other amino acids)
9 are essential(we can only get them from the food we eat)
6 are conditionally essential(only needed by infants and growing children).

119
Q

Explain the synthesis of proteins?

A

The amine group of one amino acid and the carboxyl of another interact. the hydroxyl group from the carbxoyl as the hydrogen from the amine react to form water and a peptide bond. This is a condensation reaction.The resulting compound is a dipeptide. Many amino acids joined by peptide bonds are in a polypeptide. One or more polypeptides arrange as macro molecules to make a protein.The different R groups

A Level Biology OCR A (2 decks)

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