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Biology A- Level > Core Concepts (Biological Compounds) > Flashcards

Core Concepts (Biological Compounds) Flashcards

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1
Q

Name the four key inorganic ions
in living organisms

A

● Magnesium ions (Mg2+)
● Iron ions (Fe2+)
● Calcium ions (Ca2+)
● Phosphate ions (PO43-)

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2
Q

What is the role of Mg2+ in plants?

A

Mg2+ is used to produce chlorophyll.

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3
Q

What is the role of Fe2+ in animals?

A

Fe2+ is found in haemoglobin and is
involved in the transport of oxygen.

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4
Q

What is the role of PO43- in living
organisms?

A

PO43- is used to produce ` ADP and ATP`.

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5
Q

What is the role of Ca2+ in living
organisms?

A

Ca2+ is used to strengthen tissues such
as bones and teeth in animals and cell walls in plants.

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6
Q

Why is water a polar molecule?

A

O is more electronegative than H. O attracts
the electron density in the covalent bond
more strongly, forming δ- O and δ+ H.

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7
Q

Describe hydrogen bonding between
water molecules

A

Weak intermolecular forces of attraction
form between a lone pair on a δ- O and a
δ+ H on an adjacent molecule.

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8
Q

What is a metabolite?

A

A molecule formed or used in metabolic
reactions.

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9
Q

Describe the role of water as a
metabolite.

A

Water is a reactant in photosynthesis
and hydrolysis reactions. Water is a
product in aerobic respiration and
condensation reactions.

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10
Q

Why is water’s high specific heat
capacity important for organisms?

A

Water acts as a temperature buffer, enabling
endotherms to resist fluctuations in core
temperature and to maintain optimum enzyme
activity.

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11
Q

Why is water’s high latent heat of
vaporisation important for organisms?

A

When water evaporates, it has a cooling effect.
This is important in homeostasis; organisms can
lose heat through sweating or panting.

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12
Q

Why is water an important solvent for
organisms?

A

Water is a polar universal solvent. It enables
chemical reactions to take place within cells,
the transport of materials in the plasma and
the removal of metabolic waste.

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13
Q

Why does water have a high surface
tension?

A

Due to the ordered arrangement and
cohesion of molecules at the surface of
water.

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14
Q

Why is the high surface tension of water
important for organisms?

A

● Enables the transport of water and nutrients
through plants stems and small blood
vessels in the body
● Allows small insects to ‘walk’ on water

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15
Q

What is a monosaccharide? (3)

A

● Simple sugar
● General formula (CH2O)n
● Soluble in water

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16
Q

Give some examples of
monosaccharides.

A

● Glyceraldehyde
● Ribose
● Deoxyribose
● α- and β- glucose
● Fructose
● Galactose

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17
Q

What is the name of the bond formed
when two monosaccharides react?

A

Glycosidic bond

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18
Q

What is a disaccharide? (3)

A

● Molecule formed by the condensation of two
monosaccharides, forming a glycosidic bond
● Formula C12H22O11
● Soluble in water

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19
Q

Give some examples of disaccharides and their
monosaccharide constituents.

A

● Sucrose (Glucose-Fructose)
● Maltose (α-Glucose-α-Glucose)
● Lactose (Glucose-Galactose)

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20
Q

What is a polysaccharide?

A

A polymer of monosaccharides, formed
by many condensation reactions.

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21
Q

Give some examples of polysaccharides.

A

● Starch
● Glycogen
● Cellulose
● Chitin

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22
Q

What is the function of starch?

A

Energy storage in plants

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23
Q

Describe the structure of starch.

A

● Polymer of α-glucose monomers
● Two forms: amylose and amylopectin
● Amylose: α-1,4-glycosidic bonds, unbranched
● Amylopectin: α-1,4- and α-1,6-glycosidic bonds,
branched

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24
Q

What is the function of glycogen?

A

Energy storage in animals.

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25
Q

How does the structure of glycogen
relate to its function?

A

It is highly branched enabling the rapid
hydrolysis of glucose molecules.

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26
Q

Describe the structure and function of
cellulose.

A

● Linear polysaccharide that is the main component of the cell wall
in plants
● Consists of many β-glucose molecules joined by β-1,4-glycosidic
bonds
● Alternate glucose molecules rotated 180° allowing hydrogen bonds
between parallel chains, forming myofibrils

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27
Q

Describe the structure and function of
chitin.

A

● Linear polysaccharide found in the exoskeletons of insects and
crustaceans as well as fungal cell walls
● Consists of many β-glucose molecules (with amino acid side chains)
joined by β-1,4-glycosidic bonds
● Alternate glucose molecules rotated 180° allowing hydrogen bonds
between parallel chains, forming myofibrils

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28
Q

Explain how a triglyceride is formed

A

One molecule of glycerol forms ester bonds
with three fatty acids via condensation
reactions.

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29
Q

Relate the structure of triglycerides to
their functions.

A

● High energy-to-mass ratio - energy storage, high calorific value
from oxidation
● Insoluble hydrocarbon chain - no effect on water potential of cells,
used for waterproofing
● Slow conductor of heat - thermal insulation, e.g. adipose tissue
● Less dense than water - buoyancy of aquatic animals

30
Q

What is a phospholipid?

A

A type of lipid formed by the condensation of
one molecule of glycerol, two molecules of fatty
acid and a phosphate group.

31
Q

Relate the structure of phospholipids to
their functions.

A

Glycerol backbone attached to two hydrophobic fatty acid
tails and one hydrophilic polar phosphate head:
● Forms phospholipid bilayer in water - component of cell
membranes
● Tails splay outwards - waterproofing, e.g. skin

32
Q

What is the difference between saturated
and unsaturated fats?

A

● Saturated fats have no C=C bonds, and are solid at room
temperature due to strong intermolecular forces
● Unsaturated fats have one or more C=C bonds, and are liquid
at room temperature due to weak intermolecular forces

33
Q

Differentiate between monounsaturated
and polyunsaturated fatty acids.

A

● Monounsaturated fatty acids contain one
C=C bond
● Polyunsaturated fatty acids contain more than
one C=C bond

34
Q

What is meant by a low density
lipoprotein (LDL)?

A

● Combination of triglycerides from saturated fats
and protein
● Blocks receptor sites, reducing cholesterol
absorption
● Known as ‘bad’ lipoproteins

35
Q

How do LDLs contribute to the risk of
cardiovascular disease?

A

The high blood cholesterol level caused
by LDLs leads to formation of
atherosclerosis plaques.

36
Q

Describe the general structure of an
amino acid.

A

● Amine group (-NH2)
● Variable side chain (R)
● Carboxyl group (-COOH)
● H atom

37
Q

How are polypeptides formed?

A

Many amino acid monomers join together
in condensation reactions, forming
peptide bonds (-CONH-).

38
Q

What is the primary structure of a
protein?

A

The individual sequence of amino acids
in a protein.

39
Q

Describe the secondary structure of a
protein.

A

The local interactions of the amino acids in
the polypeptide chain resulting in α-helixes or
β-pleated sheets. Hydrogen bonds hold the
arrangements in place.

40
Q

Describe the tertiary structure of a
protein.

A

The folding of a protein to make a three-dimensional
structure. Held in place by various interactions and bonds:
● Disulfide bonds
● Ionic bonds
● Hydrogen bonds
● Hydrophobic interactions

41
Q

Describe the quaternary structure of a
protein.

A

● Interactions of more than one polypeptide chain
● May involve addition of prosthetic groups, e.g.
metal ions or phosphate groups

42
Q

Describe how the structure of fibrous
proteins relates to their function.

A

● Long polypeptide chains, folded in parallel
● Little tertiary/quaternary structure aside from cross-linkages for strength
● This makes them insoluble and good for structural roles

43
Q

Describe how the structure of globular proteins relates to their function.

A

● Spherical, compact, highly folded with complex
tertiary/quaternary structures
● Hydrophilic R groups face outwards and hydrophobic
R groups face inwards therefore water-soluble
● Metabolic roles, e.g. enzymes

44
Q

What is the difference between a
reducing and non-reducing sugar?

A

● A reducing sugar has a free aldehyde or ketone functional
group so can act as a reducing agent
● A non-reducing sugar does not have a free aldehyde or
ketone functional group so it cannot act as a reducing
agent

45
Q

Describe the Benedict’s test for reducing
sugars.

A
  1. Add an equal volume of the sample being tested and
    Benedict’s reagent
  2. Heat the mixture in an electric water bath at 100°C for 5
    minutes
  3. Observe the colour of the precipitate formed
46
Q

Describe the positive result for reducing
sugars.

A

Colour change from green to yellow to
orange to brown to a brick red depending
on the quantity of reducing sugar present.

47
Q

Describe the Benedict’s test for
non-reducing sugars.

A
  1. Negative test for reducing sugar
  2. Hydrolyse non-reducing sugars with an equal volume of dilute HCl
  3. Heat in a boiling water bath for 5 minutes
  4. Add NaHCO3
    to neutralise the acid
  5. Re-test resulting solution with Benedict’s reagent
  6. Observe the colour of the precipitate formed
48
Q

Describe the positive result for
non-reducing sugars.

A

Colour change from green to yellow to
orange to brown to brick red depending on
the quantity of non-reducing sugar present.

49
Q

Name the food test used to identify
proteins.

A

Biuret test

50
Q

Describe the biuret test.

A
  1. Add an equal volume of the sample to be tested
    and NaOH
  2. Add a few drops of dilute copper (II) sulfate solution
  3. Mix gently and record any observations
51
Q

Describe the positive result of a
biuret test.

A

Colour change from pale blue to purple.

52
Q

Describe the iodine-potassium iodide
test for starch.

A

● Add iodine-KI solution
● Colour change from orange to
blue-black in the presence of starch

53
Q

Describe the emulsion test for fats
and oils.

A

● Add ethanol to the sample and shake
● Allow the mixture to settle
● Add an equal volume of water
● Record any observations

54
Q

Describe the positive result of an
emulsion test.

A

White, cloudy emulsion forms.

55
Q

Describe the emulsion test for fats
and oils.

A

● Add ethanol to the sample and shake
● Allow the mixture to settle
● Add an equal volume of water
● Record any observations

56
Q

Describe the structure of centrioles.

A

● Cylindrical structure
● Organised into microtubules in a 9+0 pattern
● Found in pairs in centrosomes

57
Q

Describe the structure of a chloroplast.

A

● Disk shaped surrounded by double membrane
● Thylakoids - flattened discs stacked to form grana
● Grana - contain photosystems with chlorophyll
● Intergranal lamellae - tubes attach thylakoids in adjacent
grana
● Stroma - fluid-filled matrix

58
Q

What is the function of a chloroplast?

A

Site of photosynthesis

59
Q

Describe the structure of the permanent
vacuole in plants

A

● Surrounded by a single membrane, tonoplast
● Contains cell sap (mineral ions, water,
enzymes, soluble pigments)

60
Q

Describe the function of the permanent
vacuole in plants.

A

● Controls turgor pressure
● Water storage
● Isolates harmful waste products
● Maintains pH

61
Q

Define plasmodesmata

A

Microscopic channels between plant cell
walls that facilitate communication and
symplastic transport.

62
Q

Define prokaryotic cell

A

A type of cell that does not contain any
membrane-bound organelles or a true
nucleus.

63
Q

Describe the structure and function of
the flagella in prokaryotic cells.

A

● Long, whip-like protrusion made of flagellin
● Rotates to propel the organism
● Sensory organ

64
Q

Describe the structure and function of
the flagella in prokaryotic cells.

A

● Long, whip-like protrusion made of flagellin
● Rotates to propel the organism
● Sensory organ

65
Q

How is genetic information stored in
prokaryotes?

A
66
Q

Describe the positive result of an
emulsion test.

A

White, cloudy emulsion forms.

67
Q

Micronutrients definition

A

Inorganic nutrients needed in minute (trace) amounts e.g. copper and zinc

68
Q

Inorganic definition

A

Compounds that do not contain carbon bonded to hydrogen e.g. water, carbon dioxide, nitrogen gas

69
Q

Macronutrients definition

A

Inorganic ions needed in small amounts e.g. magnesium, iron, phosphate and calcium

70
Q

Organic definition

A

Compounds that are based on carbon and contain carbon bonded to hydrogen e.g. carbohydrates, proteins and lipids

Biology A- Level (11 decks)

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