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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
How does the structure of glycogen relate to its function?
It is highly branched enabling the rapid hydrolysis of glucose molecules.
26
Describe the structure and function of cellulose.
● 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
27
Describe the structure and function of chitin.
● 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
28
Explain how a triglyceride is formed
`One molecule of glycero`l forms `ester` bonds with `three fatty acids` via condensation reactions.
29
Relate the structure of triglycerides to their functions.
● 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
What is a phospholipid?
A type of lipid formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group.
31
Relate the structure of phospholipids to their functions.
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
What is the difference between saturated and unsaturated fats?
● 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
Differentiate between monounsaturated and polyunsaturated fatty acids.
● Monounsaturated fatty acids contain one C=C bond ● Polyunsaturated fatty acids contain more than one C=C bond
34
What is meant by a low density lipoprotein (LDL)?
● Combination of triglycerides from saturated fats and protein ● Blocks receptor sites, reducing cholesterol absorption ● Known as ‘bad’ lipoproteins
35
How do LDLs contribute to the risk of cardiovascular disease?
The high blood cholesterol level caused by LDLs leads to formation of atherosclerosis plaques.
36
Describe the general structure of an amino acid.
● Amine group (-NH2) ● Variable side chain (R) ● Carboxyl group (-COOH) ● H atom
37
How are polypeptides formed?
Many amino acid monomers join together in condensation reactions, forming peptide bonds (-CONH-).
38
What is the primary structure of a protein?
The individual sequence of amino acids in a protein.
39
Describe the secondary structure of a protein.
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
Describe the tertiary structure of a protein.
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
Describe the quaternary structure of a protein.
● Interactions of more than one polypeptide chain ● May involve addition of prosthetic groups, e.g. metal ions or phosphate groups
42
Describe how the structure of fibrous proteins relates to their function.
● 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
Describe how the structure of globular proteins relates to their function.
● 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
What is the difference between a reducing and non-reducing sugar?
● 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
Describe the Benedict’s test for reducing sugars.
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
Describe the positive result for reducing sugars.
Colour change from green to yellow to orange to brown to a brick red depending on the quantity of reducing sugar present.
47
Describe the Benedict’s test for non-reducing sugars.
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
Describe the positive result for non-reducing sugars.
Colour change from green to yellow to orange to brown to brick red depending on the quantity of non-reducing sugar present.
49
Name the food test used to identify proteins.
Biuret test
50
Describe the biuret test.
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
Describe the positive result of a biuret test.
Colour change from pale blue to purple.
52
Describe the iodine-potassium iodide test for starch.
● Add iodine-KI solution ● Colour change from orange to blue-black in the presence of starch
53
Describe the emulsion test for fats and oils.
● Add ethanol to the sample and shake ● Allow the mixture to settle ● Add an equal volume of water ● Record any observations
54
Describe the positive result of an emulsion test.
White, cloudy emulsion forms.
55
Describe the emulsion test for fats and oils.
● Add ethanol to the sample and shake ● Allow the mixture to settle ● Add an equal volume of water ● Record any observations
56
Describe the structure of centrioles.
● Cylindrical structure ● Organised into microtubules in a 9+0 pattern ● Found in pairs in centrosomes
57
Describe the structure of a chloroplast.
● 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
What is the function of a chloroplast?
Site of photosynthesis
59
Describe the structure of the permanent vacuole in plants
● Surrounded by a single membrane, tonoplast ● Contains cell sap (mineral ions, water, enzymes, soluble pigments)
60
Describe the function of the permanent vacuole in plants.
● Controls turgor pressure ● Water storage ● Isolates harmful waste products ● Maintains pH
61
Define plasmodesmata
Microscopic channels between plant cell walls that facilitate communication and symplastic transport.
62
Define prokaryotic cell
A type of cell that does not contain any membrane-bound organelles or a true nucleus.
63
Describe the structure and function of the flagella in prokaryotic cells.
● Long, whip-like protrusion made of flagellin ● Rotates to propel the organism ● Sensory organ
64
Describe the structure and function of the flagella in prokaryotic cells.
● Long, whip-like protrusion made of flagellin ● Rotates to propel the organism ● Sensory organ
65
How is genetic information stored in prokaryotes?
66
Describe the positive result of an emulsion test.
White, cloudy emulsion forms.
67
Micronutrients definition
**Inorganic nutrients** needed in **minute** (trace) amounts e.g. copper and zinc
68
Inorganic definition
Compounds that **do not** contain **carbon bonded to hydrogen** e.g. water, carbon dioxide, nitrogen gas
69
Macronutrients definition
**Inorganic ions** needed in **small amounts** e.g. magnesium, iron, phosphate and calcium
70
Organic definition
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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