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Biology A-level > 1.1 - Chemical elements and biological compounds > Flashcards

1.1 - Chemical elements and biological compounds Flashcards

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1
Q

What does inorganic mean?

A

A molecule or ion that has no more than 1 carbon atom

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2
Q

All organisms need inorganic ions to survive, these inorganic ions are often called minerals. What are micronutrients and macronutrients?

A

Macronutrients are minerals needed in minute (trace) conc
Macronutrients are needed in small conc

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3
Q

What is the biological role of these 3 macronutrients?

Magnesium
Iron
Nitrate

A

Mg2+ - Constituent of chlorophyll needed for photosynthesis
Fe2+ - Constituent of Haemoglobin, transports O2 in blood
NO3- - Nitrogen is derived from it to form Nucleotides including ATP, DNA, RNA
- Amino acid acid formation

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4
Q

What is the biological role of these 2 macronutrients?

Phosphate and Calcium

A

Po4 3- - Used for making nucleotides, including ATP, DNA and RNA.
- Constituent of phospholipids
- Hardens bones
Ca2+ - Hardens bones and teeth,
- Component a of cell walls

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5
Q

What does Organic mean?

A

Molecules that have a high proportion of carbon and hydrogen atoms

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6
Q

Water is a polar molecule (has a dipole). When in close contact with another water molecule the opposing charges attract each other forming a hydrogen bond. What is a hydrogen bond?

A

The weak attractive force between a partial positive charge of a H atom and the partial negative charge of another atom, usually O or N.

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7
Q

Individually hydrogen bonds are weak, but why is it hard to separate water molecules in water?

A

Due to the very large number of H bonds (between many water molecules) present in water it forms a lattice-like framework which is much stronger. (attraction between H20 molecules is cohesion)

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8
Q

Give 9 properties of water:

A

Universal solvent
Transport medium
Metabolite
High latent heat of vaporisation
High specific heat capacity
Cohesion
High density
High surface tension
Water is transparent

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9
Q

Give the functions of these properties of water:

Water is a solvent
Water as a transport medium
Water is a metabolite

A

The + and - parts of the water molecule attract other charged particles, such as ions and other polar molecules such as glucose. Ions and polar molecules can dissolve water, non-polar molecules (lipids) can’t.

Water acts as transport medium e.g. in animals, plasma transports dissolved substances and in plants, water transports minerals in xylem.

Water is used in many biological reactions as a reactant e.g. with CO2 to produce glucose in photosynthesis.

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10
Q

Give the functions of these properties of water:

High specific heat capacity
High latent heat of vaporisation

A

A large amount of heat energy is needed to raise the temp of water. This keeps the temp of aquatic environments stable so that organisms do not have to endure extremes of temp
Due to cohesion between water molecules (caused by H bonding) a large amount of heat energy is needed to change water from a liquid to a vapour state (gas), important in temp control, where heat is used to vapourise water from sweat on the skin.

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11
Q

What is the definition for specific heat capacity and latent heat of vaporisation?

A

Specific heat capacity - The energy required to raise the temp of 1g of a substance through 1 degrees C

Latent heat of vaporisation - The energy required to convert 1g of a liquid into vapour

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12
Q

Give the functions of these properties of water:

Cohesion
Transparent

A

Cohesion - Water molecules attract each other forming H bonds, individually these are weak, but, because there’re many of them, the molecules stick together in a lattice

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12
Q

Give the functions of these properties of water:

Cohesion
High surface tension

A

Cohesion - Water molecules attract each other forming H bonds, individually these are weak, but, because there’re many of them, the molecules stick together in a lattice

High surface tension - Water has highest surface tension of any liquid except mercury (at ordinary temp). Cohesion between water molecules at the surface produces surface tension so that the body on an insect (pond-skater) is supported

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13
Q

Give the functions of these properties of water:

High density
Transparent

A

High density - Water is denser than air, and as a habitat for aquatic organisms, provides support and buoyancy. Ice is less dense than liquid water, because the H bonds hold the molecules further apart than if they were are in the liquid. So ice floats on water and is a good insulator and prevents large bodies of water loosing heat and freezing completely, so organisms beneath survive

Transparent - allowing light to pas through, this lets aquatic plants photosynthesize effectively

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14
Q

Carbohydrates are organic (high proportion of C atoms) compounds which contain the atoms carbon, hydrogen and oxygen. What is the basic unit of carbohydrate, when 2 basic units combine and when there are many?

A

Monosaccharide
Disaccharide
Polysaccharide

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15
Q

A monosaccharide is an individual sugar molecule. What is the general formula of a monosaccharide and how are they grouped?

A

(CH20)n
Grouped dependent on amount of C atoms they have. 3 - triose, 5 - pentose, 6 - hexose

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16
Q

Glucose has 2 isomers (molecules that have the same chemical formula but a different arrangement of atoms) - α glucose and β glucose, based on the positions of an (OH) and (H). Does an α glucose have the H or the OH on the top (the side of CH2OH)

A

H

See Nc 1

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17
Q

Monosaccharides have several functions and can act as:

A source of ____ in respiration. C-C and C-H bonds are ______ to release energy, which is transferred to make _______ ___________ (ATP)
_______ blocks for larger molecules
__________ in reactions
__________ of nucleotides

A

energy
broken
adenosine triphosphate
Building
Intermediates
Constituents

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18
Q

What 2 components make each of these disaccharides: What are there biological roles?
Maltose
Sucrose
Lactose

A

Glucose + Glucose ( in germinating seeds)
Glucose + Fructose ( product of photosynthesis which is transported in the phloem)
Glucose + Galactose (in mammalian milk)

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19
Q

How are disaccharides formed? What bond is formed? What is the process called?

A

When 2 monosaccharide units are bonded together with the formation of a glycosidic bond and the elimination of water. This is a condensation reaction.

See NC 2

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20
Q

What is needed to test for the presence of reducing sugars?

A

Benedict’s reagent and heat (70 degrees or above). Reducing sugars reduce blue copper II sulphate forming Copper I sulphate, which is a brick red precipitate. (qualitive test as it doesn’t give conc)

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21
Q

What is needed to test for the presence of non-reducing sugars

A

A non-reducing sugar (e.g. Sucrose) is hydrolysed by boiling in dilute HCL. Glucose and fructose are formed. The acid must be neutralised with dilute sodium hydroxide before testing with Benedict’s reagent. Should now give positive result as glucose and fructose are reducing sugars which will readily donate an electron to reduce copper II sulphate.

22
Q

Glucose (monosaccharide) is the main source of energy in cells and is stored as glycogen (animals) and starch (plants), they are polysaccharides. Why are they more suitable than glucose for storage?

A

Insoluble so has no osmotic effect
Compact molecules and can be stored in small space
Cannot diffuse out the cell
Contains a lot of energy in its C-C and C-H bonds

23
Q

Starch is made up of α glucose monomers, added one at a time by condensation reaction. Glucose can be easily added or removed. What are the 2 types of starch polysaccharides?

A

Amylose
Amylopectin

24
Q

What is Amylose?

A

linear, unbranched molecule, coiled
Each α glucose added creates a C1 – C4 glycosidic bond with the adjacent
glucose molecule. (α-1,4-glycosidic)

See NC 3

25
Q

What is Amylopectin?

A

Branched, chains of glucose monomers joined with α-1,4-glycosidic bonds, cross linked with α-1,6-glycosidic bonds.

See NC 3

26
Q

How do you test for the presence of starch?

A

Iodine solution (iodine dissolved in aqueous potassium iodide) interacts with starch. There is colour change from the orange-brown of the iodine solution to blue-black

Th depth of the colour gives an indication of relative conc of starch. An accurate conc cannot be determined so this test is qualitive.

27
Q

Glycogen is the main storage product in animals. It is similar in structure to amylopectin. What is its structure?

A

α glucose molecules are joined by C1 – C4 and C1 – C6 glycosidic bonds

glycogen has shorter C1-C4 α glucose chains and more branches than amylopectin

28
Q

Both starch and glycogen are easily __________ to α glucose, which is soluble and can be transported to wherever its needed.

A

hydrolysed

29
Q

What is the structure of cellulose? (polysaccharide found in plant cell walls)

Bonds present?
Rotation?
Fibres?

A

Long, straight, unbranched chain of β glucose units, joined by β-1,4-glycosidic bonds.

β-link rotates adjacent glucose molecules by 180. Allows H bonds to form between the OH groups of adjacent cellulose chains. These parallel cellulose molecules become tightly cross-linked by H bonds to form a bundle called a microfibril. Microfibrils are bunched together in bundles to form fibres.

Cell wall has several layers of fibres, which run parallel within a layer but at and angle to adjacent layers

See NC 4

30
Q

Cellulose is unreactive and stable (due to being __________) and has a high tensile strength (due to formation of __________ and fibres)

A

unbranched
microfibrils

31
Q

What is chitin? (similar like structure to cellulose)

Group added?

A

long chains of β glucose molecules linked by C1 – C4 glycosidic bonds
Each monomer has a group derived from amino acids added, called an acetylamine group
Rotated 180, H bonds form between OH groups, cross-linked paralell chains form microfibrils

32
Q

Where is chitin found and what is its properties?

A

Found in exoskeleton of arthropods, such as insects, and fungal cell walls.
Chitin is strong, waterproof and light weight.

33
Q

Lipids contain _, _ and _. The most common type of lipid are _________ (fats and oils) They are non-polar compounds and so are insoluble in _____.

A

C, H, O
triglycerides
water

34
Q

How are triglycerides formed? Reaction? Bonds formed?

A

Condensation reaction between
3 molecules of fatty acids and 1 Glycerol molecule. 3 molecules of water are removed and ester bonds are formed between the glycerol and fatty acids.

See NC 5

35
Q

Why are phospholipids a special type of lipid?

A

Each molecule has 1 end that is soluble in water and one that is not. The end of the molecule has a glycerol group and phosphate and so has lot of oxygen atoms, and is hydrophilic.
See NC 6

36
Q

What are unsaturated fatty acids, give examples.

A

Unsaturated fatty acids have double bonds between neighbouring C atoms (doesn’t contain the max possible number of H atoms)
Double bonds make fatty acids and lipids melt more easily, most oils are unsaturated.

37
Q

What are saturated fatty acids, give examples

A

Have no double bonds between neighbouring carbon atoms in the hydrocarbon tail (carries max possible number of H atoms). Saturated fatty acids (e.g. butter) are solid.

38
Q

Give some functions of triglycerides:

A

Energy reserve in plants and animals, because lipids contain more C-H bonds than carbohydrates
Thermal insulator - stored under skin
Protection - Stored around delicate internal organs
Producing metabolic water - is released from the body’s chemical reactions

39
Q

Give some functions of phospholipids:

A

Forms a bilayer which is the basis of all cell membranes. The phospholipid bilayer allows for the transport of non-polar molecules across cell membranes by simple diffusion.
The myelin sheath that surrounds the axons of nerve cells

40
Q

Give some functions of waxes:

A

Waterproofing- reduces water loss, such as in the exoskeleton and the cuticle of plants

41
Q

How do you test for fats and oils?

A

Emulsion test - Sample is mixed with absolute ethanol, which dissolves any lipids present. It is shaken with equal volume of water. The dissolved lipids come out the water as they’re insoluble in water. They form a white cloudy emulsion

42
Q

Main causes of heart disease are fatty deposits on the inner wall of the coronary artery (______________) and high blood pressure (_____________)

A

atherosclerosis, hypertension

43
Q

What happens to the heart and coronary arteries if the diet is high in saturated fats?
What is the fatty material called?

A

Low density lipoproteins (LDL) build up.
Fatty material called atheroma is deposited in the coronary arteries, restricting blood flow and, therefore, oxygen delivery to the heart. Can cause heart attacks

44
Q

What happens to the heart and coronary arteries if the diet has a high proportion of unsaturated fats?

A

The body makes more high-density lipoproteins (HDL), which carries harmful fats away to the liver for disposal.

45
Q

Proteins contain ,,_ AND _ atoms. Proteins are polymers made of __________ called ______ ______. A chain of amino acids is called a _________. There are 20 amino acids. There are thousands of different proteins and their shape is determined by the specific __________ of amino acids in the chain. Shape of a protein determined it’s function.

A

H,C,O,N
monomers
amino acids
polypeptide
sequence

46
Q

All amino acids have the same strcuture:

A

An amino group (-NH2), which is basic
A carboxylic acid group (COOH), which is acidic
A hydrogen atom
The R-group, (variable group of atoms)

See NC 7

47
Q

Proteins are linear sequences of amino acids. How is a peptide bond formed?

A

The amino group of one amino acid reacts with the carboxyl group of another by condensation reaction, water is eliminated and a peptide bond is formed , resulting compound is a dipeptide.

See NC 8

48
Q

The structure of proteins is determined by the order and the number of amino acids, bonding present and the shape of the protein. What is the primary and secondary structure of a protein?

A

The order and number of amino acids in a protein
The shape that the polypeptide chain forms as a result of hydrogen bonding, ionic bonds and disulphide bridges. Either alpha helix or beta pleated sheets.

See NC 9

49
Q

What is the tertiary structure of proteins?

A

The 3D shape of the protein, The alpha helix of a secondary protein structure can be folded and twisted to give a more complex, compact 3D structure. This is the tertiary structure

50
Q

What is the Quaternary (arises from a combination of 2 or polypeptide chains in tertiary form) structure of proteins?

A

Some polypeptide chains are not functional unless they’re in combination. They may combine with another polypeptide chain or be with non-protein groups and form large complex molecules, such as haemoglobin.

51
Q

What are globular proteins and what are there functions? Example is haemoglobin

A

functions such as enzymes, antibodies and hormones
Compact and folded into 3D spherical molecules
Soluble in water

52
Q

What are Fibrous proteins and what are there functions? Example is collagen.

A

Preform structural functions
Consists of polypeptides in parallel chains or sheets with numerous cross linkages to form fibres
Insoluble in water, strong and tough

53
Q

What is the test for proteins?

A

Few drops of biuret reagent (sodium hydroxide and copper (II) sulphate) are added.
Sodium hydroxide and copper sulphate react to make copper hydroxide
If protein is present, the copper hydroxide interacts with the peptide bonds in the protein to make biuret. Blue —-> purple

Biology A-level (11 decks)

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