1. 1. Chemical elements are joined together to form biological compounds Flashcards

Question

Why is glucose a polar molecule?

Answer 1

Due to the uneven distribution of charge caused by δ⁻ on oxygen and δ⁺ on hydrogen in hydroxyl groups.

Answer 2

Glucose is soluble in water due to polarity, allowing it to be easily transported in plant phloem and animal blood.

Answer 3

3 carbons Triose 5 carbons, pentose eg ribose, deoxyribose 6 carbons, hexose eg glucose

Answer 4

glucose fructose galactose

Answer 5

Molecules with the same molecular formula but with different arrangements of their atoms are called structural isomers.

Answer 6

1. Glucose: The -OH group on carbon 4 is on the right side in the Fischer projection. 2. Galactose: The -OH group on carbon 4 is on the left side in the Fischer projection.

Answer 7

Type of bond: A covalent bond formed between two monosaccharides. Formed by: Condensation reaction (removal of water). Broken by: Hydrolysis (addition of water).

Answer 8

α-glycosidic bond: Found in starch (amylose, amylopectin) and glycogen. β-glycosidic bond: Found in cellulose.

Answer 9

Energy storage: Help form compact polysaccharides (e.g. starch, glycogen) for efficient energy storage. Structural support: Create rigid structures (e.g. cellulose microfibrils in plant cell walls). Energy release: Hydrolysis of bonds releases monosaccharides used in cellular respiration.

Answer 10

isomers C6H12O6 same molecular formula different structural formula

Answer 11

Definition: A class of carbohydrates made up of two monosaccharide units. Formula: General molecular formula is C₁₂H₂₂O₁₁. Formation: Made by a condensation reaction (removal of H₂O). Bond type: Monosaccharides are joined by a glycosidic bond (a covalent bond).

Answer 12

The glycosidic bond can be broken by the chemical insertion of water – this reforms the OH groups and is called a hydrolysis reaction.

Answer 13

sucrose = α glucose + fructose maltose = α glucose + α glucose lactose = α or β glucose + galactose

Answer 14

Definition: Complex carbohydrates made of long chains of monosaccharides linked by glycosidic bonds. Formation: Formed by condensation reactions, where water is removed to link monosaccharides together. Structure: They are polymers — long chains of repeating monosaccharide units.

Answer 15

short chain polysaccharides 3-10 monosacharide residues

Answer 16

Starch glycogen cellulose heparin peptidoglycan

Answer 17

amylose and amylopectin both of which are polymers of α-glucose.

Answer 18

Glycogen is an α-glucose polymer stored as granules in animal cells (liver & muscles).

Answer 19

α-1,4 and α-1,6 glycosidic bonds, making it highly branched.

Answer 20

More branches mean more ends for hydrolysis allowing rapid glucose release.

Answer 21

It is insoluble, so doesn’t affect osmosis, and compact, so stores lots of glucose in a small space.

Answer 22

Branches provide more ends for the hydrolysis of glycosidic bonds, allowing faster glucose release for energy production.

Answer 23

The branches create more ends where glycosidic bonds can be hydrolysed, providing rapid glucose release for ATP production during respiration.

Answer 24

Glucose is broken down in respiration to produce ATP, which is used for energy in cells.

Answer 25

Cellulose is a complex carbohydrate made of β-glucose molecules linked by β-1,4 glycosidic bonds.

Answer 26

The linkages cause glucose molecules to be rotated 180° relative to each other, placing the −CH2OH groups on opposite sides.

Answer 27

The hydrogen bonds between chains give cellulose high tensile strength and make it insoluble and resistant to breakdown.

Answer 28

Microfibrils of cellulose provide support and strength, preventing osmotic lysis by limiting water intake and helping resist stretching.

Answer 29

The high number of hydrogen bonds between chains makes it resistant to breakdown, especially in organisms that lack the enzyme cellulase.

Answer 30

Chitin is found in the exoskeletons of insects and in the cell walls of fungi.

Answer 31

Chitin contains nitrogen in the form of N-acetylglucosamine and is classified as a heteropolysaccharide.

Answer 32

Chitin is similar to cellulose but contains side groups with nitrogen, allowing for more hydrogen bonds to form, providing greater tensile strength.

Answer 33

Chitin provides structural support in the exoskeletons of insects and cell walls of fungi, offering strength and protection.

Answer 34

Chitin consists of N-acetylglucosamine molecules joined by β-glycosidic bonds.

Answer 35

The additional hydrogen bonds between the N-acetylglucosamine molecules form strong microfibrils, giving chitin greater tensile strength than cellulose.

Answer 36

due to hydrigen bonds and cross linking between chains hydroxyl groups on adjacent cellulose molecules form hydrogen bonds strong cross links between cellulose fibers makes structure rigid

Answer 37

polymer of sugar and amino acids deposited between cellulose molecules to lignify tissue

Answer 38

giant molecules some are polymers

Answer 39

three condensation reactions, forming ester bonds Triglycerides have key roles in respiration and energy storage due to its insolubility and high carbon to hydrogen ratio.

Answer 40

Lipids are organic compounds made of carbon, hydrogen, and oxygen, with a high proportion of CH2 groups. Phospholipids also contain phosphorus.

Answer 41

Lipids have low solubility in water but are highly soluble in organic solvents (e.g., ethanol, tetrachloromethane).

Answer 42

Long-term energy storage: Lipids have a high energy density (9 kcal per gram), are hydrophobic, and are stored compactly.

Answer 43

No, lipids are not polymers and are too small to be classified as macromolecules.

Answer 44

Lipids are made of glycerol and fatty acids.

Answer 45

The size of the molecule; more carbon atoms mean a higher melting point due to stronger intermolecular forces.

Answer 46

A glycerol molecule and three fatty acids, joined by condensation reactions.

Answer 47

Ester bonds.

Answer 48

Three water molecules (one per ester bond formed).

Answer 49

By hydrolysis, requiring three molecules of water to break the ester bonds.

Answer 50

R group can be saturated or unsaturated

Answer 51

hydrophillic head - allows exchange of substances between cell and environment hydrophobic tail fat and water soluble, can form lipid bilayer, crucial for role in cell membranes

Answer 52

The different properties of the phosphate heads and the fatty acids affect how easily different molecules can cross a cell membrane (see Unit 1.3: Cell membranes and transport). If phospholipids are poured into water, the molecules arrange themselves in a single layer. But in cell membranes, phospholipids form a bilayer. The hydrophilic phosphate groups are attracted to water molecules in the cytoplasm and outside the cell. The hydrophobic tails are repelled by water molecules and ‘hide’ from water in the cytoplasm and outside the cell.

Answer 53

A glycerol backbone, two fatty acid tails (hydrophobic), and a phosphate group (hydrophilic).

Answer 54

They arrange into a single layer with hydrophilic heads facing water and hydrophobic tails hidden.

Answer 55

They form a bilayer: hydrophilic phosphate heads face the cytoplasm and extracellular fluid, while hydrophobic tails face inwards, away from water.

Answer 56

It creates a selectively permeable barrier, controlling which substances can enter or leave the cell.

Answer 57

Their hydrophobic tails and hydrophilic heads influence how easily molecules can cross the membrane, affecting membrane permeability.

Answer 58

triglyceride - 3 fatty acids, and no phosphate phospholipid - 2 fatty acids and a phosphate group

Answer 59

essential - obtained in diet non-essential - synthesised

Answer 60

between R groups

Answer 61

amino acids oxidise to form disulphide bridge

Answer 62

non-covalent bonds between water and hydrophobes

Answer 63

Amino group (-NH₂) Carboxylic acid group (-COOH) Hydrogen atom (H) Variable R group

Answer 64

It gains a H⁺ to form an -NH₃⁺ group.

Answer 65

It loses a H⁺ to form a -COO⁻ group.

Answer 66

Beta pleated sheets are parallel or antiparallel depending on direction of polypeptide chain

Answer 67

Ionic bonds are formed from charged variable groups and can interact with water, which helps a protein to dissolve.

Answer 68

Disulfide bridges are strong covalent bonds formed between the sulfur atoms of two cysteine amino acids.

Answer 69

Disulfide bridges form in the tertiary and quaternary structures of proteins.

Answer 70

They are covalent bonds, so they are stronger and require higher temperatures or extreme pH to break.

Answer 71

They help stabilise protein structure, especially in enzymes and extracellular proteins.

Answer 72

Additional hydrogen bonds can also form between polar variable groups.

Answer 73

Hydrophobic interactions take place when the variable groups are non-polar. They are repelled by water and are usually found on the inside of the protein as far away from water as possible; a protein rich in non-polar side groups will be less soluble in water.

Answer 74

Hydrophobic interactions occur between non-polar R-groups of amino acids that are repelled by water.

Answer 75

They are usually found on the inside of the protein, away from the surrounding aqueous environment.

Answer 76

Proteins with many non-polar side groups are less soluble in water because they avoid contact with water.

Answer 77

They help stabilise the tertiary structure by driving the folding of the protein so that non-polar regions are hidden inside.

Answer 78

Denaturation is the process where a protein's structure is altered, causing it to lose its function. This typically involves the breaking of weak bonds like hydrogen bonds and ionic interactions.

Answer 79

Weak bonds, such as hydrogen bonds and ionic bonds, are broken. Covalent bonds between amino acids (peptide bonds) are not broken.

Answer 80

Denaturation destroys secondary and tertiary structures (such as the shape of the active site), but the primary structure (the peptide sequence) remains intact.

Answer 81

The active site of the enzyme changes shape, preventing substrate binding and thus stopping enzyme function.

Answer 82

Renaturation is the process where a denatured protein reverts back to its functional shape, as hydrogen bonds and other weak interactions reform.

Answer 83

No, if the primary structure (the amino acid sequence) is disrupted, the protein cannot renature and will remain denatured.

Answer 84

change in pH increase in temp heavy metals ionising radiation

Answer 85

long term energy store

Answer 86

ATP captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular process

Answer 87

breaks last covalent bond between phosphate groups releases chemical energy energy used for: active transport, muscle contraction, formation of large molecules

Answer 88

muscle contraction active transport DNA replication cell divison

Answer 89

no charge – non-polar or a slight charge – polar.

Answer 90

Ions and polar compounds attract oppositely charged particles and play important roles in the structure of molecules, such as in the formation of ionic bonds and hydrogen bonds.

Answer 91

Polar compounds dissolve in water because they are attracted to the partial charges in water molecules, allowing them to form hydrogen bonds.

Answer 92

Non-polar compounds do not dissolve in water because they lack charged regions and cannot form hydrogen bonds with water molecules.

Answer 93

Non-polar compounds are lipid-soluble, meaning they dissolve in fats/oils due to the similarity of their non-polar nature to that of lipids.

Answer 94

Organic compounds always contain the elements carbon and hydrogen, and many contain oxygen and/or nitrogen.

Answer 95

also contain carbon, hydrogen, oxygen and nitrogen, but can be made without the involvement of living organisms.

Answer 96

Water is polar because it has partial positive charges on the hydrogen atoms (δ+) and a partial negative charge on the oxygen atom (δ−). The molecule as a whole has no overall charge.

Answer 97

Water molecules attract each other by forming hydrogen bonds due to their polarity. These bonds are usually shown as a series of vertical lines in diagrams.

Answer 98

Surface tension is caused by hydrogen bonds between water molecules. At the surface, water molecules experience a net inward force, creating a "skin" of tension.

Answer 99

Pond skaters can stay afloat due to water's high surface tension, which provides enough resistance to external force, allowing them to "walk" on water without breaking the surface.

Answer 100

Hydrogen bonds between polar water molecules result in a net inward force at the surface, creating surface tension.

Answer 101

The high surface tension of water creates a strong surface "skin" that resists external forces, such as the weight of lightweight organisms like pond skaters.

Answer 102

Water is a solvent, meaning it can dissolve essential substances like carbon dioxide, oxygen, and minerals, which are required for processes like photosynthesis and metabolism.

Answer 103

Water is transparent, allowing light to penetrate through it, enabling aquatic plants like pond weed to photosynthesise underwater.

Answer 104

Water has a high specific heat capacity, meaning it resists rapid temperature changes, helping to maintain a stable temperature environment for pond weed growth.

Answer 105

Water can dissolve ionic and polar compounds due to its polar nature and ability to form hydrogen bonds.

Answer 106

Water can form hydrogen bonds with other polar substances (e.g., salts and minerals), aiding in their dissolution.

Answer 107

When ionic compounds like NaCl dissolve, water molecules surround and separate the positive and negative ions, a process known as hydration.

Answer 108

It can dissolve a wide range of ionic and polar compounds. Its polar nature allows it to interact with other polar molecules and ions. Water can form hydrogen bonds, which helps in dissolving substances. It plays a key role in transporting essential substances in biological systems.

Answer 109

The carbon chain in fatty acids is often represented by the letter R, a variable group containing a chain of between 4 and 24 carbon atoms.

Answer 110

Lipids with long hydrocarbon chain fatty acids are more likely to be solid at room temperature (fats). Lipids with short hydrocarbon chains form oils, which are liquid at room temperature.

Answer 111

Long hydrocarbon chains have greater forces of attraction between the fatty acid chains, leading to a higher melting point compared to lipids with shorter chains.

Answer 112

The longer the carbon chain, the greater the force of attraction between the chains, which results in a higher melting point.

Answer 113

Triglycerides store more energy per gram than carbohydrates: 1g of fat provides 38 kJ of energy. 1g of carbohydrate provides 17 kJ of energy. Because of this, fats and oils are the preferred energy storage molecules in animals and seeds.

Answer 114

Triglycerides are less dense than water, providing buoyancy to help many aquatic animals stay afloat.

Answer 115

Triglycerides are good thermal insulators, helping to conserve heat in animals. They also provide mechanical protection for delicate organs by acting as a cushion.

Answer 116

Some animals spread oil onto their fur or feathers because fats are hydrophobic and repel water, making them waterproof.

Answer 117

Saturated fatty acids contain only single bonds between carbon atoms. They contain the maximum number of hydrogen atoms. They are usually solid at room temperature, forming fats.

Answer 118

Saturated fatty acids have straight tails that can pack closely together, allowing stronger forces of attraction to form between them. This means more energy is needed to break the bonds and melt the fat, resulting in a higher melting point.

Answer 119

Unsaturated fatty acids contain one or more double bonds between carbon atoms. They do not contain the maximum number of hydrogen atoms. For each carbon-carbon double bond, the fatty acid contains two fewer hydrogen atoms.

Answer 120

The double bonds in unsaturated fatty acids cause the fatty acid tails to kink, preventing them from packing closely together. This results in weaker forces of attraction between the fatty acids, so less energy is needed to break the bonds and melt the fat, giving it a lower melting point. Therefore, unsaturated lipids are usually liquid at room temperature.

Answer 121

It raises the low-density lipoprotein (LDL) cholesterol level, which increases the incidence of atheromas in coronary arteries (and in other arteries). This leads to blockages and eventually, heart disease.

Answer 122

An essential fat that we must get from food because our bodies cannot produce it. It lowers LDL (bad cholesterol). Found in: most cooking oils, pumpkin seeds, pine nuts, sesame seeds, fatty fish. Also known as: omega-3 and omega-6 fatty acids.

Answer 123

Considered a healthy fat: it lowers LDL (bad cholesterol) and maintains HDL (good cholesterol). Found in: olive oil, avocado and avocado oil, most nuts and nut butters.

Answer 124

Increases total cholesterol and LDL (bad cholesterol). Best to consume in moderation. Found in: red meat, whole milk, cheese, coconut, butter, processed meat, many baked goods, and deep fried foods.

Answer 125

A by-product of processing healthier fats to give them a longer shelf life. Raises your LDL (bad cholesterol) and lowers your HDL (good cholesterol). Intake should be limited. Also known as: partially hydrogenated oil

Answer 126

dipeptides and polypeptides.

Answer 127

The linkage between two amino acids is called the peptide bond. Peptide bonds form between the carboxyl group of one amino acid and the amino group of another.

Answer 128

This means that the dipeptides can have different properties because of the arrangement of the amino acids on either side of the peptide bond.

Answer 129

This can affect the charges on the amino acid and therefore the properties of the dipeptide. This is also shown in the diagram.

Answer 130

a series of peptide bonds holding amino acids together - form a chain

Answer 131

The sequence or order of amino acids in a polypeptide affects the organisation of the molecule as it is processed to form a functional protein.

Answer 132

(e.g. glucose, maltose) Reagent: Benedict’s solution (blue) Steps: Add Benedict’s reagent to sample Heat in a water bath at ~80°C for 2–5 mins Positive result: Brick-red precipitate Green/yellow/orange/red = increasing concentration

Answer 133

glucose and maltose

Answer 134

Steps: First, do the reducing sugar test (should be negative) Add dilute HCl to hydrolyse sugar → boil gently Neutralise with sodium hydrogen carbonate Repeat Benedict’s test Positive result: Brick-red precipitate

Answer 135

Reagent: Iodine solution (iodine + potassium iodide) Steps: Add iodine solution directly to sample Positive result: Blue-black colour

Answer 136

Reagents: Biuret A = sodium hydroxide (NaOH) Biuret B = copper(II) sulfate (CuSO₄) Steps: Add Biuret A (NaOH) Add Biuret B (CuSO₄) Mix gently Positive result: Lilac/purple colour

Answer 137

Reagents: Ethanol and cold water Steps: Add ethanol to sample and shake Add cold water Positive result: Cloudy white emulsion forms

Answer 138

• The sequence of amino acids in a polypeptide chain. • Determined by the DNA base sequence. • Held together by peptide bonds formed in condensation reactions.

Answer 139

• Local folding of the polypeptide chain due to hydrogen bonding between peptide bonds. • Two main types: • Alpha helix – spiral structure stabilised by hydrogen bonds. • Function: structural support in fibrous proteins (e.g., α-keratin in hair, collagen in skin). • Beta-pleated sheet – folded, sheet-like structure (can be parallel or antiparallel). • Function: structural strength (e.g., fibroin in silk).

Answer 140

• Further folding into a specific 3D globular shape, determined by R-group interactions: • Hydrogen bonds • Ionic bonds • Disulfide bridges (between cysteines) • Hydrophobic interactions • Function: determines protein’s biological activity: • Enzymes – active site • Antibodies – antigen binding • Hormones – receptor binding • Globular proteins: compact and soluble (e.g., enzymes, insulin).

Answer 141

• Involves two or more polypeptide chains joined together. • Held by similar bonds as tertiary structure. • Can be: • Globular (e.g., haemoglobin – 4 polypeptide chains + prosthetic haem group) • Fibrous (e.g., collagen – 3 polypeptide chains in a triple helix) • Function depends on structure: support (fibrous) or transport/metabolism (globular).

Answer 142

phosphodiester via a condensation reaction

Answer 143

bile acids break down large lipid droplets into smaller ones, increasing the surface area for digestive enzymes.

1. 1. Chemical elements are joined together to form biological compounds Flashcards

(228 cards)