Molecules Flashcards

Question

Monomers to polymers and back to monomers

Answer 1

Each time a monomer is attached it forms a water molecule so water is released – just like when we breath out on a cold day and we breath out water vapour. This is Condensation The opposite reaction is the addition of water to break down polymers into monomers so a water molecule is used – the is hydrolysis = water splitting in Latin.

Answer 2

Glucose (C6H12O6) is a common monosaccharide and an important source of energy. Other monomers on interest are galactose and fructose

Answer 3

Glucose has two isomers – alpha and beta glucose which has the OH group in a different place which means that polysaccharides made from beta glucose form straight polymers such as cellulose unlike glycogen and starch which form from alpha glucose which is curved.

Answer 4

Many monosaccharides can be joined together to make polysaccharides by condensation reactions. The glucose monomers are joined by 1-4 glyosidic bonds and 1-6 glyosidic bonds

Answer 5

During digestion salivary amylase hydrolyses starch (polysaccharide) into maltose (disaccharide) Salivary amylase is denatured by stomach acid Pancreatic amylase in added to the intestines after the stomach which continues hydrolysis of starch to maltose The membrane bound disaccharidases found in the lining of the ilium hydrolyse maltose into alpha glucose for absorption

Answer 6

Lipids are insoluble in water They contain carbon, hydrogen and oxygen. The two main types for us are triglycerides and phospholipids

Answer 7

Phospholipids Found in cell membranes and membranes around organelles, they provide flexibility and transfer of lipid soluble substances across the membrane. Energy Lipids contain more energy for the same mass as carbohydrate and release water when oxidised. Stored in adipocytes Insulation slow conductors of heat so storage under the skin helps retain body heat and provide electrical insulation as myelin. Protection fat is stored around the body to provide additional protection

Answer 8

A group of three fatty acids (tri) combined with glycerol (glyceride). Each fatty acids forms an ester bond with glycerol in a condensation reaction and three molecules of water. Hydrolysis of a triglyceride produces glycerol and three fatty acids and requires three water molecules. Differences in molecules come from the range of fatty acids that get attached to the glycerol (over 70 different types can be combined)

Answer 9

Triglycerides have a high ratio of energy storing carbon and hydrogen bonds and so are a richer source of energy than glycogen. They have a low mass to energy ratio so many can be stored in a small volume as it reduce the mass that needs to be carried as a food source. They are insoluble and non polar so their storage doesn’t effect osmosis in cells unlike glucose which needs to be stored as glycogen or starch They have a high ratio of hydrogen to oxygen atoms and release water for when oxidised so provide an important source of water.

Answer 10

Phospholipids are really important molecules in your body because all of your cell membranes and some of the organelles are made of them! They are made of one molecule of glycerol, two fatty acid chains and one phosphate molecule – hence the name. Fatty acid chains are hydrophobic. Phosphate molecules are hydrophilic. In water they orientate into a layer facing towards and away from the water.

Answer 11

The hydrophobic and hydrophilic properties of the lipids mean that they orientate to create a bilayer in an aqueous solution. This is our cell membrane, the micelles (that you will look at in digestion) and our lysosomes and endosomes as well as other sub cellular structures.

Answer 12

The heads will face towards water and tails away from water so will form a bilayer in an aqueous environment The head is also negatively charged and the tail is neutral so this creates an electrochemical barrier to ionic material entering the cell. They are polar molecules Some phospholipids are made of two different fatty acid chains. The ‘kink’ caused by the unsaturated fatty acid chain prevents packing too closely together so helps the cell membrane remain fluid.

Answer 13

Amino acids are the monomers that make up polymers of proteins – polypeptides - which in turn can be combined to form proteins. There are 20 amino acids that occur in all living organisms and they have the same basic structure with a single change (the R group) that makes them different. They contain nitrogen (N). Of the 20 amino acids we cannot form all of them in our bodies so we must ingest the 9 essential ones from food sources.

Answer 14

Every amino acid has a central carbon atom (C) to which are attached four chemical groups: Amino group (-NH2) the basic group where amino part of the name comes from. Carboxyl group (-COOH) an acidic group which gives the acid part of the name. A Hydrogen atom (H) R (side ) group - each one has a different R group and the 20 naturally occurring ones all have a different side group but are otherwise identical.

Answer 15

Just like carbohydrates – condensation and hydrolysis can bond and split protein monomers The combination is from an OH group on one amino acid and the –H from the other amino acid (H20). They then form a peptide bond from the carbon atom of one and the nitrogen atom from the other.

Answer 16

Proteins form together into polypeptides through a series of condensation reactions and this is the primary structure of the protein. The primary structure determines its three dimensional shape and therefore its function and change in the amino acid sequence can change the shape which means the protein cannot carry out its function. Proteins have a primary, secondary, tertiary and quaternary structure – this is quite complex but essential to understand so stick with it.

Answer 17

The primary structure of the protein is the amino acids that make it up. These are joined by peptide bonds This is the structure as it is assembled by the ribosome

Answer 18

As we saw with water molecules the hydrogen on the NH bond has a slightly positive charge and the oxygen in the –C=H has an slightly negative charge. These hydrogen bonds cause the polypeptide to twist into a 3d shape such as the alpha helix or beta sheets where the chains becomes folded.

Answer 19

The alpha-helices of the secondary protein structure can be twisted and folded again into specific 3d shapes which form the tertiary structure which is held together through an range of additional bonds and areas that are hydrophilic and hydrophobic. Disulphide bridges – are strong so not easily broken between amino acids Ionic bonds – formed between the carboxyl and amino groups, less strong so can be broken by pH changes Hydrogen bonds – numerous and easily broken

Answer 20

Large molecules can often form complex polypeptides with non protein structures such as the iron contain haem group where the globin protein complex shape also include the haem group. The primary structure always determines that 3d shape

Answer 21

In the initial order of the amino acids some will be positive charged, some negative, some hydrophilic, some hydrophobic, some that will create hydrogen bonds, others disulphide bonds and so on. So to get the desired 3D shape of the final protein the order of the amino acids must be correct.

Answer 22

Enzymes and hormones are usually ‘globular’ proteins, meaning they are more or less spherical, or globe- shaped such as haemoglobin. Globular proteins that are water soluble have hydrophilic R groups on the outside and those that are not have Hydrophobic R groups on the outside.

Answer 23

Most bonds that hold the 3d shape are fairly weak and can be broken by heat or changes in pH. Heat and pH can break the bonds causing an unravelling of the 3d shape so the protein no longer functions as it is the wrong shape.

Answer 24

Denaturing means changing shape from the original structure and it is not reversible which is why egg white doesn’t become clear again as the cooked egg cools.

Answer 25

Two key processes: Transcription Translation

Answer 26

A copy is made of the genetic code of the DNA inside the nucleus

Answer 27

The code is translated from DNA instructions into an amino acid sequence by the ribosome.

Answer 28

.Enzymes catalysis reactions – pepsin for example • Actin and myosin cause muscle contraction • Cytoskeleton of cells – tubulin and microtubules • Fibrous proteins give strength – collagen, tendons, ligaments • Blood clotting – plasms proteins act as clotting factors • Transport of oxygen and carbon dioxide via haemoglobin • Cell adhesion – membranes proteins linking to other cells • Membrane transport channels and pumps • Hormones and receptors on cell membranes • Packing of DNA around histones

Molecules Flashcards

(52 cards)