Biological Molecules Flashcards

Question

Iodine test A common test for the presence of _______, particularly in food testing, is to add iodine solution. Iodine solution is made by ... Step 1: ... Step 2: ... If starch is present, the solution will change colour from ...

Answer 1

Iodine test A common test for the presence of starch, particularly in food testing, is to add iodine solution. Iodine solution is made by mixing iodine and a solution of potassium iodide. Step 1: Place a small sample into the dimple of a spotting tile or to a boiling tube. Step 2: Add a few drops of iodine solution and observe any colour change. If starch is present, the solution will change colour from orange → blue-black.

Answer 2

Types of Starch Amylose Amylopectin

Answer 3

Types of Starch Amylose Unbranched Good for energy storage Amylopectin Branched Good for quick energy release

Answer 4

Glycogen Glycogen is formed by condensation reactions of alpha-glucose molecules and is the main energy storage material in animals. It can be thought of as the animal equivalent of starch.

Answer 5

Function of glycogen Glycogen is a highly branched molecule, similar to amylopectin (a form of starch). When animals need to release energy, glycogen's highly branched structure means that glucose can quickly be released.

Answer 6

Glycogen in the human body Glycogen is a good storage molecule because it is so compact. When blood glucose levels decrease, glycogen is broken down to release glucose. This is called glycogenolysis

Answer 7

When blood glucose levels decrease, glycogen is broken down to release glucose. This is called glycogenolysis

Answer 8

Cellulose is the major component of cell walls in plants

Answer 9

Structure of cellulose Cellulose is a long chain of beta-glucose. Beta-glucose molecules are linked by glycosidic bonds to form linear cellulose chains that are unbranched. Microfibrils are strong fibres that are made of many cellulose chains that are held together by hydrogen bonds.

Answer 10

Function of cellulose Cellulose is the most abundant natural polymer. The cell walls of plant cells are mostly made of cellulose. These cell walls offer structural support because of the strength of the microfibril fibres that they are made of.

Answer 11

Digestion of cellulose Cellulose cannot be broken down by human digestive enzymes. Herbivores, such as cows and horses, are able to digest plant material rich in cellulose.

Answer 12

Triglycerides are a type of lipid that are mainly used as energy storage molecules.

Answer 13

Formation of triglycerides Triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acid. Ester bonds form between the glycerol and the fatty acid chains. One water molecule is released per ester bond. So, three molecules of water are released per triglyceride formed.

Answer 14

Structure of fatty acids Fatty acids have long 'tails' made of a chain of hydrocarbons with 4-36 carbon atoms. The hydrocarbon tail is variable but most fatty acids contain 12-18 carbons. Glycerol links to the central carbon atom on fatty acids.

Answer 15

Types of fatty acids The three fatty acids in the triglyceride may be similar or dissimilar. Fatty acids may be saturated or unsaturated. Some fatty acids have names that come from their origin. E.g. Palmitic acid is a saturated fatty acid that comes from the palm tree.

Answer 16

Formation of Triglycerides Triglycerides are formed by the condensation of one molecule of glycerol and three molecules of fatty acid. Three molecules of water are released per triglyceride formed: - 1 molecule of glycerol. - 3 molecules of fatty acid. - 3 molecules of water.

Answer 17

Functions of Triglycerides The structures of triglycerides are related to their functions as molecules responsible for storing energy.

Answer 18

Triglycerides in energy release Chemical energy is stored in the fatty acid hydrocarbon tails. So, lots of energy is released when triglycerides are broken down.

Answer 19

Lipids contain lots of energy Carbohydrates contain half the amount of energy per gram as lipids do.

Answer 20

Triglycerides repel water Triglycerides are insoluble in water because the fatty acid tails are hydrophobic. This means that the cell's water potential is NOT affected by triglycerides. This is important because if triglycerides didn't repel water, the water would enter the cell through the process of osmosis. This would make the cells swell up.

Answer 21

Lipid droplets In cells, the insoluble triglycerides crowd together as droplets because the hydrophobic fatty acid tails face inwards.

Answer 22

Phospholipids are a type of lipid that forms a bilayer. They are the main component of cell membranes and are responsible for controlling what goes into and out of cells.

Answer 23

Structure of phospholipids Phospholipids and triglycerides are quite similar. They are both composed of fatty acid chains attached to glycerol . The main difference is that one of the three hydrophobic fatty acid tails is replaced by a hydrophilic phosphate group in phospholipids. This means that a phospholipid molecule has a hydrophobic and hydrophilic part. This kind of molecule is called an amphipathic molecule.

Answer 24

Hydrophobic tail Phospholipids have two fatty acid chains. The two fatty acid chains in phospholipids are hydrophobic and cannot interact with water. In membranes, the hydrophobic fatty acid tails face inwards in the bilayer. This means that water-soluble substances can't easily pass through the membrane.

Answer 25

What is the approximate maximum magnification of a light microscope? 1500 x

Answer 26

Types of microscopes: Electron microscope Use a beam of electrons. Light microscope Use a beam of light.

Answer 27

What is a glycerine? A fatty acid Ester of glycerol ``` E.g. Caprylic acid. Capric acid. Lauric acid. Myristic acid. Palmitic acid. Stearic acid. ```

Answer 28

Saturated Fatty Acids A fatty acid is saturated if there are only single bonds between carbon atoms in the hydrocarbon chain.

Answer 29

Structure of saturated fatty acids Carbon atoms are NOT joined by double bonds in saturated fatty acids. In saturated fatty acids, the number of hydrogen atoms attached to the carbon skeleton is maximised. This means that the fatty acid is saturated.

Answer 30

Function of saturated fatty acids Saturated fats are solid at room temperature and usually of animal origin. Saturated fats are linked to an increased risk of cardiovascular disease in humans. Examples of foods with a high proportion of saturated fat include cream, cheese, butter, other whole milk dairy products and fatty meats.

Answer 31

Unsaturated fats When the hydrocarbon chain contains at least one double bond, the fatty acid is unsaturated.

Answer 32

Structure of unsaturated fats The main difference between saturated and unsaturated fatty acids is their hydrocarbon tails. Unsaturated fatty acids have one or more double bond between carbon atoms in the hydrocarbon chain. Cooking oils are examples unsaturated fatty acids.

Answer 33

Unsaturated fats Liquid at room temperature Double bonds 'kink' the carbon chain so unsaturated fats cannot pack together tightly. This explains why they remain liquid at room temperature.

Answer 34

There are two types of fatty acids: Saturated - no double bonds Unsaturated - one ore more double bonds

Answer 35

Emulsion Test An emulsion is when small droplets of a substance are suspended in another solution. The emulsion test returns a positive result if a sample contains a lipid.

Answer 36

Emulsion test/test for presence of a lipids 1) Add sample Place sample in a boiling tube with ethanol. 2) Shake solution Shake well and leave upright for 2-3 minutes. 3) Transfer solution Pour the solution into a boiling tube containing distilled water. 4) Observe results If a lipid is present, a white and milky layer will form.

Answer 37

Describe how a triglyceride is formed. 3 marks 1 Triglycerides are formed by a condensation reaction between hydroxyl groups on glycerol and carboxyl groups on fatty acids. 2 An ester bond is formed. 3 A molecule of water is made for each ester bond that is formed.

Answer 38

hydrophillic - water soluble | hydrophobic- doesn't interact w water

Answer 39

How do phospholipids interact with water? 3 marks 1 The phosphate group is water-soluble, i.e. it is hydrophilic. 2 Therefore only the phosphate group of a phospholipid can interact with water, and the rest of the phospholipid is hydrophobic. 3 Water is a polar molecule which can interact with the negatively charged phosphate head of phospholipids.

Answer 40

Compare saturated and unsaturated fatty acids in terms of their structures. 4 marks 1 Both saturated and unsaturated fatty acids have a hydrocarbon chain. 2 In saturated fatty acids, carbon atoms are joined together by single bonds. 3 In unsaturated fatty acids, there is one or more double bond between carbon atoms in the hydrocarbon chain. 4 The double bonds in unsaturated fatty acids cause the carbon chain to kink. Therefore unsaturated fats cannot pack together tightly.

Answer 41

The word hydrolysis is defined as the lysis of water. How does this apply to polymers? polymers seperate by breaking bonds into h and oh groups that are added to the monomers

Answer 42

What are three functions that lipids serve in plants and/or animals? lipids serve in the storage of energy structural components of hormones (cell membranes) and as signaling molecules

Answer 43

How do phospholipids contribute to cell membrane structure? phospholipids orient their heads towards the polar molecules and tails in the interior of the membrane forming a bilayer

Answer 44

What type of compound functions in hormone production, contributes to membrane flexibility, and is the starting molecule for bile salts? cholesterol which is also a lipid and also a steriod functions here

Answer 45

Cholesterol is a precursor to hormones, such as testosterone. Testosterone is a male sex hormone that has a key role in sperm production. How is testosterone most likely to enter target cells? directly thru the membrane

Answer 46

Amphipathic molecules are both hydrophobic and hydrophilic. Which of the following molecules could be described as amphipathic? phopholipid

Answer 47

What monomers are bonded together to form polypeptides? amino acids

Answer 48

Functions of proteins: Enzymes Biological catalysts. Structural proteins Long, strong polypeptide chains that are connected by cross-links in order to hold the chains parallel to each other. Transport proteins Carry large or polar molecules across the cell membrane. Antibodies Immunological proteins.

Answer 49

What are the four groups surrounding the central carbon atom in an amino acid? ``` 1 Amine group 2 Carboxyl group 3 Hydrogen atom 4 R group ```

Answer 50

draw an amino acid

Answer 51

Antibodies Antibodies are involved in the immune response.

Answer 52

buiret test tests for what brotein (protein :))

Answer 53

What are the stages in the biuret test? 1 Add sample to distilled water and biuret solution 2 Shake the solution and leave for five minutes 3 See if the biuret solution changes from blue to violet

Answer 54

The Biuret test will only be positive if amino acids are joined by peptide bonds in a polypeptide chain. If the amino acids are free, the result will not be positive.

Answer 55

What determines the sequence of amino acids in the primary structure? genes encodig the proteins

Answer 56

Hydrogen bonds allow the polypeptide chains to coil into an alpha helix and fold into a beta pleated sheet.

Answer 57

the folding of the polypeptide in some regions determines its secondary structure the structure is made more stable by h bonds

Answer 58

Interactions between R groups creates the complex 3D tertiary structure of a protein. The structure is usually coiled or folded.

Answer 59

The four structural levels of a protein are: Primary structure Sequence of amino acids. Secondary structure Local folding of the polypeptide chain. Tertiary structure 3D structure of a polypeptide chain. Quaternary structure The final 3D structure of a protein. This may contain multiple polypeptides.

Answer 60

Name three common examples of quaternary proteins: collagen insulin haemoglobin

Answer 61

Structures Primary Sequence of amino acids Secondary Folding between amino acids in the polypeptide chain Hydrogen bonds ``` Tertiary 3D structure Ionic bonds Hydrogen bonds Disulfide bridges ``` Quaternary Multiple polypeptides joined in one protein

Answer 62

The quaternary structure of proteins is formed from several polypeptides, also known as subunits. An example of a quaternary protein is haemoglobin, which is made from four polypeptides.

Answer 63

the active site of an enzyme is determined by its tertiary structure

Answer 64

Models of enzyme action have changed over time. For many years, it was thought that enzymes worked in a lock and key manner. The induced fit model is now more widely accepted.

Answer 65

factors that influence specificity environmental factors active site

Answer 66

Specificity of enzymes is determined by the active site and environmental factors. If the tertiary structure is changed, the active site will stop working and the enzyme is denatured.

Answer 67

The amount of energy required for a chemical reaction to start is the activation energy. Enzymes increase the rate of reactions by lowering the activation energy.

Answer 68

What is the name given to enzymes that have experienced a change in their active site due to environmental factors? denatured

Answer 69

Enzymes are proteins. The chemical reactants to which an enzyme binds are called the enzyme’s substrates. substrates

Answer 70

Changing pH changes the number of hydroxide ions and hydrogen ions surrounding the enzyme. The ions can alter the hydrogen and ionic bonds between amino acids.

Biological Molecules Flashcards

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