structure and functions in living organisms

Question 1

describe the nucleus/function of the nucleus

Answer 1

• controls activity of cell (by making proteins)
• contains chromosomes - strands of DNA which carry genes (each gene codes for a protein)

Question 2

describe the cell membrane/function of it

Answer 2

the boundary between cytoplasm & the cell’s surroundings, controls what substances enter/leave cell (selectively permeable)

Question 3

describe cytoplasm/function of it

Answer 3

jelly-like liquid where chemical reactions occur

Question 4

describe the mitochondria/function of it

Answer 4

carries out some reactions of aerobic respiration, producing ATP (energy carrier molecule)

Question 5

describe ribosomes/function of it

Answer 5

synthesise (assemble) proteins from amino acids

Question 6

describe chloroplasts/function of them

Answer 6

they absorb light energy and use it to carry out the chemical reactions of photosynthesis, making biological molecules for plant cells

Question 7

describe the cell wall/function of it

Answer 7

made of cellulose (a carbohydrate) in plants, helps to keep plant cells in a fixed shape (so keeps the plant upright)

Question 8

describe the vacuole/functions of the vacuole

Answer 8

it’s filled with a watery liquid called cell sap; stores dissolved sugars, mineral ions and other substances

Question 9

similarities in structure of plant and animal cells?

Answer 9

• nucleus
• cell membrane
• cytoplasm
• mitochondria
• ribosomes

Question 10

differences in structure of plant and animal cells?

Answer 10

only plant cells have chloroplasts, vacuoles, and cell walls

Question 11

identify the chemical elements present in carbohydrates

Answer 11

carbon, hydrogen, oxygen

Question 12

identify chemical elements present in proteins

Answer 12

carbon, hydrogen, oxygen, nitrogen

Question 13

identify chemical elements present in lipids

Answer 13

carbon, hydrogen, oxygen

Question 14

describe the structure of carbohydrates

Answer 14

• simple sugars (e.g. glucose & fructose) smallest units of carbohydrates
• 2 sugar molecules can be joined together, e.g. glucose + fructose makes sucrose - a complex carbohydrate
• many sugar molecules (1000s) joined together to make complex carbohydrates
• starch & glycogen made from simple sugars

Question 15

what is starch used for?

Answer 15

used to store glucose in plants

Question 16

what is glycogen used for?

Answer 16

used to store glucose in animals & fungi

Question 17

describe the structure of proteins

Answer 17

• large molecules made up from smaller basic units - made of many amino acids joined together
• 20 different amino acids which can be combined in any order, resulting in millions of different protein structures
• shape of a protein helps it to carry out its job

Question 18

what are the functions of protein in the body?

Answer 18

• structural molecules (e.g. collagen & keratin)
• controlling chemical reactions - these are enzymes
• messenger molecules - hormones
• combating disease - antibodies
• transport - e.g. haemoglobin & cell membrane proteins

Question 19

describe the structure of lipids

Answer 19

• large molecules made up of 3 fatty acids joined to 1 glycerol molecule

Question 20

functions of lipids?

Answer 20

• energy storage (can also be used in respiration)
• part of cell membranes
• thermal insulation
• electrical insulations - around nerve cells
• buoyancy - helps marine animals like whales to float

Question 21

practical: investigate food samples for presence of glucose/reducing sugars

Answer 21

• crush up food sample
• add benedict’s solution to it (in solution)
• place in a water bath at 80°C for 5 mins
• if a reducing sugar is present the colour will change from blue to—> brick red
• if it’s green, yellow, orange it’s still positive result but lower concentration of the sugar

Question 22

practical: investigate food samples for presence of starch

Answer 22

• add few drops of orange iodine solution to sample on a spotting tile
• a blue-black colour indicates presence of starch

Question 23

practical: investigate food samples for presence of protein

Answer 23

• add 2cm squared water to food sample & shake (if not already liquid)
• add equal volume of dilute potassium hydroxide & shake
• add 2 drops of 1% copper sulfate solution
• if protein present then pale purple colour will develop

Question 24

practical: investigate food samples for presence of lipids

Answer 24

• emulsion
• food sample placed in test tube
• add small volume of absolute ethanol & shake to dissolve any lipid in the alcohol
• add equal volume of water
• a cloudy white colour (caused by an emulsion forming) indicates presence of lipid

Question 25

what is the role of enzymes?

Answer 25

biological catalysts in metabolic reactions

Question 26

definition for a catalyst

Answer 26

a catalyst is a chemical which increases the rate of a reaction without being used up itself in the reaction

Question 27

how does temperature affect enzyme function?

Answer 27

• temperature increase = enzyme & substrate have more KE, move faster & so more successful collisions
• all proteins held together by forces between different parts of amino acid chain. high temps & changes of ph disrupt these forces, so shape changes
• protein is denatured
• in enzymes, active site changes shape so no longer complementary to substrate