2a, b & c structure and functions in living organisms

Question 1

2.2/2.3 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

2.2/2.3 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

2.2/2.3 describe cytoplasm/function of it

Answer 3

jelly-like liquid where chemical reactions occur

Question 4

2.2/2.3 describe the mitochondria/function of it

Answer 4

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

Question 5

2.2/2.3 describe ribosomes/function of it

Answer 5

synthesise (assemble) proteins from amino acids

Question 6

2.2/2.3 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

2.2/2.3 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

2.2/2.3 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

2.4 similarities in structure of plant and animal cells?

Answer 9

• nucleus
• cell membrane
• cytoplasm
• mitochondria
• ribosomes

Question 10

2.4 differences in structure of plant and animal cells?

Answer 10

only plant cells have chloroplasts, vacuoles, and cell walls

Question 11

2.7 identify the chemical elements present in carbohydrates

Answer 11

carbon, hydrogen, oxygen

Question 12

2.7 identify chemical elements present in proteins

Answer 12

carbon, hydrogen, oxygen, nitrogen

Question 13

2.7 identify chemical elements present in lipids

Answer 13

carbon, hydrogen, oxygen

Question 14

2.8 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

2.8 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

2.8 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

2.9 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

2.9 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

2.9 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

2.9 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

2.10 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

2.11 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

Question 28

2.12 practical: investigate how enzyme activity can be affected by changes in temperature

Answer 28

- add 5cm cubed **starch solution** to test tube & heat to temp being investigated using water bath - add drop of **iodine** to each of the wells of a spotting tile - use syringe to add 2cm cubed **amylase** to starch solution & mix well - every min, transfer droplet of solution to new well of iodine solution (which should turn blue-black) - repeat this transfer process until iodine solution **stops turning blue-black** (this means amylase broken down all starch) - record time taken for reaction to be completed - repeat investigation for range of temps (20°C-60°C)

Question 29

2.12 practical explanation (investigate how enzyme activity can be affected by changes in temp)

Answer 29

- amylase enzyme which **breaks down starch** - quicker reaction completed, faster enzyme is working investigation shows: 1. at **optimum temp**, iodine stopped turning blue-black the fastest: this bc enzyme working at its fastest rate & has digested all starch 2. at **colder temps** (below optimum), iodine took longer time to stop turning blue-black: this bc amylase enzyme working slowly due to low kinetic energy & few collisions between amylase & starch 3. at **hotter temps** (above optimum) iodine turned blue black throughout whole investigation: this bc amylase enzyme denatured & so can no longer bind w starch or break it down

Question 30

2.13 how can enzyme function be affected by changes in pH?

Answer 30

all proteins held together by forces between different parts of the amino acid chain. changes of pH disrupt these forces, so shape changes - protein is **denatured** - in enzymes, active site changes shape so no longer complementary to substrate

Question 31

2.1 describe levels of organisation in organisms: organelles

Answer 31

structures that carry out specific processes the cells need to survive

Question 32

2.1 describe levels of organisation in organisms: cells

Answer 32

the smallest functional unit of life & contain a number of organelles

Question 33

2.1 describe levels of organisation in organisms: tissues

Answer 33

groups of similar cells, which work together to carry out the same function

Question 34

2.1 describe levels of organisation in organisms: organs

Answer 34

made up of several different tissues working together to carry out a more complex function

Question 35

2.1 describe levels of organisation in organisms: organ systems

Answer 35

made up of several different organs working together to carry out a complex function essential to life

Question 36

2.5B explain the importance of cell differentiation in the development of specialised cells

Answer 36

- **all** specialised cells & organs constructed from them have developed as result of **cell differentiation** - undifferentiated cells receive **signals** which **stimulates the expression of genes** for cell to undergo **change in metabolism & shape,** enabling them to carry out specialised functions - forming a specialised cell - therefore, this allows organism to **develop cells necessary to grow & develop** as specialised cells can undertake **specific functions** - e.g. stem cells can differentiate into nerve cells to carry electrical impulses, hence allowing muscle movement

Question 37

2.5B definition for cell differentiation

Answer 37

process involving the development of newly formed cells into more specialised & distinct cells as they mature

Question 38

2.6B understand the advantages of using stem cells in medicine

Answer 38

advantages: - medical benefits in therapeutic cloning to heal diseases & chronic illnesses - potential in discovering treatments & cures for diseases e.g. Parkinson's disease & cancer - ability to test potential drugs & medicine w/o use of animals/human simulation - reduced risk of rejection as patient's own cells can be used

Question 39

2.6B what two key qualities do stem cells have?

Answer 39

- **self-renewal:** capable of continuous division & replication - **potency:** capacity to differentiate into specialised cell type

Question 40

2.6B understand the disadvantages of using stem cells in medicine

Answer 40

- ethical issues surrounding the use of embryonic stem cells involving the destruction of human embryos - uncertainties regarding long-term effects - rejection by patient's body as certain stem cells are obtained from embryos instead of their own cells - difficulty in controlling differentiation of pre-specialised cells into desired cell