1. Proteins, Enzymes and Mutations
Smart Teach-B2 Topic 4
Proteins, Enzymes and Mutations
Digestive System
Plant systems

2. What are proteins?

3. The genes in your DNA determine which amino acids are used an the order they are put in.

4. Past question model Explain how a gene mutation can affect the structure of a protein. (3) (3)
Mutation: Change
This is actually from a Foundation paper, but I think it is needed to get across to students about mutations since this can link with the next bit on enzymes.

5. Enzymes are a type of protein They are BIOLOGICAL CATALYSTS (they speed up chemical reactions)

6. Complete the sentences:
(i) Enzymes are
A cells
B hormones
C proteins
D sugars
(ii) An enzyme is a biological catalyst that
A slows down all chemical reactions
B speeds up a chemical reaction
C prevents all chemical reactions taking place
D has no effect on a chemical reaction

7. Different enzymes have different amino acids and different structures, so work with different substrates.

8. Which substrate will fit into this enzymes active site?
This is the Lock and Key model
Active site

9. Now lets have a look at an exam question about this..........

10. Explain how the lock and key hypothesis models how enzymes work.
You may use labelled diagrams in your answer.
(3)

12. DENATURE= Change shape so can’t work
You need to know that enzymes can be affected by temperature and pH. Different enzymes work best at different temperature and pH. If it is not correct, the enzyme can DENATURE.
DENATURE= Change shape so can’t work

13. Exam example: Usually it’s interpreting a graph….
Complete the sentence. The graph shows that:
A pepsin only works at a pH of 3
B pepsin has an optimum pH of 3
C trypsin only works at a pH of 3
D trypsin has an optimum pH of 3
OPTIMUM = the best

14. Enzymes that break down your food
Must write these down and learn them!!!
Enzymes that break down your food
Carbohydrases, such as amylase, digest carbohydrates to simple sugars in the mouth and small intestines
Proteases, such as pepsin, digest proteins to amino acids in the small intestines
Lipase digests fats to fatty acids and glycerol in the small intestines

15. Digestive System You need to know the structure and job of each
May want to print a copy of this for students as it could take a while to draw!

16. The Digestive System 26/11/201826/11/2018
Match these functions with the parts of the digestive system that do them…
In here the food is chewed to start breaking it down. An enzyme (amylase) is also added.
This tube uses muscle contractions to push the food down
Bile is produced here
This organ mixes the food with hydrochloric acid to kill bacteria
Bile is stored here
Excess water is absorbed here
Enzymes are made here
Food is absorbed into the bloodstream here

18. Small intestine and villi
The villi and microvilli are the protusions on the small intestine that enable it to absorb the nutrients from broken down food.

19. Small intestine and villi
Villi are adapted to their role because they are only one cell thick, provide a large surface area and have a good blood supply.

20. Small intestine and villi
Coeliac disease causes the villi to become damaged.
What effect will this have on absorption?

21. Small intestine and villi
Damaged villi means less absorption of nutrients.
Coeliac sufferers often feel tired and are lacking certain vitamins because their small intestine is not absorbing sufficient amounts.

22. Role of bile
Quite often there is a question on the role of bile such as....
 Explain the roles of bile in digestion.(2)
It’s easy if you just learn the key points...

23. Role of bile neutralises stomach acid emulsifies fats
This basically means it is an alkaline solution that increases the pH of stomach acid so that the next lot of enzymes can work. It also clumps together fat droplets to give a bigger surface area for lipase to work on.

24. Now lets put all this together in an exam question..........

25. Had to print screen this as it wouldn’t copy properly
Had to print screen this as it wouldn’t copy properly. Rest of question is on next slide.

26.  (b) State two roles of bile in digestion.
(2)
      
 *(c) Describe the roles of the enzymes involved in digestion.
(6)

27. (d) Explain how the structure of the villi allows efficient
absorption in the small intestine.
(3)
      

28. Answer Acceptable answers Mark (a) C peristalsis (1) (b)
Answer
Acceptable answers
Mark
(a)
C  peristalsis
(1)
(b)
· neutralisation (of stomach acid) / raise pH (1) · emulsification / break down of fats (1)
Accept makes stomach / intestine contents more alkaline Accept breaks down large droplets /globules / increases surface area of fats Reject molecules broken down
(2)

29. How many of these points did you get?
Indicative Content
A description including some of the following points in a logical sequence Names of enzymes: · carbohydrases· named carbohydrase eg amylase · proteases · named protease eg pepsin · lipases · named lipase
General points about enzyme action: · breakdown of large / insoluble / named molecules into small / soluble / named molecules · for absorption · catalysts · speeds up reactions · active sites that bind to substrate · idea of specificity
Specific points: · carbohydrates/ starch are broken down · into sugars / glucose · proteins /named protein are broken down · into amino acids · fats / oils / lipids / named lipid are broken down · into fatty acids /glycerol
On the next slide are the specific marking guide, you may want to talk students through the answers, and show where they get the marks.

30. 1
1 - 2
· a limited description of enzyme action that includes at least three points · the answer communicates ideas using simple language and uses limited scientific terminology · spelling, punctuation and grammar are used with limited accuracy 2
3 - 4
· a simple description of enzyme action that includes at least six points · the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately · spelling, punctuation and grammar are used with some accuracy 3
5 - 6
· a detailed description of at least nine points · the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately · spelling, punctuation and grammar are used with few errors

31. Answer Acceptable answers Mark (d)
Answer
Acceptable answers
Mark
(d)
An explanation linking three of the following points · (E) more /fast / maximises diffusion / absorption (1) · (S) microvilli (1) · (E) large surface area (1) · (S) single layer of cells / one cell thick / thin walls (1) · (E) small diffusion distance (1) · (S) capillary network / good blood supply / capillaries inside villus (1) · (E) maintains diffusion gradient (1)
To award all three marks at least one structure (S) and explanation (E) must be linked together. Award once, linked to any structure Ignore efficient (in stem) / easier       Reject ref to cell wall
(3)

32. Visking tubing
This model of the digestion system often comes up on exam questions so lets do a Walking Talking Mock question about it.

33. The results are shown in the table. (On next slide)
Visking tubing is made of a plastic material through which small molecules can pass.
The diagram shows how the equipment for an investigation using visking tubing was set up.
In this investigation, the concentration of glucose in the distilled water was measured at the start and then every five minutes.
The results are shown in the table. (On next slide)
Talk through with students the diagram as it is likely they have not seen this model in a long time if ever. If time, get them to say what parts of the digestive system each bit represents.

34. Describe the results of this investigation. (2)
You can make it very explicit here what the difference between describe and explain actually mean. Answers are on the next page, then there is an evaluate question after.
Describe the results of this investigation. (2)
Explain the results of this investigation (3)

35. A description including the following points: ·
A description including the following points: · increase in concentration of glucose / glucose diffused into water/eq (1) · levels off after 20 mins / at 0.79 g/cm3(1)
small increase, followed by greater increase / eq
(2)
An explanation including three of the following points: · starch broken down into glucose (1) · by enzymes / amylase / carbohydrase (1) · glucose passes through visking tubing / eq (1) · by diffusion (1) · down the (glucose) concentration gradient (1) · (net) diffusion stops when all starch is broken down / concentration of glucose is equal inside and outside the tubing
          reject: references to osmosis or active transport accept: from area of high concentration to area of low concentration
(3)

36. The diagram shows how visking tubing can be used to model the small intestine.
  This model does not fully represent the structure and functions of the small intestine.
  Evaluate the strengths and weaknesses of this model.
(6)

37. How many of these points did you get?
An evaluation including some of the following points: Strengths · thin membrane · permeable membrane · presence of amylase · presence of (large) starch molecules · digestion into glucose · glucose diffuses out · concentration gradient · water represents the blood weaknesses · membrane not one cell thick · not a large surface area · shorter length / not same size · no villi /micro villi · only carbohydrate digestion · no other enzymes present · no peristalsis · no blood movement · other factors e.g. pH

38. 1 - 2
· a limited evaluation of the model including at least one strength OR weakness of the model · the answer communicates ideas using simple language and uses limited scientific terminology · spelling, punctuation and grammar are used with limited accuracy
3 - 4
· a simple evaluation of the model showing evidence of at least one strength AND at least one weakness of the model OR a detailed evaluation of several strengths or several weaknesses of the model · the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately · spelling, punctuation and grammar are used with some accuracy
5 - 6
· a detailed evaluation, commenting on several of the strengths AND weaknesses of the model and its limitations · the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately · spelling, punctuation and grammar are used with few errors

39. Plants
Questions about this could ask you to give the adaptations of the leaf and say why each structure is good at its role.
The photosynthesis equation could come up as well as the limiting factors of photosynthesis.
There could also be questions about the transport structures in the plant and transpiration.

40. Structure of the Leaf Large surface area Lots of chlorophyll
Transparent – to let light through
Lots of chlorophyll
Thin structure
Packed with chloroplasts
I wouldn’t get students to draw this, I would just talk about each part. The waxy cuticle is transparent to allow light to enter. It is waxy to stop water loss. The mesophyll has palisade cells which are packed with chloroplasts to allow maximum rate of photosynthesis. The air spaces and holes (stoma) are to allow maximum diffusion of gases.
Network of veins
Lots of air spaces – to allow diffusion of air
Holes to allow diffusion of air
26/11/2018

41. Photosynthesis equations
Carbon dioxide + water glucose + oxygen
Sunlight
Chlorophyll

42. Limiting Photosynthesis
What factors could limit the rate of photosynthesis?
Temperature – the best temperature is about 300C – anything above 400C will slow photosynthesis right down
CO2 – if there is more carbon dioxide photosynthesis will happen quicker
Light – if there is more light photosynthesis happens faster

43. Drawing graphs of these factors
1. Temperature
Photosynthesis is controlled by enzymes – these are destroyed at temperatures above 400C
2. Carbon dioxide
Photosynthesis increases at first but is then limited by a lack of CO2
3. Light
Photosynthesis increases at first but is then limited by a lack of light

44. Phloem - transport dissolved food for respiration and storage.
Xylem and Phloem
Xylem - transport water and mineral ions from the roots to the stem and the leaves.
Phloem - transport dissolved food for respiration and storage.
A way to remember...
ph = f sound = food

45. Transpiration 1) Water evaporates through the stomata
2) Water passes back into the leaf through xylem vessels by osmosis
3) Water is then pulled upwards through the xylem tissue
4) This is replaced by water entering from the root tissue
5) Water enters root hair cells by osmosis to eventually replace the water lost through respiration

46. Moving substances Diffusion Osmosis Active transport
Movement of particles from an area of high concentration to an area of low concentration
Water molecules move from an area of high concentration to an area of low concentration across a semi-permeable membrane
Moves molecules from an area of low concentration to an area of high concentration
Down the concentration gradient
Against the concentration gradient
Passive
Requires energy

47. Now lets put all this together in an exam question..........

49. Describe how carbon dioxide enters the leaf.(2)
      
Describe the process that takes place in the leaf to produce
oxygen. (3)

50. (b) Root hair cells take in water and mineral ions from the soil.
 Draw one straight line from each substance to the process by which it enters the root hair cell.
(2)

51. Photograph A shows a Coleus plant that has wilted due to lack of water.
If this plant is given some water it will recover and stand upright again.
Photograph B shows the plant after it has been watered.
(i) Describe how a plant takes in water from the soil. (2)
      

52. The soil surrounding the roots of the Coleus
plant contains water with a higher concentration
of dissolved mineral ions than the plant cell
vacuole.
Which row of the table gives the method of
transport of mineral ions into the plant cell of
this Coleus and the type of vessel which
transports mineral ions to its leaves?
Put a cross in the box next to your answer. )
(1)
method of transport into the plant cell
type of vessel which transports mineral ions A
active transport
phloem B
xylem C
diffusion D

53. Answer
Acceptable answers
Mark
(a)(i) B
(1)
(a)(ii)
Any two from the following: · diffusion (1) · from an area of high concentration to an area of low concentration/down a concentration gradient (1) · through stoma / stomata (1)
Accept pores / between guard cells Ignore through guard cells
(2)
(a)(iii)
Any three from the following: · (by) photosynthesis (1) · ref to chloroplast / chlorophyll (1) · requires carbon dioxide and water (1) · light (energy) needed (for photosynthesis)(1) · (to produce) glucose (1)
Ignore incorrect balancing of equations throughout Reject (and) respiration Accept if written on arrow in word / formula equation Accept correct formulae word / formula equation Accept if written on arrow in word / formula equation Reject energy is created / produced Accept sugar from word / formula equation
(3)
(b)
water          osmosis (1)                (1)
3 lines, 1 correct = 0 mark 3 lines, 2 correct = 1 mark 4 lines, 1 correct = 0 mark 4 lines, 2 correct = 0 mark

54. Answer
Acceptable answers
Mark b
(2)

55. Question Number
Answer
Acceptable answers
Mark
(a)(ii) D
(1)
Question Number
Answer
Mark
(a)(i)
An explanation linking the following points •   by osmosis / diffusion (of water) (1) •   from an area where it is in high concentration to an area where it is in low concentration (1) •   through the root hair cells (1)
(2)