Ocr as f211 biology unofficial mark schemeWatch
1a) Which pore does the leaf lose the majority of its water from? (1)- Stomata1b) How is the guard cell adapted for its job? (2)- Thickening on inner side of the stoma so that when it becomes turgid it opens.- Sensitive to light e.g. it opens in bright sunlight.1c) Where else does the plant lose water from? (1)- Upper surface of leaf/ cuticle/ waxy cuticle/ upper epidermis1d) Fill in the gaps. (4)- Water potential (as it was talking about inside the cell that it is lost from, I think)- Osmosis- Partially permeable- Turgidity1e) Using the cohesion-tension theory describe how water molecules get from the roots to the leaves. (4)I think there is a lot that is creditworthy here, it just depends on the mark scheme.Roots:- Minerals actively transported from endodermal cells to the xylem.- This lowers the water potential so water moves into the xylem by osmosis - root pressure.- High hydrostatic pressure at the base of the xylem.- Water molecules leaving the xylem at the top of the xylem pull up a chain of water molecules - cohesive forces which are hydrogen bonds.- The difference in pressure causes tension in the xylem.2a) Fill in the grid. (4)Yeast - buddingYes for nucleus for all except bacteria.Plants - cellulose, bacteria - peptidoglycan/mureinYes for ribosomes for all.2c) What cells are present in the phloem? (2)- Sieve tube elements- Companion cells2d) What features are would not be present in a mature xylem vessel which are present in the image? (2)- Nucleus is present- End walls are present- Organelles/cytoplasm is present2e) How would a xylem vessel's walls look different from those of the cells in the image? (2)- Lignin- Pits are present2f) What kind of cells/tissue are the undifferentiated cells found in? (1) - Meristematic I'm not sure where this question was in the sequence of questions.Also, it is very likely that OCR will give the mark for cambium in my opinion.3a) What two types of endothelium are present in the alveoli and airways? (2)- Ciliated epithelial tissue- Squamous epithelial tissue3b) How are the alveoli adapted for gas exchange? (5)I think a lot could be said here. There will probably be a mark for an adaptation and then a mark for an explanation and then the QWC mark.- Walls are one cell thick/ made of squamous epithelial tissue.- Reduces the diffusion distance for gas exchange.- Many alveoli due to bunching and thin cell walls.- Increases surface area for gas exchange.- Have elastic fibres in the walls.- Able to expel stale air from the alveoli and replace it with fresh air.- Moist lining.- Gases can diffuse into the moisture and so gases can be exchanged across the alveolar wall.- Surfactant present.- Prevents the walls of the alveoli sticking together and ripping which would decrease the surface area of the alveoli.4a) Name the apparatus used to measure the breathing rate. (1)- Spirometer.4b) Work out breathing rate? (1)- It was actually 13.5 but I think 13 would be accepted.4c) Work out the oxygen uptake? (2)- 0.5 cm cubed.5a) Describe the structure of a membrane. (4)There are many things that could be creditworthy here.- Phospholipid bilayer is made up of two phospholipid molecules facing each other in a mirror image. The hydrophobic tails point inwards and the hydrophilic heads point outwards. This creates a hydrophilic centre of the membrane.- Cholesterol is present. The cholesterol binds to the tails of the phospholipids.- Carrier proteins and channel proteins span the width of the membrane.- Carbohydrate groups may be attached to a protein and/or a phospholipid to make a glycoprotein or a glycolipid. The carbohydrate group would face out, away from the cell interior.5b) Experiment - How do the indicator molecules move into the yeast cells? (2)Mechanism - Active TransportFeature - Carrier proteins.5c) Ammonia solution is added but no change is seen - what can be deduced here? (1)- The membrane is not permeable to ammonia solution.5d) Effect of heat on the membrane? (2)- Heating gives the molecules more kinetic energy.- This increased movement makes the molecules move further apart slightly.- This makes the membrane leaky.- If the temperature is high enough, the membrane may melt completely.- Proteins are denatured.- Proteins now allow substances through which previously they did not.- QWC mark.6a) Match the letter to the event which goes after it. (4)- C- E- A- B6b) Draw an ECG of someone with the described condition. (1)This is only worth one mark so I doubt that it will be highly prescriptive.- Two QRS peaks for each P peak.6c) What effect does this have on the blood flow? (2)- More contractions of the heart.- Higher heart rate- Blood pushed out of the heart twice for every atrial contraction.- Less blood pushed out each time.6d) Why might a fetus have a hole in its septum? (2)- Fetus does not need to transport the blood to the lungs to be oxygenated.- Fetus gains its oxygen via the placenta.- Therefore the blood does not need to be separated between the deoxygenated and oxygenated blood.- There must be a hole in the septum to allow the blood coming in from the Vena Cava be pumped around the body.6e) Difference between fetal and adult haemoglobin? (2)Difference - Fetal haemoglobin has a higher affinity for oxygen.Effect - Fetal haemoglobin needs to become saturated with oxygen at a lower partial pressure of oxygen than adult haemoglobin as it gains its oxygen across the placenta from its mother's blood which has a low partial pressure of oxygen and will be releasing oxygen.7a) What are the functions of the named organelles? (3)SER: Lipid synthesisLysosomes: contains digestive enzymes/lysis to break down dead organelles and substances taken into the cell.Ribosomes: protein synthesis.7b) Evidence for the endosymbiotic relationship? (3)- Mitochondria have smaller ribosomes than those in the cytoplasm.- The mitochondria are roughly the same size as bacteria.- Bacteria have their own DNA. I am one mark short but I can't locate where it should be!There are most likely many other acceptable and valid answers guys so do not panic!Feel free to message me if you want to question something or ask me about something you wrote!Last edited by JustAGuyy; 1 day ago at 15:43. Reason: Forgot a question.
Do you think 14 will be accepted? Can you remember what was in the both of the heart tables?
OCR tend not to be too picky some questions so they may give a range of 13-14 since it was 13.5. However that said, they could be mean and only accept one answer. It was only 1 mark I think so nothing too much to worry about.
Unfortunately I can not remember what was in the heart tables.
However I am quite sure that the order was CEAB.
Feel free to message me if you have any more questions!