5-6 MARKERS Flashcards
Compare and contrast the structure and properties of triglycerides and phospholipids.
COMPARE:
• Both have ester bonds and contain glycerol
• Fatty acids may both be saturated or unsaturated
• Both are insoluble in water
• Both contain C, H and O
CONTRAST
• Triglyceride has 3 fatty acids whereas phospholipids have 2 fatty acids plus PO43- group.
• Triglycerides are hydrophobic/non-polar whereas phospholipids have both a hydrophilic and hydrophobic region
• Phospholipids form monolayer/micelle/bilayer whereas triglycerides don’t.
Describe how the structures of starch and cellulose molecules are related to their functions. (5)
Starch (max 3)
1. Helical/ spiral shape so compact;
2. Large (molecule)/insoluble so osmotically inactive;
3. Branched so glucose is (easily) released for respiration;
4. Large (molecule) so cannot leave cell/cross cell-surface membrane;
Cellulose (max 3)
5. Long, straight/unbranched chains of β glucose;
6. Joined by hydrogen bonding;
7. To form (micro/macro)fibrils;
8. Provides rigidity/strength;
Explain why the diffusion of chloride ions involves a membrane protein and the diffusion of oxygen does not. (5)
- Chloride ions water soluble/charged/polar;
- Cannot cross (lipid) bilayer (of membrane);
- Chloride ions transported by facilitated diffusion OR diffusion involving channel/carrier protein;
- Oxygen not charged/non-polar;
- (Oxygen) soluble in/can diffuse across (lipid) bilayer;
Use your knowledge of protein structure to explain why enzymes are specific and may be affected by non-competitive inhibitors. (5)
1 each enzyme / protein has specific primary structure / amino acid sequence;
2 folds in a particular way / has particular tertiary structure giving an active site with a unique structure;
3 shape of active site complementary to / will only fit that of substrate;
4 inhibitor fits at site on the enzyme other than active site;
5 distorts active site;
6 so substrate will no longer fit / form enzyme-substrate complex
Describe the role of the enzymes of the digestive system in the complete breakdown of starch. (5)
Amylase;
(Starch) to maltose:
Maltase;
Maltose to glucose;
Hydrolysis;
(Of) glycosidic bond;
Describe the role of the enzymes of the digestive system in the complete breakdown of starch. (5)
Amylase;
(Starch) to maltose:
Maltase;
Maltose to glucose;
Hydrolysis;
(Of) glycosidic bond;
In humans, the enzyme maltase breaks down maltose to glucose. This takes place at normal body temperature.
Explain why maltase:
-only breaks down maltose
-allows this reaction to take place at normal body temperature. (5)
- Tertiary structure / 3D shape of enzyme (means);
- Active site complementary to maltose / substrate / maltose fits into active site / active site and substrate fit like a lock and key;
- Description of induced fit;
- Enzyme is a catalyst;
- Lowers activation energy / energy required for reaction;
- By forming enzyme-substrate complex;
Scientists have investigated the effects of competitive and non-competitive inhibitors of the enzyme maltase.
Describe competitive and non-competitive inhibition of an enzyme. (5)
- Inhibitors reduce binding of enzyme to substrate / prevent formation of ES complex;
(Competitive inhibition), - Inhibitor similar shape (idea) to substrate;
- (binds) in to active site (of enzyme);
- (Inhibition) can be overcome by more substrate;
(Non-competitive inhibition), - Inhibitor binds to site on enzyme other than active site;
- Prevents formation of active site / changes (shape of) active site;
- Cannot be overcome by adding more substrate;
Explain how the structure of DNA is related to its functions. (6)
- Sugar-phosphate (backbone)/double
stranded/helix so provides strength/stability
/protects bases/protects hydrogen bonds; - Long/large molecule so can store lots of
information; - Helix/coiled so compact;
- Base sequence allows information to be
stored/ base sequence codes for amino
acids/protein; - Double stranded so replication can occur
semi-conservatively/ strands can act as
templates; - Complementary base pairing / A-T and G-C
so accurate replication/identical copies can
be made; - (Weak) hydrogen bonds for replication/
unzipping/strand separation; - Many hydrogen bonds so stable/strong;
Atheroma formation increases a person’s risk of dying. Explain how. (5)
- Atheroma is fatty material/cholesterol/foam cells/plaque/calcium deposits/LDL;
- In wall of artery;
- (Higher risk of) aneurysm/described;
- (Higher risk of) thrombus formation/blood clot;
- Blocks coronary artery;
- Less oxygen/glucose to heart muscle/cells/tissue;
- Reduces/prevents respiration;
- Causing myocardial infarction/heart attack;
- Blocks artery to brain;
- Causes stroke/stroke described;
Describe how DNA is replicated. (6)
- Strands separate / H-bonds break;
- DNA helicase (involved);
- Both strands/each strand act(s) as (a) template(s);
- (Free) nucleotides attach;
- Complementary/specific base pairing / AT and GC;
- DNA polymerase joins nucleotides (on new strand);
- H-bonds reform;
- Semi-conservative replication / new DNA molecules contain one old strand and one new strand;
Describe how tissue fluid is formed and how it is returned to the circulatory system. (6)
Formation
1. High blood / hydrostatic pressure /
pressure filtration;
2. Forces water / fluid out;
3. Large proteins remain in capillary;
Return
4. Low water potential in capillary /
blood;
5. Due to (plasma) proteins;
6. Water enters capillary / blood;
7. (By) osmosis;
8. Correct reference to lymph;
Some substances can cross the cell-surface membrane of a cell by simple diffusion through the phospholipid bilayer.
Describe other ways by which substances cross this membrane. (5)
By osmosis (no mark)
1. From a high water potential to a low water potential/down a water potential gradient;
2. Through aquaporins/water channels;
By facilitated diffusion (no mark)
3. Channel/carrier protein;
4. Down concentration gradient;
By active transport (no mark)
5. Carrier protein/protein pumps;
6. Against concentration gradient;
7. Using ATP/energy (from respiration);
By phagocytosis/endocytosis (no mark)
8. Engulfing by cell surface membrane to form vesicle/vacuole;
By exocytosis/role of Golgi vesicles (no mark)
9. Fusion of vesicle with cell surface membrane;
The events that take place during interphase and mitosis lead to the production of two genetically identical cells. Explain how. (4)
- DNA replicated;
- (Involving)
specific/accurate/complementary
base-pairing; - (Ref to) two identical/sister
chromatids; - Each chromatid/ moves/is separated
to(opposite) poles/ends of cell;
A mutation can lead to the production of a non-functional enzyme. Explain how. (6)
- Change/mutation in base/nucleotide
sequence (of DNA/gene); - Change in amino acid
sequence/primary structure (of
enzyme); - Change in hydrogen/ionic/disulfide
bonds; - Change in the tertiary
structure/shape; - Change in active site;
- Substrate not complementary/cannot
bind (to enzyme/active site) / no
enzyme-substrate complexes form;
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta. (5)
- Atrium has higher pressure than ventricle (due to filling/contraction);
- Atrioventricular valve opens;
- Ventricle has higher pressure than atrium (due to filling/contraction);
- Atrioventricular valve closes;
- Ventricle has higher pressure than aorta;
- Semilunar valve opens;
- Higher pressure in aorta than ventricle (as heart relaxes);
- Semilunar valve closes;
- (Muscle/atrial/ventricular) contraction causes increase in pressure;
Explain how selection occurs in living organisms (6)
- Variation due to mutation;
- Different environmental/ abiotic/biotic conditions / selection pressures;
- Selection for different/ advantageous, features/ characteristics/mutation/ /allele;
- Differential reproductive success / (selected) organisms survive and reproduce;
- Leads to change in allele frequency;
- Occurs over a long period of time;
RP7
Outline the procedure of using chromatography to separate photosynthetic pigments (6)
- Draw the origin pencil line 1cm from the bottom
- Add 2cm^3 of acetone and use the mortar and pestle to grind up leaf sample and release the pigments
- Use a capillary tube to transfer the pigment onto the origin
- Place filter paper in solvent (below pencil line) and leave until solvent is 1cm from top
- Remove paper from solvent and draw solvent front
- Calculate Rf value for each spot
Describe the process of succession
Pioneers cause change in environmental abiotic / biotic factors (give an example);
• Pioneers make the environment less hostile for new species;
• New species change/make conditions less suitable for previous species;
• Change/increase in diversity/biodiversity;
• Stability increases population/richness/abiotic factors:
• Climax community;
Explain how water enters the xylem from the endodermis in the root and is then transported to the leaves (6)
(In the root)
1. Casparian strip blocks apoplast pathway / only allows symplast pathway;
2. Active transport by endodermis;
3. (Of) ions into xylem;
4. Lower water potential in xylem so water enters by osmosis/down water potential gradient;
(Xylem to leaf)
5. Transpiration (from leaves);
6. (Creates) cohesion / tension / H bonds between H2O / NEGATIVE PRESSURE;
7. Adhesion / H20 binds to xylem;
8. (Creates) continuous column of water.
Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer (7)
- Some light energy fails to strike/is reflected/not of appropriate wavelength;
- Efficiency of photosynthesis in plants is low/around 2% efficient;
- Respiratory loss / excretion / faeces / not eaten;
- Loss as heat;
- Efficiency of transfer to consumers greater than transfer to producers/approximately 10%;
- Efficiency lower in older animals/herbivores/primary consumers/warm blooded animals;
- Carnivores use more of their food than herbivores;
The concentrations of carbon dioxide in the air at different heights above ground in a forest changes over a period of 24 hours.
Use your knowledge of photosynthesis to describe these changes and explain why they occur (6)
- High concentration of carbon dioxide linked with night/darkness;
- No photosynthesis at night/in dark/light required for photosynthesis/light-dependent reaction;
- (In dark) plants (and other organisms) respire;
- In light net uptake of carbon dioxide by plants/plants use more carbon dioxide than they produce/ rate of photosynthesis greater than rate of respiration;
- Decrease in carbon dioxide concentration with height;
- At ground level fewer leaves/less photosynthesising tissue/more animals/less light.
Describe how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium of the aorta.
- Atrium has higher pressure than ventricle (due to filling/contraction);
- (so) Atrioventricular valve opens;
- Ventricle has higher pressure than atrium (due to filling/contraction);
- (so) Atrioventricular valve closes;
- Ventricle has higher pressure than aorta;
- (so) Semilunar valve opens;
- Aorta has higher pressure than ventricle;
- (so) Semilunar valve closes;
- (Muscle/atrial/ventricular) contraction causes increase in pressure.
Describe the gross structure of human gas exchange system and how we breathe in and out (5)
- Named structures O2 IN - Trachea, Bronchi, Bronchioles, Alveoli
- BREATHING IN/INHALATION - Diaphragm contract and external intercostal muscles contract, volume increase and pressure in thoracic cavity decrease;
- BREATHING OUT/EXHALATION - Diaphragm relaxes and internal intercostal muscles contract, volume decrease and pressure increase in thoracic cavity.
