SL Biology Paper 1A &B Previous mistakes

D - a tripeptide formed by the condensation of two amino acids

What are linked by hydrogen bonds?

A. hydrogen and oxygen within a water molecule

B. phosphate and sugar within a DNA molecule

C. base and sugar between DNA nucleotides

D. hydrogen and oxygen in different water molecules

D. hydrogen and oxygen in different water molecules

Which statement applies to enzymes?

A. enzyme function depends on collisions between substrate and active sites

B. one active site on the substrate is specific to one enzyme

C. the active site on the substrate is specific to one enzyme

D. when the enzymes are immobilised they stop working

D. when the enzymes are immobilised they stop working

D. all the enzyme active sites are occupied by the substrate

What is a function of the enzyme helicase?

A. it coils DNA up into a double helical shape

B. it links DNA nucleotides in a new DNA strand

C. it breaks hydrogen bonds between DNA strands

D. it forms temporary hydrogen bonds to produce messenger RNA

C. it breaks hydrogen bonds between DNA strands

B

define hemolysis

the rupture or destruction of red blood cells.

D. at X water has moved by osmosis into the blood cells

onion epidermis was placed in pure water and observed with a light microscope using high magnification, what would happen if these cells were transfered to a hypertonic solution

A. cells would gain mass

B. cells would take in water by osmosis and swell

C. cells would burst open, releasing their content

D. cell membranes would detatch from walls at some points

D. cell membranes would detatch from walls at some points

define plasmolysis

contraction of the protoplast of a plant cell as a result of loss of water from the cell.

If a question says compare and contrast, what do you have to do.

Similarity & difference

evaluate the relibiality of the results

1. Controlled Variables: Reliability is enhanced when all variables, except the independent variable, are controlled. If the experiment fails to control variables such as temperature, pH, or light intensity, it may introduce confounding factors and decrease reliability.

2. Sample Size: A larger sample size generally increases reliability by reducing the impact of random variations. However, if the sample size is too small, the results may not be representative of the population, leading to lower reliability.

3. Replication: Conducting multiple trials or replicating the experiment increases reliability by providing consistency in the results. If the experiment lacks replication or only has a single trial, the reliability of the findings may be questioned.

4. Data Collection Methods: Reliable results are obtained through accurate and precise data collection methods. If the data collection procedures are not standardized or if there are inconsistencies in measurement techniques, it can undermine the reliability of the results.

5. Statistical Analysis: Proper statistical analysis enhances the reliability of results by providing objective interpretations of the data. If statistical tests are not appropriately applied or if inappropriate tests are used, the reliability of the conclusions may be compromised.

6. Validity of Instruments: The reliability of results depends on the validity and calibration of instruments used for measurements. If instruments are faulty, improperly calibrated, or not suitable for the experiment, it can introduce errors and reduce reliability.

7. Bias and Subjectivity: Any bias in the experimental design, data collection, or analysis can affect the reliability of results. Researchers must remain objective and minimize bias to ensure the credibility of their findings.

8. Peer Review: Peer review of the experimental design and results by experts in the field can enhance reliability by identifying potential flaws or biases. Lack of peer review or scrutiny may raise doubts about the reliability of the study.

9. Reproducibility: Reliability is strengthened when other researchers can replicate the experiment and obtain similar results. If the findings cannot be reproduced by independent researchers, it raises concerns about the reliability of the original study.

10. Contextual Considerations: Consider the context in which the experiment was conducted, including the limitations of resources, time constraints, and ethical considerations. These factors can influence the reliability of results and should be acknowledged in the evaluation.

Explain one reason for calculating percentage changes in mass

1. starting mass differences

2. so therefore you can make comparisons with % changes

Which statement(s) is/are a necessary requirement for the evolution of the first cells?

I.	DNA having the ability to catalyse reactions
II.	Polymerisation of carbon compounds
III.	Spontaneous formation of vesicles

• A. I and II only

• B. II and III only

• C. I and III only

• D. I, II and III

B

There is evidence that simple carbon-containing molecules were present on Earth, millions of years ago, however, for early cells to evolve, they would have needed these simple molecules to form more complex structures such as polysaccharides and polynucleotides (Statement II). Phospholipids can spontaneously form vesicles (Statement III) or microspheres (microscopic hollow spheres made from a phospholipid bilayer), which resemble the plasma membrane of a small cell, this would allow for early cells to develop a different internal chemical environment from their surroundings. Choice B is correct.

DNA cannot catalyse reactions, Statement I is incorrect. Choices A, C and D are incorrect as they include Statement I.

Bacteriophages and coronaviruses are both viruses that affect living organisms. Which structures are present in both bacteriophages and coronaviruses?

I.	cytoplasm
II.	capsid
III.	genetic material

• A. I only

• B. I and II only

• C. II and III only

• D. I, II and III

• C. II and III only

Choice C is correct because bacteriophages and coronavirus have a capsid and genetic material, and do not have cytoplasm (Choice A, Choice B, and Choice D).

Which of these statement(s) is/are correct concerning the Polymerase Chain Reaction (PCR)?

I.	It creates RNA copies of DNA
II.	It uses a special DNA polymerase that can withstand high temperatures
III.	It requires helicase and ligase to work

• A. I only

• B. II only

• C. II and III only

• D. I, II and III

B

define polymerase chain reaction

1. a method of making multiple copies of a DNA sequence, involving repeated reactions with a polymerase.

• A. Energy is lost as heat, a waste product of respiration, at each level

• B. There are a higher number of giraffes in tropical grasslands than lions

• C. Giraffes have a higher rate of respiration than lions

• D. Giraffes can derive more energy from acacia trees than lions are able to from hyenas

A

Which pair of structures would be considered analogous?

D

Analogous structures refer to structures found in different species which serve a similar function, but are not the result of common ancestry. Sharks are cartilaginous fish, and their fins are modified pectoral fins made of cartilage. Whales are mammals, and their fins are modified forelimbs, which are homologous to the forelimbs of land-dwelling mammals. Whale and shark fins serve the same purpose, are similar in structure, and are the product of convergent evolution.

define analogous structures

Analogous structures refer to structures found in different species which serve a similar function, but are not the result of common ancestry.

what’s the opposite of an analogous structure

homologous

define homologous structures

Structures with similar anatomy, morphology, embryology and genetics but dissimilar functions are known as homologous structures.

only _______ muscle cells are both branched and contain contractile muscle fibres

only cardiac muscle cells are both branched and contain contractile muscle fibres

only ______ muscle fibres have multiple nuclei and contractile muscle fibres

only striated muscle fibres have multiple nuclei and contractile muscle fibres

label these

features of skeletal muscle

features of smooth muscle

features of cardiac muscle

Which of the following is not a factor required for coral reef formation?

• A. Low pH

• B. Shallow enough water

• C. Temperatures between 20 ^oC and 30 ^oC

• D. High enough salinity

a

Which of the following is/are correct for amino acid R-groups?

I.	R-groups can be hydrophobic or hydrophilic.
II.	Hydrophobic R-groups are polar.
III.	Hydrophilic R-groups can be acidic or basic.

• A. I only

• B. I and II only

• C. I and III only

• D. I, II and III

c

hydrophobic = polar/nonpolar

non polar

c

During the repolarisation phase of an action potential, voltage-gated potassium channels are open and the voltage-gated sodium channels are closed. This allows K⁺ ions to leave the cell, returning the cell to a negative state.

What is the role of the A-site in the ribosome?

• A. It is where the initiator tRNA binds to the start codon

• B. It holds the tRNA with the growing polypeptide chain whilst a peptide bond forms between adjacent amino acids

• C. To allow complementary base pairing between codons and anticodons, so that the correct amino acid is incorporated into the polypeptide

• D. It is where the discharged tRNA exits from the ribosome

c

what’s the role of the p site in the ribosome

The P-site (for peptidyl) is the second binding site for tRNA in the ribosome.

what’s the role of the e site in the ribosome

The E site, or the exit site, is where the tRNA molecules, now without their amino acids, are released from the ribosome.

what is a non competitive inhibitor

A non-competitive inhibitor has a dissimilar shape to the substrate and binds to the allosteric site of an enzyme, which causes a conformational change in the enzyme so that the substrate can no longer bind.

Which biological molecule is the substrate for glycolysis, the common initial stage of both aerobic and anaerobic cellular respiration?

• A. Protein

• B. Cholesterol

• C. Carbohydrate

  • D. Water

c

define glycolysis

1. the breakdown of glucose by enzymes, releasing energy and pyruvic acid.

Which of the following is not a way light is used in the light-dependent reactions in photosynthesis?

• A. In the breakdown of water

• B. To produce ATP and reduced NADP

• C. To release carbon dioxide from photosystem I

• D. To excite electrons in photosystem II

The carbon dioxide used during photosynthesis comes from the atmosphere, not from photosystem I, Choice C is, therefore, correct.

Which technique was first developed to separate cellular components and isolate organelles?

• A. Separation based on adhesion, using chromatography

• B. Separation based on charge, using gel electrophoresis

• C. Separation based on density, using the ultracentrifuge

• D. Separation based on size, using the Polymerase Chain Reaction (PCR)

c

estimate the molarity of the potato cells

• A. 0.01 molmol dm−3dm−3

• B. 0.22 molmol dm−3dm−3

• C. 0.38 molmol dm−3dm−3

• D. 0.57 molmol dm−3dm−3

c

Which process(es) is/are sources of variation during meiosis?

I.	Crossing over during prophase I
II.	Random orientation of sister chromatids during metaphase I
III.	Formation of chiasmata during prophase II

• A. I only

• B. I and II only

• C. I and III only

• D. I, II and III

why are the others not the answer

Crossing over is the exchange of DNA material between non-sister chromatids in homologous pairs, and it occurs during prophase I (Statement I), which results in variation. Choice A is correct.

Random orientation of homologous pairs, not sister chromatids, occurs during metaphase I, Statement II is incorrect.

Chiasmata are the point where non-sister chromatids of homologous pairs cross over, resulting in the exchange of genetic material and genetic variation. Chiasmata are formed during prophase I, Statement III is incorrect.

what is Monogenic inheritance

In monogenic inheritance, a single gene determines a single trait.

what is Polygenic inheritance

Polygenic inheritance refers to the inheritance of a trait governed by more than one genes.

what is Directional selection

Directional selection is a type of natural selection in which one extreme phenotype is favored over both the other extreme and moderate phenotypes.

what is Disruptive selection

Diversifying (or disruptive) selection: Diversifying selection occurs when extreme values for a trait are favored over the intermediate values.

identify actin

During muscle contraction, myosin filaments pull the actin filaments inwards towards the centre of the sarcomere. Line B is pointing to an actin filament. Choice B is correct.

a

b

b

c

a

d

c

c

d

b

c

d

d

b

a

a

d

define action potential

An action potential is described as a sudden and spontaneous change or reversal in the membrane potential above a threshold value due to increased permeability of the cell membrane.