To maintain steep concentration gradients for gas exchange.
What does PMAT stand for with regards to mitosis and meiosis?
Order of phases - prophase, metaphase, anaphase and telophase
What does tRNA do?
Carries amino acids to the ribosome
How does biodiversity benefit humans?
Provides food, medicine, and ecosystem services
How many different codons are there?
64
What are alveoli?
Small air sacs where gas exchange occurs.
What is the apoplast pathway?
Movement of water through cell walls and intercellular spaces
What happens to the hydrogen ions produced in the carbonic acid reaction?
They bind to haemoglobin to form haemoglobinic acid (haemoglobin acts as a buffer)
What are bordered pits in xylem?
Thin areas in xylem walls where there is no lignin that allows lateral water movement to other xylem vessels or cells
Why do sieve tube elements have no nucleus?
To allow space for sap flow
What is systematic sampling?
Sampling at regular intervals or locations, perhaps using a transect
Where are semi-lunar valves found?
Between ventricles and arteries (pulmonary artery and aorta)
What forces water to move from the apoplast to the symplast pathway in roots at the endodermis?
The Casparian strip
What is the name for cells without membrane-bound organelles and a nucleus?
Prokaryotic cells
If the image size is 20 mm and the actual size is 0.02 mm, what is the magnification?
×1000
Describe all the steps of what happens in inhalation.
Diaphragm contracts and moves down. External intercostal muscles contract and move ribs up/out. Thoracic volume increases and pressure decreases, air flows in
What is independent (random) assortment?
Random arrangement of chromosomes along the equator during metaphase I
Why is binding H⁺ ions to haemoglobin important?
It prevents the pH of the blood from becoming too acidic
What is lymph?
Fluid similar to tissue fluid but containing lymphocytes
Name 3 major threats to biodiversity.
Habitat destruction, pollution, invasive species, over-exploitation of resources etc
Which chamber pumps blood to the lungs?
Right ventricle
What type of muscle is found in bronchioles and why?
Smooth muscle to control the diameter to regulate airflow (may constrict in event of allergens)
Where does transcription take place in a cell and what is its aim?
In the nucleus, and aim is to make mRNA
What are the three levels of biodiversity?
Habitat, species and genetic
How does water enter a bony fish's mouth?
By opening the mouth and lowering the buccal cavity floor.
What is the function of the diaphragm?
Contracts and relaxes during breathing in order to change thoracic volume.
What was the purpose of the Meselson and Stahl experiment?
To show that DNA replication is semi-conservative by using nitrogen isotopes in bacterial colonies and then centrifuging their DNA after replication
What is an anticodon?
A triplet of bases on tRNA complementary to mRNA codon
Why does the trace go down over time in a spirometer?
As oxygen is used for aerobic respiration and carbon dioxide waste is absorbed by the soda lime
What is the function of the trachea?
Carries air to and from the lungs.
What is the first lens used when focusing on a specimen and why?
Low-power objective lens to get the widest field of view
What is the difference between magnification and resolution?
Magnification enlarges an image; resolution is the ability to distinguish two points
Which phase takes up the most time in the cell cycle?
Interphase
What happens to excess tissue fluid?
Drains into the lymphatic system as lymph
Why is the Bohr effect important?
Helps release oxygen in actively respiring tissues
Why do you need to calibrate the eyepiece graticule?
To convert graticule divisions into actual units of measurement (e.g., µm).
What is the function of cilia in the bronchi?
To move mucus toward the throat for removal
Where is the natural pacemaker of the heart and where is it found?
Sinoatrial (SAN) node in right atrium
What is cytokinesis?
The division of the cytoplasm and cell membrane to form two cells
What is the function of tracheoles in insects?
They deliver oxygen directly to tissues.
What happens if the cell fails a checkpoint?
It may leave the cell cycle (G0) and be marked for destruction/apoptosis
How can a gene mutation affect the function of a protein?
By changing its amino acid sequence and structure
Name three features of a good exchange surface.
Large surface area, thin barrier, good blood supply.
Why do small plants not need a transport system?
They have a large surface area to volume ratio for diffusion
What enables arterioles to change their lumen diameter?
Smooth muscle
Why is the shoot cut underwater when setting up a potometer?
To prevent air entering the xylem
What enzyme joins new nucleotides to the template strand?
DNA polymerase
What type of reaction joins nucleotides together and what is formed?
Condensation reaction and water is formed7
What are intracellular enzymes and give an example?
Enzymes that work inside cells, like catalase, or DNA polymerase/gyrase/helicase/ligase
If 20 graticule divisions align with 200 μm on the stage micrometer,, how many μm is 1 graticule unit?
10 μm
What type of bond forms between amino acids and what enzyme catalyzes their joining?
Peptide bond catalyzed by peptidyl transferase
What are some top tips for biological drawings of a cell?
Unshaded, continuous non-sketchy lines, cells in proportion, horizontal label lines with no arrow-heads, annotations, title, magnification
Why is ECG useful clinically?
Diagnoses heart abnormalities and monitors heart function
What is used to move the stage up and down when focusing?
Coarse focus wheel
What is the main advantage of an electron microscope over a light microscope?
Much higher resolution and magnification
Why is biodiversity important for ecosystems?
It increases ecosystem stability and resilience
What type of bond joins complementary bases and what are the rules?
Hydrogen bonds (2 bonds between adenine and thymine, and 3 bonds between cytosine and guanine)
What is the function of platelets?
Blood clotting
What happens in metaphase?
Chromosomes line up at the cell equator and attach to the spindle fibres at the centromere
What are sieve tube elements?
Living phloem cells with few organelles and sieve plates at their ends
What is the function of ribosomes?
Protein synthesis
What is the function of the mitochondria?
Produce energy (ATP) by respiration
What is the rough endoplasmic reticulum (RER) called "rough"?
Because it is studded with ribosomes
Which base is found in RNA but not in DNA and what does it replace?
Uracil replaces thymine
What kind of images does a TEM produce?
Flat, highly detailed 2D internal images
What does rRNA form?
Ribosomes
What does higher resolution mean in microscopy?
Ability to distinguish two close points as separate
How does meiosis contribute to genetic variation?
Through crossing over and independent assortment
Why is a thin barrier important in exchange surfaces?
To reduce diffusion distance and increase diffusion rate.
What enzyme joins fragments on the lagging strand and what are the short fragments of DNA on the lagging strand called?
DNA ligase joins Okazaki fragments
What is the source in translocation?
Where sugars are loaded into the phloem; typically where they are made (e.g., leaves)
How does pH affect enzymes?
Extreme pH levels change the enzyme’s shape as H+ ions or OH- ions interfere with interactions between amino acids that compose the enzyme's active site
What is habitat fragmentation?
Breaking habitats into smaller, isolated patches making interbreeding more difficult, leading to a decrease in genetic biodiversity
Why is ex situ conservation important?
It safeguards species that are extinct or endangered in the wild as perhaps their habitat is too fragmented
What does tidal volume mean?
Volume of air inhaled or exhaled during normal breathing.
How should labels be drawn on biological drawings?
With straight lines pointing to structures, no arrows
What happens to the graticule scale when you change objective lenses?
It stays the same size, but the value of each division changes.
Name two types of white blood cells.
Phagocytes and lymphocytes
What is the function of the septum in the heart?
Separates oxygenated and deoxygenated blood
What is translocation?
Movement of sugars in the phloem
What is the main function of the Golgi apparatus?
To modify, sort, and package proteins and lipids for transport
Which artery carries oxygenated blood away from the heart?
The aorta
How many chambers does the human heart have?
Four (two atria, two ventricles)
How does the shape of red blood cells help their function?
Biconcave shape increases surface area for oxygen diffusion
What occurs during the S phase of interphase?
DNA is replicated
What is a plasmid?
Small circular DNA in prokaryotes
Where are adult stem cells found?
In tissues like bone marrow
What are the three components of a nucleotide?
Phosphate group, pentose sugar, nitrogenous base
What is the role of lignin in xylem walls?
Provides strength and prevents collapse under tension
Why do companion cells have many mitochondria?
To supply energy for pumping of H+ ions out of the companion cell, so they can then diffuse back co-transporting sucrose (for active loading)
What is the role of companion cells?
Support sieve tube elements by assisting with active loading
If 100 graticule units align with 500 μm on the stage micrometer, what is one graticule unit worth?
5 μm
What organelle contains digestive enzymes in animal cells?
Lysosome
How many amino acids are there?
20
What is a stem cell?
An undifferentiated cell that can divide by mitosis and differentiate to become different cell types
What does the lock and key model suggest?
The enzyme's active site and substrate fit exactly like a key into a lock
How does non-competitive inhibition appear on a rate graph?Z The maximum rate is lower
regardless of substrate concentration
What is the role of xylem vessels?
Transport water and minerals in the transpiration stream
What keeps the trachea open?
C-shaped rings of cartilage.
Why do mammals, fish and insects need exchange surfaces?
They have a small surface area to volume ratio and high metabolic demand.
Name the four DNA bases.
Adenine, thymine, cytosine, guanine
What is the chloride shift?
The movement of Cl⁻ ions into red blood cells to balance the loss of negative charge from HCO₃⁻ leaving
What is crossing over?
Exchange of genetic material between homologous chromosomes during prophase I
What is the main driving force for water movement in the xylem?
Transpiration pull
What happens during anaphase?
Sister chromatids are pulled apart to opposite poles
What is the mark-recapture method used for?
Estimating population size of mobile animals
What is a silent mutation?
A mutation that does not change the amino acid produced
What does a high Simpson’s Diversity Index indicate?
High biodiversity with many species evenly distributed
What is ex situ conservation and give some examples?
Protecting species outside of their natural habitat, such as zoos, seed banks, or botanical gardens
What is the role of the atrioventricular (AVN) node?
Delays the electrical impulse to ensure atria have finished contracting before it passes to the Bundle of His and then Purkyne fibres in the ventricles
What is an enzyme?
A biological catalyst made of protein
What is the function of soda lime in a spirometer?
To absorb carbon dioxide.
What happens at the metaphase (spindle) checkpoint?
It ensures all chromosomes are properly attached to the spindle.
How can you measure enzyme activity?
By measuring product formation or substrate disappearance
What happens during prophase?
Chromosomes condense and become visible, spindle forms, nuclear envelope breaks down
What does iodine stain in plant cells?
Starch (turns blue-black)
What are 3 examples of substances found in the plasma of blood?
Glucose, carbon dioxide, water, ions, amino acids
What happens to a polypeptide after translation?
It folds into a 3D protein
What are the two main vascular tissues in plants?
Xylem and phloem
What helps veins return blood to the heart against gravity?
Valves and muscle contractions
What is bradycardia?
Lower than normal heart rate
What is flagella used for?
Cell movement
What is Simpson’s Diversity Index used for?
Measuring species biodiversity by taking into account species richness and evenness
Once calibrated, if a cell measures 15 graticule units and each unit = 5 μm, what is the cell length?
75 μm
What happens to enzyme activity above the optimum temperature?
It decreases due to denaturation which is where the active site changes shape due to changes in bonding between amino acids that compose it
Which valve prevents backflow between the left atrium and left ventricle?
Bicuspid atrio-ventricular valve
What is meant by 'semi-conservative replication'?
Each DNA molecule contains one old and one new strand
Where is CO₂ converted back to CO₂ gas for exhalation?
In the lungs, when HCO₃⁻ re-enters the red blood cells and the reverse reaction occurs
What does it mean that the genetic code is universal?
The same codons code for the same amino acids in all organisms
What causes most tissue fluid to return to the capillaries?
Oncotic pressure from plasma proteins remaining in the capillaries (as they are too large)
What is hydrogen carbonate’s chemical formula?
HCO₃⁻
What would happen to enzyme activity if a competitive inhibitor is present?
It would decrease as the competitive inhibitor competes with the substrate to bind to the active site
What is the countercurrent flow system in fish?
Water flows opposite to blood flow, maintaining a favourable concentration gradient for oxygen to diffuse into blood
What is the backbone of a DNA strand made of?
Sugar-phosphate backbone
What is species evenness?
How even the number of individuals between species in an area are
What is residual volume?
The air remaining in the lungs after maximum exhalation.
What is the purpose of using a coverslip on a slide?
To prevent the specimen drying out
What is a polypeptide?
A chain of amino acids
What is meant by enzyme specificity?
Enzymes only work with specific substrates as the shape of the active site is complementary to the substrate
What can cause errors in mark-recapture?
Death, immigration, emigration, or marks falling off
How do transport vesicles move around a cell?
Cytoskeleton
What is the purpose of CITES?
To regulate international trade of endangered species
What is the main tissue type in xylem vessels?
Dead cells with thick lignified walls
How many cells are produced by meiosis?
Four
What is a tissue?
A group of similar cells working together to perform a function.
How does fetal haemoglobin differ from adult haemoglobin?
It has a higher oxygen affinity
How many cells are produced by mitosis?
Two
How is tissue fluid formed?
By ultrafiltration through capillary walls at the arteriole end due to high hydrostatic pressure
What are the three stages of interphase?
G1, S, G2
What is the purpose of meiosis?
To produce haploid gametes for sexual reproduction
What is tissue fluid?
Fluid that surrounds cells in tissues that forms from the plasma in the capillaries
What is the potential of adult stem cells?
Limited to certain cell types (multipotent)
What does TEM stand for?
Transmission Electron Microscope
What is diastole?
Relaxation phase of the heart
What happens to mRNA after transcription?
It leaves the nucleus via a nuclear pore
What type of muscle makes up the heart wall?
Cardiac muscle
What is random sampling?
Selecting samples without a pattern or bias
What is the purpose of mitosis?
To produce genetically identical diploid cells for growth and repair of tissues (or asexual reproduction)
Name 2 pieces of equipment used for sampling insects.
Pitfall trap, sweep-net or pooter
What is the Bohr effect?
Decreased oxygen affinity in haemoglobin at higher CO₂ concentrations (like the respiring muscles)
What is the bony flap covering fish gills called?
The operculum
What is the function of the Casparian strip?
Prevents passive flow of water via the apoplast pathways and forces selective uptake into xylem
What does an ECG measure?
The electrical activity of the heart
What happens during atrial systole?
The atria contract to push blood into ventricles
What happens in telophase?
New nuclear envelopes form around the chromosomes and chromosomes decondense (no longer visible)
What is vital capacity?
The maximum volume of air that can be forcibly exhaled after a deep inhalation.
Why are meristems important in plant tissue culture?
They provide a source of stem cells for cloning and regeneration.
Why do larger or more active insects ventilate their tracheal system?
To increase air movement and maintain oxygen supply.
If a cell appears 15 mm in an image, and the actual cell size is 0.015 mm, what is the magnification?
×1000
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