Biology BY1 - THINGS I KEEP FORGETTING

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  • Created by: Tasha.L
  • Created on: 13-05-16 17:54
Why is it important that water has a high latent heat of vaporisation?
It is important in temperature control, where heat is used to vaporise water from sweat on the skin. As the water evaporates, the body cools.
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What two units form maltose, and where is it found?
Glucose + glucose --> Maltose + water. Maltose is found in germinating seeds.
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What two units form sucrose, and where is this found?
Glucose + fructose --> Sucrose + water. Sucrose is found in the phloem of plants.
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What two units form lactose, and where is this found?
Glucose + galactose --> Lactose + water.
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How can reducing sugars be broken down into their original monosaccharides?
By heating with HCl.
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Why are glycogen and amylopectin excellent for storage?
Glycogen and amylopectin both contain alpha-1,6 glycosidic bonds, and so have branches of alpha-glucose molecules. These can easily be hydrolysed to release the glucose monomers. These are soluble and can be transported to where they are needed.
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How does the structure of cellulose relate to its function?
Cellulose's chains are linked by hydrogen bonds, which form microfibrils. These are strong and tough and therefore are structurally important in plant cell walls.
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Where are waxes found in plants and insects?
Plants - waxy cuticle. Insects - exoskeleton.
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What is added to a sample to test for lipids?
Ethanol and distilled water of equal volume.
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What is collagen comprised of?
Three polypeptide chains joined by hydrogen bonds, making them strong and tough
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How long is a typical mitochondrion?
Between 3 and 5 micrometers.
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What is the important role of a vacuole?
They play a major role in supporting soft plant tissues.
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What is the role of chromatin?
During cell division, it condenses to form chromosomes.
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What is the function of the nucleus?
To retain the DNA, which codes for protein synthesis.
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Define the term tissue.
A group of cells of similar structure and function working together.
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Define the term organ.
A group of tissues in a structural unit, working together to perform a specific function.
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Where can squamous epithelium be found?
Forming the walls of the alveoli or lining the Bowman's capsule of the nephron.
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When using the equation, magnification = image size/object size, what must you ensure?
That the units are the same.
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What is the average thickness of the membrane?
7 to 8 nanometers
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What types of molecules cannot pass through the phospholipid bilayer?
Water-soluble molecules, large molecules, charged particles.
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What is facilitated diffusion?
The movement of molecules or ions from a region of high to low concentration, down a concentration gradient, in the transport molecules of the membrane.
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Why is the state of turgor important?
It provides young seedlings with support and helps to maintain their shape.
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What is the process called by which a red blood cell bursts?
Haemolysis
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Define the term endocytosis.
This is a transport mechanism where materials are engulfed by the cell membrane and cytoplasm, forming a vesicle.
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Define the term phagocytosis
The process by which the cell obtains materials that are too large to be taken into the cell by diffusion.
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Define the term exocytosis.
This is the transport of materials out of the cell via a vesicle, which moves through the cytoplasm and fuses with the cell membrane.
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Enzymes act extracellularly. Give an example of this.
Amylase, which is produced in the salivary glands, travels down the salivary ducts and into the mouth.
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Enzymes act intracellularly in solution. Give an example of this.
Enzymes in the stroma of a chloroplast catalyse the synthesis of glucose.
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Define the term active site.
This is a region of an enzyme with a particular shape that permits binding with a specific substrate.
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Give an example of a competitive inhibitor and what it inhibits.
Malonic acid is a competitive inhibitor that binds with the enzyme succinic dehydrogenase. It competes with the substrate succinic acid. This reaction occurs in the mitochondrial matrix.
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Give an example of a non-competitive inhibitor.
Any heavy metal, e.g. Lead, Pb2+, Arsenic, As3+
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What is a biosensor?
A device that combines the use of immobilised enzymes with an electrode to rapidly detect minute concentrations of a specific molecule. They then turn this chemical signal into an electrical signal.
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Which enzyme is used for the detection of blood glucose?
Glucose oxidase.
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What does ATP transfer from energy rich compounds, such as glucose?
Free energy.
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What base does uracil replace in RNA?
Thymine.
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Why is the genetic code non-overlapping?
Each bases occurs in only one triplet.
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Define the term transcription.
This is the use of one strand of DNA as a template strand for the formation of mRNA, which is complimentary to the specific sequence of bases on the DNA strand. This occurs in the nucleus.
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Define the term translation.
The mRNA strand acts as a template to which complimentary tRNA molecules attach, and the amino acids they carry link together to form a polypeptide. This occurs on ribosomes in the cytoplasm.
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The anticodon of a tRNA molecule is complimentary to a codon of the mRNA strand. Once it attaches to the ribosome, what happens next?
Hydrogen bonds form between the complimentary base pairs.
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Define the term gene.
A sequence of DNA bases that codes for a polypeptide.
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What types of proteins are produced during interphase?
Histones and proteins, therefore requiring ATP.
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Where does asexual reproduction take place?
Unicellular organisms, e.g. bacteria
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Define the term meiosis.
This is a two stage cell division is sexually reproducing organisms that produces four genetically different daughter cells with half the number of chromosomes compared to that of the parent cell.
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How are chiasmata formed?
The chromatids wrap around each other, then repel each other, but remain attached at areas called a chiasma. At a chiasmata, the segment of DNA from one chromatid may be exchanged with the equivalent section on the other chromatid of the homologous c
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How does 'crossing over' provide for genetic variation?
It produces a number of different combinations of alleles. Furthermore, as it can occur across the length of each chromatid, a huge variety of genetic combinations can be produced.
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What happens at prophase II?
THE CENTRIOLES SEPARATE and organise the formation of new spindle at right angles to the old spindle.
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What is the importance of reducing the chromosome number when the cell divides by meiosis?
It allows for later cell fertilisation and the restoration of the diploid number of the cell.
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Give an advantage of a DNA molecule having two strands?
Protects the bases.
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What are the advantages of having a membrane?
a. They isolate potentially harmful chemicals from the remainder of the cell. b. Molecules of specific functions(e.g. chlorophyll) are concentrated in one area.
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What are the advantages of having a membrane?
c. They provide a larger surface area for the attachment of enzymes involved in metabolic processes. d. They provide a transport system within cells.
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Where is cuboidal epithelium found?
In the ducts of the salivary gland and kidney nephron.
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Where is smooth muscle found?
In the walls of blood vessels, under the skin and in the digestive and respiratory tracts.
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What occurs in channel proteins?
The active transport of ions.
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What is lyzozyme?
Lyzozyme is an enzyme in human saliva, mucus and tears, whose job is to weaken the cell wall of bacteria. As the sugars of the cell wall join with the active site, the enzyme changes shape around the sugar and hydrolyses the bond between them.
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Define catalysis.
The increase in the rate of a chemical reaction due to the involvement of a catalyst.
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What exactly causes enzymes to denature at high temperatures?
The increasing internal vibrations of the enzymes causes the hydrogen bonds maintaining its shape to break. This alters the shape of the active site.
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Why do excess OH- and H+ ions affect the rate of reaction involving an enzyme?
Excess H+ ions are attracted to the negative charges of the active site and neutralise them, whilst OH- ions neutralise the positive charges. This disrupts the hydrogen bonds maintaining the shape of the active site.
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Why do the graphs produced by the presence of competitive inhibitors look the way they do?
The mass of product produced will always be the same as what would be produced without a competitive inhibitor, as they only temporarily bind to the active of an enzyme. The inhibition is reversible.
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Why do the graphs produced by non-competitive inhibitors look the way they do?
Non-competitive inhibitors permanently damage the shape of an enzyme molecule, reducing the amount of product that can be produced overall.
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Why do enzymes immobilised in beads have a lower rate of reaction than those on a gel membrane?
Some of the active sites are inside the beads and so the substrate first has to diffuse across the bead to the center before it can join with the enzymes active site. This therefore takes longer and so the rate of reaction is lower.
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What is a biosensor and how does it work?
A biosensor is a device that combines the use of immobilised enzymes with an electrode. They rapidly detect minute concentrations of a specific substrate. They then convert this chemical signal into an electrical signal.
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Give an example for a use of a biosensor.
The monitoring of diabetes.
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How do the components of a nucleotide join?
Via condensation reactions.
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If you were to draw a pyrimidine, what shape would it make?
Hexagon.
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If you were to draw a purine, what shape would it make?
A hexagon attached to a pentagon.
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What is a reaction that releases energy called?
An exergonic reaction.
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What is a reaction that requires energy called?
An endergonic reaction.
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How are introns removed in RNA?
Using endonucleases.
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How are exons joined together in RNA?
Using ligases.
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What happens to the RNA formed by prokaryotes?
The RNA produced is the mRNA and is directly used for protein synthesis.
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Explain the function of the codons at each end of a strand of mRNA, during the process of translation.
There are stop and start codons, which are needed to begin polypeptide synthesis and stop codons end polypeptide synthesis.
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Why does independent assortment occur at metaphase ii of meiosis?
As either chromatid can face either pole.
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What does diploid mean?
Containing two complete sets of chromosomes, one from each parent.
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What does haploid mean?
When a cell has half the usual number of chromosomes.
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What is meant by the cell cycle?
Cellular events that repeat in order between one cell division and the next.
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A mule is a cross between a female donkey and a male horse. A mule is infertile. Suggest why.
Its chromosomes cannot form homologous pairs, so meiosis is not possible, so not gametes can form.
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How many bases are there per turn of a double helix?
10
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What solution do you use when preparing white onion cells?
Methyl blue
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What solution do you use when preparing red onion cells?
Water
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Why is glycerol added to a sample of amoeba?
It slows down its movements so it can be analysed under a microscope but does not harm it.
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When analysing amoeba, why should an fluorescent light be used rather than a incandescent light?
The heat given off a incandescent light would damage the amoeba after a couple of minutes.
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When determining the water potential, for example, by measuring the changes in mass or length of a potato, why is percentage change used?
Percentage change rather than actual change is used due to the initial differences in mass of the potatoes.
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Why is a line of best fit more suitable for this experiment?
It ensures that all data points are included
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What happens if the samples have different times in sucrose concentrations?
Some may not reach equilibrium and so when weighed their mass may still be changing.
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What is a control experiment?
A controlled experiment is one in which everything is held constant except for one variable.
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Describe a control experiment for the aforementioned practical.
A potato cylinder could be placed in a solution and be weighed after varying times: at the point where it is weighed several times and the mass has not changed is the point of equilibrium
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The absorbance of the Betalain solution from beetroot cells is read using a calorimeter. The higher the number...
... the greater the concentration of betalain solution that has been released into the water.
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Why is the absorbance of betalain greatest at high temperatures?
High temperatures disrupt the phospholipids and denature the proteins, creating gaps. Therefore, increasing temperatures increasingly disrupts the membrane causing more dye to leak out.
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What is the affect of SODIUM CHLORIDE on the absorbance of the solution?
As its concentration increases, the absorbance of the solution decreases as the Na+ ions are attracted to the hydrophilic heads, reducing the movement of the phospholipid molecules and making the membrane more stable.
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What is the affect of DETERGENT on the absorbance of the solution?
As its concentration increases, so does the absorbance. This is because detergent reduces the surface area and disperses the membrane, so more dye is released more rapidly.
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What is the affect of an ORGANIC SOLVENT on the absorbance of the solution?
As its concentration increases, the absorbance of the solution increases. This is because they dissolve they dissolve the phospholipids and so the membrane structure is destroyed.
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When separating DNA from an onion sample, what first happens?
A salt detergent mixture is added at 60 'C. The detergent destroys the phospholipid membrane, the sodium chloride changes the DNA into a semi-solid state, and the high temperature denatures cellular enzymes so they cannot digest the DNA.
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Trypsin is then added. Why?
To digest histone proteins and any enzymes that might digest the DNA.
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Give an example of a tissue in a plant.
Phloem/ xylem.
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Give an example of an organ in a plant.
Leaf/ flower.
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Why can mitochondria sometimes appear an oval shape, and other times a circular shape?
It depends whether it is a transverse section or a longitudinal section.
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What temperature does bacterial enzymes denature at, compared to enzymes in humans?
Bacterial enzymes: 100'C, Human enzymes: 40'C
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What does a control experiment show?
That it is the independent variable that causes the changes in the dependent variable.
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What does a control experiment show?
No change in the dependent variable, as the independent variable has been inactivated. No change in the dependent variable shows that it is the changes in the independent variable that generate the different readings.
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What is a independent variable?
The variable that you can choose and manipulate.
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What is a dependent variable?
The variable you are measuring.
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Describe a control experiment for a practical involving enzymes?
The enzymes are boiled for five minutes to denature them and cooled before use.
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Describe a control experiment for a practical involving algae or enzymes in alginate beads.
The algae and enzymes should be boiled and cooled before being placed in the alginate beads.
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What do waxes contain that differs from triglycerides?
An alcohol group.
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What do shorter range bars indicate?
That the readings are more consistent and therefore produce a more reliable mean.
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When measuring the % mass change of potato cylinders, the potato is cut by hand? How could this be improved?
They could be cut using a specific mechanical device that cuts the cylinders accurately.
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How do you increase the accuracy of readings if measuring volume?
You use a piece of apparatus with smaller graduations, or simply a better piece of equipment. To improve the accuracy ensure you remove any possible sources of error.
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What does reliability mean?
It indicates how consistent the results are.
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How can you increase the reliability of the experiment?
Repeat it several times.
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When a question asks you to assess the validity of a source, what do you do?
You state what is wrong with the experiment, e.g. the results vary greatly, only three temperatures used etc.
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When writing a conclusion, what MUST you include?
You must explain an explanation as to how the results have been achieved. DON'T DESCRIBE, EXPLAIN!!
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Card 2

Front

What two units form maltose, and where is it found?

Back

Glucose + glucose --> Maltose + water. Maltose is found in germinating seeds.

Card 3

Front

What two units form sucrose, and where is this found?

Back

Preview of the front of card 3

Card 4

Front

What two units form lactose, and where is this found?

Back

Preview of the front of card 4

Card 5

Front

How can reducing sugars be broken down into their original monosaccharides?

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