B3 revision cards: Cells

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  • Created on: 08-05-16 10:14
Why do muscle and liver cells have large numbers of mitochondria?
Mitochondria are the site of respiration; where energy is released from glucose. Liver and muscle cells need large amounts of energy to carry out theirfunctions and so need lots of energy from the mitochondria.
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What are Ribosomes?
They are the site of protien synthesis found in the cytoplasm of a cell.
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Why can't ribosomes be seen under a normal microscope?
They are too small, a light microscope is needed to see the ribosomes in a cell.
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Decsribe the structure of DNA.
Two strands twisted into a double helix. These strands are held together by cross links in the bases. The four bases are a-t, c-g. A always binds with T, and C always binds with G. (and vice versa)
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What is a chromosome?
Chromosomes are long coiled molecules of DNA. They are divided into genes.
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How does DNA code for protien structure?
The sequence of bases in a gene codes for the sequence of amino acids and therefore the shame of the protien.
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How many bases code for a single amino acid?
3 bases code for one amino acid
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Describe protien synthesis.
gene is copied (mRNA), the copy leaves the nucleus to the cytoplasm. Attaches to a ribosome. sequence of bases puts the amino acids in the right order. The finished protien folds into a specific shape for its function.
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How does DNA control cell activities?
By controlling the production of protiens, Some of which are enzymes. (This is also how DNA controls the cells function)
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who discovered the structure of DNA and how?
Watson and Crick are credited with finding the sturcture of DNA. They used data from other scientists e.g. Xray data to indicate a double helix and data that proved the existence of complimentary base pairs.
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Why arent scientific discoveries rewarded immediately?
Other scientists need to check the work and repeat the results in order to prove it.
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What are protiens made of?
Long chains of amino acids.
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Name 3 functions of protiens and give examples.
Structural to support - e.g collagen provides support for skin to grow over. Hormones control body processes - e.g. Insulin controls blood sugar levels. Carrier molecules transport materials - e.g. Haemoglobin carries oxygen around in the blood.
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Name the basic function of an enzyme and give an example.
Enzymes control and catalyse reactions without affecting the end product. An example is lipase which breaks down fats in the digestive system.
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WHy do different protiens have different functions?
They have their own unique sequence of amino acids and therefore have a different shape in order to do a different job.
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How do enzymes control chemical reactions?
Each enzyme has an active site. The reaction being catalysed has a substrate of the same shape as the active site. Only a specific substrate will fit into a specific active site. This is likened to a lock and key.
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What are enzyme catalysed reactions affected by?
temperature and pH
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a denatured enzyme changes shape, so the active site will also change shape. this means it wont fit the substrate anymore and the reaction wont be catalysed.
Why is it a problem if an enzyme denatures?
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Organisms can be much larger, The cells can differentiate and organisms can be much more complex.
What are the advatages of a multicellular organism? (versus a single celled organism)
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Materials can't diffuse throughout the whole organism and so specialised organs and transport systems must be developed.
What are the issues with being multicellular? (versus being a single celled organism)
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What is the type of cell division for growth?
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Cell divison for growth. A diploid cell copies its DNA, divides and the cell splits.The two daughter cells are diploid and are genetically identical.
What is mitosis?
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A cell with two copies of each chromosome
What is a diploid cell?
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The DNA unzips and new complimentary bases are added to the original strands, making two full double helixes. The chromosomes line up in the centre of a cell. The copies divide. They move to opposite sides(poles) of the cell. The cell divides.
What happens in mitosis?
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How are sex cells produced?
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cell division to produce sex cells, four haploid cells. In meiosis there are two divisions and the chromosome number is halved.
What is meiosis?
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A cell with only one of each chromosome. Gametes/Sex cells are haploid.
What is a haploid cell?
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The cell divides (see mitosis), and then divides again, leaving four genetically different haploid gametes.
What happens in meiosis?
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When two haploid sex cells (a sperm and an egg) combine. They form a diploid zygote.
What is fertilisation?
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The zygote inherits alleles from both parents. Th combination controls the characteristics of the zygote. Which allele is expressed depends on whether the allele is recessive or dominant, and whether the zygote is homozygous or heterozygous.
How does this result in genetic variation?
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The nucleus carries genes, The tail allows for swimming, Produced in large numbers to increase chance of ferilisation, lots of mitochondria to provide energy, acrosome released to digest egg membrane
How are sperm cells adapted?
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What is the Q10?
the temperature coefficient, it is the effect of a 10 degrees C temperature rise on a chemical reaction.
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How is Q10 calculated?
rate of reaction at a higher temp divided by the rate of reaction over a lower temp
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What would a Q10 of 2 mean for the rate of the rection?
That the rate of reaction doubles (is times 2) for every increase in temp by 10 degrees.
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What is a mutation?
A change to a gene. It can occur spontaneously, but s also thought to be brought on by radiation or chemicals.
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What is the danger of mutations?
They could have no effect or be beneficial, however they could have harmful effects - e.g. cystic fibrosis.
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What is the word equation for aerobic respiration?
glucose + oxygen -> carbon dioxide + water + energy (ATP)
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What is the symbol equation for aerobic respiration?
C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP (energy)
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What is the rate of respiration affected by?
Temperature and pH because respiration is an enzyme catalysed reaction.
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How is respiratory quotient calcuated?
Carbon dioxide produced / oxygen used
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What is anaerobic respiration and when does it occur?
Anaerobic respiration is the incomplete breakdown of glucose (without oxygen) to produce ATP. It can occur during hard exercise in muscle cells that are starved of oxygen.
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What is the word equation for anaerobic respiration?
Glucose -> lactic acid + energy (ATP)
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What is the oxygen debt?
The extra oxygen needed to break down the lactic acid. This is why people are still out of breath after difficult exercise, to re pay the oxygen debt.
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Why is a persons pulse still accelerated after exercise has stopped?
So the blood can carry lactic acid away quickly, oxygen can be taken to the liver to break down lactic acid quickly, to provide oxygen for aerobic respiration.
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how is a red blood cell adapted to its function?
No nucleus, so more room for carrying oxygen; Small to carry oxygen to every part of the body; contains haemoglobin; small size and biconcave shape means a large surafce area to volume ratio for absorbing lots of oxygen more quickly.
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What chemical carries oxygen and how?
haemoglobin carries oxygen. It reacts with oxygen in the lungs to form oxyhaemoglobin. In the tissues the reverse reaction occurs to provide the oxygen.
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What is the function of Plasma?
To transport: -digested food molecules (glucose, amino acids) -hormones -antibodies -water -waste products around the body
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What is an artery?
a blood vessel that transports blood away from the heart at high pressure.
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What is a vein?
A blood vessel that carries blood towards the heart at a lower pressure.
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What happens in the capillaries?
Materials are exchanged between blood and tissues.
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How are arteies adapted to their function?
Thick, muscular, elastic wall to withstand high pressures
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How are veins adapted to their function?
Large lumen and valves to transport blood at lower pressures in one direction.
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How are capillaries adapted to their function?
Thin permeable wall so there is a rapid exchange of materials between blood and tissues.
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Why does the left ventricle have a thicker more muscular wall than the right ventricle?
The left ventricle has to pump blood at higher pressure to get it around the whole body.
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What is the advantage of a double circulatory system?
Blood is pumped at higher pressuers so there is a greater rate of flow of oxygenated blood to tissues.
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Why are some babies born with a hole in the heart ?
In the womb all blood in the heart is mixed. After birth the oxygenated and deoxygenated blood dont mix. Sometimes the wall in the centre of the heart doesnt close up and babies have holes in their hearts.
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Why is a hole in the heart a problem?
If deoxygenated blood and oxygenated blood mix there is less oxygen getting to tissues and less respiration.
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What are the advantages and disadvantages of using length to measure growth?
Advantage - Quick and Easy. Disadvantage - Organism may increase in size but the length might remain the same.
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What are the advantages and disadvantages of using Wet Mass to measure growth?
Advantage - Live organisms can be measured. Disadvantage - Water content of an organism varies throughout a day.
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What are the advantages and disadvantages of using Dry Mass to measure growth?
Advantage - Most accurate. Disadvantage - Organism must be dead.
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When are a humans most rapid phases of growth?
Just after birth and during adolescence.
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what is a stem cell?
An undifferentiated cell that can develop into different cells, tissues and organs by switching different genes on and off.
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How is this different from a normal body cell?
Body cells loose the ability to differentiate as genes are switched off.
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Why are stem cells being researched?
They have the potential to cure genetic diseases and replace damaged cells.
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Why are embryonic stem cells better than adult stem cells?
Embryonic stem cells can become all types of other cells, adult stem cells can only become some cell types ( e.g. cant become a nerve cell)
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What are the ethical issues with embryonic stem cell research?
Some people think its wrong because it results in the death of an embryo, and therefore ends a potential life.
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Where does mitosis occur in plants?
In the tips, called meristems.
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How do plants gain height?
Cell enlargement/elongation
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What is the other main difference between plant and animal growth?
Plants grow continously all their lives, animals grow to a finite/predetermined size.
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What is selective breeding?
Selective breeding is the act of cross breeding organisms with desired characteristics over generations in order to produce offspring with ideal characteristics, and improve agricultural yeild.
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What are the problems with selective breeding?
animals with the ideal characteristics may be related, and inbreeding can occur.More closely related organisms mean a smaller gene pool and recessive characteristics are more common.
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What is genetic engineering?
Transferring genes from one organism into another species. The new organism produced is called a TRANSGENIC ORGANISM
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Describe the process of genetic engineering.
IDENTIFY the target gene. ISOLATE the gene from the dna (using a restriction enzyme). (use the enzyme to cut open the dna of the other organism). INSERT the gene. REPLICATE the transgenic organism by cloning.
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What are some examples of uses for genetic engineering?
genetically engineering bacteria to produce human insulin to treat diabetics. GE-ing rice to prodcue Vitamin A incountries that rely on rice but lack vitA. GE-ing crops to give them resistance to herbicides, frost damage or disease.
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What are the advantages of GE?
Organisms with desired features are produced rapidly.
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What are the disadvantages of GE?
May have unexpected harmful effects, for exapmle with the crop, the resistance to herbicides may move into weeds or the yeild of edible crop may not be as high.
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Why else do people have objections to genetic engineering?
People think its worng for humans to think they are superior to animals and to maipulate them in such a way. The technology could also be used on humans and people object because of religious reasons.
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What is gene therapy?
Changing a persons DNA to cure or treat a genetic disease -e.g. cystic fibrosis. It can be used on body cells or gametes.
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Why is gene therapy on gamtes controversial?
Because it affects all cells in the body, and any modifications are passed on to the next generation. This means if anything goes wrong it will affect all descendants.
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What is the technique use for cloning?
Nuclear transfer
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Describe the technique used for cloning?
The nucleus is removed from an egg cell, Replaced wiht the nucleus from an udder cell(or other skin cell), Given an electric shock in order to form an embryo, Embryo implanted into another sheep(surrogate), Grows into clone of the skin cell.
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What could cloning be used for?
Mass producing animals with useful characteristics. Producing embryos to provide stem cells for therapy.
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What are the risks of cloning?
Low rate of success; cloned organisms have shorter life spans as their DNA is already aged.
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What are the ethical argument against cloning?
Destroying the embryo loses a potential life, Surrogate pregencies end in miscarriage, Clones may be unhealthy and die early.
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How could genetically modified Pigs solve problems with organ transplants?
They could be used to grow organs for organ transplants to reduce the shortage of donors, and the organs could be made to have the right tissue type.
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What are the risks of GM pig organs?
Any diseases from the pigs could be transferred to the transplant patient.
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What are the advantages of Cloning plants?
You are sure to get the right characteristics; Mass produce plants difficult to grow from seeds.
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What are the disadvantages of cloning Plants?
Susceptible to disease; Lack of genetic variation.
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How do you clone a plant? Describe this process.
Clone plants by tissue culture. SELECT a plant. Take lots of small pieces of tissue. Put in sterile test tubes (aseptic technique) containg growth medium. Grow genetically identical plants.
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Why is it easier to clone plants than animals?
Plant cells retain the ability to differentiate, Animal cells loose this.
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Other cards in this set

Card 2


What are Ribosomes?


They are the site of protien synthesis found in the cytoplasm of a cell.

Card 3


Why can't ribosomes be seen under a normal microscope?


Preview of the front of card 3

Card 4


Decsribe the structure of DNA.


Preview of the front of card 4

Card 5


What is a chromosome?


Preview of the front of card 5
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