GCSE Biology OCR Gateway Higher Tier- B3
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- Created by: LavleenGill
- Created on: 13-03-17 23:03
What is the structure of DNA?
Double helix, made up of 4 bases: A,C,G and T
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What are the base pairings? -DNA
A pairs with T, G pairs with C.
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What is transcription?
A copy of the DNA - called mRNA - is made in the nucleus.
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What is translation?
The mRNA attaches to a ribosome by complementary base pairs. Every three bases code for an amino acid. Amino acids join to make proteins.
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Explain the triplet code.
Every 3 bases = one amino acid
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What is mutation in terms of DNA?
Alters the sequence of bases so alters the triplet code.
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What are enzymes?
Proteins which speed up chemical reactions in a cell. Affected by temperature and pH.
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What is selective breeding?
Breeding organisms to have desired characteristics that are already in that species.
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Explain the technique for Genetic Engineering and definition.
Introduce a feature into a species that does not normally exist in that species. Isolate the gene, cut it out using enzymes, insert it into a plasmid. Insert into DNA.
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What does the nucleus do?
Contains DNA in the form of chromosomes
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What does the cell membrane do?
Gives the cell its shape and controls what goes in and out of the cell
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What do the mitochondria do?
Most of the reactions involved in respiration take place in mitochondria
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What do the ribosomes do?
Where proteins are synthesised
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What does the Cytoplasm do?
Where most of the cells chemical reactions happen
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What features do plant cells have that animal cells don't and what do they do?
Chloroplasts -where photosynthesis happens. Vacuole - large internal structure containing sap, salts, sugar and water. Cell wall - supports the cell's structure
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Why does DNA need to replicate itself whenever a cell divides?
To make sure the new cell has a full set of chromosomes
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How does DNA replicate itself?
The two strands 'unzip' to separate exposing the bases. Nucleotides floating around the nucleus join onto the bases using complementary base pairing to make two identical strands of DNA
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What molecule carries the genetic code from the nucleus to the ribosome?
messenger RNA (mRNA)
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Briefly evaluate the protein synthesis process
DNA strand unzips and mRNA matches bases; mRNA carries code out of nucleus through cytoplasm to ribosome; mRNA travels through the ribosome which reads the base code; 3 bases codes an amino acid which the ribosome links into a chain to form a protein
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What is the optimum temperature for human body enzymes?
37 degrees Celcius
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What other factor affects enzymes' reactions in a similar way to temperature and has an optimum?
pH levels
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What are gene mutations and what effects do they have?
A change in the DNA base sequence - can stop the production of a protein or cause another to be produced
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What problems can gene mutations cause if they occur in reproductive cells?
The offspring might develop abnormally or die during early development
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What is Mitosis?
A cell reproduces itself by splitting to form two identical offspring
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What is Mitosis used for?
Growth and repair
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How does Mitosis happen?
DNA is replicated; DNA coils into double-armed chromosomes, both arms are identical; chromosomes line up in centre of cell and arms are pulled to opposite poles by cell fibres; membranes form around two sets of chromosomes; Cell divides into two
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What is Meiosis?
Creation of Gametes
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What do the terms Diploid and Haploid mean?
Diploid - a cell with two copies of each chromosome in its nucleus, one from mother and one from father (46 in humans). Haploid - only one copy of each chromosome (23 in humans)
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How does Meiosis happen?
DNA replicates and forms double-armed chromosomes; chromosomes arrange into pairs with info about the same features (23 pairs in humans); pairs split up to form two cells with 23 in each; both cells go through mitosis to make four haploid gametes
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What is the diploid cell created by fertilisation called?
A Zygote
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How does fertilisation cause genetic variation?
The zygote will have half its chromosomes from each parent so will have features of both but won't be exactly like either
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What are stem cells?
Undifferentiated cells that can develop into different types of cell
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Explain how plants can be cloned easily
All plant cells are undifferentiated so cuttings can be planted and grow into exact genetic copies of the original plant because their cells can develop into all types of cell needed
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What is stem cell therapy?
Scientists extract stem cells from early human embryos and grow tissue to eventually repair damage e.g. spinal injuries and brain damage
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Why are some people for/against stem cell research?
Some believe that each embryo used is a potential human life destroyed and think it is unethical. Others say People who are already living and are injured should be prioritised over embryos.
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What is Wet mass?
Weigh the plant or animal as it is. Ad: Easy to measure (depending on size). Dis: Very changeable i.e. a plant will be heavier just after rain fall and an animal will be heavier with a full bladder
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What is Dry mass?
Dry out the organism before weighing it. Ad: Not affected by amount of water in the organism or how much it has eaten. Dis: The organism must be killed beforehand which could be tricky if you're weighing a person
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What are the five phases of human growth?
Infancy, childhood, adolescence, maturity/adulthood, old age
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What is respiration?
Provides energy. Takes place in the mitochondria.
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What are the two types of respiration?
Aerobic and anerobic
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Give the balanced symbol equation for Aerobic respiration
C6H12O6 + 6O2 ---> 6CO2 + 6H2O + Energy Released
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When does Anerobic respiration happen?
When the body cannot supply enough oxygen to your muscles
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Give the word equation for Anerobic respiration
Glucose ---> Lactic Acid + Energy Released
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What is an oxygen debt?
After stopping exercise, if anaerobic respiration has occurred, the body needs extra oxygen to break down the built-up lactic acid to allow you to respire aerobically again so you continue to breathe heavily for a while
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What happens during Anerobic respiration?
Not enough oxygen. Lactic acid builds up which is painful and causes muscle cramps and fatigue. Oxygen is used to break down the lactic acid - oxygen debt.
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What is a Respiratory Quotient?
A calculated value to tell if someone is respiring Aerobically or Anaerobically
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Give the RQ equation
Amount of CO2 produced/Amount of O2 used
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What does a RQ of more than 1 mean?
More CO2 is being produced than oxygen used so the person is respiring Anaerobically
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What is a gamete?
A reproductive cell e.g sperm, egg, pollen.
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What is blood plasma and what seven things does it carry?
Pale yellow liquid part of the blood carries: Blood cells (Red, white and platelets); water; digested food products (glucose, amino acids etc.); CO2; Urea (from liver to kidneys); Hormones; Antibodies
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What do red blood cells do and how are they adapted to their function?
Carries oxygen around the body - biconcave shape and no nucleus gives large surface area to volume ratio and a large amount of haemoglobin means they can carry lots of oxygen
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Why are red blood cells flexible?
So they can easily pass through narrow capillaries
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What are the three types of blood vessel?
Arteries, Veins and Capillaries
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What is the lumen of a blood vessel?
The hole (tube) in the middle that blood flows through
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Give the properties of an artery and the reasons for them
Thick elastic walls that can expand to accommodate for high pressure, smaller lumen to keep blood pressurised
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Give properties of veins and reasons
Thinner walls than arteries because the pressure is not as high so the lumen is also larger. They also have valves to stop blood flowing backwards, away from the heart
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Give properties of Capillaries and reasons
Very small lumen (sometimes only wide enough for one red blood cell) so very low blood pressure, single cell thick wall that is permeable to allow gas exchange
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What is a Double Circulatory system?
Blood passes through the heart twice in a full cycle (Heart to lungs to heart to the rest of the body).
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Why do mammals have a double circulatory system?
Mammals have a double circulatory system so blood can be pumped around the body faster at a higher pressure to increase the rate of blood flow. This is useful as mammals use lots of oxygen maintaining body temperature
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Describe what happens in the right-hand side of the heart
Deoxygenated blood comes into right Atrium through Vena Cava; Blood moves through tricuspid valve into right ventricle; muscle contracts pushing blood through semiluar valve to lungs through pulmonary artery
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Describe what happens in the left-hand side of the heart
Oxygenated blood comes into left Atrium through pulmonary vein; blood moves into left ventricle through bicuspid valve; muscle contracts pushing blood through semilunar valve into Aorta to the rest of the body at high pressure
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Why has genetic engineering been used in rice and how?
Populations around the world rely on rice; Rice has very little vitamin A, causing vitamin A deficiency in these populations (other sources are scarce); Scientists put the gene that controls beta-carotene production from carrots in rice; This give vA
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Why and how is genetic engineering used in crops?
Some plants are resistant to herbicides, frost and disease but not most crops; The genes that give plants these features can be put into common crops to increase yield and allow them to grow in different conditions (e.g. in winter)
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What is gene therapy?
Altering a person's genes in an attempt to cure a genetic disorder
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What effect does altering genes of body cells have?
Changes the cells that are most affected by the disorder to have different alleles and cure the disorder. This does not affect gametes so the faulty genes will still be passed on to the offspring
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How was Dolly created?
Nucleus removed from egg cell. Nucleus from another cell inserted. Electric shock to make it divide. Needs sterile conditions
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Give benefits of cloning
Mass production of animals with desired characteristics
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What are the risks of cloning animals?
Low success rate. "Old before her time"
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How do you clone a plant?
Plant a cutting. Asceptic conditions required.
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Other cards in this set
Card 2
Front
What are the base pairings? -DNA
Back
A pairs with T, G pairs with C.
Card 3
Front
What is transcription?
Back
Card 4
Front
What is translation?
Back
Card 5
Front
Explain the triplet code.
Back
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