AQA Biology, Unit 1

model answer style revision notes which are ideal for condensed answers in exams whilst learning important key points.

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Why is it important that samples are collected at random?
to avoid bias
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What is a correlation?
when a change in one of two variables is reflected by a change in the other variable
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How could you show whether there is a correlation between two variables?
1) plot a scatter graph, 2) plot a line of best fit
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What is the purpose of a controlled experiment?
to ensure that any change in the results is due to the changing in the IV and nothing else
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How is a controlled experiment set up?
remove the factor that is being changed e.g. placebo (dummy drug) or for an enzyme reaction, a denatured one of distilled water, KEEP EVERYTHING ELSE THE SAME
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Advantage of expressing results as a ratio or percentage...
allows for comparison, as they have different starting values, (relate second point to give an example)
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How to improve reliability of results...
Identify anomalies, allow for calculation of a more reliable mean,
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A large sample is beneficial because...
the data is more representative
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How taking additional readings can improve a graph
line of best fit may be more reliable, point where the line crosses may be more reliable, error bars can be plotted, to show variability about the mean
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Standard Deviation for large and small mean values
the LARGER the mean value, the GREATER the standard deviation so the MORE variation there is in the data. the SMALLER the value of the mean, the LOWER the standard deviation so the LESS variation there is in the data
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Points to consider for EVALUATION (how science works)
sample size (is it representative)...repeats (can you identify anomalies)...scientists may have vested interest to present biased results...peer review...not carried out on humans...no control experiment
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Suggest why certain Protein/Enzyme drugs can not be taken orally
protein may be digested/broken down my enzymes; protein may be denatured by stomach acid
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Calculating % INCREASE
NEW VALUE - ORIGINAL VALUE/ORIGINAL VALUE X 100
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Calculating % DECREASE
ORIGINAL VALUE - NEW VALUE/ORIGINAL VALUE X 100
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What is the difference between accuracy and reliability?
Accuracy is being free from error, making no mistakes (1) reliability means that there is little variation from the true value (1) i.e. results are concordant when repeated
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Pros of Transmission Electron Microscopes
small objects can be seen, high resolution as wavelengths of electrons are short
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Cons of Transmission Electron Microscopes
living cells can't be seen, has to be carried out in a vacuum, specimen has to be very thin, artefacts can be produced in the image
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Estimating the size of a cell/organelle without any figures
measure length with eyepiece scale (1); calibrated against something of known AND UNIFORM length (1) e.g. red blood cell
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Ice cold, Isotonic, Buffer solution...
ICE COLD - to slow down (not stop) enzyme activity (or prevent self digestion by enzymes in lysosomes); ISOTONIC - to prevent water movement by osmosis and organelle won't shrivel; BUFFER - to prevent changes in PH that may affect protein structure
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Why is tissue homogenised?
to release the cell contents (organelles)
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Osmosis is...
Net movement of water, from an area of less negative water potential to an area of more negative water potential across a SELECTIVELY PERMEABLE MEMBRANE
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How to find the water potential the same value as the tissue used, e.g. potato
plot a graph of results and draw a line of best fit; find the concentration where the ratio is 1 or there is no change in mass
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Passive Transport
DIFFUSION is the net movement of solutes from a HIGH to a LOW concentration
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Facilitated Diffusion
is the transport of a large or charged particle through membrane proteins (channel or carrier)
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Active Transport
the net movement of molecules against a concentration gradient from a LOW to a HIGH concentration that requires energy in the form of ATP and carrier molecules
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Gradients of Transport
Facilitated and Passive diffusion occur DOWN a concentration gradient, Active Transport occurs AGAINST a concentration gradient
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Why do some cells have a lot of Mitochondria?
mitochondria produce ATP, by RESPIRATION, releasing ENERGY for muscle contraction
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Fick's Law (relate to this in ALL instances of DIFFUSION)
Rate of Diffusion is proportional to; (surface area x concentration gradient) / length of diffusion pathway
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How are Prokaryotes different from Eukaryotes
A loop of DNA (no nucleus), no mitochondria, golgi, ER, smaller ribosomes (70s), have a; capsule, flagellum, plasmids and cell wall of MUREIN
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Mechanism of Cholera (6)
bacteria enter via CONTAMINATED water, some survive acidity of stomach (1) bacterium PROPELS through intestinal lining with flagellum (1) secretes a PROTEIN that binds to RECEPTORS on epithelial cells (1) ...
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Mechanism of Cholera...continued
bacterium also secretes a toxic protein that interferes with chloride channels (1) chloride ions flood lumen, water potential is more negative in lumen (1) from cells to lumen by osmois, causes diarrhoea (1)
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What is an EXOTOXIN?
a toxic protein secreted by bacteria
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Why does the CHOLERA PROTEIN bind to RECEPTORS on the SMALL INTESTINE
protein is a complementary shape (1); to the specific tertiary structure of the receptor protein (1)
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ORT (Oral Rehydration Therapy)
Contains; water to rehydrate tissues (1); electrolytes to rebalance the osmotic potential (1)
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Explain why ORT, REPLACES water loss (3)
encourages the cells to uptake SODIUM and GLUCOSE (1); water potential in the cells becomes more negative (1); water moves from intestine to cells by osmosis (1)
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Protein Structure - Hierarchy of Folding (6)
animo acids join to form primary structure (1); by condensation (1); forming PEPTIDE BONDS; then folds to Alpha helix or Beta pleated sheet (1); forming HYDROGEN bonds between O and H atoms (1);
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Protein Structure - Hierarchy of Folding (6)...continued
Further folding to tertiary structure held together by ionic and disulphide bonds (1); quaternary structre is where more than one polypeptide chain folds together, e.g. haemogobin (1)
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Enzyme activity with TEMPERATURE
particles have more KINETIC enery (1); therefore more movement (1); so they more frequently collide and react (1)
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Induced Fit Theory
the substrate has a complementary shape to the active site of the enzyme (1); upon binding to the active site of the enzyme around the substrate (1)
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Lock and Key Theory
Enzymes has an active site of a specific shape (1); the substrate that is complementary (1); binds to the active site (1)
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Enzyme Denaturation
Heat about OPTIMUM breaks HYDROGEN BONDS (1); causing TERTIARY STRUCTURE to unfold (1); active site CHANGES SHAPE (1); substrate can no longer bind to ACTIVE SITE (1); fewer E-S COMPLEXES form
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Effect of PH on Enzyme activity
IONIC BONDS break in TERTIARY structure (1); active site changes shape, substrate can't bind to ACTIVE SITE (1); charges on AMINO ACIDS in active site affected (1); fewer E-S COMPLEXES form
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Competitive Inhibition
Inhibitor has a SIMILAR shape to substrate (1); Binds competitively to the active site (1); has a complementary shape (1); less E-S COMPLEXES form
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Non-Competitive Inhibition
Inhibitor binds somewhere other than the active site (1); causing conformational damage in the shape of the active site (1); substrate can no longer bind (1); less E-S COMPLEXES FORM
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How starch digestion occurs in the human body
SALICARY AMYLASE (1) breaks down STARCH to MALTOSE (1); MALTASE breaks down MALTOSE to GLUCOSE (1); by HYDROLYSIS (1); enzymes CATALYSE the breakdown of the GLYCOSIDIC bond (1)
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How lactose intolerance causes diarrhoea
Undigested lactose in small intestine causes water potential to become MORE negative (1); water moves from the epithelial cells into the lumen (1); by OSMOSIS (1)
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Adaptations of the Micro Villi for EFFICIENT DIFFUSION (Fick's law)
1) increase surface area 2) one cell thick wall, reducing length of diffusion pathway 3) able to MOVE to maintain the concentration gradient and well supplied with blood vessels (circulation of blood)
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Co-Transport of Glucose
Na+ ions actively pumped OUT of epithelial cell (1); INTO BLOOD (1); maintaining a LOW CONC of sodium in the cell (1); GLUCOSE moves IN with sodium (1); via MEMBRANE PROTEINS (1) GLUCOSE moves from cell to blood by FACILITATED DIFFUSION (1)
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The adaptations of the human lungs in relation to Ficks Law
SMALL DIFFUSION PATHWAY - caused by thin squamous epithelial cells (1) LOW CONC GRADIENT - constant removal of o2 by the blood and renewal by the alveoli (1) SURFACE AREA - small and numerous alveoli (1)
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Pathway of oxygen from the Alveolus to the Blood
DIFFUSION through the ALVEOLAR EPITHELIUM into the blood via the CAPILLARY ENDOTHELIUM
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How ventilation maintains a concentration gradient
Air HIGH in oxygen is continuously ENTERING the alveoli, air LOW in oxygen is constantly REMOVED from the alveoli, BLOOD HIGH in oxygen is removed
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Inspiration...
Intercostal muscles contract (1) ribs move up and out (1) diaphragm contracts and flattens (1) volume of chest increases (1) pressure decreases (1) atmospheric air moves in (1)
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Expiration...
Intercoastal muscles relax (1) ribs move down and in (1) diaphragm returns to original dome shape (1) volume of chest cavity decreses (1) pressure increases (1) atmospheric air moves out (1)
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How can paralysis of the DIAPHRAGM lead to breathing difficulty?
Diaphragm will not flatten so the volume of the chest cavity will not increase
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Course of TB infection
1) bacteria grow in upper lung regions where o2 is plentiful 2) white blood cells accumulate site 3) leads to lymph node inflammation 4) bacteria may re emerge to make second infection 5) can result in scar tissue in lungs 6) suffer can cough blood
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Effect of allergies on ASTHMA
Allergens cause WBC lining the bronchioles to release HISTEMINE (1) lining of airway becomes INFLAMED (1) cells of epithelial lining secrete MUCUS (1) fluid enters airways (1) airways become constricted as surrounding muscles contract (1) LACK OF VEN
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Explain why less o2 diffuses to the blood during an ASTHMA ATTACK
Airways restricted (1) air in alveoli is not replaced so less oxygen (1) CONC GRADIENT not maintained (1) rate of diffusion of oxygen is LOWER
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Symptoms of ASTHMA
DIFFICULTY BREATHING - constriction of bronchioles, WHEEZING - air passing through restricted airway, TIGHT CHEST - non adequate ventilation, COUGHING - reflex to obstructed bronchioles
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Effect of EMPHYSEMA
Elastin lung tissue is permanently stretched (1) no longer force air from alveoli (1) lack of VENTILATION, NO CONC GRADIENT (1) surface area is reduced (1) rate of diffusion is SLOWER (1)
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Symptoms of EMPHYSEMA
SHORTNESS OF BREATH - difficulty inhaling, CHRONIC COUGH - trying to get rid of damaged tissues, BLUISH SKIN - low levels of oxygen as a result of poor gas exchange, FATIGUE - low level of respiration
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Effect of PULMONARY FIBROSIS
Elastin may be destroyed so no longer able to force out air form the alveoli (1) lack of VENTILATION cannot maintain a CIONC GRADIENT (1) scar tissue increased the LENGTH OF DIFFUSION PATHWAY (1)
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Symptoms of PULMONARY FIBROSIS
SHORTNESS OF BREATH - lungs being occupied by fibrous tissue (length of pathway increased) , CHRONIC COUGH - fibrous tissue, PAIN - pressure and scarring due to coughing, FATIGUE - reduced intake of oxygen into the blood and less respiration
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Other cards in this set

Card 2

Front

What is a correlation?

Back

when a change in one of two variables is reflected by a change in the other variable

Card 3

Front

How could you show whether there is a correlation between two variables?

Back

Preview of the front of card 3

Card 4

Front

What is the purpose of a controlled experiment?

Back

Preview of the front of card 4

Card 5

Front

How is a controlled experiment set up?

Back

Preview of the front of card 5
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Comments

Jaypark

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Thanks for a great flash cards. For the 6th flash card is there any other disadvantages?

Rosie

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Great flash cards! Just to say, the cell wall of the prokaryotic cells is made from peptidoglycan, I've never heard the term murein!

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