AQA unit 1 biology notes

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  • Created by: sehar
  • Created on: 12-04-13 16:18
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3.1.1- Disease may be caused by infectious pathogens or may reflect the
effects of lifestyle
A disease is a disorder of the body, leading to a departure of good health
Acute-sudden onset with rapid changes, chronic is a long-term disease
Pathogens include bacteria, viruses and fungi
Carrier-a person infected with a pathogen,
but not suffering from the disease
Parasite-an organism that lives in or on the
body-some can be harmful
Diseases can also be caused by genetic
defects, caused by mutations in a person's genes.
Transition occurs when an organism
penetrates a host organism's interface, which can
occur through droplet infection, water, contaminated
food and vectors etc.
A risk factor is something that increases the chances of something bad happening-smoking is
a risk factor for heart disease.
Risk Factor Diseases
Smoking Mouth, lung and throat cancer, cardiovascular
disease, emphysema
Drinking too much alcohol Cardiovascular disease, mouth, stomach, liver
and breast cancer
High blood pressure Diabetes, cardiovascular disease
Overweight/ obese Cancers, diabetes, cardiovascular disease
Unbalanced diet Same as above
Too much sun exposure (e.g. Using sun beds) Skin cancer

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Pathogens cause disease by damaging host cells (so it can avoid the host's immune
response) and by producing exotoxins or endotoxins which interfere with host cell
metabolism (faster than host's immune response)
Pathogens recognise and attach to host cells due to protein molecules called ligands, and
enter the cell by endocytosis (infolding of the cell membrane) or by producing enzymes that
breach the host cell membrane
Changes in lifestyle, such as exercise, can reduce the risk of contracting these conditions
Exercise can-reduce blood pressure, enlarges…read more

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The digestive system is made up of the mouth, stomach, duodenum, ileum, colon and anus
In the mouth, food is mechanically digested, and mixes with salivary amylase which lubricates
the food. This increases the surface area and allows enzymes to break down the starch. The
food is pushed down in the oesophagus by peristalsis
In the stomach, further mechanical digestion allows food to mix with the digestive enzymes,
such as protease which turns proteins into amino acids.…read more

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A peptide (covalent) bond is formed between two amino acids by a condensation reaction to
form a polypeptide/dipeptide
The primary structure of a protein determines the order/sequence in which amino acids are
The secondary structure is the way in which the primary structure folds, it can fold into an
alpha helix or beta pleated sheet (held together by hydrogen and peptide bonds)
The tertiary structure is a further folding to give a globular shape, which is held together by
hydrogen, disulphide and ionic bonds…read more

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Anabolism-building things up from smaller units, catabolism-breaking things down into
smaller units
Enzymes (a tertiary structure) work as biological catalysts, which lower activation energy,
through the formation of enzyme-substrate complexes
Enzymes work using a `lock and key' or `induced fit' action
In the `lock and key' model, the substrate is complementary to the shape of the active site
In the induced fit model, the substrate and active site are not fully complementary, so when
the substrate binds, it causes the enzyme to mould around it.…read more

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Carbohydrates are made of C, H and O
A Monomers is called a monosaccharide, dimers are called disaccharides and a polymer is
called a polysaccharide
The general formula for a monosaccharide (or hexose sugar) is
Glucose + glucose makes maltose, glucose + fructose (pentose
sugar) makes sucrose and glucose + galactose makes lactose
Monosaccharides form disaccharides by a condensation reaction
(removal of water, e.g.…read more

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This is in most eukaryotic cells, and is bound by a double membrane-the pores allow
molecules to move between the nucleus and cytoplasm
Ribosomal RNA is also made in the nucleolus
The endoplasmic reticulum is the continuation of the outer nuclear membrane-it is made up of
flattened sacs called cisternae
It is described as `rough' because of the ribosomes on the outside, and is therefore involved
in protein synthesis (smooth is involved in lipid synthesis)
Ribosomes are made of a large and a small subunit,…read more

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Light microscope Colour image can be seen by the Cannot resolve less than 0.…read more

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The addition of other proteins creates a fluid-mosaic structure
Soluble lipids and small molecules (such as oxygen) can pass through unassisted through the
bilayer, and so molecules must therefore be a liquid, gas or in solution
Transport proteins consist of channels, pumps and carriers
The carbohydrates are involved in cell recognition-in tissue formation and in
antigen/antibody interaction
Molecules move across the membrane by diffusion (simple and facilitated), osmosis and
active transport
Diffusion is the passive movement of substances down a concentration gradient ­from a high…read more

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For example in sodium-potassium pumps, the sodium ions bind to the specific binding site,
which triggers the hydrolysis of ATP-causing the phosphate group to become attached,
which causes the protein to change shape and the sodium ions are released
On the other side, a potassium ion binds, causing the phosphate group to become detached,
changing the shape and releasing the potassium
In the small intestine, the absorption of
ions increases the water potential of the
lumen, meaning water is absorbed into
the cells by osmosis…read more


Tamara Abrahams

Amazing notes thank you so much

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