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OCR Gateway B Module B1: Understanding Organisms

Blood pressure:

Measured in mmHg
It can be measured in two ways: systolic and diastolic. Systolic is the pressure when the heart beats, and diastolic is the pressure between heart beats
Increased by: stress, alcohol, smoking, being overweight
Reduced by: exercise, balanced diet
High pressure can make blood vessels burst, damaging the brain (a stroke). It can also damage the kidneys
Low pressure can cause dizziness, fainting and poor circulation of blood around the body

Fitness:

The ability to do physical activity
Measures of fitness: flexibility, stamina, agility, speed. Some measures are more effective than others in different situations

Health:

Being free of disease (bacteria/viruses)

Smoking:

Carbon monoxide in cigarette smoke combines with haemoglobin in the blood (instead of oxygen)
Nicotine also directly increases heart rate

Heart disease:

Restricted blood flow to the heart
Caused by saturated fat, which creates cholesterol (plaque) in arteries
Plaques make blood clots and thrombosis more likely

Balanced diets contain:

Carbohydrates (simple sugars such as glucose)
Proteins (amino acids), which are used for energy only when fats and carbohydrates are not available
Fats (fatty acids, glycerol)
Water
Fibre
Minerals (e.g. iron)
Vitimins (e.g. vitimin C)

Fat and carbohydrates are stored in the body:

Carbohydrates are stored in the liver as glycogen or are converted into fats
Fats are stored around the skin and around organs

EAR (daily requirement of protein):

Calculated with: 0.6 x body mass (kg)
Too little protein can cause kwashiorkor

BMI (body mass index)

Calculated with: Mass (kg) ÷ Height (m)²
25-30 is overweight, under 20 is underweight, 30+ is obese, 20-25 is normal
However, the BMI does not take into account other factors, such as muscle mass
Being overweight is linked to arthritus, heart disease, diabetes and breast cancer

Amino acids:

Some can be converted into other amino acids
Meat proteins are first class proteins, which contain all essential amino acids

Infectious diseases:

Caused by pathogens
Examples: athletes foot (caused by fungi), flu (caused by viruses), cholera (caused by bacteria)
The body defends against pathogens by:
- The skin provides a barrier
- Blood clotting prevents easy entry of pathogens
- They are trapped by mucus in airways
- Hydrochloric acid in the stomach kills pathogens

Malaria:

Caused by protozoan called plasmodium, which is a parasite (it feeds on another living organism)
Feeds on red blood cells, through their vector: mosquitoes. Vectors are not affected by the disease

Cancers:

Malignant, with fast, uncontrolled growth
However, benign tumour cells (eg warts) are harmless

Antibodies:

Produced by white blood cells, lock onto antigens on pathogens, destroying them
Create active immunity
Each pathogen has different antigens

Immunity:

Memory cells provide long-term immunity
Antivirals slow down a pathogen's development
Micro-organisms can become resistant to antibiotics, which are being overused - resistant MRSA has thrived

Trials:

Blind trials are where the patient testing the medication does not know if it is real or a placebo
In double blind trials, the doctor doesn't know either

The eye:

Cornea reflects light to the retina's light receptors. Some are sensitive to different colours
The len's shape changes for different distances, this is called accomodation
With distant objects, the cilary muscles relax and suspensory ligaments tighten
With near objects, the cilary muscles tighten and suspensory ligaments relax - the opposite
Long sightedness (close objects out of focus) is caused by the image being focused behind the retina, corrected by convex lenses
Short sightedness (far objects out of focus) is caused by the image being focused in front of the retina, corrected by concave lenses
Both can be corrected with corneal surgery, but this may move the focal point too far in a direction so eyesight still might not be perfect
Organisms with monocular vision have a wider field of view but poorer distance judgement
Organisms with binocular vision have a better judgement of distance but smaller field of view

Nerve cells (neurones):

Nerve impulses pass across the axon in each neurone. Neurones are adapted by being very long and having branched endings to pick up impulses
A reflex action has the following process:
stimulus -> receptor -> sensory neurone -> central nervous system -> motor neurone -> effector -> response
There is a gap between neurones, the synapse. A transmitter substance diffuses across the gap and binds with receptors on the next neurone
A spinal reflex has the following action: receptor -> sensory neurone -> relay neurone -> motor neurone -> effector

Drugs:

Depressants (eg alcohol, solvents) block transmission of nerve impulses across synapses by binding with the molecules in the membrane, slowing brain activity
Stimulants (eg nicotine, MDMA, caffeine) cause more neurotransmitter substances to cross synapses, increasing brain activity
Other types of drug: painkillers (eg aspirin, which block nerve impulses), performance enhancers (eg anabolic steroids, which enhance muscles), hallucinogens (LSD, which distort what is seen and heard)

Long-term effects on the body:

Smoking can cause mouth, throat, oesophagus and lung cancer
Particulates in the smoke collect on cilia in the tranchea, bronchi and bronchioles
Smokers cough caused by these particulates irritating the epithelial lining, and mucus not being moved
Liver damage (cirrhosis) caused by the liver breaking down lots of toxic substances like alcohol by enzymes, this breaking down creates toxic products

Homeostasis (control of internal conditions):

Constant internal environment
Uses negative feedback controls
37 °C optimal for enzymes
High temperature can cause heat stroke and dehydration. Both can be fatal
Sweating increases heat transfer, requires body heat to evaporate
Low temperature can cause hypothermia - a slow pulse and violent shivering. Can be fatal
Blood temperature is monitored by the hypothalamus gland in the brain
Vasoconstriction is the narrowing of blood vessels, causing less heat transfer, reducing heat loss in cold conditions
Vasodilation is the widening of blood vessels, causing more heat transfer, so the body can lose more heat in hot conditions
Body temperature can be measured with a clinical thermometer, sensitive strips, digital recording probes or thermal imaging

Blood sugar levels:

Controlled by the insulin hormone, which is produced in the pancreas
Type 1 diabetes is caused by the body not producing insulin
Type 2 diabetes is caused by the body producing too little insulin and is controlled by diet
Insulin is stored in the liver and regulates blood sugar level, by converting glucose into glycogen
Insulin given to type 1 diabetics needs to vary based on diet and activity

Plant responses:

Phototropism is the response to light
Geotropism is the response to gravity
These can be negative or positive
Auxins are hormones, made in the root and shoot tips
- More auxin is found on the darker side of shoots, which causes curvature towards the sun

Uses of plant hormones:

Selective weedkillers, rooting powder, seed dominancy, delaying/accelerating fruit ripening

Inheritance:

Inherited features can be dominant or recessive
Alleles are different versions of genes
There is a debate of nature vs nurture in intellegence, sporting ability and health
Number of chromosomes varies by organism, humans have 23 pairs
There are two sex chromosomes which determine the sex of an organism: females have XX and males have X and Y
Genetic variation is caused by mutations (random changes) and the rearrangement of genes during the formation of gametes (sex cells)
Each characteristic has 2 alleles:
- If you have two of the same alleles, eg two for brown eyes, this is homozygous and you will definitely have brown eyes
- If you have two different ones, you are heterozygous, one will be dominant and one recessive (weaker). Recessive genes have no effect
- Most inherited disorders are caused by faulty genes, most of which are recessive. Examples include red-green colour blindness, sickle cell anaemia and cycstic fibrosis
The genotype is the alleles present for a particular characteristic, e.g. BB
The phenotype is the characteristic from the inherited information, e.g. 'brown eyes'

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