B1 ocr gateway science

being fit is not the same as being health

• healthy means being free of any infections or diseases
• being fit is a measure of how well you can perform physical tasks
• fitness is not a precise term and can be measure in different ways
• fitness profiles are a measure of strength , speed and flexibility together with stamina
• stamina is a good measure of cardiovascular efficiency
• this is the ability of the heart to supply the muscles with oxygen
• it can be measured by measuring oxygen uptake and blood pressure during exercise.
• stamina is how long you can keep going

blood is pumperd around the body by contractions of the heart

• the blood is pumped around under pressure
• the pressure gets lower as it flows through the system
• blood pressure is highest when the heart contracts - this is the systolic pressure
• blood pressure is lowest when the heart relaxes - this is the dystolic pressure
• an average persons blood pressure is 135/85
• blood pressure can get higher due to - too much salt in the diet , being overweight, getting older and not doing lots of excercise. 
• Having high blood pressure could cause blood vessels to burst which leads to strokes, brain damage or kidney damage
• Having low lood pressure casues poor circulation which also causes dizziness,fainting  because the tissues arent getting enough food or oxygen that they need.

respiration is the process of releasing energy from glucose, which happens constantly in every cell

• aerobic respiration needs plenty of oxygen 
• its the time of repiration that takes place most of the time 
• the energy is used to do things build up larger molecules like proteins,contract muscles,maintain a steady body temperature
• aerobic respiration is the most efficient way of releasing energy from glucose.

anaerobic respiration doesnt use oxygen at all ,it occurs when you do really vigourous excercise

• lactic acid builds up in the muscles. which means after you stop respiring anaerobically you will have oxygen debt.
• this is because your muscles are still short of oxygen beacuse they havent been getting enough for a while. 
• so you need extra oxygen to supply the muscles and also to break down the lactic acid thats built up in the muscles.
• This means you have to keep breathing heard for a while after you stop excercising to repay the debt.
• GLUCOSE ---> LACTIC ACID (+ENERGY)
• the lactic acid is taken to the liver to be broken down so your heart rate has to stay high too
• anaerobic does not relases as much energy as much as aerobic respiration.
• Unfit people repire anaerobically quicker than fitter people

A balanced diet supplies all yout essential nutrients .

• Carbohydrates- provide energy
• Fats- provide energy and act as energy store and insulation
• Proteins- need for growth and repair of tissue
• Minerals- various functions
• Vitamins- various functions
• Water- replaces water loss

• carbohydrates are made up of simple sugars like glucose
• fats are made up of fatty acids and glycerol
• proteins are made from amino acids
• some amino acids cant be made by the body so have to be taken from the food you eat, these are called essential amino acids
• you can gain all essential amino acids by eating protein that comes from animals - these are called first class proteins.

energy and nutrient needs variation between people

a balanced diet isnt a set thing its different for everyone.The balance of different nutrients a person needs depends on different things

• Age - children and teenagers need more protein than adults for growth
• Gender- females need more iron to replace iron lost in menstruation
• Physical Activity - active people need more protein for muscle development

Some people choose to eat a different diet

• religious reasons - Hindus do not eat cows,  they believe they are scared
• Personal Reasons- vegetarians dont eat meat because its cruel to animals
• Health Reasons- some people are intolerant to certain foods like dairy

Eating too much or too little can lead to illnesses,diseases or disorders

• eating too much can lade to obesity
• this is 20% over recommended body weight
• Eating too little can also cause problems
• eating too little protein can cause a condition called kwashiorkor
• to work out the RDA of protein : RDA (g) = 0.75 x body mass (kg)
• some psychological disorders such as anorexia nervosa leads to being underweight

Body Mass Index indicates whether your under or overweight

• to calculate BMi              BMI= Body mass / (height)2
•  a normal Bmi is between 18.5-24.9
• BMI isn't always reliable, athletes have a lot more muscle which weighs more than fat so they appear overweight although they are not 
• an alternative is %body fat

Digestion is the breaking down of nutrients in your food so they can be absorbed

• Physical Digestion is chewing and churning your food
• Chemical Digestion is then breaking down molecules
• There are three main enzymes used

CARBOHYDRASE- break down carbohydrates into simples sugars, in the mouth and small intestine

PROTEASE- convert protein to amino acids in the stomach , where it is called   pepsin, and the small intestine

LIPASE-  convert fats to fatty acids and glycerol inside the small intestine.

• stomach acid lowers the pH of the stomach giving the right conditions 
• Bile is made in the liver and gall bladder and is used to emulsify fat to give a bigger surface area for lipase enzymes to work and also neutralises stomach acid

after the molecules are broken down the smaller molecules can then diffuse through the blood.

1) glucose and amino acids are small enough to diffuse into the blood plasma but the products of fat digestion cant get into the blood plasma so they diffuse out of the gut and into a fluid called lymph , inside the lymphatic system. From here they're emptied into the blood

2) the nutrients then travel to where they need to be and then diffuse out again. (eg glucose travels to muscles for respiration during exercise.

Infectious Diseases are caused by pathogens

There are four main types of pathogens

fungi- athletes foot
bacteria- cholera
viruses- flu
protozoa (single celled organisms)- dysentery

The symptoms of a infectious disease are caused by cell damage or by toxins produced by the pathogens

• Malaria is caused by a protozoan
• the protozoan is a parasite and the animal it affects is the host
• the mosquitoes are the vectors as they carry the diseases without catching it themselves

Your immune system deals with pathogens 

• once micro-organisms have entered your body they'll reproduce rapidly unless they are destroyed.Which is the job of the immune systems and the white blood cells are the biggest part of it.
• white blood cells travel around your body looking for micro-organisms.Once one is attacked , there three lines of attack.

1) CONSUMING THEM- white blood cells can engulf foreign cells and digest them

2) PRODUCING ANTITOXINS- this counters the effect of any poisons in bacteria

3) PRODUCING ANTIBODIES- when your white blood cells comes across a foreign antigen they'll start to produce proteins called antibodies. which lock on to and kill the new invading cells.The antibodies produced are specific to that pathogen so they wont lock onto any other pathogen.Antibodies are then produced rapidly and flow all around the body to kill all similar bacteria or viruses. 

immunisations stops you getting infections

• to avoid you being infected by infectious diseases or bacteria you can be immunised against some dieaseas
• immunisation involves injecting dead or inactive micro-organisms into the body.
• These carry antigens so even though they're harmless your body makes antibodies to attack them.
• If live micro-organisms of the same type appear after that they'll be killed immediately.

Active immunity is where the immunes system makes its own antibodies after being stimulated by a pathogen.it includes being naturally immune and artifically immune

Passive Immunity is where you use antibodies made by another organism. e.g antibodies are passed from mother to baby through breast milk.Passive Immunity is only temporary.

There are risks and benefits associated with immunisation

• immunisations stops people getting ill and if people are immunised it means diseases wont spread as quickly
• there can be short term side effects such as swelling or redness at the site of infection
• you cant have some vaccines if your already ill 
• and there are links between immunisations and other disorders

You can take antibiotics to get rid of bacterial infections

• antibiotics are drugs that kill bacteria and fungi
• they're useful for killing infections your body is having trouble with
• however they do not kill viruses like the flu or cold
• some bacteria are naturally resistant to antibiotics which is why a course of antibiotics always should be fully finished
• otherwise you leave the risk of the resistant bacteria to thrive and multiply , and get passed on to other people.

health disorders can be caused n various ways

• vitamin deficiency- scurvy caused by a lack of vitamin c
• mineral deffieciency- lack of iron causes a lack of haemoglobhin
• genetic inheritance- red-green colour blindness
• body disorders- diabetes and cancer

cancer is caused by body cells growing out of contol. Benign is where the tumours grows but stays where they are. Malignant is where the tumout grows and spreads to other sights

Drugs developed to treat disease need to be tested

• when drugs are tested they are tested by computer models, then on human tissues, then on animal in laboratories 
• after it is tested on humans in double blind trials
• a double blind trial is when there is a placebo drug ( a fake drug) but the doctor nor the patient doesn't no which is the placebo

drugs are substances which alter the way the body works

• some drugs are medically useful but some drugs are very harmful
• some people can get addicted to drug or a tolerance can be developed with some drugs

there are 5 main types of drugs

• DEPRESSANTS- decrease the brain activity ( alcohol and tamazepam)
• STIMULANTS- increase the brain activity ( nicotine, ecstasy, caffeine)
• PAINKILLERS- reduced the number of painful stimuli (aspirin, ibuprofen) 
• PERFORMANCE ENHANCERS- build muscle, allow harder train (anabolic steroids)
• HALLUCINOGENS- distort what is seen or heard by altering the pathways of nerve impulses (cannabis and LSD)
• illegal drugs - CLASS A heroin, LSD, ecstasy,CLASS B  cannabis and amphetamines ,CLASS C anabolic steroids and tranqulisers.

Alcohol is a depressant drug

• alcohols main effect is to reduce the activity of the nervous system
• it makes you feel less inhibited
• however its very poisonous
• can cause death of liver cells, cirrhosis, dehydration and poor co-ordination

Burning cigarettes produces four main things

• CARBON MONOXIDE- stops heamoglobhin being carried in oxygen
• NICOTINE- the stimulant drug which makes it addictive
• TAR- covers the ciliapreventing them moving bacteria and mucus
• PARTICULATES- accumulate in lung tissue causing irritation

Smoking causes all sorts of illnesses

• causes heart attacks , strokes, lung/throat cancer, emphysema, bronchitis, loss of lung function, oesophageal cancer, mouth cancer.

each part of the eye has a different job

• the cornea refracts light into the eye
• the iris controls how much light enters the pupil
• the lens focuses the light onto the retina 
• the retina is the light sensitive part and its covered in receptors called rods and cones which detect the light
• rods are more sensitive in dim light but cant sense colour
• cones are sensitive to colours but aren't good in dim light
• the optic nerve carries impulses from the receptor to the brain                                          

focusing on near and distant objects

• to look at distant object :ciliary muscles relax, suspensory ligament tightens, lens goes thing                                                       
• to look at a near objects : ciliary muscles contract, suspensory muscles slacken ,lens goes fat

• long sighted people are unable to focus on near objects - a convex lens fixes this. 
• short sighted people are unable to focus on faro object- a concave lens fixes this
• binocular vision is when your two eyes work together (can judge depth , cant see predators 
• Monocular vision is when each eye works speratly ( wider field of view, cant see distance,

neurones tansmit information around the body 

• the electrical impules are passed along the axon of the cell
• neurones have branched endings so they can connect with lots of other neurones. they have a sheath along the axon that acts as an electrical insulator which stops the impulse gettinjg lost. It also speeds up the electrical impulses. they're long which also speeds us the impulse

the connection between the two neurones is called a synapse

• the nerve signal is transferred by transmitter chemicals which diffuse across the gap
• these chemicals then set off anew electrical impulse in the nest neurone
• stimulant drugs increase the amount os transmitter chemicals at some synapses which increase the frequency of impulses along neurone 2
• depressants increase the amount of a different transmitter chemical at some synapses,which decrease the frequency of impulses set off along neurone 2.this decrease brain activity

the CNS co-ordinates information

the CNS consists of the brain and spinal cord.When you detect a change in your enbiroment your sensory neurones carry the information from receptors to the CNS. the CNS then send information to an effector along a motor neurone the effector the responds accordingally.Thejob of the CNS is to co-ordinate information

STIMULUS > RECEPTOR>SENSORY>CNS>MOTOR>EFFECTOR>RESPONSE

Reflex actions stop you injuring yourself

The nervous system uses electrical impulses to allow very quick responses. Reflex actions are automatic so they're even quicker. The conscious brain isn't invovled in a reflex arc.The sensory neurone joins to a relay neurone in the spinal cord which links directly to the motor neurone. Reflex actions often have a protective role.

STIMULANT>SENSORY>RELAY>MOTOR>REPSONSE

Homoeostasis is maintaining a constant internal environment

conditions in the body are kept steady by homoeostasis.For example: 

• Levels of CO2
• Water content
• Body temperature

Negative Feedback :changes in the environment tridder a reponse that conteracts the changes.This means that the internal environment tends to stay around the norm. It only works within limits.

body temperature is controleld by the brain                                                        When you're too hot: hair lires flat, sweat is producd so when it evaporates it transfers heat to the enviroment,blood vessels close to the surface fo the skin widen alowing more blood flow to the surface so more heat can radiate out (vasodilation). when your too cold hairs stand on end to trap and insulating layer of air.Very little sweat is produced.Blood vessels near the surface constrict (vaso constriction)You shiver and the movement generates heat.

Insulin controls blood sugar levels 

• levels of glucose in the blood must be kept steady.Changes in blood glucose are monitored by the pancreas, using insulin

blood glucose level too high = insulin is addded

blood glucose level too low = insulin is not added

• glycogen can be stored in the liver until the blood sugar levels get low again.Muscles have their own store.

Diabetes - the pancreas stops making enough insulin

• the result of this is that a persons blood glucose level can rise to a level that can kill them
• the problem can be controlled by either avoiding foods rich in carbohydrates, and injecting insulin into the blood at mealtimes
• the amount of insulin depends on the persons diet and activity level

Hormones promote sexual activity at puberty

• in women: extra hair on underarms, hips widen, development of breasts, egg release and start of periods.
• in men, extra hair on face and body,muscle development,penis and testicles enlarge,sperm production and deepening of voice

Hormones also control the menustral cycle

• oestrogen - causes the lining of the uterus to thicken and stimulates the release of an egg on day 14
• progesterone - maintains the lining of the uterus and when the levels fails the lining breaks down.
• Oestrogen and Progesterone are used as contraception- the pill contains both  
• FSH is used to stimulate egg production in fertility treatment

chromosomes are long lengths of DNA coiled up

•  gene is a short section of this DNA.
• Chromosomes are divided into different regions called genes and each gene codes for a different protein. Genes are chemical instructions 
• DNA is a long list of instructions into how to put an organism togehter and make it work
• proteins are important because they control most processes in the body
• cells make proteins by stringing amino acids together in a particular order
• genes simply tell us the correct order
• the DNA double helix is made up of two strands that are joined together by things called bases 
• there are four different kinds of bases - A,T,C,G
• we only use 20 different amino acids but in thousands of combinations
• genes control what proteins are made in a cell, this determines what type of cell it is 
• not every gene is used to produce a protein in every cell- some genes are switched off.

there are two sources of genetic variation

1) gamete formations - when reproductive cells split into two some of dads chromsomes are grouped with some from your mum.This shuffling leads to variation in the new generation.And in fertilisation you dont know which two gametes are going to join together .. causing more variation

2) Mutations. These are changes to the genetic code which will change the sequence of the DNA bases.This could stop the production of a protein or might mean a different protein is created instead.Mutations are normally harmful and might been the offspring develops abnormally or even die. However occasionally the mutations are useful and it can live in certain conditions whereas other die (Natural Selection) 

most features are determined by your genes and your enviroment

• health- genes can determine health but lifestyle can affect health 
• intelligence - can be inherited but also depends on upbringing 

genetic diagrams show the possible genes of offspring

• alleles are different versions of the same gene
• dominant alleles are the version of the characteristic that appears
• recessive alleales are the version do the characteritis that doesnt appear
• in genetic diagram the dominant allele is represented by a capital and the recessive by a small letter
• homozygous means have two alleles the same (CC , cc) 
• heterozygous means having two different alleles (Cc)