AQA combined science trilogy Biology paper 1 Biology

AQA combined science trilogy Biology paper 1

Biology paper 1 Cell biology Organisation Infection and response Bioenergetics

Cell biology v. Cells v. Diffusion v. Microscopy v. Osmosis v. Cell differentiation and specialization v. Active transport v. Chromosomes and mitosis v. Exchanging substances v. Stem cells v. Exchange surfaces

Cell biology Controls the activity in the cell. Contains the Nucleus DNA (chromosomes and genes). Carries the instructions for making new cells. A jelly like liquid where most the chemical Cytoplasm reactions take place. Controls what comes in and out of the cell (gas Cell membrane exchange) The site of respiration, oxygen is used here to Mitochondria release energy for the body. Protein synthesis. All the proteins needed in the Ribosomes cell are made here. Found in green parts of a plant, they contain Chloroplasts chlorophyll. Chlorophyll is needed to absorb sunlight during photosynthesis.

Cell biology Eukaryotic and prokaryotic cells § All eukaryotic cells have a cell membrane, cytoplasm and genetic information in a nucleus. § All prokaryotic cells consist of cytoplasm, a cell membrane surrounded by a cell wall. The genetic material is not in a nucleus, it forms a single DNA loop. They can contain one or more extra small rings of DNA called plasmids. Bacteria are examples.

Cell biology Light microscopes Electron microscopes § Light microscopes magnify up to about x 2000, and have a resolving power of about 200 nm. § Electron microscopes magnify up to about x 2 000, and have a resolving power of around 0. 2 nm. 1 km = 1000 m 1 m = 100 cm 1 cm = 10 mm 1 mm = 1000µm 1µm = 1000 nm 1 nm = 0. 000 001 m (1 x 10 -9 m)

Cell biology Differentiation § In the early stages of development the embryo cells are unspecialised (called stem cells). § Cells can then become specialised due to some genes being switched on and some off. § Specialised cells will only then divide to make that specific type of cell. § Some cells can differentiate throughout their lives.

Cell biology Cell Division § Chromosomes are found in pairs § Body cells divide to make new cells for growth, repair, replacement or in some cases asexual reproduction. § The process of making identical daughter cells is called mitosis. § During mitosis, a copy of each chromosome is made. § The cell divides in 2 to form 2 new cells. § Each new cell has a nucleus containing a copy of every chromosome from the parent cell.

Cell biology § Stem cells are cells that can differentiate into different types of cell. § Stem cells can be obtained from embryos, umbilical cords and adult bone marrow. § Stem cells can be cultured in labs and encouraged to grow into different types of specialised cell. § It is hoped that stem cells could be used to make new nerve cells that could then be implanted into patients suffering from spinal damage. This could mean that paralysed patients might regain the use of limbs. § The use of stem cells has ethical issues. Some people think that embryos should only be used to create new lives rather than being used to produce replacement.

Cell biology Diffusion Active Transport § Net movement of particles from an area of high concentration to an area of lower concentration. § Movement of particles from an area of low concentration to an area of higher concentration § No energy involved § Requires energy § Bigger the difference in concentration and higher temperature the faster the rate of diffusion § Allows plant root hair to absorb mineral ions from the soil § Dissolved substances such as glucose, urea and gases are transported this way. § Allows sugar molecules to be absorbed from lower concentrations in the gut

Cell biology Osmosis § Movement of water from a high water concentration (dilute solution) to a low water concentration (concentrated solution) through a partially permeable membrane § No energy involved § Isotonic – concentration is the same inside and out § Hypertonic – concentration outside the cell is higher than inside the cell § Hypotonic – concentration outside the cell is lower than inside the cell § Important for plants to maintain turgor Exchanging materials § Single celled organisms have relatively large surface area : volume ratio § Exchange surfaces usually have large surface area, thin walls, and an efficient blood supply

Cell biology - Exam practice

Organisation v. Cell organization v. Cardiovascular disease v. Enzymes v. Health and disease v. Enzymes and digestion v. Risk factors for non communicable diseases v. Food tests v. The lungs v. The heart v. Blood vessels v. Blood v. Cancer v. Plant cell organisation v. Transpiration and translocation v. Transpiration and stomata

Organisation A tissue is a group of cells with similar structure and function. Ø Muscular tissue – contracts to cause movement Ø Glandular tissue – contains cells that release chemicals such as enzymes and hormones Ø Epithelial tissue – covers the outside of the body and internal organs Ø Epidermal tissue – covers and protects the surface of plant cells Ø Mesophyll tissue – contains lots of chloroplasts for photosynthesis Ø Xylem tissue – carry water and minerals in plants Ø Phloem tissue – carry dissolved food in plants Plant Organs - Include stems, roots and leaves. Organs - An organ is made of tissues. One organ may contain several types of tissue Organ Systems - Organ systems are groups of organs that perform a particular function. Digestive System Ø Mouth – contains teeth that physically start to breakdown food Ø Salivary glands – release saliva that contains enzyme to start chemical breakdown of food Ø Stomach – releases enzymes to start breakdown of proteins and HCl to make the right p. H. Muscular wall starts to churn food Ø Small intestine – main area of digestion and absorption of soluble nutrients Ø Large intestine – absorption of water and faeces storage

Check point therapy REVIEWHow can I improve my learning on Cell organisation RED PEN Therapy/Review BIOLOGY : ENZYMES, BLOOD VESSELS, HEART, COMMNUNICABLE AND NON-COMMUNICABLE DISEASES (CANCER, TUMOURS]

Organisation Enzymes Ø Enzymes speed up chemical reactions in organisms. They are known as biological catalysts. Ø Enzymes lower the activation energy needed by reactions and are protein molecules made up of long chains of amino acids. Ø The chains are folded to make an active site. Ø The substrate (thing being broken down) needs to fit exactly into the active site for the break down to occur. Ø Enzymes are specific. They will only breakdown 1 type of substance. Ø Enzymes work best at specific temperatures and p. H. Ø High temperatures and the wrong p. H can change the shape of the active site. This means that the substrate won’t fit the active site exactly, so break down can’t occur. Ø Enzymes used for reactions in organisms like respiration, digestion and photosynthesis and in some industrial processes. Ø Metabolism is the sum of all chemical reactions in the body

Organisation Digestive enzymes work outside of cells. Uses of Products of Digestion Carbohydrates Ø Glucose – respiration Ø Broken down by carbohydrases (amylase) to make glucose. Ø Amino acids – making proteins for use in the body Ø Made in the salivary glands, pancreas and small intestine. Ø Fatty acids and glycerol – source and store of energy, making cell membranes and hormones Ø Work in slightly alkaline conditions in the mouth and small intestine. Proteins Ø Broken down by proteases to make amino acids. Ø Made in the stomach, pancreas and small intestine. Fats Ø Broken down by lipases to make fatty acids and glycerol. Ø Made in the pancreas and small intestine Ø Enzymes in the stomach work best in acidic conditions. Hydrochloric acid is released into the stomach. Ø Enzymes in the small intestine work best in alkaline conditions. Bile is made in the liver, stored in the gall bladder and released into the small intestine. Ø Bile also emulsifies fats. This means the fats are physically broken into smaller droplets. This increases the surface area for lipase enzymes to act upon.

Organisation ØCarbohydrates are made up of units of sugar § Simple sugars are carbohydrates that contain only one or two sugar units – they turn blue Benedict’s solution brick red on heating § Complex carbohydrates contain long chains of simple sugar units bonded together. Starch turns yellow-red iodine solution blue-black ØLipids consist of three molecules of fatty acids bonded to a molecule of glycerol. The ethanol test indicates the presence of lipids ØProtein molecules are made up of long chains of amino acids. Buiret reagent turns from blue to purple in the presence of proteins.

Organisation Exchange in the Lungs Ø Occurs in the alveoli in the lungs Ø O 2 diffuses into the blood Ø CO 2 diffuses from the blood Ø Alveoli are adapted for maintaining effective rate of gas exchange by: Ø Having a large surface area Ø Being thin which provides a short diffusion path Ø Efficient blood supply – each has its own capillary. This moves the diffusing gases away and maintains a diffusion gradient Comparison of inhaled and exhaled air § Inhaled – N 2 ≈ 80%, O 2 = 20%, CO 2 = 0. 04% § Exhaled – N 2 ≈ 80%, O 2 ≈ 16%, CO 2 ≈ 4%

Organisation The Heart Flow Through The Heart/Lung System § Double circulatory system (blood pumped to the lungs, then blood pumped around the body) § Vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium →left ventricle → aorta § Heart consists of 4 chambers – left atrium, right atrium, left ventricle, right ventricle § Ventricles contract and force blood out of the heart § Valves make sure that blood flows in the right direction through the heart § Right side of the heart contains deoxygenated blood § Left side of the heart contains oxygenated blood

Organisation Blood vessels Veins Arteries § Carry blood back to the heart from the organs § Carry blood away from the heart to other organs § Contain deoxygenated blood except for the pulmonary vein (from the lungs) § Contain oxygenated blood except for the pulmonary artery (to the lungs) § Blood at high pressure so the walls are thick layers of muscle and elastic tissue so the vessels don’t burst § Blood at lower pressure so thinner walls § Contain valves to prevent backflow of blood Capillaries § Form networks through organs to connect arteries to veins § Very thin walls to allow fast diffusion

Organisation The blood consists of: - § Plasma – yellow liquid that carries other components of the blood, CO 2, urea and soluble digested food (glucose and amino acids) § Red blood cells – contain haemoglobin which transports O 2 around the body. They are biconcave in shape to increase surface area to volume ratio so diffusion occurs faster. They don’t have a nucleus so there is more space to carry O 2. § White blood cells – involved in the immune system. They destroy microorganisms by either producing antibodies or digesting them. § Platelets – small cell fragments that are involved with clotting blood at the site of wounds

Organisation Helping the heart § Stents can be used to keep narrowed or blocked arteries open § Statins reduce cholesterol levels in the blood, reducing the risk of coronary heart disease § Damaged heart valves can be replaced using biological or mechanical valves § Artificial pacemakers are electrical devices used to correct irregularities in the heart rhythm § Artificial heart are occasionally used to keep patients alive while they wait for a transplant.

Organisation Health and disease § Health is a state pf physical and mental well-being § Diseases, both communicable and non-communicable, are major causes of ill health § Other factors include diet, stress and life situations may have a profound effect on both mental and physical health. § Different types of diseases may and often do interact.

Organisation Non-communicable diseases Risk factors § A non-communicable disease cannot be passed form one person to another. § Smoking can cause cardiovascular disease including coronary heart disease, lung cancer and lung diseases such as bronchitis and COPD. § Risk factors are aspects of a person’s lifestyle or substances present in a person’s body or environment that have shown to be linked to an increased rate of disease. § A fetus exposed to smoke has restricted oxygen, which can lead to premature birth, low birthweight and even stillbirth. § For some non- communicable diseases, a causal mechanism for some risk factors has been proven but not for others. § Obesity is a strong risk factor for type 2 diabetes. § Diet affects your risk of developing cardiovascular and other diseases directly though cholesterol levels and indirectly through obesity. § Exercise levels affect the likelihood of developing cardiovascular disease. § Alcohol can damage the liver and cause cirrhosis and liver cancer. § Alcohol can cause brain damage and death. § Alcohol taken in by a pregnant woman can affect the development of the unborn baby.

Organisation ØBenign and malignant tumours result from abnormal uncontrolled cell division ØBenign tumours form in one place and do not spread to other tissues ØMalignant tumour cells are cancers. They invade neighbouring tissues and may spread to different parts of the body in the blood where they form secondary tumours. ØLifestyle risk factors for various types of cancer include smoking, obesity, common viruses and UV exposure. There is also genetic risk factors for some cancers.

Organisation Tissues and organs in plants § Plant tissues are collections of cells specialised to carry out specific functions § The roots, stem and leaves form a plant organ system for the transport of substances around a plant. § Palisade mesophyll – lots of chloroplasts for photosynthesis § Spongy mesophyll – big air spaces and large surface area for diffusion of gases § Stomata – allow gases to move in and out of the plant Xylem vessels - Transport water and mineral ions from the root to the stems and leaves Phloem vessels - Transport dissolved sugars from the leaves to the rest of the plant, including the growing regions and storage organs

Organisation Evaporation and transpiration Transpiration § Plants have stomata that allow them to obtain CO 2 from the atmosphere § Is the loss of water vapour from the surface of leaves § CO 2 enters the leaf by diffusion § H 2 O is lost through the stomata § Leaves have a flat, thin shape and internal air spaces to increase the surface area for diffusion § Occurs more rapidly in hot, dry, windy or bright conditions § Most of the water and mineral ions needed by a plant are absorbed by the root hair cells which increase the surface area. § Water enters into the roots by osmosis § Mineral ions enter the roots by active transport

Organisation – Exam practice

Infection and response Communicable disease Viral, fungal and protest diseases Fighting disease Vaccination Drugs Developing drugs

Infection and response Pathogens and Disease Infection Methods § Pathogens – microorganisms such as bacteria and viruses which cause infectious diseases. § Droplets – From coughs, sneezing and talking. E. g. colds, flu and TB § Communicable diseases are cause by microorganisms § Direct contact – touch of skin. E. g. impetigo, genital herpes § Bacteria – single-celled organisms that can cause diseases, but some are useful. Cause disease by either damaging body cells or by releasing toxins (poisons). § Contaminated food and drink. E. g. diarrhoea, salmonella. § Viruses – very small, always cause diseases because they take over body cells as they reproduce and damage and destroy cells. § Break in the skin. E. g. Hepatitis, HIV. Semmelweis § Semmelweis was a doctor who realised that hand-washing was important in preventing the spread of infectious diseases in hospitals. § His work wasn’t recognised at the time because bacteria and viruses weren’t known about so people didn’t think that something invisible passed from person to person. § The spread of disease can be prevented by simple hygiene measure, destroying vectors, isolating individuals and vaccines.

Infection and response Viral diseases Bacterial diseases § Measles is spread by droplet infection, it causes a fever, rash and can be fatal. There is no cure, but isolation and vaccination prevent the spread. § Salmonella is spread through undercooked food and poor hygiene. Symptoms include fever, abdominal cramps, diarrhoea and vomiting caused by the toxins produced by the bacteria. In the UK poultry are vaccinated against salmonella to control the spread. § HIV initially causes flu like symptoms, unless controlled with drugs the virus attacks the immune system. HIV is spread by sexual contact or the exchange of bodily fluids. Late stage HIV or AIDS occurs when the body’s immune system is so badly damaged it cannot cope with other infections. § Tobacco mosaic virus is spread by contact and vectors. It damages leaves and reduces photosynthesis. There is no treatment and spread can be prevented by field hygiene and pest control. § Gonorrhoea is a sexually transmitted disease, symptoms include discharge from the penis or vagina and pain when urinating. Treatment involves antibiotics, although many strains are resistant. Using condoms and limiting sexual partners prevents the spread. § There are few bacterial diseases of plants but agrobacterium tumefaciens causes galls.

Infection and response Fungal and protist diseases § Rose black spot is a fungal disease spread in the environment by wind and water. It damages leaves so they drop off, affecting growth as photosynthesis is reduced. Spread is controlled by removing affected leaves. § Malaria is caused by parasitic protists and is spread by the bite of female mosquitos. It damages blood and liver cells, causes fevers and shaking and can be fatal. Some drugs are effective if given early but protists are becoming resistant. Spread is reduced by preventing the vectors from breeding and by using mosquito nets to prevent people from being bitten.

Infection and response Defence Mechanisms White Blood Cells (wbc) § Skin – acts as a barrier against pathogens entering. § White blood cells can protect against disease in 3 ways. § Scabs – forms a seal over wounds to prevent pathogens from entering. § Ingesting microorganisms – some wbc take in pathogens, destroying them so they can’t make you ill. § Mucus – traps pathogens in the breathing system which can then be removed by the action of ciliated cells. It is swallowed into the stomach where the acid kills the pathogens. § Stomach acids – kills pathogens on food in the stomach. § Producing antibodies – Some wbc produce special chemicals called antibodies. These target particular bacteria or viruses and destroy them. You need a unique antibody for each type of pathogen. Once your wbc have produced antibodies once against a particular pathogen, they can be made quickly if that pathogen gets into your body again. § Producing antitoxins – Some wbc produce antitoxins. These cancel out the toxins released by pathogens.

Infection and response Immunity § Antigens – Unique proteins found on the surface of cells § Antibodies – Produced by white blood cells. Each antibody recognises a specific antigen. § Antibodies join up with antigens to destroy the pathogen. § People become immune to a disease either as a result of having the disease (white blood cells remember which antibody to make) or from being vaccinated. Vaccinations § Person is given a small dose of dead or inactive pathogen. § White blood cells produce antibodies for the antigens on the pathogen. § White blood cells then remember how to produce the antibodies if the body is infected by the live pathogen.

Infection and response Antibiotics and painkillers § Painkillers and other medicines treat the symptoms but don’t kill the pathogens that cause it. § Antibiotics cure bacterial diseases by killing the bacterial pathogens inside your body. § The use of antibiotics ahs greatly reduced deaths from infectious diseases. § The emergence of strains of bacteria resistant to antibiotics is a matter of great concern. § Antibiotics do not destroy viruses because viruses reproduce inside the cells. It is difficult to develop drugs that can destroy viruses without damaging body cells.

Infection and response Discovering drugs Developing drugs § Traditionally drugs were extracted from plants, for example, digitalis, or from microorganisms, for example, penicillin. § New medical drugs are extensively tested for efficacy, toxicity and dosage § Penicillin was discovered by Alexander Fleming from the penicillin mould. § Most new drugs are synthesized in pharmaceutical industry, but the starting point may still be from a plant. § New drugs are tested in the lab using cells, tissues and live animals § Preclinical testing of new drugs takes place in a lab on cells, tissues and live animals. Clinical trials use healthy volunteers and patients. Low doses are used to test for safety, followed by higher doses to test for optimum dose. § In double blind trials some patients are given a placebo.

Infection and response – Exam practice

Bioenergetics v. Photosynthesis and limiting factors v. The rate of photosynthesis v. Respiration and metabolism v. Aerobic and anaerobic respiration v. Exercise

Bioenergetics Photosynthesis – endothermic reaction § Carbon dioxide + water → glucose + oxygen § Light absorbed by chlorophyll in chloroplasts in the leaves. § Carbon dioxide diffuses in to leaf via stomata. § Water enters root hair cells and travels up to leaves by transpiration. Rate limited by: - § Temperature levels Light Carbon dioxide § Uses of glucose by the plant: § Respiration § Making starch for storage § Making cellulose for cell walls § Combine with minerals from the soil to make proteins § Making a food store for seeds

Bioenergetics Aerobic Respiration § Process in all living cells where stored glucose reacts with oxygen to release energy. It also produces carbon dioxide and water. § Aerobic respiration is an enzyme-controlled chain of reactions which occur in the mitochondria of cells. § The energy released by respiration is used for: § Making large molecules from smaller ones to make new cells § Making muscles contract (heart, breathing and movement). § Maintaining body temperature in mammals and birds § Muscle and sperm cells contain lots of mitochondria because they need to respire a lot as they use a lot of energy.

Bioenergetics The Effect of Exercise on the Body § The energy that is released during respiration is used to enable muscles to contract. § When you use your muscles, you need more glucose and oxygen and produce more carbon dioxide. § Body responses to exercise include: § An increase in heart rate, breathing rate and in depth of breathing § Glycogen stores in the muscle are converted to glucose for cellular respiration § The blood flow to the muscles increases § These act to increase the supply of glucose and oxygen to the muscle and remove more carbon dioxide.

Bioenergetics § If muscles work hard for a long time they become fatigued and don’t contract efficiently. § If they don’t get enough oxygen they will respire anaerobically. § Anaerobic respiration is respiration without oxygen. Glucose is incompletely broken down to form lactic acid. § The anaerobic breakdown of glucose releases less energy than aerobic respiration. § After exercise, oxygen is still needed to break down the lactic acid that has built up. § The amount of oxygen needed is known as the oxygen debt. § Anaerobic respiration in plant cells and some microorganisms such as yeast results in the production of ethanol and carbon dioxide.

Bioenergetics § Metabolism is the sum of all the reactions in the body § The energy transferred by respiration in cells is used by the organism for the synthesis of new molecules § Metabolism includes the conversion of glucose to starch, glycogen and cellulose. § Metabolism also include the formation of lipid molecules and the use of glucose and nitrate ions to form amino acids, which are used to synthesise proteins and breakdown excess protein to form urea.

Bioenergetics – Exam practice