GCSE BIO - Organisation

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The basics

Cells - the basic building blocks that make up all living organisms (the foundation for everything) 

Tissues - groups of similar cells that work together to carry out a specific function

Organs - groups of different tissues that work together to carry out a specific function

Organ Systems - groups of organs that work together to carry out a specific function

Organ systems work together to make entire Organisms.

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Enzymes

Enzymes - biological catalysts that speed up useful reactions e.g in digestion. They're all large proteins that have a specific shape

Catalysts speed up reactions without being used up

The Lock and key Model:

Enzymes have an active site, which has a very specific shape. This allows enzymes to bind (stick) to the substance involved in a reaction. This binding speeds up the reaction. If the substance doesn't fit the enzyme's active site, the reaction will Not be catalysed. 

Conditions: Enzyme acitivty is affected by temperature and pH

If temp too low: Enzymes have less kinetic energy, move less and slower, rate of reaction decreases. If temp too highbonds holding the active site together Break, the active site Changes Shape, can no longer catalyse reactions; the enzyme is Denatured.

If pH too low or high: the same bonds holding the active site together get broken; the enzyme is Denatured. Most enzymes have an optimal pH, usually 7.

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Digestive Enzymes

Amylase is a Carbohydrase, an enzyme that digests carbohydrates. Amylase breaks down Starch into simple sugars. Amylase is made in the: Salivary Glands; Pancreas and Small intestine.

Proteases digest proteins into amino acids. Proteases are made in the: Stomach (this protease is called pepsin); Pancreas and Small intestine.

Lipases digest lipids into glycerol and fatty acids. Lipids are made in the Pancreas and Small intestine.

Digestion is essential as big molecules like starch protein and lipids need to be broken down into smaller, soluble substances before they can be easily absorbed into the bloodstream.

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Digestive system:

Mouth Mechanical digestion (Chewing), Chemical digestion, amylase from Salivary glands

StomachMechanically Churns food with muscular walls. Produces protease and Hydrochloric acid, which kills bacteria and maintains the right pH for protease to work.

Small intestine - Produces amylase, protease and lipase to complete digestion and absorb digested food into the blood.

Large intestine - Absorbs excess water from food.

Rectum - where the faeces are stored before they are ejected through the anus.

LiverProduces Bile which neutralises stomach acid, making conditions better for other enzymes to work. Bile emulsifies fats, it inreases their surface area; easier to digest them.

Gall Bladder - where Bile is stored, until it;s released inton the small intestine.

Pancreas - Produces Protease, Amylase and Lipase.

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The Lungs

STRUCTURE: The Lungs are located in the Thorax and separated from the lower part of the body by the diaphragm. Air travels through the mouth, down the trachea, into each lung through the bronchi, which spilt into smaller tubes called bronchioles, finally ending at small air sacs called Alveoli.

Alveoli - small air sacs, specialised for efficient gas exchange between the lungs and the blood. The alveoli have a very large surface area to Volume ratio and there are millions of them.   They have a very thin cell membrane next to the bloodstream and they have a good blood supply, which maintains a high concentration gradient between the Alveoli and the blood. 

All these factors increase the rate of diffusion of Oxygen from the alveoli into the blood. At the same time Carbon Dioxide diffues out of the blood and into the alveoli.

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The Heart

Humans have a Double Circulatory System, because blood passes through the heart twice before it is pumped to the rest of the body. The first time: deoxygenated blood passes through the right ventricle of the heart to get to the lungs to become Oxygenated. Then this oxygenated blood comes back through the left ventricle, to be pumped to the rest of the body.

The Heart is made mostly from muscular tissue. It has valves to prevent blood backflow. There are 4 chambers involved in pumping blood:

Deoxygenated Blood flows into the Right Atrium from the Vena Cava (a vein). The Right Atrium contracts, blood flows into the Right Ventricle. The Right Ventricle contracts, blood flows through the Pulmonary Artery into the lungs to become oxygenated. Oxygenated blood flows from the lungs into the Left Atrium, through the Pulmonary Vein. The Left Atrium contract, blood flows into the very thick Left Ventricle. The Left Ventricle contracts, and oxygenated blood is pumped to the rest of the body, through the Aorta,

The natural resting heart rate is controlled by cells in the right atrium, that act as a pacemaker by emitting electrical impulses that cause the heart to contract regularly.

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Blood Vessels

Arteries - Carry blood AWAY from the heart. Since they carry Oxygenated blood which has a high pressure, the muscular walls are strong and have elastic fibres so they can contract and stretch. Arteries have a smaller Lumen than Veins (hole that blood flows through).

Vein- Carry blood INto the heart. They carry blood at lower pressures, so have less muscular walls that aren't as thick as artiery walls. They have Valves to prevent the backflow of blood and they have a bigger Lumen than arteries, to help blood flow.

Capillaries - Involved in exchange of materials at tissues e.g. Oxygen. They are very small, only one-cell thick to increase the rate of Diffusion. They have permeable walls to allow diffusion to occur.

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Blood

Blood - a Tissue consiting of Plasma, in which there are Red Blood Cells, White Blood Cells and Platelets.

Red Blood Cells: their purpose is to carry Oxygen from the lungs to all the cells in the body. The have a Biconcave shape (like a doughnut). This gives them a large Surface area to volume ratio, to increase the rate of diffusion. They have no Nucleus, which gives them more space for Oxygen.

White Blood Cells: defend againt Pathogens. They Engulf and Digest pathogens in Phagocytosis, they produce Antibodies which kill Pathogens, and Antitoxins which neutralise toxins.

Platelets: are small fragments of cells with no nuclei. Their function is to Clot blood, to prevent bleeding out from wounds and to stop harmful micoorganisms from getting in.

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Coronary Heart Disease

Coronary Heart Disease is when the Coronary arteries that supply the blood to the heart get blocked by layers of fatty material. This restricts blood flow and therefore Oxygen to the heart - increasing the risk of a Heart attack.  You need to Evaluate Treatment options:

Stents - Tubes of mesh wiring, inserted into arteries, keeping them open and maintaining blood flow. Effective for a long time and have a short recover time from surgery. However, Risk of infection and other complications from Surgery and developing a Blood clot near the stent.

Statins - Drugs that reduce the amount of 'bad' Cholesterol, which increase the risk of CHD, in the bloodstream. So Statins reduce the risk of CHD and may help prevent other diseases. However, they have to be taken regularly for a long-time; they can have negative side effects.

Artificial Heart: used to keep people waiting for a transplant alive. Metal won't be rejected by immune system, but surgery can have complications. 

Faulty/Leaky Valves: Lead to Backflow of Blood. Biological valves can be Rejected, but Mechanical Valves may malfunction. Surgery required either way; can cause blood clots.

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Health and Disease

Health is the state of physical and mental well-being. Both Communicable and Non-communicable Diseases often cause ill-health. Other factors like diet, stress and life situations can also affect health.

Different Diseases can interact with each other. Defects with your immune system make you more likely to suffer from infectious diseases like influenza. Immune reactions can trigger allergic reactions e.g. skin rashes, asthmaCancer can be triggered by viruses. Severe physical ill health can lead to ill mental health e.g. depression.

Risk Factors (things that increase risk) for Non-communicable Diseases: Smoking - C.H.D, Lung Cancer and health issues for unborn babies. Obesity - type 2 Diabetes. Alcohol - liver disease, brain function and health issues for unborn babies. Carcinogens (Cancer causing chemical) - increase the risk of Cancer.

There are human (death) and financial costs of Non-communicable diseases. E.g. Research and treatments are expensive. Illness can prevent people working, reducing their income.

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Cancer

Cancer is caused by uncontrolled cell division. This causes a tumour to form. 2 types:

Benign - not cancerous and can't spread but could become dangerous. 

Malignant - tumours spread to neighbouring healthy tissues and form secondary tumours. They can also spread through the bloodstream. They're Dangerous and Cancerous.

Risk Factors: 

Smoking - biggest preventable cause; strongly linked to Lung cancer

Obesity - Linked to many different cancer, also a preventable cause

UV exposure - UV radiation increases the risk of skin cancer; people in sunnier climates

Viral Infection - Viruses can increase risk of Cancer, e.g. Hepatitis B for liver cancer

Genetics - Can inherit faulty genes or have mutations that increase the risk of cancer

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Plant Tissues

Epidermal tissues - cover plant with a waxy cuticle which reduces water loss by evaporation. The Upper epidermis is Transparent, to allow photosynthesis to occur.                               

Palisade Mesophyll - where photosynthesis occurs, contains many chloroplasts to facilitate this.

Spongy Mesophyll - contains big air spaces, that increase the rate of diffusion of gases. 

Xylem and Phloem -  form a Vascular bundle to Transport Water and Food.                   

Meristem tissue - found at the tips pf the roots and shoots; able to Differentiate into any plant cell.

Lower Epidermis - contains many Stomata, which allow Carbon Dioxide to siffus into the leaf. The stomata are controlled by Guard cells, this helps reduce water loss.

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Transpiration & Translocation

Translocation: Phloem tubes Transport Food (dissolved sugars) made from photosynthesis in the leaves to the rest of the plant. They're made from columns of elongated living cells with small pores in the end walls, which allow cell sap to flow through. Transport in both directions.

Transpiration: Xylem tubes are made of dead cells. They're Hollow tubes and strengthened by a material called Lignin. They carry Water up the plant, from the roots to the leaves. This is called the transpiration stream.

Transpiration is the loss of water from a plant. Factors affecting the Rate:                            Light intensity - If LOW, then stomata close; reduces water loss

Temperature - If HIGH, particles have more energy to evaporate; increases water loss.

Air Flow - Stronger wind flowmaintains a high concentration gradient between leaf and air, increased rate of Diffusion; increases water loss. 

Humidity - If air around leaf is drier, there's a high concentration gradient between leaf and air, increased rate of Diffusion; increases water loss. If air humid; decreased diffusion; less water loss.

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