GCSE Biology

Cell specialisation and differentiation.

• What is cell differentiation?
• Living organisms can be made of a single cell, such as bacteria, or they can be multicellular ike plants,animals and fungi. Unicellular organisms, like bacteria, are able to perform all life functions with one singe cell. They can metabolize, transport molecules, and produce within this one cell. Organisms made of more tha one cell need many different types of cells to carry out the same life processes. Each of these special types of ell has a different structure that helps it to perform that specific function. Humans have different types of cells with different jobs, such as blood cells that carry out oxygen , and nerve cells that transmit signals throughout the whole body. Cell differentiation is the process by which cells become specialised in order to perform different functions.
• Even multicellular organisms begin as just a single cell. Getting from one single cell to billions of specialised cells that perform different functions is a process that happens with the regulation of DNA. It can also be influenced by factors in the environment.

Microscopy

• Microscopy is the technical field or using microscopes to view samples and objects that cannot be seen with the unaided eye (objects that are not within the resolution range of the normal eye). Light microscopy is the general term used for any type of microscopy where the light is transmitted from a source on the opposite sides of the specimen to the objective lens. Usually the light is passed through to a condenser to focus it on the specimen to get maximum illumination. After the light passes through the specimen it goes through to the objective lens to magnify the image of the sample and then to the oculars where the enlarged image is viewed.
• Light microscopy techniques have significantly developed over the past 20 years and now provide an indispensable tool to study molecular events at subcellular level in order to gain temporal and spatial information at high resolution. To achieve optimal results, it is essential to carefully plan and carry out microscopy based experiments, which requires the understanding or at least the basics of cell biology, sample preparation and fluorescence light microscopy.

Blood

• Blood is bodily fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste ( metabolic waste or excretes are substances left over from excretory processes which cannot be used by the organism, and therefor must be excreted. This includes nitrogen compounds, water Co2, phosphates and sulphates.) products away from those same cells. When it reaches the lungs, gas exchange occurs when carbon dioxide is diffused out of the body and into the pulmonary alveoli (in the lung, the pulmonary alveoli are spherical outcroppings of the respiratory bronchioles and are the primary sites of gas exchange with blood) and oxygen is diffused in to the blood. This oxygenated blood is pumped to the left side of the heart in the pulmonary vein ( a vein carrying oxygenated blood from the lungs to the left atrium of the heart.) and enters the left atrium. From here it passes through the mitral valve (the valve between the left atrium and the left ventricle of the heart, which has two tapered cusps.) through the ventricle and taken all around the body by the aorta (the main artery of the body, supplying oxygenated blood to the circulatory system. In humans it passes through over to the heart from the left ventricle and runs down in front of the backbone..) Blood contains antibodies, nutrients, oxygen and much more to help the body function the way it does.

Diffusion

• Diffusion is the net movement of particles from an area of high concentration to an area of low concentration. All living things rely on diffusion for two reasons, to take in substances and to get rid of waste products. There are four ways to speed up diffusion, short diffusion distance, high temperature, large surface area and steep concentration gradient.
• If there is a big difference in the concentration between the areas, diffusion will take place quickly. Many particles will move randomly towards the area of lower concentration. However if there is only a small difference in concentration between two areas, the net movement by diffusion will be quite slow. The number of particles moving into an area of low concentration by random movement will only be slightly bigger than the number of particles leaving the area.

Osmosis

• Osmosis is a special case of diffusion. Osmosis is the movement of water particles from a dilute to a more concentrated solution through a partially permable membrane that allows water to pass through. Differences in the concentration of solutions inside and outside a cell cause water to move inside or outside of the cell by osmosis.
• Key words:
• partially permeable - allowing only certain substances to pass through.
• osmosis- the net movement of water particles from an area of high concentration to an area of low concentration on a steep gradient.
• Investigating Osmosis:
• You can make model cells using bags made or partially permable membrane. You can see what happens to them if the concentrations of the solutions inside or outside the 'cell' change.

Active transport

• Active transport is the movement of molecules across a cell membrane from a region of high concentration to a region of low concentration in the direction against some gradient of other obstructing factor ( often a concentration gradient.) In active transport, particle move against the concentration gradient, and therefor require an input of energy from the cell.

Tissues and organs

• All living things are made up of cells. One kind of cell makes one kind of tissue. Only nerve cells can make nerve tissue. Our bodies have many different types of cells because we have we have many different types of tissues. Tissues are large groups of cells all doing the same job . The difference kinds of tissues are sectioned into four groups. Muscular tissue, which can contract to bring about movement. Glandular tissue, which can produce substances such as enzymes and hormones. Epithelial tissue, which covers some parts of the body. Cardiac muscle tissues make our hearts. Organs are groups of tissues that work together to do a job. Our skin is made or hair tissue, oil and sweat gland tissues, nerve tissues, blood tissue, and many other tissues to make the organ called skin. Our bodies are made of cells, tissues and organs. The cell is the smallest unit of life. All living things are made up of cells. One kind of cell makes one kind of tissue. Only nerve cells can make nerve tissue. Our bodies have many different types of cells because we have we have many different types of tissues. Tissues are large groups of cells all doing the same job .

Enzyme #1

• An enzyme is a biological catalyst that speed up a chemical reaction that take place in a cell, enzymes occur in all organisms. Enzymes are made of protein molecules, and so are made up of amino acids. Most enzymes contain between 100 and 100,00 amino acids. An example of a protein is a an enzyme. The shape of an enzyme id important because it has a direct effect on how It catalyses a reaction. At the active sight the substrate fits into the enzymes active site in the same way that a key would fit into a lock.
• Collision theory:
• Enzyme controlled reaction happen because the substrates "collide" or hit the enzyme. By increasing the chances of collision we increase the chances of a reaction happening. The collisions need to have enough energy for the reaction to occur. This is called "activation energy". The enzymes lower the amount of activation energy that a reaction needs.
• Factors affecting enzymes:
• Factors that affect the rate of a reaction include
• *temperature
• *pH
• *enzyme concentration
• *substrate concentration
• 8surface area
• *pressure
• All enzymes work best at only one particular temperature and pH this is called the optimum temperature.

Enzyme #2

• If the temperature and pH changes sufficiently beyond ad enzymes optimum, the shape of the enzyme irreversibly changes, The affects the shape of the active site and means the enzyme will no longer work. When this happened the enzyme is denatured.
• Low temp= low rate
• Enzymes have too little kinetics energy and move slowly.
• Optimum temp= high rate
• Enzymes have a lot of kinetic energy and move quickly.
• Hugh temp= low rate
• Heat brakes the bonds maintaining the territory structure of the enzyme.
• Low pH= Low rate
• Acidity breaks the bond maintaining the territory structure of the enzyme.
• What are enzymes used for in the digestive system?
• Enzymes are used to break down large insoluble substances into small soluble substances.
• Protien:
• Perpsin and trypsin are proteas enzymes and are found in the stomach.
• Fats:
• Fats are made up of molecules, fatty acid chains and a glycerol "backbone" Fats are broken down by lipase enzymes. Lipase enzymes are found in he pancreatic juices and small intestine

Enzyme #3

• Carbohydrates:
• Carbohydrates such as starch are large molecules formed from many sugars molecules. Amylase is the main carbohydrate enzyme, and is found in saliva, the pancreas and the small intestine.
• When food enters the stomach in stimulates the secretion of hydrochloric acidic (HCI) from the stomach wall. HCI increases the acidity of the stomach to about pH2- the optimum pH for stomach enzymes.
• Digestive enzymes are found in the small intestine are damaged by strongly acid pH. The liver produces bile, which is stored in the gall bladder and released into the small intestine. Bile neutralizes the acidic contents coming from the stomach, creating alkaline environment that the intestinal enzymes need to work.

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