Biology Revision - BTEC Applied Science

• Cells


  Building blocks of living things
• Microscopes


  Magnify images so it is easier to see cells and their structures more clearly
• Magnification


  The number of times larger the image appears compared to the actual size
• Resolution


  Ability to distinguish between objects that are close together
• Electron Microscopes


  • A beam of electrons is fired at the specimen, electrons are detected and an image is produced
  • High(er) magnification (x500 000) and resolution (0.1nm)
  • Specialist training is required
  • Can only view dead specimen
• Light Microscope


  • Uses visible light and magnifying lens to observe small objects
  • Can observe live specimens
  • Specialist training not required
  • Easier to use
  • Low(er) magnification (x500) and resolution (200nm)
• Prokaryotic Cells


  Single-celled organisms, simple structures and do not have a nucleus or any membrane-bound organelles
• Eukaryotic Cells


  Make up multi-cellular organisms such as plants and animals, complex cells with a nucleus and membrane-bound organelles
• Animal Cell (eukaryotic)


  • Plasma membrane - Protects the cell from its surroundings, regulates movement of substances in and out of the cell
  • Cytoplasm - Where metabolic reactions take place
  • Nucleus - Surrounded by a double membrane (envelope) and contains genetic information, controls/regulates metabolic cell activity
  • Nucleolus - Region of dense DNA and protein, makes ribosomes
  • 80S ribosomes - Site of protein synthesis
  • Rough Endoplasmic Reticulum - A series of single, flattened sacs enclosed by a membrane, has ribosomes on the surface, proteins are made here
  • Smooth Endoplasmic Reticulum - A series of single, tubular sacs made of membrane, lipids are made here
  • Vesicles - Small, membrane-bound sacs, transports and stores substances in the cell
  • Golgi Apparatus - A series of single, curved sacs enclosed by a membrane, modified proteins and packages them in vesicles for transport
  • Lysosomes - Enclosed by a single membrane, contains digestive enzymes, destroys old organelles and pathogens, breaks down waste material
  • Centrioles - Two hollow cylinders arranged at right-angles to each other, makes the spindle in cell division
  • Mitochondria - Site of respiration
• Plant Cell (eukaryotic)


  • Chloroplasts - Where photosynthesis occurs
  • Vacuole - Stores water and other substances, maintains turgor in the cell
  • Cell Wall - For support and protection
  • Tonoplast Membrane - Controls movement of molecules in and out of the vacuole
  • Amyloplasts - Stores starch
  • Middle Lamella - Sticks cells together
  • Plasmodesmata and Pits - Allows communication between one cell and another
• Bacterial Cell (prokaryotic)


  • Cell Wall - Made of long-chained molecules (made up of sugar and amino acids) called peptidoglycan, supports/protects the cell
  • Plasmids - Double-stranded DNA in a circular structure, contains additional genes that aid in the bacterium's survival
  • Slime Capsule - Polysaccharide layer outside the cell wall, prevents the cell from drying out as it is hydrophilic, helps cells to stick to surfaces
  • 70S Ribosomes - Makes proteins
  • Nucleoid - Single circular length of DNA Is folded, DNA carries all essential information, controls cellular activity
• Gram-positive (purple)


  No outer membrane, thick peptidoglycan cell wall to absorb the stain
• Gram-negative (pink)


  Outer membrane, thin cell wall
• Gram-negative bacteria are more resistant to antibiotics than gram-positive bacteria. This is because gram-negative bacteria have a cell wall with an outer membrane, which protects them from the antibiotic.
• Palisade Cell


  • Cylindrical shaped, pack tightly in the upper part of a leaf, contain many chloroplasts near to the edge of the cell, have a large vacuole, long, narrow gaps between cells to allow air to circulate for gas exchange, have a thin and transparent cellulose cell wall for easy gas diffusion
• Root Hair Cell


  • Found in the epithelium (surface cells) near the root tip, main function is to collect water and mineral ions from the soil, cell membrane is thin and partially permeable to water which enables easier water absorption, short distance across the cell wall increases the rate of diffusion, contain many mitochondria to help supply energy for ATP of minerals from the soil into the cell
• There are no chloroplasts in root hair cells as they cannot get light meaning photosynthesis cannot take place.
• Differentiation


  The process by which cells become specialised for a particular function from stem cells
• Sperm Cell


  • Delivers genetic information to the egg, contains many mitochondria to supply the energy needed for the movement
• Egg Cell


  • Contains a nucleus which houses the genetic material, Zona Pellucida (jelly layer) - Outer protective layer/membrane of the egg to stop more than one sperm fertilising the egg, Corona Radiata - Consists of two or three layers, supplies vital proteins
• Red Blood Cells


  • Mature red blood cells have no nucleus or other organelles, so there is room for more haemoglobin, small, round and biconcave disc, this allows more oxygen and carbon dioxide to diffuse into the haemoglobin, their size and shape also allow them to squeeze through narrow blood vessels
• White Blood Cells


  • Job is to protect the body against infections, diseases and foreign invaders, can change shape to squeeze through gaps, different types of white blood cells with different functions, lymphocytes contain T and B cells, neutrophils have a flexible and mobile nucleus with several lobes, can squeeze between cells in the capillary wall and travel to areas of infection, neutrophils are phagocytic which means they engulf pathogens then destroy them
• Similarities between neutrophils and lymphocytes


  • Both have nuclei/mitochondria
  • Both involved in defence against pathogens, travels through the plasma membrane
• Differences between neutrophils and lymphocytes


  • Lymphocytes - T and B cells, T cells send signals to the B cells to produce antibodies, T cells then destroy the infect cells, smaller than neutrophils
  • Neutrophils - Flexible and mobile - can squeeze through (narrow) capillaries, most common type of WBC (than lymphocytes)
• Tissue


  Made up of collections of specialist cells which perform specific functions
• Types of muscle tissue


  • Skeletal muscle - found attached to bones
  • Cardiac muscle - found only in the heart
  • Smooth muscle - found lining the walls of hollow organs e.g., stomach
• Epithelial Tissue


  • Epithelial cells line any surface that is in contact with the external environment, may also line the surface of internal organs, such as the lungs, two types in the lungs - squamous epithelium and columnar epithelium
• Columnar Epithelium


  • Made up of column-shaped (tall) ciliated cells with hair-like structures called cilia covered the exposed cell surface, the upper airway (trachea and bronchi) is mainly lined with ciliated columnar epithelium cells which have a lot of mitochondria, the cilia move mucus away from the lungs in order to trap and prevent any inhaled particles from causing infection, goblet cells are column shaped and produce mucus
• Squamous Epithelium


  • Very flat and thin with egg-shaped nuclei which makes them ideal when rapid diffusion is necessary, often only one cell thick and very good for surfaces where diffusion occurs as in the lungs (alveoli) where oxygen and carbon dioxide are exchanged
• Chronic Obstructive Pulmonary Disease (COPD)


  Includes several conditions and is more common in smokers than non-smokers, because substances in smoke damages the lungs
• Chronic Bronchitis


  Inflammation of the airways in lungs and squamous epithelium thickens, excessive secretion of mucus, severe coughing to try and clear the mucus, blocks the airways which makes breathing difficult
• Emphysema


  Usually develops because of long-term damage to the lungs from breathing in harmful substances such as cigarette smoke, the membranes of the alveoli break apart and create abnormally large air spaces in the lungs, decreased surface area for gas exchange to take place, so less oxygen can enter the body and less carbon dioxide can leave the body
• Skeletal Muscle


  • Striated, forms bundles of muscle fibres which are surrounded by protective membranes, can contract under voluntary control to product movements
• Blood Vessels


  • Arteries - Takes blood away from the heart
  • Veins - Takes blood to the heart
  • Capillaries - Tiny blood vessels
• Endothelial tissue


  Lines the inside of blood vessels, made up of a single layer of flat, long cells which are orientated lengthways in the direction of blood flow, function is to provide a smooth surface so that blood flows easily over them
• Endothelium reduces friction and allows for smooth flow of blood. Damaged endothelial cells release substances that cause blood vessels to constrict.
• Capillaries


  • Only have a single layer of endothelium to allow for easy exchange of nutrients and oxygen into the tissue and the removal of waste products
• Arteries and Veins


  • Made of the same tissue but in different proportions, have an outer layer of connective and elastic tissue (thicker in veins to prevent collapse), middle layer composed of smooth muscle, connective and elastic tissue (thicker in arteries to maintain blood pressure), inner layer is made up of endothelial tissue
• Atherosclerosis


  Fatty deposits (atheroma) can block an artery directly or increase its change of being blocked by a blood clot (thrombosis)
• Atherosclerosis


  Fatty deposits produce plaques (also known as atheroma) in the artery walls which reduce the lumen diameter and eventually blocks the artery completely or increases its chance of being blocked by a blood clot (thrombosis), when plaque forms, this has the potential to cause a rupture of the protective membrane over the plaque which can then lead to major problems such as a heart attack or stroke