Bio- Cells

• The active site is the part of an enzyme where substrates bind.
• Active transport is the movement of materials against a concentration gradient. It requires the use of energy and takes place through protein channels in the cell membrane.
• Aerobic respiration occurs in the mitochondria and is when glucose is broken down in the presence of oxygen to form carbon dioxide, water, and lots of ATP (energy).
• The equation for aerobic respiration is: glucose + oxygen -> carbon dioxide + water + 36 ATP
• Anaerobic respiration occurs in the cytoplasm and is when glucose is broken down into lactic acid and ATP (energy) without oxygen.
• The equation for anaerobic respiration is glucose -> lactic acid + 2 ATP
• ATP is adenosine triphosphate, the energy currency of the cell
• Cellular respiration is the breakdown of glucose to release energy in the form of ATP
• A chloroplast is an organelle that is the site of photosynthesis
• Chlorophyll is the pigment in chloroplasts that absorbs light to drive the photosynthesis reaction
• A competitive inhibitor is a molecule that prevents the substrate from binding with the active site
• The concentration gradient is the difference in the concentration of a substance between two areas
• Cristae are folds in the inner membrane of a mitochondrion that increase the surface area
• The cell membrane forms the boundary that separates the living cell from its non-living surroundings.
• The cell membrane is semi-permeable which means that allows some substances to pass through but prevents the passage of others.
• The cell membrane is made up of a phospholipid bilayer. Each phospholipid has a head which is hydrophilic (attracted to water) and a tail which is hydrophobic (repelled by water). The hydrophilic heads of the bilayer form the surfaces of the membrane.
• Passive transport does not require energy. Diffusion, facilitated diffusion and osmosis are all methods of passive transport.
• Diffusion is the net movement of molecules from regions of high concentration to areas of low concentration along a concentration gradient.
• Facilitated diffusion is the movement of specific molecules down a concentration gradient with the aid of a protein channel. Large molecules, polar molecules, and ion use channel membranes to enter the cell.
• Protein channels are highly specific, meaning they can only transport one kind of molecule through the cell membrane.
• Osmosis is the net movement of water across a semi-permeable membrane from an area of higher concentration to an area of low water concentration.
• Small cells have a much greater SA:V ratio, allowing material to diffuse throughout the entire volume of the cell quickly and efficiently.
• Tonicity is the measure of the concentration of solutes on either side of the membrane.
• A hypertonic solution contains a low concentration of water.
• A hypotonic solution contains a high concentration of water.
• Isotonic solutions have the same water concentration.
• When a plant cell is placed in a hypertonic solution and loses water, the cell membrane can pull away from the cell wall and the cell will shrink and lose its shape. We say that the cell becomes plasmolysed.
• When a plant cell is placed in a hypotonic solution and swells, the cell becomes firm/turgid.
• When an animal cell takes on too much water it can burst or lyse.
• When a cell shrinks and shrivels, it becomes flaccid.
• Carrier proteins are a type of active transport where molecules bind to a specific carrier protein which changes shape to then release the molecules to the other side of the cell membrane
• Cytosis is the process in which molecules are transported into or out of a cell by the folding of the cell membrane into vesicles. It does not involve specific carrier proteins.
• Exocytosis is when molecules are moved from inside the cell to outside the cell, using membrane-bound vesicles.
• Endocytosis is when molecules are transported from the outside of a cell to the inside of a cell.
• Pinocytosis is a type of endocytosis when liquids are transported into a cell.
• Phagocytosis is a type of endocytosis when large particles of 'food' are transported into cells.
• Enzymes are biological catalysts that speed up chemical reactions in living organisms. They have an active site, which joins or breaks specific substrates. They are a type of globular protein, made up of a long chain of amino acids that are folded into a very specific 3D shape.
• An enzyme can only catalyse one kind of reaction because the active site of an enzyme is highly specific.
• Enzymes speed up chemical reactions because they lower the activation energy (the amount of energy needed to start a chemical reaction) needed for the reaction to occur.
• A catabolic reaction is the breaking down of a substrate