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73 Cards in this Set
- Front
- Back
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What are the elements that form a lipid? |
Elements in lipids are carbon, hydrogen and oxygen. |
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What are the properties of lipids? |
Large, non-polar molecules (don’thave a + or – charge) that are insoluble in water but dissolve easily inorganic compounds. |
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What are the important groups of lipids called? x2 |
The important groups of lipids are triglycerides and phospholipids |
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What is a triglyceride made up from? |
Triglycerides are made of 3 fatty acids and 1 molecule of glycerol. |
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What makes up glycerol? |
3 hydroxyl groups (-OH), each of which can combine with a fatty acid forming a triglyceride. |
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What makes up a fatty acid? |
Fatty acids are made up of a carboxylic acid group (-COOH) and a long hydrocarbon chain of varying length. The hydrocarbon chain can be unsaturated or saturated |
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What is meant by the term a saturated hydrocarbon chain? |
Saturated is a hydrocarbon chain which has no double bonds between the carbon atoms |
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What is meant by the term an unsaturated hydrocarbon? |
An unsaturated hydrocarbon is a chain which has one or more double bonds between the carbon atoms |
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What is the structure of a saturated fatty acid? |
No double bonds! |
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What is the structure of an unsaturated fatty acid? |
Double bonds! |
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What is the structure of glycerol? |
3 carbon 3 oxygen 8 hydrogen |
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What reaction causes a triglyceride form? What molecule is formed? How many of this molecule is formed? |
A triglyceride is a condensation reaction resulting in 3 molecules of water being formed |
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What are the bonds called which form between the –OH group of the glycerol and the –COOH of the fatty acids? What type of bonds are these? |
Ester Bonds Strong Covalent bonds |
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Why are triglycerides not classified as polymers? |
A polymer has many monomers joined together but a triglyceride is not made of a single type of monomer but 2 molecules |
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Draw a diagram to show the formation of a triglyceride. |
Glycerol 3 Fatty Acid molecules 3 water molecules Triglyceride |
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What are the biological roles of triglycerides? |
- Storage of energy - Insulation - Protection |
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What is the structure and properties of triglycerides related to their function? |
They have a high ratio of energy storing carbon-hydrogen bonds to carbon atoms so are an excellent source of energy. They have a low mass to energy ratio, making them good storage molecules because so much energy can be stored in a small volume. They are large, non polar molecules, insoluble in water so they have no osmotic effect and do not affect the water potential in cells. |
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What are phospholipids? What is one of the fatty acids substituted for? |
Phospholipids are lipids In which one of the fatty acids is substituted for a phosphate group. |
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What are phospholipids composed of? |
A polar / hydrophilic (attracts to water) head(glycerol and phosphate) Non- polar / hydrophobic (repels water) tail (fatty acids) |
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Draw the structure of a phospholipid. |
P = phospholipid |
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What is the test for lipids? |
Ethanol Emulsion Test: - Add ethanol to the sample to be tested in a dry clean test tube - Shake to dissolve any lipid in sample - Add water to the sample and shake gently - A milky white colour indicated the presence of a lipid |
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What are the membrane functions? |
Control the transport of substances into and out of the cell/organelle -Such as glucose, water, carbon dioxide and oxygen Receptor site to recognise chemicals which need to enter the cell or organelle Separate off the cell from the environment and the different reactions of the cell by compartmentalisation. |
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What is the structure of the membrane? What are the lipids found in cell membranes called? |
The membrane is partially permeable Doesn't let water-soluble, charged or polar substances pass through them easily Acts as a barrier to separate cell from the environment. The lipids found in cell membranes are called phospholipids. |
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What is the structure of a phospholipid? |
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What do phospholipids form in water? Where do the hydrophobic tails point towards and where does the hydrophilic heads point? What does this separate in a cell? |
In water these form a two-layered structure, called a bilayer, where the hydrophobic tails all point towards each other and the hydrophilic heads point out into the water. In a cell the membranes separate the watery cytoplasm from the water outside. |
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What does the bilayer act as a barrier to? What molecules does it allow to pass through it? |
This bilayer actsas a barrier to polar / water-soluble / large molecules It will allow non-polar / lipid soluble / small molecules to pass through |
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What do the protein molecules floating in the bilayer form? |
A fluid mosaic structure |
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What are the proteins called that are in one layer of the membrane? |
Extrinsic Proteins |
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What are the proteins called that go across the whole membrane? |
Intrinsic Proteins |
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Which substances would be able to move through hydrophilic channels? |
Polar molecules such as ions & glucose |
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What is the function of intrinsic proteins? |
Transport as: Channels and Carriers |
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What are some of the functions of extrinsic proteins? |
Enzymes- e.g. maltase Mainly glycoproteins: Receptors- for binding to hormones etc. (role in cell signalling) Antigens- for cell recognition (note: last two are mainly roles of glycoproteins) |
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What is a glycoprotein? What are the functions of glycoproteins in the membrane structure? |
Short, branching carbohydrate chains attached to proteins in the membrane. The function is to allow the proteins to act as receptors or antigens. |
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What is a glycolipid? What is the function of a glycolipid in the membrane structure? |
Glycolipid is made up of a carbohydrate covalently bonded to a lipid. They act as recognition sites, help to maintain the stability of the membrane and help cells attach to one another, so forming tissues. |
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What are the functions of cholesterol in the membrane structure? |
Cholesterol restricts the movement of othermolecules making up the membrane Increases strength and stability ofmembranes by making them less flexible. It helps to prevent the loss of water and dissolved ions from the cell. |
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In the fluid-mosaic model: What is meant by the term fluid? What is meant by the term mosaic? |
Fluid: All the different molecules can move around. Mosaic: There are different types of molecule The proteins and carbohydrates ‘float around’ in the phospholipid bilayer. |
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What can the molecules in the membrane do? |
Move sidewaysabout the membrane Leave the membrane to join vesicles in the cell’s cytoplasm Join the membrane from vesicles in the cytoplasm This fluidity means that cells are able to change their shape (e.g. phagocytes) |
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What is meant by the term polar? |
The molecules which move only slowly through the phospholipid bilayer |
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What are the 2 transport processes that are passive? What does passive mean? |
Diffusion and Osmosis Do not require energy in the form of ATP |
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Which transport process is an active process? What is meant by the term active? |
Active Transport Requires the cell to provide energy in the form of ATP. |
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What is diffusion? |
Diffusion is the movement of substances From a region of their higher concentration to a region of their lower concentration Down a concentration gradient. |
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As a result of diffusion what do substances reach when they are evenly spread although still moving? |
Dynamic Equilibrium |
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What is this process called? |
Diffusion Dynamic Equilibrium |
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What are the 3 main factors which affect the rate of diffusion? |
1) Surface Area 2) Thickness of the exchange surface / diffusion pathway 3) The concentration gradient |
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How does surface area effect the rate of diffusion? |
The greater the surface area of the membrane over which diffusion occurs, the greater the rate of diffusion |
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How does the thickness of the exchange surface / diffusion pathway effect the rate of diffusion? |
The thinner the surface, the faster the rate of diffusion (shorter diffusion pathway) |
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How does the concentration gradient effect the rate of diffusion? |
The steeper the gradient, the faster the rate of diffusion |
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How does 1) The size of the diffusing molecule 2) Temperature 3) Water solubility / polarity effect the rate of diffusion? |
1) The smaller the diffusing molecule, the faster the rate of diffusion 2) The higher the temperature, the faster the rate of diffusion 3) Non-polar molecules diffuse faster than polar ones |
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To increase diffusion rate we need to: |
Maximise the surface area Maximise the concentration difference Minimise the thickness of the exchange surface |
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State Fick's Law: |
Surface area x difference in concentration Divided by Length of diffusion pathway |
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Which molecules can diffuse across the membrane easier and faster? Which molecules can't diffuse across the membrane? |
Small, non-polar molecules e.g. O2 and CO2 rapidly diffuse across a membrane. Small, polar molecules, such as water diffuse across, but much more slowly. Charged particles (ions) cannot diffuse across a membrane, even if they are very small. |
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Describe this graph to show how the concentration gradient effects rate of diffusion: |
The channel / carrier proteins are occupied. The rate of reaction if limited by the number of carrier proteins So limits the amount of substrate that can move down a concentration gradient. |
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What are the main points about facilitated diffusion? |
Specific Molecules move down a concentration gradient but may be limited to the number of channel and carrier proteins Passive so doesn't require energy in the form of ATP Moves charged, polar molecules e.g. ions |
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What is osmosis? |
The movement of water Across a partially permeable membrane Down a water potential gradient i.e. from higher to a lower water potential. |
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What does this diagram show? |
Osmosis |
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How is the partially permeable membrane for osmosis made? |
By channel proteins |
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Which diagram shows high water potential? Which diagram shows low water potential? |
A) High Water Potential C) Low Water Potential |
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What is meant by high water potential? |
A high concentration of water is either a very dilute solution of something like glucose or pure water. Such a solution has a very high water potential. |
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What is meant by low water potential? |
A low concentration of water molecules is a concentrated solution of a solute such as glucose, i.e. there is much less water. Such a solution is described ashaving a low water potential |
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What is a hypertonicsolution? |
A Concentrated solution or low water potential solution |
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Osmosis: What happens to the animal cell if the solution is hypertonic? |
A concentrated salt solution will have a lower water potential than the cell So water leaves the cell by osmosis. This causes the cell to shrink (or crenate). |
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What is a hypotonic solution? |
A dilute solution or pure water, with high water potential |
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Osmosis: What happens to the animal cell if the solution is hypotonic? |
A dilute solution or pure water will have a higher water potential than the cell So water enters the cell by osmosis. The cell swells and eventually bursts, when the pressure inside the cell becomes too great. The bursting of cells in this way is known as osmotic lysis |
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What is a isotonic solution? |
A solution with the same concentration and waterpotential |
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Osmosis: What happens to the animal cell if the solution is isotonic? |
An isotonic solution has the same water potential as the cell. When placed in an isotonic solution, there is no net osmotic movement of water (there is no water potential gradient) and so the shape and size of the cell remains the same. |
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Osmosis: What happens to the plant cell if the solution is hypertonic? |
A concentrated salt solution will have a lower water potential than the cell so water leaves the cell cytoplasm and vacuole by osmosis. This causes the cytoplasm to shrink away from the cell wall leaving gaps between the cell membrane and the cell wall, which is filled with the concentrated solution of salt. This is called plasmolysis. |
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Osmosis: What happens to the plant cell if the solution is hypertonic? |
A dilute solution or pure water will have a higher water potential than the cell and so water enters the cell by osmosis. The cytoplasm and vacuole gains some water, but because of its high tensile strength of the cellulose cell wall the cell will not burst. The cell is said to be turgid. |
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Osmosis: What happens to the plant cell if the solution is isotonic? |
When placed in an isotonic solution, there is no net osmotic movement of water ( there is no water potential gradient ) So the shape and size of the cell remains the same. |
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Active Transport: Describe the parts labelled in the diagram: |
1) Energy from cell required to achieve carrier protein. 2) Transported substance binds with carrier protein. 3) Carrier protein changes shape, releasing transported substance into the cell. |
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Active Transport: |
Movement against a concentration gradient Requires energy in the form of ATP energy Needs specific proteins |
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What is meant by endocytosis? |
Importing particles into vesicles |
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What is meant by exocytosis? |
Exporting materials into vesicles. |
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When is endocytosis and exocytosis used? What is the process involved? |
Large amounts of material. Making of a container after endocytosis which are called vesicles which contain digestive enzymes. This is to transport solids or liquids into and out the cell. |
