The Plasma Membrane The plasma membrane is a semi-permeable lipid bilayer found in all cells that controls water and certain substances in and out of the cell. Function of the Plasma Membrane 1. Protects the cell. 2. Separates the intracellular components from the extracellular environment. 3. Controls what enters and exits the cell Necessities for the Movement of Substances across the Plasma Membrane 1. To transport nutrients into the cell. 2. For gases exchange 3. To excrete metabolic waste. 4. To maintain the pH value and ionic concentration of the cell. Substances In and Out through the Membrane pic] Permeability of the Phospholipids Bilayer The permeability of the phospholipids bilayer is determined by: 1. the size 2. the charge and 3. the polarity of the substances pass through it. [pic] Passive Transport – Simple Diffusion What is passive transport? Passive transport is the movement of substances across the cell membrane without the use of energy by the cell. During passive transport, substances move down their concentration gradient, hence no energy is required. Passive transports can happen through three different channels, namely 1. lipid bilayer 2. pore protein 3. carrier protein
What is diffusion? Diffusion is the movement of particles from a high density region to a low density region. No energy is needed and no membrane involves in diffusion. The Dynamic Equilibrium Diffusion will continue until the concentration in all region is the same. When this happen, we say it has reached the dynamic equilibrium. Factors Affecting the Rate of Diffusion (How fast diffusion happens) [pic] Particles that Move Through the Plasma Membrane Through Diffusion 1. Substances soluble in fat: fatty acid, glycerol, some vitamins (A,D,E,K) 2. Neutral particles: water, oxygen, carbon dioxide,
Example of Diffusion: Between alveoli and blood capillaries in the lung during gases exchange. Passive Transport – Osmosis What is Osmosis? Osmosis is the diffusion of a water through a semi-permeable membrane, from a solution of low solute concentration to a solution with high solute concentration. It is a physical process in which a solvent moves, without input of energy, across a semi-permeable membrane separating two solutions of different concentrations. Important Points: • It is the diffusion of water (normally) through a semi-permeable membrane. • It is from a dilute solution to a more concentrated solution.
Passive Transport – Facilitated Diffusion What is Facilitated Diffusion? Facilitated diffusion is the passive transport of substances across the plasma membrane with the help of transport proteins such as the channel protein and the carrier protein. Substances Pass through the Plasma Membrane through Facilitated Diffusion Particles undergo facilitated diffusion are the particles that cannot diffuse through the phospholipid bilayer such as 1. Large particles such as glucose, amino acids, proteins and nucleic acids 2. Some ions such as the sodium ions and chloride ions 2 Types of Transport Protein
Facilitated diffusion occurs through 2 types of transport protein, namely 1. Channel Protein 2. Carrier Protein [pic] Mechanism of Facilitated Diffusion Click on the links below to see how facilitated diffusion happen through the plama membrane of the cell. Concentration Gradient Facilitated diffusion happens down a concentration gradient. Similarities between Simple Diffusion and Facilitated Diffusion 1. Down the concentration gradient (From high concentration to low concentration) 2. No energy is required Differences between Simple Diffusion and Facilitated Diffusion [pic]
Active Transport What is Active Transport? Active transport is the movement of substances across the plasma membrane of cells against the concentration gradient (From lower concentration to higher concentration). Since it is against the concentration gradient, energy is needed in the process. Video below shows how particles are transported through the carrier protein in active transport. Take notes that the process only happens when the carrier protein receives energy from an ATP. Basic Requirements in Active Transport 1. Presence of the carrier protein 2. Presence of ATP (Adenosine Triphosphate)
Function of the ATP ATP is the source of energy in active transport. It supplies energy to the carrier protein to carry out the process. It is converted into ADP (Adenosine Diphosphate) after the reaction. Mechanism of Active Transport The video below shows how sodium ions and potassium ions are transported through the plasma membrane by a carrier protein. Examples of Active Transport: Intake of mineral ions by the root hairs of a plant. Types of Solution – Hypotonic What is Hypotonic Solution? Hypotonic solution is the solution that has higher water potential than the other solution.
Water Concentration and Solute Concentration of a Cell in a Hypotonic Solution Water concentration: Water concentration inside the cell is lower than outside the cell. Solute Concentration: Solute concentration inside the cell is higher than outside the cell. Effect of Hypotonic Solution on Animal Cell [pic] 1. If an animal cell such as red blood cell is placed into a hypotonic solution, water molecules is transported into the red blood cells by osmosis (as shown in the diagram above). 2. The red blood cells will inflate and finally burst because the thin membrane cannot withstand the high pressure inside the cell. . The red blood cells are said to undergo haemolysis. Effect of Hypotonic Solution on Plant Cell [pic] 1. When a plant cell is placed in a hypotonic solution, water molecules is transported into the cell by osmosis. 2. The water is then stored in vacuole causing it to expand and exerts pressure on the cell wall. This pressure is called turgor pressure. 3. The turgor pressure caused the plant cell to become firm or turgid. 4. The rigid cell wall prevents cell from bursting. Types of Solution – Isotonic What is Isotonic Solution? In isotonic solutions, both solutions have equal water potential.
Water Concentration and Solute Concentration of a Cell in a Isotonic Solution Water concentration and solute concentration are equal in both solutions. Effect of Isotonic Solution on Animal Cell [pic] 1. If an animal cell such as red blood cell is placed into a isotonic solution, amount of water molecules is transported into the red blood cells by osmosis is equal to the amount of water molecules transported out from the cell (as shown in the diagram above). 2. Therefore the amount of water in the cell remain unchanged. 3. The red blood cells maintain their shape.
Effect of Isotonic Solution on Plant Cell [pic] 1. When a plant cell is placed in an isotonic solution, solute concentration in the external solution is equal to the solute concentration in the cell sap. 2. Therefore the rate of diffusion of water into the cell is equal to the rate of diffusion of water out from the cell. 3. As a result, the shape of the cell remain unchanged. Types of Solution – Hypertonic What is Hypertonic Solution? Hypotonic solution is the solution that has lower water potential than the other solution. Water Concentration and Solute Concentration of a Cell in a Hypertonic Solution
Water concentration: Water concentration inside the cell is higher than outside the cell. Solute Concentration: Solute concentration inside the cell is lower than outside the cell. Effect of Hypertonic Solution on Animal Cell [pic] 1. If an animal cell such as red blood cell is placed into a hypertonic solution, water molecules is transported out from the red blood cells by osmosis (as shown in the diagram above). 2. The red blood cells will shrink due to the lost of water from the cell and probably die. 3. The red blood cells are said to undergo crenation . Effect of Hypertonic Solution on Plant Cell pic] 1. When a plant cell is placed in a hypotonic solution, water molecules is transported out from the cell by osmosis. 2. The vacuole and cytoplasm are then shrink due to lost of water. 3. The plasma membrane is pulled away from the cell wall.. 4. The process is called plasmolysed. Summary: [pic] Chemical Composition of the Cell [pic] Elements in the Cell An element is a substance cinsist of only one kind of atom. [pic] Major Elements Carbon (C), oxygen (0), hydrogen (H) and nitrogen (N) are the most common elements in a human body. There are the major elements of the body. Ultratrace Elements
Iron Importance of: Human: 1. Important component of haemoglobin in red blood cells. 2. Involved in the synthesis of red blood cells and respiratory enzymes. Plants: 1. Formations of chlorophyll. 2. As an electron carrier during photosynthesis and respiration. Trace Elements Some important trace elements found in a human body are: • Sodium (Na), • magnesium (Mg), • Calcium (Ca), • phosphorus (P), • potassium (K), • sulphur (S), ) and • chlorine (Cl) They make up about 4% of the mass of the human body Importance of the Trace Elements Sodium (Na) 1. Controls osmotic pressure in the cell. . Helps in the transmission of nerve impulses. Magnesium (Mg) Human: Help in protein synthesis. Plants: Needed in the synthesis of chlorophyll. Calcium (Ca) Human 1. Main component of the bones and teeth. 2. Triggers contraction of muscle cells. 3. Promotes blood clotting. Plants 1. Formation of cell walls (cellulose). 2. Regulates the semi-permeability of plasma membranes. Phosphorus (P) Human 1. Constituent of bones and teeth. 2. Helps in the contraction of muscle cells. 3. Formation of adenosine triphosphate (ATP). 4. Essential constituent of nucleic acids (DNA and RNA).
Plants 1. Involves in cell division. 2. Involves in the formation of ATP and nucleic acids. 3. Induces the formation of flowers and seeds Potassium (K) Human 1. Required in muscle contractions 2. Involves in transmission of nerve impulses. Plants: 1. Formation of carbohydrates. 2. Activates certain enzymes. Sulphur (S) Human/Plants:Components of some proteins and vitamins. (in the body) Chlorine (Cl) Human: 1. Formations of hydrochloric acid in the stomach. 2. Maintains pH value of the stomach. Plants 1. Photolysis of water during photosynthesis. Chemical Compounds in the Cell 1.
A compound is a substance which consists of two or more elements combined in a fixed ratio. 2. Common elements such as carbon, oxygen, hydrogen, nitrogen, sulphur and phosphorus combined with each other to form various chemical compounds in the cell. 3. The chemical compounds can be divided into two types: a. Organic compounds which contain the element carbon. b. Inorganic compounds which do not contain carbon. Organic Compounds 1. Organic compounds are chemical compounds which contain carbon and hydrogen. They are usually big and complex, present as macromolecules and associated with living organisms. 2.
The examples organic compounds found in a cell are carbohydrates, lipids, proteins and nucleic acids. Inorganic Compounds 1. Inorganic compounds do not contain carbon and usually associated with non-living things. 2. Example of inorganic compound in a cell is water. Carbohydrates Classification of Carbohydrates [pic] Importance of Carbohydrates 1. As main source of energy in a cell. 2. Forming the external skeletons of insects 3. As energy store in animal cells (in the form of starch) and plant cells (in the form of starch). 4. Building cell walls in plant cells 5. It is the important constituent of dietary fibre.
Reducing and Non-Reducing Sugar 1. A reducing sugar is any sugar that can act as a reducing agent. 2. Reducing sugars include glucose, fructose, galactose, lactose, and maltose. [pic] Test for Reducing and Non-Reducing Sugar 1. Benedict’s reagent is used to determine if a reducing sugar is present. If it is a reducing sugar, the mixture will turn orange or red. 2. Fehling’s solution can also be used for the same purpose. 3. A non-reducing sugar can be tested for in much the same way, but first the non-reducing sugar must be hydrolised by using dilute HCL Hydrochloric acid. Then neutralised.
Then heat gently with Benedicts Solution, a positive result will show brick red. Carbohydrates – Monosacharides Monosaccharides 1. Monosaccharides are the basic building blocks of carbohydrates. It cannot be broken down further into smaller units of carbohydrates. 2. Also known as simple sugars. 3. All monosaccharides are reducing sugars,are soluble in water. 4. Some monosaccharides have sweet taste. 5. Examples of monosaccharides are glucose, fructose and galactose. Glucose Formula: C6H12O6 1. Most common monosaccharide in living organisms 2. Monomer of most polysaccharides 3. End product in the digestion of starches and glycogen.
Fructose Formula: C6H12O6 1. Constituent of sweet fruits and honey. Galactose Formula: C6H12O6 1. Found in milk Carbohydrates – Disacharides Disaccharides 1. Disaccharides are complex sugars. It consists of two monosaccharides joined together chemically. 2. Disaccharides are also known as double sugar. 3. Examples of disaccharides are maltose, sucrose and lactose. Taste of Disaccharides All disaccharides taste sweet and soluble in water. Condensation and Hydrolysis Reaction 1. 2 monosacharides combine together to form 1 disaccharide molecule through a process call condensation. 2.
Disaccharides can also be broken down to monosaccharides by hydrolysis. [pic] Condensation of Monosacharides Figure below shows the examples of formation of disaccharides from condensation of monosacharides. [pic] Hydrolysis of Disaccharides Hydrolysis is a chemical reaction that breaks up large molecules by adding water to them. [pic] Sucrose (cane sugar) 1. Sucrose is made up of glucose and fructose. 2. It is commonly found in sugar cane, sugar beet and sweet fruits. 3. It is generally extracted from sugar cane or sugar beet and then purified and crystallized to be used as a sweetener in beverages.
Lactose (milk sugar) 1. Consists of glucose and galactose. 2. Present in the milk. Maltose (malt sugar) 1. Made up of two glucose molecules. 2. Product of the partial digestion of starch. Reducing Sugar and Non-Reducing Sugar Maltose and lactose are reducing sugars, while sucrose is a non-reducing sugar. Chemical Test for Disaccharides 1. Since maltose and lactose are reducing sugar, they can be tested directly by Benedicts Solution. 2. When maltose or lactose is boiled with Benedicts Solution, a brick red precipitate will be produced, indicating the presence of reducing sugar. . Sucrose is non-reducing sugar. There is no direct test for non-reducing sugar. 4. However, the monomers of sucrose – glucose and fructose, are reducing sugar. Therefore, we can detect the presence of sucrose by breaking down sucrose into glucose and fructose through hydrolysis reaction (heating sucrose solution with hydroclhoric acid), follow by the heating the products with Benedicts Solution. 5. Formation of brick red precipitate indicates the presence of reducing sugar, and hence presence of sucrose in the solution.
