View PUTERI NUR AISYAH BINTI JUBIR H1T01A flipbook.
Lecturer’s name : PN. LAILI SYAHIDAH BINTI MOHAMED ASINS E T C Name : PUTERI NUR AISYAH BINTI JUBIR Matric number : MS2513171065BIOLOGY 1 (SB015) ASSIGNMENT 2026/2027 BIO FLIPBOOK: MOLECULES OF LIFE & CELL STRUCTURES AND FUNCTIONS P r a c t i c u m : H 1 T 0 1 A1
Lipids THE MAIN TYPES OF MOLECULES OF LIFEWater CarbohydrateS ProteinS DNA AND RNA MOLECULES 2
classified into three main types based on their structure: Classification of Lipidsalso know as triacylglycerol (Fats and Oils): Composed of one glycerol molecule and three fatty acids.The lipids are a large and diverse group of organic compoundsTriglyceridesfatty acid is a long linear hydrocarbon chain and a carboxyl groupGlycerol is 3 carbon atom & 3 hydroxyl goup 3chemical linkage found in triglycerides is an ester linkage (or ester bond. Reaction: Formed through a dehydration synthesis (condensation) reaction.Components: It links the hydroxyl group (-OH) of the glycerol molecule to the carboxyl group (-COOH) of a fatty acid.Byproduct: Each triglyceride molecule forms three ester linkages, releasing three water molecules in the process.
condensationFormation and Breakdown of Triglycerides Formation of triglyceride: 1. Formed by 3 fatty acids and 1 glycerol 2. Each fatty acid joins to glycerol by condensation reaction /esterification 3. Three water molecules are removed. 4. The hydroxyl (OH) from carboxyl end of fatty acid and hydrogen from the hydroxyl group of glycerol are removed. 5. Three ester linkages are formed. 6. The first reaction yields a monoacylglycerol/monoglyceride 7. The second reaction yields a diacylglycerol/diglyceride 8. The third reaction yields a triacylglycerol/triglycerideBreakdown of triglyceride: 1. Undergoes hydrolysis: 3 water molecules are added 2. The hydroxyl (OH) reacts with the carboxyl end and hydrogen reacts with the hydroxyl group. 3. Carboxyl group of each fatty acid and hydroxyl group of glycerol are formedhydrolysis 4
Hydroxyl Group (-OH): Steroids carrying this group are classified as sterols. For example, cholesterol contains an - OH group, which makes it a structural alcohol critical for maintaining cell membrane fluidity and acting as a precursor to other steroids.Ketone & Hydroxyl Groups (- C=O and -OH): By varying these functional groups on the core ring, a wide array of steroid hormones are formed. For instance, cortisol and aldosterone are adrenocorticoids that regulate metabolism and blood pressure, while testosterone and estradiol are sex hormones defined by specific functional group arrangements. Ketone & Hydroxyl Groups (-C=O and -OH): By varying these functional groups on the core ring, a wide array of steroid hormones are formed. For instance, cortisol and aldosterone are adrenocorticoids that regulate metabolism and blood pressure, while testosterone and estradiol are sex hormones defined by specific functional group arrangements.Component in cell membrane. Characterized by a carbon skeleton consisting of four fused rings (e.g., cholesterol). precursors for sex hormone Steroids: 5
6Component of the cell membrane and contain nutrient choline found in egg yolk, peanut, milk, and soya beanPhospholipids(lecithin): Phospholipids are essential components of neuronal membranes and play a critical role in maintaining brain structure and function. Membrane is composed of 2 layers (bilayer) of phospholipids with globular proteins embedded in the bilayer .Fluid: phospholipids & proteins can move laterally (can move side to side).Mosaic: proteins are embedded in the phospholipid bilayer lik the mosaic tiles embedded in mortar Accounted for the amphipathic characteristic of phospholipids & proteins Amphipathic molecules: have both hydrophobic regions & hydrophilic regions Hydrophobic: non-polar / "water hating" Hydrophilic: polar / "water loving"COMPONENTS OF A PHOSPHOLIPID One glycerol molecule Two fatty acid talls (hydrophobic) One phosphate group attached to a polar group (hydrophilic) HYDROPHOBIC "tails derived from fatty acids, joined by an alcohol residue a molecule that "hates water" It not attracted to water, but will dissolve in olls or fats HYDROPHILIC "head containing a phosphate group a molecule that "loves water" It is attracted to water molecule and can usually dissolve in water
7 Plasma membrane Phospholipid bilayer
Membrane is composed of 2 layers (bilayer) of phospholipids with globular proteins embedded in the bilayer Fluid: phospholipids & proteins can move laterally (can move side to side). Mosaic: proteins are embedded in the phospholipid bilayer like the mosaic tiles embedded in mortar. Plasma membrane described by Fluid Mosaic Model and proposed by S.J Singer & G.L Nicolson (1972) According to the Fluid Mosaic Model, the plasma membrane consists of a phospholipid bilayer. 8Proteins: Intrinsic / Integral proteins: partially embedded or fully embedded: transmembrane protein Extrinsic / Peripheral proteins: attached to the outer & inner surfaces of the membraneCarbohydrate chain / oligosaccharides Found on the external surface of the plasma membrane Carbohydrate chain attaches to protein →glycoprotein Carbohydrate chain attaches to phospholipids → glycolipid Function as cell identity markers / recognition. Cholesterol Found between phospholipids Function: Increase flexibility & stabilizes the membrane structure by regulating the fluidity of the membrane Cholesterol stabilises the membrane structure: at moderately warm temperatures, Cholesterol reduce membrane fluidity by preventing movement of phospholipids molecules at cool temperatures,Cholesterol prevent close packing of phospholipids & slow down solidification Functions of plasma membrane 1. Forms a protective barrier 2. Selectively permeable membranes Allow movement of molecules such as lipid soluble substances, non-polar molecules, water, urea, gases (O2, CO2) in and out of cell Do not allow movement of charged/ions, polar and large molecules (glucose)phospholipid bilayer is arranged with the hydrophilic phosphate heads facing the aqueous environments on both the extracellular and intracellular sides of the plasma membrane, while the hydrophobic fatty acid tails face inward towards each other, forming the membrane's hydrophobic core.
The fluidity of the plasma membrane are dynamic and static. Phospholipid can move laterally side by side. Phospholipids is actively regulated by cholesterol molecules embedded within the bilayer. This is because phospholipids containing unsaturated fatty acid tails have C=C double bonds that create structural double bond "kinks", which prevent the molecules from packing tightly together, thereby ensuring the membrane remains fluid even at lower temperatures. In animal cells, cholesterol acts as a critical fluidity buffer by being wedged between the hydrophobic tails of the phospholipids, so it stabilizes the membrane at higher temperatures. The presence of cholesterol prevents the membrane from becoming too fluid at moderate temperature.While observing animal cells under the microscope, a biology student noticed that the plasma membrane is neither too rigid nor too fluid. Explain how the different types of lipid in the plasma membrane causes and regulate membrane fluidity 9
REFERENCEBritannica.(2026).MOLECULE OF LIFE .https://share.google/U0zqsGMNknUZkReiQMichael W. King, PhD.(2026).Synthesis of Triglycerides .https://themedicalbiochemistrypage.org/synthesis-of-triglycerides/Earth.com.(2026).How Steroid Structure Dictates Biological Function.https://biologyinsights.com/how-steroid-structure-dictates- biological-function/