STPM Biology Biological Molecules Part 9 Lipid

1. Lipid is a compound that contains carbon, hydrogen, and oxygen. But the ratio of hydrogen atoms and oxygen atoms molecules is higher than 2:1.

2. All lipids are formed from fatty acids and glycerol.

3. Glycerol is a type of alcohol known as propane1,2,3-triol. 

4. The structural formula for glycerol:

Glycerol

5. Fatty acid is carboxylic acid with long hydrocarbon chains. Fatty acid differs with the length of the hydrocarbon chain. It can be divided into 2 groups:

• Saturated fatty acids
• Unsaturated fatty acids

Saturated Fatty Acids

a. Saturated fatty acid does not have C=C bonds in their molecules.

Saturated fatty acid

b. The common formula for this acid is RCOOH, where R= CnH2n+1 (R= CH3, C2H5...)

c. Examples of saturated fatty acids:

• Stearic acid
• Lauric acid
• Miristic acid
• Palmitic acid
• Aracidic acid

Unsaturated Fatty Acids

a. Unsaturated fatty acid has one or more double bonds C=C in the molecules.

Unsaturated fatty acid

b. Example of unsaturated fatty acids:

• Oleic acid
• Linoleic acid
• Linolenic acid
• Arachidonic acid
• Palmitoleic acid

6. Non-essential fatty acids are fatty acids that can be synthesized by the body. For examples, oleic acid, stearic acid, cerotic acid and palmitic acid.

7. Essential fatty acids are fatty acids required by the body but are not synthesized by the body. For examples, linolenic acid, linoleic acid, and arachidonic acid. 

8. Lipids are often referred to as alcohol ester because it is formed form acid and alcohol (glycerol).

Structure of alcohol ester

9. Lipids can be classified into 3 major groups:

• Triglyceride
• Phospholipid
• Waxes

SPM Biology 2 Cell Biology & Organization Part 5 Levels of Organization in Multicellular Organisms

Multicellular organisms - Living things with multiple or many cells organized together (eg. animals, plants)

Cell specialization in multicellular organism

• Cell changes in structure or function in order to carry out a specific function
• Most of them rely on cooperation of other cells to survive.

Cell organization in multicellular organism

Cells organization

Levels of organization in multicellular organism 

Meristematic tissue in plants 

Meristematic tissue in plants 

Organs and systems in plants 

Shoot system - stems, leaves, buds, flower, fruits and etc.

Root system - all roots 

Systems in plants

Organs in plants

Notes for plants: 

• Parenchyma tissue - to store starch, protein and water.
• Collenchyma tissue - giving support to young, non-woody stems.
• Sclerenchyma tissue - giving support to mature parts of the plant.

• Vascular tissue / bundle = xylem tissue + phloem tissue
• Xylem tissue - transport water and mineral salts from the roots to other parts of the plant,
• Phloem tissue - transport organic matters (sucrose etc.) from the leaves to all parts of the plant.

STPM Biology Biological Molecules Part 8 Carbohydrate - Polysaccharides - Cellulose

1. Distribution:

• Cellulose is the most common organic materials. It is found in all plant cells. 20% to 50% of the cell wall of plants is cellulose.
• Also found in cotton (90% cellulose).

2. Physical properties:

• Not soluble in water.
• Cannot crystallize.
• Not sweet.
• High relative molecular mass.

3. Chemical properties:

• Can undergo hydrolysis to form β-glucose.
• Reacts with iodine solution to form brownish-yellow complex.

Structure of Cellulose

1. Cellulose has long unbranched chain molecules. Cellulose molecule consists of β-glucose molecules linked by 1,4-glycosidic bonds.

2. Neighboring cellulose molecules are cross-linked by hydrogen bonds.

3. Cross-linking between neighboring chains by hydrogen bonds produces a strong structure.

4. In cell walls, numerous cellulose molecules (about 2,000) are cross-linked to form cellulose microfibrils. Many microfibrils are bound together to form fibrils that form the cell walls.

Cellulose

Functions and properties of cellulose related to its function

1. Cellulose is source of food and energy for herbivorous animals, bacteria and fungi. It is because it can undergo hydrolysis to form glucose. Glucose is the main substrate for respiration.

2. Cellulose are structural materials for plants. It is due to:

• Cellulose have long straight-chain molecules.
• Cellulose is not soluble in water.
• Hydrogen bonds between neighboring molecules produce a strong structure.

Structural differences between cellulose and starch

1. Cellulose molecules consist of β-glucose monomers; while the starch molecules consist of α-glucose monomers.
2. Cellulose molecules are long straight-chain molecules; while starch molecules are coiled into helix and having branched chain.
3. Hydrogen bond occurs between neighboring cellulose molecules. However there are no hydrogen bonding between neighboring starch molecules.

STPM Biology Biological Molecules Part 7 Carbohydrate - Polysaccharides - Glycogen

1. Molecular formula: (C6H10O5)n

2. Plant stores starch and animals stores glycogen. Glycogen is referred to as "animal starch".

3. Physical properties:

• not soluble in water.
• not sweet.
• cannot crystallize.
• high molecular mass.

4. Chemical properties:

• undergoes hydrolysis to become glucose.
• reacts with iodine solution to form a purplish red color.

5. Distribution of glycogen (mainly):

• liver
• muscles
• brain

6. Structure of glycogen:

• Glycogen has branched-chain molecules. The structure of glycogen molecule is similar with amylopectin, but glycogen molecule has more branches.
• Glycogen molecules are built from α-glucose molecules that are linked together by 1,4-glycosidic bond. Branches are linked by 1,6-glycosidic bonds.
• The chain are coiled into helix.

Glycogen structure

7. Functions:

• Glycogen is storage carbohydrate in animals.
• Source of energy for animals.

Properties and structure of glycogen related to its function

1. Glycogen is a storage compound. It is due to:

• It is not soluble in water. Thus, stored glycogen does not change the osmotic pressure of the organ.
• Glycogen molecules are compact. A large mass can be stored in a small space.

2. Glycogen is a source of energy for animals. Glycogen can carry out this function because it can undergo hydrolysis to form glucose. Glucose is the substrate for respiration.

SPM Biology 2 Cell Biology & Organization Part 4 - Living Processes in Multicellular Organisms

There are various types of cells in multicellular organisms which are different in:

• size
• shape
• arrangement

Each type of cell is specialized to carry out a specific function.

Specialized cells found in humans

White blood cell

1. White blood cell

• Various shape
• Function: Destroy pathogen

Red blood cell

2. Red blood cell

• X nucleus
• Shape: biconcave disc
• Function: Transport oxygen

Epithelial cell

 3. Epithelial cell

• Thin, flat
• Coats the surface of organs

Muscle cell

4. Muscle cell

• Arranged as multinuclear striated fibers
• Function: Generate movement

Nerve cell

5. Nerve cell

• Long, thin
• Function: Sending nerve impulses

Sperm cell

6. Sperm cell

• Has long tail 
• Head carries chromosomes from the male 

Specialized cells found in plants

Root hair cell

1. Root hair cell

• Long
• Function: Absorb water and mineral salts

Xylem vessel

2. Xylem vessel

• Long, continuous hollow tube
• Function: Transport water and mineral salts from roots to other parts of the plant

Sieve tube element

3. Sieve tube element

• Long cylindrical tubes
• Function: Transport organic materials from leaves to storage organs (fruits etc.)

Palisade mesophyll cell & Spongy mesophyll cell

4. Palisade mesophyll cell

• Long cylindrical cells 
• Function: Absorb sunlight for photosynthesis 

5. Spongy mesophyll cell 

• Cells arranged with lots of air space in between
• Function: Allow gases exchange from inside of the leave to palisade mesophyll cells

Guard cell

6. Guard cell

• Modified lower epidermal cells with thicker cell wall on inner side
• Function: Controls opening and closing of stoma (the opening that allows exchange of oxygen and carbon dioxide)

STPM Biology Biological Molecules Part 6 Carbohydrate - Polysaccharides - Starch

1. General formula: (C6H10O5)n

2. Distribution:

• Leaves
• Storage organs
• Seeds

3. Physical properties:

• Not soluble in water.
• Cannot crystallize.
• Not sweet.
• Has high molecular mass.

4. Chemical properties:

• Can undergo hydrolysis to form maltose.
• Reacts with iodine to form dark blue complex.

5. Functions:

• Provides energy.

Structure

1. Starch consists of 2 types of components:

• Amylose (20%)
• Amylopectin (80%)

2. Amylose has unbranched-chain molecules. Amylose molecule consists of α-glucose molecules that are linked by 1,4-glycosidic bonds. Amylose molecule is coiled into a helix.

Amylose

3. Amylopectin has branch-chain molecules. Same with amylose, amylopectin molecule consists of α-glucose molecules that are linked by 1,4-glycosidic bonds. But the branches are linked by 1,6-glycosidic bonds. The chains are coiled into helix.

Amylopectin

Comparison between amylose and amylopectin

Properties and structure of starch related to its function

1. Starch is a storage compound. Starch can carry out this function because:

• It is not soluble in water. Hence, stored starch do not change the osmotic concentration of the organ.
• Starch molecules are compact. A large mass can be stored in a small space.

2. Starch is a source of energy for organism. Starch can undergo hydrolysis to form glucose. Glucose is the substrate for respiration.

STPM Biology Biological Molecule Part 5 Carbohydrate - Polysaccharides

1. Polysaccharides are polymer.

2. Polymer = a large molecule made up of many repeating units called monomers. 

3. The monomers of polysaccharides is monosaccharides.

4. General properties:

• Not soluble in water.
• Not sweet.
• Cannot crystallize.
• Has high molecular mass compared to monosaccharides and disaccharides.
• Can undergo hydrolysis to form monosaccharides or disaccharides.

5. Examples of polysaccharides:

• Starch
• Glycogen
• Cellulose
• Hemicellulose and pectin
• Chitin

Examples of polysaccharides

SPM Biology 2 Cell Biology & Organization Part 3 - Living Processes in Unicellular Organisms

Unicellular Organisms 

Made up of only one cell.

Is a complete unit of life that can carry out all life processes.

Simplest form = Protozoans

Examples: Ameoba sp., Paramecium sp.

Structure of Ameoba sp.

Structure of Paramecium sp.

Life processes carried out by unicellular organisms

1. Respiration

• Exchange of gases (oxygen & carbon dioxide) occur through plasma membrane by simple diffusion (the transport of molecules across the plasma membrane down the concentration gradient through the phospholipid bilayer until equilibrium is reached) on the surface of cell.

2. Movement

• Amoeba sp, moves using pseudopodium (false feet).
• Paramecium sp. moves using rhythmic cilia beats.

Amoeba sp.

3. Nutrition

• Amoeba sp. moves towards food by extending its pseudopodium to trap food particles by phagocytosis.
• Food vacuole combines with lysosome, food particles are hydrolyzed by the enzyme lysozyme in lysosomes. 
• Nutrient are absorbed into cytoplasm.
• Undigested food is discharged when Amoeba sp, moves
• For Paramecium sp., cilium beat helps to transfer food particles into oral groove. Undigested food is discharged through anus.

4. Responding to stimuli

• Respond to chemicals, touch or bright light by moving away from the stimuli.

5. Reproduction

• Reproduce via binary fission (asexual reproduction) through mitosis when the conditions are suitable and have plenty of food.
• Amoeba sp. forms spores when conditions are bad (dry, low temperature, food shortage)
• For Paramecium sp., conjugation (sexual reproduction) occurs when conditions are bad

Binary fission

Paramecium sp.: Conjugation

6. Growth

• Synthesize new cytoplasm.

7. Excretion

• Waste (carbon dioxide, ammonia etc.) are removed by diffusion/
• Water diffuse via osmosis.
• Undergo osmoregulation = the process of maintenance of salt and water balance ( osmotic balance) across membranes within the body`s fluids

Similarities and differences between Amoeba sp. and Paramecium sp.

STPM Biology Biological Molecule Part 4 Carbohydrate - Disaccharides

Carbohydrate - Disaccharides

1. General formula: C12H22O11

2. Formed during condensation of 2 hexose molecules:

• α-glucose + α-glucose → maltose + water
• α-glucose + galactose → lactose + water
• α-glucose + fructose → sucrose +water

Disaccharides

3. Properties:

• Sweet
• Soluble in water
• All disaccharides are non-reducing sugars except for lactose and maltose
• Hydrolysis of disaccharide forms hexoses

4. Functions of disaccharide:

• Carbohydrates in plants are mainly transported in the form of sucrose. This is because sucrose is soluble in water and is inert (inactive).
• Source of energy for organisms.

Chemical tests for sucrose

1. Boil sucrose with solution of Fehling's solution. Result: negative.
2. Hydrochloric acid is added to sucrose and boiled. Acid cause hydrolysis of sucrose into glucose and fructose. A small amount of sodium bicarbonate (NaHCO3 ) is added to neutralize the mixture. Fehling's is added to the mixture and then boiled. Result: Brick red precipitation is formed.

STPM Biology Biological Molecules Part 3 Carbohydrate - Monosaccharides

Carbohydrate is an organic compound containing carbon, hydrogen and oxygen elements in a 1:2:1 ratio. Cx(H2O)y is the typical formula for carbohydrate. Among the roles of carbohydrate are:

1. Storage of food.
2. As a source of energy.
3. Structural components of organisms.
4. Components of polymers, for example, nucleic acid.
5. Defense and protection.
6. Provides mechanical support.

There are 3 main groups of carbohydrates, namely:

• Monosaccharide
• Disaccharide
• Polysaccharide

Monosaccharides

1. Monosaccharides also known as simple sugars. They are named with the suffix -ose.

2. Monosaccharides contain either an aldehyde group (-CHO) or ketone group (C=O). 

3. Monosaccharide with an aldehyde group is called aldo-sugars or aldose; while the other is referred as keto-sugar or ketose.

4. The general formula for monosaccharide is (CH2O)n. If n=3, the sugar is called triose; n=5, a pentose sugar; and n=6, a hexone sugar.

5. Physical properties:

• Sweet.
• The molecule is small with a low molecule mass compared to other sugars.
• Can crystallize.
• Soluble in water.

6. Chemical properties:

• Can reduce Benedict's solution and Fehling's solution due to the presence of free aldehyde or ketone group in molecule.
• Can undergo condensation reactions to form disaccharides or polysaccharides.

7. General functions of monosaccharides:

• Provide energy.
• As monomer for polysaccharides and disaccharides.
• Pentose is an important component of nucleic acid. 
• Monosaccharides are soluble in water. Most carbohydrates are transported in the form of monosaccharides.

Triose

Glyceraldehydes and dihydroxyacetone

1. Molecule formula: C3H6O3

2. Example: 

• Glyceraldehydes
• Dihydroxyacetone

3. Functions of triose:

• Triose is an important intermediate in Krebs Cycle (respiration).
• Triose is used to synthesize starch and glucose in photosynthesis.

Pentose

             ribose                            deoxyribose

1. Molecule formula: C5H10O5

2. Examples:

• Ribose
• Deoxyribose
• Arabinose
• Xylose
• Ribulose
• Xyllulose

3. Functions of pentose:

• Ribose and deoxyribose are main components of nucleic acid (DNA and RNA).
• Ribose is a component of ATP molecule.
• NAD (nicotinamide adenine dinucleotide), FAD (flavin adenine dinucleotide) [Both the FAD and NAD are electron carriers] and coenzyme A are synthesized using pentose.

Hexose

Hexose

1. Molecule formula:  C6H12O6

2. Examples:

• Glucose
• Manose
• Galactose
• Fructose
• Sorbose

3. Most glucose molecules exist in the ring form or cyclic form. The two common isomers or glucose are α-glucose and β-glucose.

Different forms of glucose

4. Fructose occurs as straight-chain or linear molecules or in a ring form.

5. Functions of hexose:

• Glucose is the main substrate for respiration.
• Hexose is the monomer for disaccharides and polysaccharides.
• Most carbohydrates are transported as hexose in the blood stream.

Chemical tests for monosaccharides

1. All monosaccharides are reducing sugar. This is due to the presence of free aldehyde or ketone group in molecule.

2. When monosaccharides are 🔥🔥heated🔥🔥 with Benedict's solution or Fehling's solution, a brick red precipitation is formed. The brick red precipitation is Copper (I) Oxide, Cu₂O.

SPM Biology 2 Cell Biology & Organization Part 2 Cell Structure & Functions

Mitochondrion

Mitochondrion (Plural: Mitochondria)

• Rod-shape / spherical
• 2 layers of membranes
• Functions: 
• A site that generates energy

Centriole

Centriole

• Small cylindrical components that exist in pairs in animal cells, X in plant cells
• Made up of microtubules 
• Functions:
• Forms spindle fiber during cell division

Golgi Apparatus

Golgi Apparatus

• Stack of parallel flattened sacs, single cell membrane
• Functions:
• Processes, modifies, packs and transports chemicals (protein, carbohydrate etc.)

Plasma Membrane

• 

  Plasma Membrane

  Outer membrane that surrounds the cell
• Made of proteins & phospholipids
• Thin, elastic
• Functions:
• Controls movement of substances into & out of the cell
• Separates content of cell from external environment
• Allows exchange of nutrients, gases and waste materials between cells & their surroundings

Lysosome

Lysosome

• Small spherical sac, single membrane
• Contains hydrolytic enzymes
• Functions:
• Hydrolyses complex organic molecules (protein, nucleic acid & lipid)
• Breaks down bacteria, damaged cells

Nucleus

Nucleus (Plural: Nuclei)

• Largest component in the cell
• Spherical, enclosed in nuclear membrane with many pores
• Double membrane
• Contains chromosomes, nucleolus and nucleoplasm 
• Functions:
• Controls all cell activities
• Chromosomes contain deoxyribonucleic acid (DNA)

Ribosome

Ribosome

• Small, compact, spherical granules
• Consists protein and ribonucleic acid (RNA)
• Present on the surface of rough endoplasmic reticulum / freely exist in cytoplasm
• Function:
• Site for protein synthesis

RER & SER

Endoplasmic Reticulum (ER)

• Folded flattened sacs
• Two types of ER
• Rough ER: has ribosomes attached on the surface
• Smooth ER: X ribosomes
• Functions:
• Act as transport system within the cell
• RER transports proteins synthesized by ribosomes
• SER synthesizes & transports glycerol and lipids, detoxify drugs and metabolic by-products 

Cytoplasm

Vacuole

Cytoplasm 

• Jelly-like medium that contains the components of cells
• Contain organic (protein, carbohydrate etc.) & inorganic (potassium ions) compounds 
• Functions:
• Medium for biochemical reactions in cells

Vacuole

• Liquid-filled sac, the liquid called cell sap
• Surrounded by tonoplast
• Exist in plant cells
• Small size in unicellular animals 
• Functions:
• Water is absorbed into the vacuole and the plant cell becomes turgid
• In unicellular animals, vacuole contracts during osmoregulation, osmosis and excretion

Chloroplast

Chloroplast

• Oval shaped
• 2 layers of membrane
• Contains chlorophyll
• Functions:
• Chlorophyll absorbs sunlight during photosynthesis

Cell Wall 

Cell Wall 

• Strong and rigid outer layer of plant cells
• Made from cellulose fiber
• Fully permeable
• Functions:
• Maintains the shape of plant cells
• Provides mechanical support to plant cells