Mod 2

Question 1

Key Organelles Involved in Synthesis and Transport

Answer 1

Nucleus: Has a double membrane called the envelope with pores for molecule transport.
Rough Endoplasmic Reticulum (RER): Processes and folds proteins using ribosomes.
Smooth Endoplasmic Reticulum (SER): Is involved in lipid production and processing.
Ribosomes: Consist of two subunits and are essential for protein synthesis.
Golgi Apparatus: Packages proteins and lipids.

Question 2

Other Important Cellular Structures and Their Functions

Answer 2

Golgi Apparatus: Produces lysosomes.
Lysosomes: Contain digestive enzymes and are enclosed by a single membrane.
Mitochondria: Are the powerhouses of the cell, facilitating respiration with their cristae and matrix.
Cytoskeleton: Provides mechanical strength to the cell, aids in intracellular transport and enables cell movement.

Question 3

Protein Synthesis Summary

Answer 3

Proteins are synthesized on ribosomes
These ribosomes can be found freely floating in the cytoplasm or attached to the Rough Endoplasmic Reticulum (RER)
The RER folds and processes the proteins that are synthesized on its surface
Proteins are then transported from the RER to the Golgi apparatus in vesicles .
The Golgi apparatus modifies and packages these proteins
Finally, some proteins, such as extracellular enzymes, exit the cell through exocytosis .

Question 4

Prokaryotic Cell Structure

Answer 4

Prokaryotic cells possess a rigid cell wall made of peptidoglycan.
They may also have a protective capsule that retains moisture and aids adhesion.
Prokaryotic cells contain plasmids, which are circular DNA structures.
Flagella are tail-like structures that enable movement by rotation.
Pili are hair-like appendages that help bacteria attach to surfaces.

Question 5

Essential Properties of Water

Answer 5

Water is a polar molecule with uneven charge distribution.
It is crucial for metabolic reactions like condensation (water elimination to join monomers) and hydrolysis (water addition to break bonds).
Water acts as a solvent for many biological processes.
Its high heat capacity and latent heat of vaporization help regulate temperature.
Cohesion in water enables effective transport in plants and provides support.

Question 6

Understanding Glucose

Answer 6

Glucose is a monosaccharide with six carbon atoms.
It serves as the main substrate for respiration.
Glucose is crucial for energy production in cells.
There are two isomers of glucose: alpha and beta.
The structural differences between alpha and beta glucose affect their function.

Question 7

Key Disaccharides

Answer 7

Maltose consists of two glucose molecules.
Sucrose is made from glucose and fructose.
Lactose is formed from glucose and galactose.
Disaccharides are formed through condensation reactions (implied by joining of monomers).

Question 8

Polysaccharides from Glucose

Answer 8

Polysaccharides are long chains of glucose units.
Glycogen and starch are made from alpha glucose.
Cellulose is made from beta glucose.
The type of glucose isomer (alpha or beta) determines the structure and function of the resulting polysaccharide.

Question 9

Energy Storage in Animals

Answer 9

Glycogen is the main energy storage molecule in animals.
It is made from alpha glucose.
Glycogen has many side branches for rapid glucose release.
It is a large but compact molecule, optimizing energy storage.

Question 10

Energy Storage in Plants

Answer 10

Starch is the energy storage molecule in plants.
Starch consists of amylose and amylopectin.
Amylose is unbranched and compact.
Amylopectin is branched for quick digestion.

Question 11

Structural Component in Plants

Answer 11

Cellulose is a component of cell walls in plants.
It is composed of long, unbranched chains of beta glucose.
These chains are joined by glycosidic bonds.
Microfibrils, which provide structural support, are made of long cellulose chains joined by hydrogen bonds.

Question 12

Comparing Energy Storage Molecules

Answer 12

Both glycogen (animals) and starch (plants) are used for energy storage.
Glycogen and starch are both made from glucose.
Glycogen and amylopectin (in starch) are branched for quicker access to glucose.
Amylose (in starch) and glycogen are described as compact for efficient storage.
Glycogen is made of alpha glucose, while cellulose (structural) is made of beta glucose, highlighting the importance of glucose isomer in determining function.

Question 13

Understanding Lipids

Answer 13

Saturated lipids, found in animal fats, lack carbon-carbon double bonds.
Unsaturated lipids, found in plants, contain double bonds and have lower melting points.
More unsaturated bonds result in weaker intermolecular forces and lower melting points.
Triglycerides, composed of glycerol and three fatty acids, serve as energy reserves.
Phospholipids have hydrophilic heads and hydrophobic tails, forming micelles in water.

Question 14

Essential Inorganic Ions

Answer 14

Inorganic ions are found in cytoplasm and body fluids of organisms.
Hydrogen ions influence the pH levels of substances like blood.
Iron ions are crucial for the formation of haemoglobin in red blood cells.
Sodium ions play a key role in the co-transport of glucose and amino acids.
Phosphate ions are essential components of DNA and ATP.

Question 15

Understanding Proteins and Amino Acids

Answer 15

Amino acids are the building blocks of proteins, consisting of an amino group, a carboxylic acid group, and a variable R group.
There are 20 different amino acids, and they are linked by peptide bonds through condensation reactions.
Proteins have four structural levels: primary, secondary, tertiary, and quaternary, which determine their function.
Collagen is a strong fibrous protein essential for the structure of bones and connective tissues, formed by wrapped molecules.
Haemoglobin is a globular protein that transports oxygen in the blood, composed of two alpha and two beta chains with haem groups.

Question 16

Understanding Protein Structure

Answer 16

Primary structure refers to the sequence of amino acids in a protein.
Secondary structure involves shapes like alpha helix or beta pleated sheet, influenced by hydrogen bonds.
Tertiary structure is the 3D shape of the protein, which can be globular or fibrous.
Globular proteins are compact and often function as enzymes.
Fibrous proteins, like keratin, are elongated and used to form fibers.

Question 17

Key Tests for Biomolecules: Reducing Sugars, Proteins, Lipids, and Starch

Answer 17

Benedict’s test detects reducing sugars by forming a red precipitate of copper (I) oxide when heated.
The biuret test identifies proteins, turning lilac in the presence of peptide bonds after adding NaOH and copper (II) sulfate.
The emulsion test for lipids involves mixing a sample with ethanol and water, resulting in a cloudy solution if lipids are present.
Starch is tested with iodine, changing the potassium iodide solution from yellow to black/blue upon its presence.

Question 18

Understanding DNA and RNA: Key Differences and Structures

Answer 18

DNA holds genetic information while RNA transfers it to ribosomes.
Both DNA and RNA are polymers made of nucleotides.
DNA nucleotides contain deoxyribose, a phosphate group, and bases A, C, G, or T.
RNA nucleotides consist of ribose, a phosphate group, and bases A, C, G, or U.
DNA forms a double helix, while RNA is a single polynucleotide chain.

Question 19

Understanding ATP

Answer 19

ATP is a nucleotide made of ribose, adenine, and three phosphate groups.
Hydrolysis of ATP to ADP releases energy, facilitated by ATP hydrolase.
Inorganic phosphate from ATP can phosphorylate other compounds, enhancing their reactivity.
ATP is regenerated from ADP and inorganic phosphate by ATP synthase.
ATP production occurs during photosynthesis and respiration.

Question 20

Understanding Semi-Conservative DNA Replication

Answer 20

DNA replication ensures genetic continuity across generations.
The double helix unwinds with the help of DNA helicase.
Hydrogen bonds between complementary bases break to separate DNA strands.
Both strands serve as templates for complementary base pairing.
DNA polymerase forms phosphodiester bonds between adjacent nucleotides.

Question 21

Understanding the Genetic Code

Answer 21

The genetic code is composed of triplets of DNA bases known as codons, each coding for specific amino acids.
A gene is a sequence of bases that corresponds to a sequence of amino acids in a polypeptide chain.
DNA contains coding regions called exons and non-coding sections known as introns.
The genetic code is non-overlapping and degenerate, allowing multiple codons to code for the same amino acid.
Mutations in the DNA sequence can affect protein synthesis and lead to conditions like cystic fibrosis and sickle cell anemia.

Question 22

Stages of Protein Synthesis

Answer 22

Protein synthesis is a two-stage process consisting of transcription and translation. In transcription, the genetic information is copied from DNA to mRNA in the nucleus, preparing it for protein assembly.

Question 24

Transcription Process

Answer 24

During transcription, the DNA strands separate, allowing RNA polymerase to use the antisense strand as a template to synthesize mRNA. Complementary nucleotides are linked together by phosphodiester bonds to create the mRNA strand.

Question 25

Translation Mechanism

Answer 25

Translation involves the assembly of amino acids into a polypeptide chain at the ribosome, where mRNA binds and tRNA delivers specific amino acids. Peptide bonds form between amino acids, and this process continues until a stop codon is reached, concluding protein synthesis.

Question 26

Understanding Enzyme Function and Factors Affecting Reaction Rates

Answer 26

Enzymes speed up reactions by lowering activation energy. The active site is where substrates interact with enzymes. Each enzyme is specific to its substrate, fitting only one type. The induced fit model describes how enzyme structure alters to accommodate substrates.

Question 27

Key Factors Influencing Enzyme Reaction Rates

Answer 27

Enzyme concentration increases reaction rate until substrate availability limits it. Substrate concentration boosts reaction rate until enzyme concentration becomes limiting. Higher enzyme concentration means more active sites for substrates. Reaction rate peaks at an optimum temperature before declining with heat. Temperature significantly impacts enzyme activity and efficiency.

Question 28

Understanding Enzyme Inhibitors

Answer 28

Inhibitors slow down or stop reactions by affecting substrate binding to enzymes. They can be classified as reversible or irreversible. Irreversible inhibitors, like heavy metals and cyanide, permanently alter enzyme activity. Reversible inhibitors bind temporarily through weak interactions. Reversible inhibitors are further divided into competitive and non-competitive types.

Question 29

Understanding Reversible Inhibitors

Answer 29

Competitive inhibitors resemble substrate molecules and bind to the enzyme's active site. They reduce the enzyme's activity by competing with substrates, slowing product formation. Higher concentrations of competitive inhibitors decrease reaction rates. Non-competitive inhibitors bind to the allosteric site, altering the enzyme's shape. Common examples include penicillin and Ritonavir, which inhibit specific enzymes in bacteria and HIV, respectively.

Question 30

Understanding Enzyme Cofactors

Answer 30

Cofactors are non-protein compounds essential for enzyme activity. Three types of cofactors include coenzymes, activators, and prosthetic groups. Coenzymes are organic and often vitamin-derived, aiding substrate binding. Activators are inorganic metal ions that temporarily modify enzyme active sites. Prosthetic groups are permanently attached to enzymes, like the haem in haemoglobin.

Question 31

Understanding Cell Membrane Structure and Function

Answer 31

Cell membranes are made of phospholipids and proteins. They control substance movement in and out of cells and organelles. Membranes contain receptors for hormones and other molecules. Adjacent cells can adhere to each other through the membrane. The fluid mosaic model describes the membrane's structure and fluidity.

Question 32

Types of Molecular Movement Across Cell Membranes

Answer 32

Diffusion allows small, non-polar molecules to passively move through the membrane. Facilitated diffusion uses channel proteins for polar and charged molecules. Osmosis specifically refers to the movement of water through a semipermeable membrane. Active transport moves molecules against their concentration gradient using ATP. Exocytosis and endocytosis involve the transport of large particles via vesicles.

Question 33

How does the diffusion rate increase?

Answer 33

The rate of gas exchange by diffusion becomes more rapid as: Surface area of the surface increases, diffusion distance decreases, diffusion gradient becomes more steep

Question 34

Understanding Mitosis and the Cell Cycle

Answer 34

Mitosis produces identical daughter cells for growth and asexual reproduction. Cells produced by mitosis are genetically identical, leading to no genetic variation. The cell cycle consists of three stages controlled by checkpoints. Mitosis includes four stages: prophase, metaphase, anaphase, and telophase. Cytokinesis divides the cytoplasm and organelles, resulting in two daughter cells.

Question 35

The Stages of Cell Division

Answer 35

Prophase involves the breakdown of the nuclear envelope and chromosome condensation. Centrioles move to opposite poles to facilitate spindle formation during prophase. In metaphase, chromosomes align at the cell equator and attach to spindle fibers. Anaphase is characterized by the separation of sister chromatids. Telophase sees the reformation of the nuclear envelope and the creation of two daughter cells.

Question 36

Understanding Meiosis and Genetic Variation

Answer 36

Meiosis is a type of cell division that creates genetic diversity. It produces haploid gametes with half the chromosome number. Genetic variation occurs through crossing over of chromatids. Chromosomes exchange genetic material during meiosis. Independent assortment allows different combinations of chromosomes.

Question 37

Understanding Meiosis: The Process of Gamete Formation

Answer 37

Meiosis generates four haploid gametes from a diploid cell. Meiosis consists of two main phases: meiosis I and meiosis II. Homologous chromosomes separate during meiosis I, while sister chromatids separate in meiosis II. Genetic variation arises from processes like crossing over and random assortment during prophase I and metaphase I. The final result is four haploid daughter cells, each with single chromosomes. It is during Anaphase II that the centromeres split separating chromatids.

Question 38

Understanding Plant Transport Systems: Xylem and Phloem

Answer 38

Xylem transports water and minerals, providing structural support. Xylem consists of dead tissue and is reinforced with lignin. Phloem consists of living cells that translocate food and nutrients. Phloem features sieve plates and companion cells for efficient transport. Both xylem and phloem are formed by meristem cells that elongate.

Question 39

Understanding Types of Tissue: Epithelial, Connective, Muscle, and Nervous

Answer 39

Epithelial tissue covers surfaces and has two types: squamous and ciliated. Squamous epithelium is smooth, flat, and thin, found in blood vessels and cheeks. Ciliated epithelium has column-shaped cells with cilia, lining the trachea and bronchi. Connective tissue provides support and holds structures together, including cartilage and bone. Muscle tissue is specialized for movement, while nervous tissue is specialized for impulse conduction.

Question 40

The Versatile Role of Stem Cells

Answer 40

Stem cells are undifferentiated cells capable of developing into various cell types. They are important in research and medicine for repairing damaged tissues. Stem cells can treat neurological disorders, including Parkinson’s and Alzheimer’s. Differentiation is the process where stem cells specialize for specific functions. Stem cells are found in bone marrow and can become red and white blood cells.

Question 41

Functions of Blood Cells and Plant Cell Division

Answer 41

Erythrocytes transport oxygen in the blood. Erythrocytes have a short lifespan, being constantly renewed. Neutrophils attack and destroy foreign microorganisms via phagocytosis. Plants can differentiate into various cell types throughout their life. Meristems are regions of high cell division that produce xylem and phloem.

Question 42

Key Types of Specialized Cells in Reproduction and Plant Function

Answer 42

Sperm cells are male gametes produced in the testes and are essential for fertilization. Palisade cells are specialized plant cells rich in chloroplasts for efficient photosynthesis. Root hair cells enhance water and mineral absorption with their thin, elongated extensions. Guard cells, located in pairs on leaf epidermis, regulate stomatal openings to control gas exchange. Guard cells can change shape in response to water levels, unlike other epidermal cells.