1. What are the principles of cell theory?
- All living things are made of cells
- Cell is the structural and functional unit of all living things
- New cells arise from pre-existing cells
- Cell contains hereditary information, which is passed from cell to cell
- All cells have same basic chemical composition within similar species
- Energy flow (metabolism) of life occurs within the cell.
2. What are the differences between prokaryotes and eukaryotes?
Factors | Prokaryotes | Eukaryotes |
|---|---|---|
Cell boundary | Cell wall | Cell membrane |
Oxygen requirement | Anaerobic/Aerobic | Aerobic |
Membrane-bound organelles
| Absent | Present |
Cytoskeleton | Absent | Present |
Histones | Absent | Present |
Reproduction | Binary fission | Mitosis or meiosis |
Genetic material | Nucleoid | Chromatin |
Examples | Bacteria, blue-green algae | Virus, plant cells, animal cells |
3. What are the functions of various organelles in a cell?
Organelle | Functions |
|---|---|
Plasma membrane | Selective transport of molecules |
Cytosol | Metabolism of proteins, carbohydrates and lipids |
Mitochondria | Metabolism of biomolecules, etc. |
Nucleus | Replication Transcription |
Endoplasmic reticulum | Rough—Protein synthesis Smooth—Lipid synthesis |
Lysosomes | Phagocytosis Degradation of proteins, carbohydrates and lipids |
Peroxisomes | Fatty acid metabolism Free radical scavenging |
Golgi complex | Post-translational modification of proteins |
Cytoskeleton | Gives shape to the cells Cell movement Mitotic spindle formation |
4. What are the markers for various organelles of the cell?
Organelle | Marker |
|---|---|
Plasma membrane | Na+, K+, ATPase, 5' nucleotidase |
Cytosol | Lactate dehydrogenase |
Mitochondria | Glutamate dehydrogenase |
Nucleus | DNA |
Endoplasmic reticulum | Glucose 6-phosphatase |
Lysosomes | Acid phosphatase, cathepsin |
Peroxisomes | Catalase |
Golgi complex | Galactosyl transferase |
5. Which membrane of the cell contains high concentration of proteins?
6. What are the sites of protein synthesis?
- Rough endoplasmic reticulum
- Cytosol.
7. Proteins synthesized in free ribosomes and rough endoplasmic reticulum (RER) respectively are targeted to where?
- Cytosolic ribosomes—Cytosol, peroxisomes, mitochondria, nucleus
- RER—Lysosomes, membranes, secretion.
8. Name the constituents of cytoskeleton?
- Actin filaments
- Intermediate filaments
- Microtubules.
9. Which is the site of origin of microtubules in cells?
Centrioles.
10. How intracellular compartment is different from extracellular compartment in composition?
Component | Intracellular | Extracellular |
|---|---|---|
Na+ | 10 mmol/L | 145 mmol/L |
K+ | 140 mmol/L | 4 mmol/L |
Ca2+ (ionic) | 0.1 µmol/L | 2.5 mmol/L |
Cl– | 4 mmol/L | 95 mmol/L |
Mg2+ | 30 mmol/L | 1.5 mmol/L |
PO43− | 60 mmol/L | 2 mmol/L |
Protein | 160 g/L | 60 g/L |
Glucose | <20 mg/dL | <100 mg/dL (fasting) |
11. What are the lipids present in the outer and inner leaflets of biomembranes?
- Outer leaflet—Phosphatidylcholine, sphingomyelin
- Inner leaflet—Phosphatidylserine, phosphatidylethanolamine, phosphatidylinositol.
12. What is transition temperature of membranes?
The temperature at which biomembranes transits from gel-like ordered state to fluid-like disordered state is called transition temperature.4
13. What are the factors that increase the fluidity of membranes?
- Increase in temperature
- Fatty acids with shorter chain lengths and higher degree of unsaturation.
14. Cholesterol is considered as a buffer in maintaining fluidity of membranes, how?
- At temperatures below the Tm, cholesterol increases fluidity.
- At temperatures above the Tm, cholesterol decreases fluidity.
15. What are lipid rafts?
- Structure of biomembranes seen in outer leaflet, rich in sphingolipids and cholesterol
- They are involved in signal transduction.
16. What are the types of membrane proteins?
Integral and peripheral proteins.
17. Name the various transport mechanisms with one example.
Passive transport—No energy required, movement of solute from high to low concentration
- Simple diffusion—Random movement, e.g. oxygen
- Facilitated diffusion—Require transporter
- Carrier proteins—Glucose transporter
- Ion channels—Calcium channels.
Active transport—Energy and transporter required
- Primary—By hydrolysis of ATP, e.g. Na+-K+ pump
- Secondary—Driven by ion gradient, e.g. SGLT.
18. How transport system can be functionally classified?
Depending on the number and direction of transport of molecules:
- Uniport—Movement of one type of molecule in either of direction, e.g. Calcium pump
- Antiport—Movement of two types of molecule in opposite direction, e.g. Na+-H+ pump
19. What is an ionophore?
A compound which can carry ions selectively across a membrane is called an ionophore, e.g. proton ionophores, valinomycin (a potassium ionophore).
20. Name the various transport mechanisms of macromolecules?
- Endocytosis
- Exocytosis.
21. What is transcytosis? Give one example for a molecule transported by transcytosis.
- Transport of molecules from one side of a cell, through the cell to the other side of the cell is transcytosis
- It is a process of macromolecule transport, e.g. immunoglobulin A.
22. Name one drug which acts by inhibiting Na+-K+ pump?
Digitoxin.
23. Name any two drugs that act by inhibiting cell wall synthesis?
- Penicillins
- Cephalosporins.
24. Name a disease associated with cell membrane defect.
Hereditary spherocytosis—Defect of proteins spectrin and ankyrin.
25. List the various stabilizing forces seen between biomolecules?
- Covalent bonds
- Electrostatic or ionic bonds
- van der Walls forces
- Hydrogen bonds.
26. What is I-cell disease?
It is due to absence of lysosomal enzymes as a result of lack of mannose 6-phosphate signal in the proteins, which targets them to lysosomes. Undegraded molecules form inclusions within lysosomes.
27. What is apoptosis?
Programed cell-death is called apoptosis.
28. What are the changes that cell undergoes during apoptosis?
- Cell shrinkage
- Condensation of chromatin
- DNA fragmentation
- Blebbing of cell membrane
- Formation of apoptotic bodies (membrane-bound organelles)
- Phagocytosis of apoptotic bodies.
29. Name any two pro-apoptotic and antiapoptotic genes of humans.
- Pro-apoptotic—Bax, Bad
- Antiapoptotic—Bcl-2, Bcl-X.
30. Name the enzyme which participates in apoptosis.
Caspases.
31. What are the stages of mitosis and meiosis?
- Mitosis: Prophase, metaphase, anaphase, telophase
- Meiosis:
- I–Prophase (leptotene, zygotene, pachytene, diplotene, diakinesis), metaphase, anaphase, telophase
- II–Prophase, metaphase, anaphase, telophase.
32. What are intermediate filaments? Give examples.
Intermediate filaments are group of proteins whose diameter is in between that of actin and microtubules. They form the part of cytoskeleton, e.g. keratin, desmin, vimentin, neurofilaments, etc.
33. How water is distributed in our body?
