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#	Question	Answer
1	What is Biology?	Biology is the study of living organisms.
2	Which theory emphasised the unity underlying the diversity of life forms?	Cell theory.
3	What does cell theory state about all life forms?	All life forms have cellular organisation.
4	What does the study of cell structure and cell growth by division help explain?	The unity and organisation of living organisms.
5	What created a sense of mystery around physiological and behavioural processes?	The requirement of integrity of cellular organisation for living phenomena to be demonstrated or observed.
6	Which approach uses cell-free systems to investigate physiological and behavioural processes?	The physico-chemical approach.
7	What does analysis of living tissues reveal?	The types of organic compounds present in living organisms.
8	What is meant by the molecular basis of physiological processes?	Understanding how biomolecules carry out processes like digestion, excretion, memory, defence and recognition.
9	What can the physico-chemical approach also explain?	Abnormal processes occurring during diseased conditions.
10	What is Reductionist Biology?	The physico-chemical approach used to study and understand living organisms.
11	Who was G.N. Ramachandran?	An outstanding figure in the field of protein structure.
12	What major discovery of G.N. Ramachandran was published in *Nature* in 1954?	The triple helical structure of collagen.
13	What is the Ramachandran plot used for?	Analysis of the allowed conformations of proteins.
14	What is the basic unit of life present in all living organisms?	The cell.
15	What are unicellular organisms?	Organisms composed of a single cell.
16	What are multicellular organisms?	Organisms composed of many cells.
17	Why is the cell called the fundamental structural and functional unit of life?	Because anything less than a complete cell cannot ensure independent living.
18	Who first saw and described a live cell?	Antonie Von Leeuwenhoek.
19	Who discovered the nucleus?	Robert Brown.
20	What advancement revealed the structural details of the cell?	The invention and improvement of the microscope leading to the electron microscope.
21	Who examined many plants and observed that all plants are composed of different kinds of cells?	Matthias Schleiden.
22	Who studied different types of animal cells and reported the presence of a thin outer layer?	Theodore Schwann.
23	What is the thin outer layer of animal cells called today?	Plasma membrane.
24	What unique characteristic of plant cells did Schwann identify?	Presence of a cell wall.
25	What hypothesis did Schwann propose regarding plants and animals?	That the bodies of plants and animals are composed of cells and products of cells.
26	Who together formulated the cell theory?	Schleiden and Schwann.
27	What important aspect was not explained by the original cell theory?	How new cells were formed.
28	Who explained that new cells arise from pre-existing cells?	Rudolf Virchow.
29	State the first principle of modern cell theory.	All living organisms are composed of cells and products of cells.
30	State the second principle of modern cell theory.	All cells arise from pre-existing cells.
31	What is the outer boundary of a typical plant cell like the onion cell?	Cell wall.
32	What lies just inside the cell wall in a plant cell?	Cell membrane.
33	What is the delimiting outer structure of human cheek cells?	Outer membrane.
34	What dense membrane-bound structure is found inside cells?	Nucleus.
35	What do chromosomes contain?	Genetic material (DNA).
36	What are eukaryotic cells?	Cells with membrane-bound nuclei.
37	What are prokaryotic cells?	Cells lacking a membrane-bound nucleus.
38	What is cytoplasm?	A semi-fluid matrix occupying the volume of the cell.
39	Why is cytoplasm called the main arena of cellular activities?	Because various chemical reactions occur in it to keep the cell alive.
40	Name the membrane-bound organelles found in eukaryotic cells besides the nucleus.	Endoplasmic reticulum, Golgi complex, lysosomes, mitochondria, microbodies and vacuoles.
41	Which membrane-bound organelles are absent in prokaryotic cells?	ER, Golgi complex, lysosomes, mitochondria, microbodies and vacuoles.
42	Which organelles are non-membrane bound and found in both prokaryotic and eukaryotic cells?	Ribosomes.
43	Where are ribosomes found inside cells?	In the cytoplasm, chloroplasts, mitochondria and on rough ER.
44	Which non-membrane-bound organelle in animal cells helps in cell division?	Centrosome.
45	What is the largest isolated single cell mentioned?	Egg of an ostrich.
46	Which cells are among the longest cells in the body?	Nerve cells.
47	Mention some shapes of cells described in the text.	Disc-like, polygonal, columnar, cuboid, thread-like and irregular.
48	What determines the shape of a cell?	The function it performs.
49	Which structures are represented by prokaryotic cells?	Bacteria, blue-green algae, mycoplasma and PPLO (Pleuro Pneumonia Like Organisms).
50	How are prokaryotic cells different from eukaryotic cells in size and multiplication?	They are generally smaller and multiply more rapidly.
51	Name the four basic shapes of bacteria.	Bacillus, coccus, vibrio and spirillum.
52	What is the shape of bacillus bacteria?	Rod-like.
53	What is the shape of coccus bacteria?	Spherical.
54	What is the shape of vibrio bacteria?	Comma-shaped.
55	What is the shape of spirillum bacteria?	Spiral-shaped.
56	How is the organisation of prokaryotic cells fundamentally similar?	All prokaryotes have a similar basic cellular organisation despite variation in shape and function.
57	Which prokaryotic organism lacks a cell wall?	Mycoplasma.
58	What fills the prokaryotic cell?	A semi-fluid matrix called cytoplasm.
59	Why is the nucleus in prokaryotes called not well-defined?	Because the genetic material is not enclosed by a nuclear membrane.
60	What is the genomic DNA in prokaryotes?	A single chromosome or circular DNA.
61	What are plasmids?	Small circular DNA present outside the genomic DNA in many bacteria.
62	What advantage can plasmid DNA provide to bacteria?	Resistance to antibiotics.
63	What is the role of plasmid DNA in higher studies?	It is used to monitor bacterial transformation with foreign DNA.
64	Is a nuclear membrane present in prokaryotes?	No, it is absent.
65	Which organelles are found in prokaryotic cells?	Ribosomes.
66	What unique structures are found in prokaryotic cells?	Inclusions and mesosomes.
67	What is a mesosome?	A specialised differentiated form of cell membrane formed by infoldings of the plasma membrane.
68	What are the three layers of the bacterial cell envelope?	Glycocalyx, cell wall and plasma membrane.
69	What is the function of the bacterial cell envelope?	It acts as a single protective unit.
70	On what basis are bacteria classified as Gram positive and Gram negative?	On the basis of differences in cell envelopes and response to Gram staining.
71	Which bacteria are called Gram positive?	Bacteria that take up Gram stain.
72	Which bacteria are called Gram negative?	Bacteria that do not take up Gram stain.
73	What is glycocalyx?	The outermost layer of the bacterial cell envelope.
74	What is a slime layer?	A loose sheath form of glycocalyx.
75	What is a capsule in bacteria?	A thick and tough form of glycocalyx.
76	What is the function of the bacterial cell wall?	It determines cell shape and provides structural support.
77	Why is the bacterial cell wall important structurally?	It prevents the bacterium from bursting or collapsing.
78	What is the nature of the plasma membrane in bacteria?	Selectively permeable.
79	How is the bacterial plasma membrane structurally similar?	It is structurally similar to that of eukaryotes.
80	How are mesosomes formed?	By extensions of plasma membrane into the cell.
81	In what forms do mesosomal extensions occur?	Vesicles, tubules and lamellae.
82	What are chromatophores?	Membranous extensions in cyanobacteria containing pigments.
83	What are bacterial flagella?	Thin filamentous extensions from the cell wall responsible for motility.
84	Name the three parts of a bacterial flagellum.	Filament, hook and basal body.
85	Which part of the bacterial flagellum is the longest?	Filament.
86	What are pili?	Elongated tubular structures made of special protein.
87	What are fimbriae?	Small bristle-like fibres sprouting out of bacterial cells.
88	What is the function of fimbriae in some bacteria?	They help bacteria attach to rocks in streams and host tissues.
89	What are eukaryotes?	Organisms that include protists, plants, animals and fungi.
90	What is a major feature of eukaryotic cells?	Extensive compartmentalisation of cytoplasm through membrane-bound organelles.
91	What type of nucleus is present in eukaryotic cells?	An organised nucleus with a nuclear envelope.
92	What kind of structures for movement are present in eukaryotic cells?	Complex locomotory and cytoskeletal structures.
93	How is the genetic material organised in eukaryotic cells?	Into chromosomes.
94	Are all eukaryotic cells identical?	No, they differ in structure and components.
95	Which structures are present in plant cells but absent in animal cells?	Cell wall, plastids and a large central vacuole.
96	Which structures are present in animal cells but absent in almost all plant cells?	Centrioles.
97	What is the function of plastids in plant cells according to the text?	They are characteristic structures present in plant cells.
98	What is the large membrane-bound space present in plant cells?	Large central vacuole.
99	What are plasmodesmata?	Structures shown connecting plant cells in the plant cell diagram.
100	Which organelle is responsible for packaging and secretion in cells?	Golgi apparatus.
101	Which organelles are involved in protein synthesis and transport?	Rough endoplasmic reticulum and ribosomes.
102	Which organelle is responsible for energy production in cells?	Mitochondrion.
103	Which structure encloses the nucleus?	Nuclear envelope.
104	Which structure is present inside the nucleus?	Nucleolus.
105	What is the outer living boundary of the cell?	Plasma membrane.
106	Which non-living outer covering is present in plant cells?	Cell wall.
107	Which structures are involved in intracellular transport?	Endoplasmic reticulum.
108	Which organelles are involved in intracellular digestion?	Lysosomes.
109	Which structures are associated with the cytoskeleton in the plant cell diagram?	Microtubules.
110	Which projection-like structures are shown in the animal cell diagram?	Microvilli.
111	What is the semi-fluid matrix of the cell called?	Cytoplasm.
112	Which organelle is associated with cell division in animal cells?	Centrosome (which contains two centrioles).
113	Which organelles are membrane-bound in eukaryotic cells?	Nucleus, ER, Golgi apparatus, lysosomes, vacuoles, mitochondria, plastids and peroxisomes.
114	What is the main distinguishing feature between prokaryotic and eukaryotic cells mentioned on these pages?	Presence of membrane-bound organelles and organised nucleus in eukaryotes.
115	Which type of cell contains plastids?	Plant cells and euglenoides.
116	Which instrument helped scientists study the detailed structure of the cell membrane?	Electron microscope.
117	During which decade was the detailed structure of the membrane studied extensively?	1950s.
118	Which cells were mainly used for chemical studies of the plasma membrane?	Human red blood cells (RBCs).
119	What are the main components of the cell membrane?	Lipids and proteins.
120	Which lipids are major components of the plasma membrane?	Phospholipids.
121	How are phospholipids arranged in the plasma membrane?	In a bilayer.
122	How are phospholipids oriented within the membrane?	Polar heads face outward and hydrophobic tails face inward.
123	Why are hydrophobic tails directed inward in the membrane?	To protect nonpolar hydrocarbon tails from the aqueous environment.
124	Which additional lipid is present in the plasma membrane besides phospholipids?	Cholesterol.
125	Besides lipids, what other major biomolecules are present in the membrane?	Proteins and carbohydrates.
126	Does the protein-to-lipid ratio remain the same in all cell membranes?	No, it varies considerably among cell types.
127	What percentage of protein is present in the human erythrocyte membrane?	Approximately 52%.
128	What percentage of lipids is present in the human erythrocyte membrane?	Approximately 40%.
129	How are membrane proteins classified based on extraction?	Integral proteins and peripheral proteins.
130	What are peripheral proteins?	Proteins lying on the surface of the membrane.
131	What are integral proteins?	Proteins partially or totally buried in the membrane.
132	Who proposed the fluid mosaic model of plasma membrane?	Singer and Nicolson.
133	In which year was the fluid mosaic model proposed?	1972.
134	According to the fluid mosaic model, what enables lateral movement of proteins?	The quasi-fluid nature of lipids.
135	What is meant by membrane fluidity?	The ability of proteins to move laterally within the lipid bilayer.
136	What is one of the most important functions of the plasma membrane?	Transport of molecules across it.
137	What does selectively permeable membrane mean?	The membrane allows only certain molecules to pass through it.
138	What is passive transport?	Movement of molecules across the membrane without energy requirement.
139	How do neutral solutes move across the membrane?	By simple diffusion along the concentration gradient.
140	Define concentration gradient.	Movement from higher concentration to lower concentration.
141	What is osmosis?	Movement of water by diffusion across a membrane.
142	Why can polar molecules not pass through the lipid bilayer directly?	Because the lipid bilayer is nonpolar.
143	How are polar molecules transported across the membrane?	With the help of carrier proteins.
144	What is active transport?	Energy-dependent transport of molecules against the concentration gradient.
145	In active transport, molecules move from which concentration to which concentration?	From lower concentration to higher concentration.
146	Which molecule provides energy for active transport?	ATP.
147	What is the cell wall?	A non-living rigid structure outside the plasma membrane in fungi and plants.
148	What is the cell wall of algae mainly composed of?	Cellulose, galactans, mannans and minerals like calcium carbonate.
149	What are the major components of plant cell walls?	Cellulose, hemicellulose, pectins and proteins.
150	What is the primary wall?	The cell wall of a young plant cell capable of growth.
151	Where is the secondary wall formed in plant cells?	On the inner side toward the membrane.
152	What is the middle lamella mainly composed of?	Calcium pectate.
153	What is the function of the middle lamella?	It glues neighbouring cells together.
154	What are plasmodesmata?	Connections traversing the cell wall and middle lamella linking neighbouring cell cytoplasm.
155	Which organelles together form the endomembrane system?	Endoplasmic reticulum (ER), Golgi complex, lysosomes and vacuoles.
156	Why are some organelles grouped as the endomembrane system?	Because their functions are coordinated.
157	Which organelles are not considered part of the endomembrane system?	Mitochondria, chloroplasts and peroxisomes.
158	What is the endoplasmic reticulum (ER)?	A network of tiny tubular structures scattered in the cytoplasm.
159	What does ER divide the intracellular space into?	Luminal (inside ER) and extra-luminal (cytoplasm) compartments.
160	What is rough endoplasmic reticulum (RER)?	ER with ribosomes attached to its outer surface.
161	What is smooth endoplasmic reticulum (SER)?	ER lacking ribosomes on its surface.
162	In which cells is RER frequently observed?	Cells actively involved in protein synthesis and secretion.
163	With which structure is RER continuous?	Outer membrane of the nucleus.
164	What is the major function of SER?	Synthesis of lipids.
165	Which substances are synthesised in SER of animal cells?	Lipid-like steroidal hormones.
166	Who first observed Golgi apparatus?	Camillo Golgi.
167	In which year did Camillo Golgi observe Golgi bodies?	1898.
168	What are Golgi bodies made up of?	Flat disc-shaped sacs called cisternae.
169	How are Golgi cisternae arranged?	Stacked parallel to each other.
170	What are the two faces of the Golgi apparatus?	Cis (forming) face and trans (maturing) face.
171	Which face of Golgi apparatus is convex?	Cis face.
172	Which face of Golgi apparatus is concave?	Trans face.
173	What is the main function of Golgi apparatus?	Packaging materials for intracellular targets or secretion outside the cell.
174	How do materials reach the Golgi apparatus from ER?	In the form of vesicles that fuse with the cis face.
175	Why does Golgi apparatus remain closely associated with ER?	Because materials from ER are modified and packaged in Golgi bodies.
176	What happens to proteins synthesised on ER in the Golgi apparatus?	They are modified in the Golgi cisternae before release.
177	Which biomolecules are formed in the Golgi apparatus?	Glycoproteins and glycolipids.
178	What are lysosomes?	Membrane-bound vesicular structures formed by packaging in the Golgi apparatus.
179	Which enzymes are abundant in lysosomes?	Hydrolytic enzymes (hydrolases).
180	Name the types of hydrolases present in lysosomes.	Lipases, proteases and carbohydrases.
181	At which pH are lysosomal enzymes optimally active?	Acidic pH.
182	Which macromolecules can lysosomal enzymes digest?	Carbohydrates, proteins, lipids and nucleic acids.
183	What is a vacuole?	A membrane-bound space present in the cytoplasm.
184	What substances are present inside vacuoles?	Water, sap, excretory products and other materials not useful for the cell.
185	What is the membrane surrounding the vacuole called?	Tonoplast.
186	How much volume of a plant cell can vacuoles occupy?	Up to 90% of the cell volume.
187	What is the function of tonoplast in plant cells?	It facilitates transport of ions and materials into the vacuole against concentration gradients.
188	Why is concentration of materials higher in vacuoles than cytoplasm?	Because tonoplast transports materials against concentration gradients.
189	What is the role of contractile vacuoles in Amoeba?	Osmoregulation and excretion.
190	How are food vacuoles formed in protists?	By engulfing food particles.
191	Why are mitochondria not easily visible under a microscope?	Because they are not easily visible unless specifically stained.
192	On what does the number of mitochondria per cell depend?	The physiological activity of the cell.
193	What is the usual shape of mitochondria?	Sausage-shaped or cylindrical.
194	How many membranes surround a mitochondrion?	Two membranes.
195	What are the two aqueous compartments of mitochondria?	Outer compartment and inner compartment.
196	What is the dense homogeneous substance inside the inner compartment called?	Matrix.
197	What are cristae?	Infoldings of the inner mitochondrial membrane toward the matrix.
198	What is the function of cristae?	They increase the surface area.
199	What is the main function of mitochondria?	Site of aerobic respiration and ATP production.
200	What genetic material is present inside mitochondria?	Single circular DNA molecule.
201	Which additional components are found in mitochondrial matrix?	RNA molecules, 70S ribosomes and protein synthesis components.
202	How do mitochondria divide?	By fission.
203	In which organisms are plastids found?	Plant cells and euglenoides.
204	Why are plastids easily observed under a microscope?	Because they are large.
205	Why do plastids impart colour to plants?	Because they contain specific pigments.
206	Name the three types of plastids.	Chloroplasts, chromoplasts and leucoplasts.
207	Which pigments are present in chloroplasts?	Chlorophyll and carotenoid pigments.
208	What is the function of chloroplast pigments?	Trapping light energy for photosynthesis.
209	Which pigments are present in chromoplasts?	Fat-soluble carotenoid pigments like carotene and xanthophylls.
210	Which colours are imparted by chromoplasts?	Yellow, orange or red.
211	What are leucoplasts?	Colourless plastids storing nutrients.
212	What do amyloplasts store?	Carbohydrates (starch).
213	Give an example of a plant containing amyloplasts.	Potato.
214	What do elaioplasts store?	Oils and fats.
215	What do aleuroplasts store?	Proteins.
216	Where are most chloroplasts found in green plants?	Mesophyll cells of leaves.
217	Mention the common shapes of chloroplasts.	Lens-shaped, oval, spherical, discoid or ribbon-like.
218	How many chloroplasts are found in Chlamydomonas?	One per cell.
219	How many chloroplasts are commonly present in mesophyll cells?	20 - 40 per cell.
220	Are chloroplasts single or double membrane-bound?	Double membrane-bound.
221	Which chloroplast membrane is less permeable?	Inner membrane.
222	What is the stroma?	The space enclosed by the inner chloroplast membrane.
223	What are thylakoids?	Organised flattened membranous sacs present in the stroma.
224	What are grana?	Stacks of thylakoids arranged like piles of coins.
225	What are stroma lamellae?	Flat membranous tubules connecting thylakoids of different grana.
226	What is the lumen in chloroplasts?	The space enclosed by thylakoid membranes.
227	What does the stroma of chloroplast contain?	Enzymes for synthesis of carbohydrates and proteins, circular DNA and ribosomes.
228	Where are chlorophyll pigments located in chloroplasts?	In the thylakoids.
229	What is the size of chloroplast ribosomes?	70S.Chloroplast ribosomes are 70S in size (measured by their sedimentation rate in Svedberg units)
230	What is the size of cytoplasmic ribosomes in eukaryotes?	80S.
231	Who first observed ribosomes under the electron microscope?	George Palade.
232	In which year were ribosomes first observed?	1953.
233	What are ribosomes made of?	RNA and proteins.
234	Are ribosomes membrane-bound?	No.
235	What are the subunits of 80S ribosomes?	60S and 40S.
236	What are the subunits of 70S ribosomes?	50S and 30S.
237	What does the Svedberg unit measure indirectly?	Density and size of ribosomes.
238	What is cytoskeleton?	A network of proteinaceous structures including microtubules, microfilaments and intermediate filaments.
239	What are the functions of cytoskeleton?	Mechanical support, motility and maintenance of cell shape.
240	What are cilia and flagella?	Hair-like outgrowths of the cell membrane.
241	What is the singular form of cilia?	Cilium.
242	What is the singular form of flagella?	Flagellum.
243	What is the function of cilia?	They work like oars causing movement of the cell or surrounding fluid.
244	How are flagella different from cilia?	Flagella are comparatively longer and responsible for cell movement.
245	Are bacterial flagella structurally similar to eukaryotic flagella?	No, they are structurally different.
246	What covers cilia and flagella?	Plasma membrane.
247	What is the core of cilia and flagella called?	Axoneme.
248	What does the axoneme contain?	Microtubules running parallel to the long axis.
249	Describe the arrangement of microtubules in the axoneme.	Nine peripheral doublets and two central microtubules.
250	What connects the central tubules in cilia and flagella?	Bridges.
251	What surrounds the central tubules?	Central sheath.
252	What connects the central sheath to peripheral doublets?	Radial spokes.
253	How many radial spokes are present in the axoneme?	Nine.
254	What connects the peripheral doublets of microtubules?	Linkers.
255	From which structure do cilia and flagella arise?	Basal bodies.
256	What are basal bodies?	Centriole-like structures from which cilia and flagella emerge.
257	What is a centrosome?	An organelle usually containing two cylindrical centrioles.
258	What surrounds centrioles in the centrosome?	Amorphous pericentriolar materials.
259	How are the two centrioles arranged in a centrosome?	Perpendicular to each other.
260	Which organisation pattern is shown by centrioles?	Cartwheel organisation.
261	What are centrioles made up of?	Nine evenly spaced peripheral fibrils of tubulin protein.
262	What is each peripheral fibril in a centriole called?	A triplet.
263	What links adjacent triplets in centrioles?	Protein linkages.
264	What is the central proteinaceous part of a centriole called?	Hub.
265	What connects the hub to peripheral triplets?	Radial spokes made of protein.
266	Who first described the nucleus as a cell organelle?	Robert Brown.
267	In which year was the nucleus first described?	1831.
268	What is chromatin?	Highly extended and elaborate nucleoprotein fibres present in the interphase nucleus.
269	What structures are present in the interphase nucleus?	Chromatin, nuclear matrix and nucleoli.
270	What is the nuclear envelope made of?	Two parallel membranes.
271	What is the space between the two nuclear membranes called?	Perinuclear space.
272	What is the width of the perinuclear space?	10 - 50 nm.
273	What is the function of the nuclear envelope?	It forms a barrier between nuclear contents and cytoplasm.
274	With which organelle is the outer nuclear membrane continuous?	Endoplasmic reticulum.
275	What is present on the outer nuclear membrane?	Ribosomes.
276	What are nuclear pores?	Minute pores formed by fusion of the two nuclear membranes.
277	What is the function of nuclear pores?	Movement of RNA and proteins between nucleus and cytoplasm.
278	Is there always only one nucleus per cell?	No, variations in the number of nuclei may occur.
279	Name two mature cells that lack a nucleus.	Mammalian erythrocytes and sieve tube cells of vascular plants.
280	What does the nuclear matrix or nucleoplasm contain?	Nucleolus and chromatin.
281	What is the nucleolus?	A spherical structure present in the nucleoplasm.
282	Is nucleolus membrane-bound?	No.
283	What is the main function of nucleolus?	Active synthesis of ribosomal RNA (rRNA).
284	In which cells are nucleoli larger and more numerous?	Cells actively carrying out protein synthesis.
285	Who formulated the cell theory?	Schleiden and Schwann.
286	Who explained that cells arise from pre-existing cells?	Rudolf Virchow.
287	How does a unicellular organism perform life activities?	Within a single cell.
288	New cells generate from which source?	Pre-existing cells.
289	What is - Cristae	Infoldings in mitochondria.
290	What is - Cisternae	Disc-shaped sacs in Golgi apparatus.
291	What is - Thylakoids	Flat membranous sacs in stroma.
292	Do prokaryotes have membrane-bound organelles?	In prokaryotes, there are no membrane-bound organelles.
293	Do all living organisms have a nucleus?	No.
294	Do both plant and animal cells have a cell wall?	No, animal cells lack a cell wall.
295	Are cells formed de novo from abiotic materials?	No.
296	What is a mesosome in a prokaryotic cell?	A specialised differentiated form of plasma membrane formed by infoldings.
297	Mention one function of mesosomes.	They help in cell wall formation, DNA replication, respiration or secretion.
298	How do neutral solutes move across the plasma membrane?	By simple diffusion along the concentration gradient.
299	Can polar molecules move across the membrane by simple diffusion?	No.
300	How are polar molecules transported across the plasma membrane?	With the help of carrier proteins.
301	Name two double membrane-bound organelles.	Mitochondria and chloroplasts.
302	What is the function of mitochondria?	Production of ATP through aerobic respiration.
303	What is the function of chloroplasts?	Trapping light energy for photosynthesis.
304	What are the characteristics of prokaryotic cells?	They lack a membrane-bound nucleus and membrane-bound organelles.
305	What is meant by division of labour in multicellular organisms?	Different cells perform specialised functions.
306	Why is the cell called the basic unit of life?	Because it is the structural and functional unit of all living organisms.
307	What are nuclear pores?	Openings in the nuclear envelope.
308	What is the function of nuclear pores?	Exchange of RNA and proteins between nucleus and cytoplasm.
309	How are lysosomes and vacuoles similar?	Both are endomembrane structures.
310	How do lysosomes differ from vacuoles?	Lysosomes contain digestive enzymes, while vacuoles mainly store materials.
311	What is a centromere?	The primary constriction of a chromosome holding chromatids together.
312	On what basis are chromosomes classified?	Position of the centromere.
313	Name the four types of chromosomes based on centromere position.	Metacentric, submetacentric, acrocentric and telocentric.