CLASS 11 BIOLOGY
CHAPTER 8
Cell: The Unit of Life
Conceptual • NCERT-Focused • NEET-Oriented
The way to study this chapter
This chapter is not a list of organelles to memorize.
Think of a cellA cellA cell is the smallest structural and functional unit of living organisms capable of independent existence and performing all essential life processes. as a working city:
Cell membrane → controlled boundary
Nucleus → information/control centre
Ribosomes → protein-making machinery
ER → manufacturing + transport network
Golgi → processing + packaging centre
LysosomesLysosomesMembrane-bound vesicles containing hydrolytic enzymes (acid hydrolases) that digest worn-out organelles, foreign particles, and macromolecules. → intracellular digestion/recycling
MitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration. → ATP production
ChloroplastchloroplastA plastid containing chlorophyll where photosynthesis occurs. → light-energy capture
CytoskeletoncytoskeletonA network of protein filaments that supports cell shape, organisation, and movement. → internal structural framework
Vacuole → storage/osmotic regulation
| CORE IDEA Once you understand the functional logic, the individual facts become much easier to remember. |
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What is a cellA cellA cell is the smallest structural and functional unit of living organisms capable of independent existence and performing all essential life processes.?
A cellA cellA cell is the smallest structural and functional unit of living organisms capable of independent existence and performing all essential life processes. is the fundamental structural and functional unit of life.
Why? Because a complete cell can maintain its internal organisation, carry out essential life processes, interact with its surroundings, and, in unicellular organisms, perform all functions necessary for independent existence.
Unicellular vs multicellular
| Unicellular organism | Multicellular organism |
|---|---|
| One cell performs all essential life activities. | Different cells become specialised for different functions. |
| Examples: bacteria, Amoeba, many protists. | This creates division of labour. |
| CORE IDEA More cells ≠ simply a bigger organism. Multicellularity allows specialisation and division of labour. |
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A small historical timeline
| Scientist | Contribution |
|---|---|
| Antonie van Leeuwenhoek | First observed and described a live cell |
| Robert Brown | Discovered the nucleusThe nucleusThe nucleus is a double membrane-bound organelle containing the cell's genetic material (DNA) and controlling all cellular activities. |
| Matthias Schleiden (1838) | Studied plants; concluded plants are composed of cells |
| Theodor Schwann (1839) | Studied animals; concluded animals are composed of cells |
| Rudolf Virchow (1855) | Proposed that new cells arise from pre-existing cells |
| NEET TRAP Do not write: Robert Brown discovered the cell. He discovered the nucleusThe nucleusThe nucleus is a double membrane-bound organelle containing the cell's genetic material (DNA) and controlling all cellular activities.. Leeuwenhoek observed live cells. |
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Cell theory
Schleiden and Schwann formulated the basic cell theory. Virchow later modified it by explaining the origin of new cells.
All living organisms are composed of cells and products of cells.
All cells arise from pre-existing cells.
| MEMORY HOOK S + S = Structure. V = Via pre-existing cells. |
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Why are cells different?
Cells differ in size, shape, structure and function. The most important relationship is: CELL STRUCTURE ↔ CELL FUNCTION.
RBC: Biconcave → specialised for efficient gas transport.
Nerve cell: Long and branched → specialised for receiving and transmitting signals.
Columnar epithelial cell: Tall/elongated → suited to its epithelial function.
| STUDY RULE Never learn cell shape as an isolated fact. Ask: “How does this shape help the cell perform its function?” |
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Prokaryotic vs eukaryotic
The defining difference is simple: a prokaryotic cell has no membrane-bound nucleus, whereas a eukaryotic cell has a membrane-bound nucleus.
| Feature | Prokaryotic | Eukaryotic |
|---|---|---|
| Nucleus | No membrane-bound nucleus | Membrane-bound nucleus |
| Genetic material | Essentially naked | Enclosed within nucleus |
| Membrane-bound organelles | Absent | Present |
| Ribosomes | 70S | 80S |
| Size | Generally smaller | Generally larger |
| Organisation | Simpler | More compartmentalised |
| Examples | Bacteria, cyanobacteria, mycoplasma | Plants, animals, fungi, protists |
| NEET TRAP Do not say “prokaryotes have no organelles.” They lack membrane-bound organelles, but they do have ribosomes. |
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Prokaryotic cell
Prokaryotes include bacteria, blue-green algae/cyanobacteria, mycoplasma and PPLO. They are generally smaller and multiply more rapidly than eukaryotic cells.
Bacterial shapes
| Term | Shape |
|---|---|
| Bacillus | Rod-shaped |
| Coccus | Spherical |
| Vibrio | Comma-shaped |
| Spirillum | Spiral |
| MEMORY HOOK Bacillus = Bar • Coccus = Ball • Vibrio = Comma • Spirillum = Spiral |
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The prokaryotic cell envelope
The bacterial cell envelope has three major layers:
Glycocalyx → Cell wallCell WallA rigid, non-living outer layer present in plant cells, fungi, and bacteria, providing mechanical support and protection. → Plasma membraneplasma membraneThe selectively permeable boundary that controls movement into and out of a cell.
| Layer | Key point |
|---|---|
| Glycocalyx | Outermost covering; may be a capsule (thick, firmly attached) or slime layer (loose). |
| Cell wallCell WallA rigid, non-living outer layer present in plant cells, fungi, and bacteria, providing mechanical support and protection. | Provides shape, protection and mechanical strength. |
| Plasma membraneplasma membraneThe selectively permeable boundary that controls movement into and out of a cell. | Selectively permeable; regulates movement of substances. |
| HIGH-YIELD Mycoplasma lacks a cellA cellA cell is the smallest structural and functional unit of living organisms capable of independent existence and performing all essential life processes. wall. |
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Mesosome
NCERT describes mesosomes as specialised infoldings of the plasma membraneThe plasma membraneThe plasma membrane is a thin, flexible, selectively permeable barrier that encloses the cytoplasm and regulates entry and exit of substances. of prokaryotes. They are associated with cell wallCell WallA rigid, non-living outer layer present in plant cells, fungi, and bacteria, providing mechanical support and protection. formation, DNA replication, distribution of DNA to daughter cells, respiration, secretion and increased plasma membraneplasma membraneThe selectively permeable boundary that controls movement into and out of a cell. surface area.
Plasmids
Some bacteria contain small circular DNA molecules in addition to their main genomic DNA. These are called plasmids.
They can carry genes that provide particular advantages, such as antibiotic resistance.
| REMEMBER Chromosomal DNA → main genetic material. Plasmid → additional circular DNA. |
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Eukaryotic cell
A typical eukaryotic cell contains cell membrane, cytoplasm, nucleus and organelles.
The major advantage of eukaryotic organisation is compartmentalisation: different reactions can occur in different compartments, allowing specialised biochemical processes to run efficiently.
Plasma membraneplasma membraneThe selectively permeable boundary that controls movement into and out of a cell.
The plasma membraneThe plasma membraneThe plasma membrane is a thin, flexible, selectively permeable barrier that encloses the cytoplasm and regulates entry and exit of substances. forms the boundary of the cell and is selectively permeable. It does not allow every substance to cross freely.
The cell must maintain a controlled internal environment: take in useful substances, remove wastes, regulate ions and maintain concentration gradients.
Fluid mosaic model
The membrane consists mainly of lipids and proteins. The lipid bilayer forms the basic framework, while proteins are embedded within or associated with this lipid arrangement.
Fluid → components can move within the membrane.
Mosaic → different proteins are distributed within the lipid matrix.
How do substances cross the membrane?
| Process | Direction / mechanism | Energy |
|---|---|---|
| Simple diffusion | Higher concentration → lower concentration | No direct cellular energy required |
| Facilitated diffusion | Down the concentration gradient with membrane-protein assistance | No direct cellular energy required |
| Active transport | Can move against the concentration gradient | Requires energy |
| MEMORY HOOK Diffusion: “I'm going downhill.” Active transport: “I'm being pushed uphill.” |
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Endocytosis
The cell can bring in material that cannot simply pass through the membrane by folding the membrane inward and engulfing material. This is endocytosis.
Phagocytosis
Pinocytosis
| MEMORY HOOK Endo = enter |
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Cell wallCell WallA rigid, non-living outer layer present in plant cells, fungi, and bacteria, providing mechanical support and protection.
Plant cells have a cellA cellA cell is the smallest structural and functional unit of living organisms capable of independent existence and performing all essential life processes. wall outside the plasma membraneThe plasma membraneThe plasma membrane is a thin, flexible, selectively permeable barrier that encloses the cytoplasm and regulates entry and exit of substances.. Main components include cellulose, hemicellulose and pectin.
Provides mechanical support, protection and shape.
Middle lamella: mainly pectin; helps hold neighbouring plant cells together.
PlasmodesmataplasmodesmataCytoplasmic connections that pass through plant cell walls and link adjacent cells.: connections between neighbouring plant cells that permit communication/material exchange.
Cytoplasm
The cytoplasm is the semi-fluid internal matrix of the cell and is the major arena for many cellular activities.
Nucleus
The nucleusThe nucleusThe nucleus is a double membrane-bound organelle containing the cell's genetic material (DNA) and controlling all cellular activities. is the major repository of genetic information in a eukaryotic cell and plays a major role in controlling cellular activities and heredity.
Structure: Nuclear envelope → Nucleoplasm → Chromatin → Nucleolus
Nuclear envelope
The nuclear envelope is a double membrane and contains nuclear pores. Nuclear pores allow exchange/transport of substances between nucleus and cytoplasm.
| NEET TRAP Nuclear envelope = double membrane. Nuclear pores = openings in the nuclear envelope. |
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Chromatin
Chromatin is the genetic material in its less-condensed state within the nucleusThe nucleusThe nucleus is a double membrane-bound organelle containing the cell's genetic material (DNA) and controlling all cellular activities.. During cell division, chromatin becomes highly condensed to form chromosomes.
| CONCEPT Chromatin → condenses → chromosomes |
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Nucleolus
The nucleolus is a dense, non-membrane-bound structure inside the nucleusThe nucleusThe nucleus is a double membrane-bound organelle containing the cell's genetic material (DNA) and controlling all cellular activities.. It is associated primarily with ribosomeribosomeA non-membranous structure made of rRNA and proteins where protein synthesis occurs. biogenesis.
| DON'T CONFUSE Nucleolus ≠ nucleus. Nucleolus is inside the nucleusThe nucleusThe nucleus is a double membrane-bound organelle containing the cell's genetic material (DNA) and controlling all cellular activities.. |
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Endomembrane system
The endomembrane system includes endoplasmic reticulum, Golgi apparatus, lysosomesLysosomesMembrane-bound vesicles containing hydrolytic enzymes (acid hydrolases) that digest worn-out organelles, foreign particles, and macromolecules. and vacuoles.
| FUNCTIONAL STORY ER → manufacture/transport → Golgi → modify + package + dispatch → LysosomelysosomeA membrane-bound vesicle containing hydrolytic enzymes for intracellular digestion. → digestion/recycling → Vacuole → storage/osmoregulation |
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Endoplasmic reticulum
ER is an extensive membrane network consisting of tubules and cisternae.
| Type | Structure | Main association |
|---|---|---|
| Rough ER | Ribosomes attached | Protein synthesis, especially proteins destined for secretion/membranes |
| Smooth ER | Lacks ribosomes | Lipid synthesis, detoxification and other metabolic functions |
| MEMORY HOOK RER → Ribosomes → Protein. SER → Smooth → Lipid. |
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Golgi apparatus
Golgi consists of flattened membrane-bound sacs called cisternae. Its major functions include modification, packaging, sorting and secretion.
| FACTORY ANALOGY If ER is the manufacturing department, Golgi is the finishing + packaging + dispatch department. |
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LysosomesLysosomesMembrane-bound vesicles containing hydrolytic enzymes (acid hydrolases) that digest worn-out organelles, foreign particles, and macromolecules.
LysosomesLysosomesMembrane-bound vesicles containing hydrolytic enzymes (acid hydrolases) that digest worn-out organelles, foreign particles, and macromolecules. are single-membrane-bound structures containing hydrolytic enzymes. Their major function is intracellular digestion.
Digest proteins, lipids, carbohydrates and nucleic acids.
Participate in degradation of worn-out cellular components.
| MEMORY HOOK LysosomelysosomeA membrane-bound vesicle containing hydrolytic enzymes for intracellular digestion. = cell's digestive/recycling compartment |
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Vacuoles
Vacuoles are membrane-bound structures. Their surrounding membrane is called the tonoplast and their interior contains cell sap.
Plant-cell vacuoles can occupy a very large fraction of the cell volume.
Functions include storage, maintaining turgidity, ion accumulation and osmoregulation.
Amoeba: contractile vacuole → osmoregulation and excretion.
Protists: food vacuoles → formed after engulfing food particles.
LysosomelysosomeA membrane-bound vesicle containing hydrolytic enzymes for intracellular digestion. vs vacuole
| LysosomelysosomeA membrane-bound vesicle containing hydrolytic enzymes for intracellular digestion. | Vacuole |
|---|---|
| Intracellular digestion | Storage, osmoregulation and other roles |
| Contains hydrolytic enzymes | Contains cell sap/materials |
| Important in intracellular breakdown | Particularly prominent in plant cells |
| Single membrane | Single membrane |
MitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration.
MitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration. are double-membrane-bound organelles and major sites of aerobic respiration and ATP generation.
Structure: Outer membrane → intermembrane space → inner membrane → matrix. The inner membrane forms folds called cristaecristaeFolds of the inner mitochondrial membrane that increase surface area..
CristaecristaeFolds of the inner mitochondrial membrane that increase surface area. increase the surface area of the inner membrane, providing more membrane surface for processes associated with ATP generation.
The mitochondrial matrix contains circular DNA, RNA, 70S ribosomes and components for protein synthesis.
| CONCEPT MitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration. are semiautonomous because they possess their own genetic material and protein-synthesising machinery, although they remain dependent on the cell for many proteins and functions. |
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PlastidsPlastidsMembrane-bound organelles found only in plant cells and euglenoids, involved in photosynthesis, storage, or colour.
PlastidsPlastidsMembrane-bound organelles found only in plant cells and euglenoids, involved in photosynthesis, storage, or colour. occur in plant cells and euglenoids.
| Type | Main role |
|---|---|
| Chloroplasts | Green; photosynthesis |
| Chromoplasts | Coloured due to carotenoid pigments |
| Leucoplasts | Colourless; storage |
| Leucoplast subtype | Stores |
|---|---|
| Amyloplast | Starch |
| Elaioplast | Oils/fats |
| Aleuroplast | Proteins |
| MEMORY HOOK Amylo → starch • Elaio → oil • Aleuro → protein |
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ChloroplastchloroplastA plastid containing chlorophyll where photosynthesis occurs.
ChloroplastchloroplastA plastid containing chlorophyll where photosynthesis occurs. is a double-membrane-bound organelle. The internal region enclosed by the inner membrane is the stromastromaThe fluid matrix of a chloroplast surrounding the thylakoids..
Within the stromastromaThe fluid matrix of a chloroplast surrounding the thylakoids. are flattened membranous sacs called thylakoids. Thylakoids are stacked into grana. Different grana are connected by stromastromaThe fluid matrix of a chloroplast surrounding the thylakoids. lamellae.
The hierarchy
Membrane sac → ThylakoidthylakoidA flattened membrane sac inside a chloroplast that contains pigments for light reactions.
Stack of thylakoids → Granum
Stacks connected by → StromastromaThe fluid matrix of a chloroplast surrounding the thylakoids. lamellae
Fluid internal matrix → StromastromaThe fluid matrix of a chloroplast surrounding the thylakoids.
| HIGH-YIELD ThylakoidthylakoidA flattened membrane sac inside a chloroplast that contains pigments for light reactions. membrane contains chlorophyll pigments. Grana are associated with light reactions. StromastromaThe fluid matrix of a chloroplast surrounding the thylakoids. contains enzymes associated with carbohydrate/protein synthesis and reactions traditionally described by NCERT as the “dark reactions.” |
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Ribosomes
Ribosomes are non-membrane-bound organelles responsible for protein synthesis. They contain RNA and proteins.
| RibosomeribosomeA non-membranous structure made of rRNA and proteins where protein synthesis occurs. | Subunits |
|---|---|
| Prokaryotic: 70S | 50S + 30S |
| Eukaryotic cytoplasmic: 80S | 60S + 40S |
| CLASSIC NEET TRAP 50S + 30S = 70S, not 80S. 60S + 40S = 80S, not 100S. Svedberg values represent sedimentation behaviour, not simple arithmetic mass units. |
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Where are 70S ribosomes found?
Prokaryotic ribosomes
MitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration.
Chloroplasts
| HIGH-YIELD 80S → eukaryotic cytoplasm. 70S → prokaryotes + mitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration. + chloroplasts. |
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CytoskeletoncytoskeletonA network of protein filaments that supports cell shape, organisation, and movement.
The cytoskeletoncytoskeletonA network of protein filaments that supports cell shape, organisation, and movement. is an internal network of proteinaceous filaments.
Microtubules
Microfilaments
Intermediate filaments
Functions include mechanical support, maintaining cell shape, motility and organisation of internal structures.
| MEMORY HOOK CytoskeletoncytoskeletonA network of protein filaments that supports cell shape, organisation, and movement. = cell's internal framework |
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Cilia and flagella
These are hair-like extensions associated with the plasma membraneThe plasma membraneThe plasma membrane is a thin, flexible, selectively permeable barrier that encloses the cytoplasm and regulates entry and exit of substances..
| Cilia | Flagella |
|---|---|
| Generally shorter | Generally longer |
| Can move the cell or fluid surrounding the cell | Primarily associated with cell movement |
The 9 + 2 array
A typical eukaryotic cilium/flagellum contains 9 peripheral doublets + 2 central microtubules = 9 + 2 arrangement.
The structure also contains a central sheath, radial spokes and linkers, and is enclosed by the plasma membraneThe plasma membraneThe plasma membrane is a thin, flexible, selectively permeable barrier that encloses the cytoplasm and regulates entry and exit of substances..
Basal body
Cilia and flagella arise from basal bodies, which are centriole-like structures.
| HIGH-YIELD Cilium/flagellum → 9 + 2. Basal body/centriole → 9 + 0. |
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Centrosome and centrioles
The centrosome is a non-membrane-bound structure found in animal cells. It contains two centrioles, generally arranged approximately perpendicular to each other.
Centrioles are associated with spindle formation during cell division and formation of basal bodies of cilia and flagella.
Centriole structure
A centriole consists of 9 peripheral triplets of microtubules. There is no central pair.
| HIGH-YIELD Centriole → 9 + 0. Cilium/flagellum → 9 + 2. |
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Double-membrane organelles
| Structure | Membrane organisation | Key point |
|---|---|---|
| MitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration. | Outer + inner membrane | Own DNA + ribosomes |
| PlastidsPlastidsMembrane-bound organelles found only in plant cells and euglenoids, involved in photosynthesis, storage, or colour. | Outer + inner membrane | Own DNA + ribosomes |
| Nucleus | Double nuclear envelope | Genetic information/control |
| EXAM SHORTCUT If asked for an organelle with double membrane + own DNA + ribosomes: think mitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration. / chloroplastchloroplastA plastid containing chlorophyll where photosynthesis occurs.. |
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The organelle map
| Structure | Membrane | Main association |
|---|---|---|
| RibosomeribosomeA non-membranous structure made of rRNA and proteins where protein synthesis occurs. | None | Protein synthesis |
| CytoskeletoncytoskeletonA network of protein filaments that supports cell shape, organisation, and movement. | None | Shape/support/movement |
| Centrosome | None | Cell division |
| LysosomelysosomeA membrane-bound vesicle containing hydrolytic enzymes for intracellular digestion. | Single | Intracellular digestion |
| Vacuole | Single | Storage/osmoregulation |
| ER | Single | Synthesis/transport |
| Golgi | Single | Modification/packaging |
| Mitochondrion | Double | Aerobic respiration/ATP |
| ChloroplastchloroplastA plastid containing chlorophyll where photosynthesis occurs. | Double | Photosynthesis |
| Nucleus | Double envelope | Genetic control/heredity |
Who does what? — the secretory pathway
When a cellA cellA cell is the smallest structural and functional unit of living organisms capable of independent existence and performing all essential life processes. makes a protein that must eventually be secreted:
DNA → transcription → mRNA → translation → RibosomeribosomeA non-membranous structure made of rRNA and proteins where protein synthesis occurs. on RER → ER → Golgi → Secretory vesicle → Plasma membraneplasma membraneThe selectively permeable boundary that controls movement into and out of a cell. → Outside the cell
| CONCEPT This is more useful than memorising “RER = protein synthesis, Golgi = packaging” because it shows how the system works together. |
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High-yield NCERT traps
Cell discovery ≠ nucleus discovery: Leeuwenhoek → live cell; Brown → nucleus.
Prokaryotic ≠ no ribosomes: prokaryotes have ribosomes but lack membrane-bound organelles.
Mycoplasma: no cell wallCell WallA rigid, non-living outer layer present in plant cells, fungi, and bacteria, providing mechanical support and protection..
RER vs SER: RER → ribosomes/protein synthesis; SER → lipid-related functions.
CristaecristaeFolds of the inner mitochondrial membrane that increase surface area. vs thylakoids: cristaecristaeFolds of the inner mitochondrial membrane that increase surface area. → mitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration.; thylakoids → chloroplastchloroplastA plastid containing chlorophyll where photosynthesis occurs..
Grana vs stromastromaThe fluid matrix of a chloroplast surrounding the thylakoids.: grana → stacks of thylakoids; stromastromaThe fluid matrix of a chloroplast surrounding the thylakoids. → fluid region surrounding them.
70S vs 80S: 70S → prokaryotes + mitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration. + chloroplasts; 80S → eukaryotic cytoplasm.
9 + 2 vs 9 + 0: cilia/flagella → 9 + 2; centriole → 9 + 0.
Cell wallCell WallA rigid, non-living outer layer present in plant cells, fungi, and bacteria, providing mechanical support and protection. vs plasma membraneplasma membraneThe selectively permeable boundary that controls movement into and out of a cell.: cell wallCell WallA rigid, non-living outer layer present in plant cells, fungi, and bacteria, providing mechanical support and protection. → structural/protective; plasma membraneplasma membraneThe selectively permeable boundary that controls movement into and out of a cell. → selective transport.
Nucleus vs nucleolus: nucleus → genetic control; nucleolus → ribosomeribosomeA non-membranous structure made of rRNA and proteins where protein synthesis occurs.-related functions.
Must-draw diagrams
| Tier | Diagram |
|---|---|
| Tier 1 — MUST KNOW | Typical prokaryotic cell; plant cell; animal cell; nucleus; mitochondrion; chloroplastchloroplastA plastid containing chlorophyll where photosynthesis occurs.; cilium/flagellum 9+2 arrangement; centriole |
| Tier 2 — Understand the structure | Golgi apparatus; ER; ribosomeribosomeA non-membranous structure made of rRNA and proteins where protein synthesis occurs. |
Study every diagram as: Structure → label → function.
Examples: CristaecristaeFolds of the inner mitochondrial membrane that increase surface area. → increased membrane surface → ATP-generating machinery. ThylakoidthylakoidA flattened membrane sac inside a chloroplast that contains pigments for light reactions. → pigments/light reactions. Centriole → 9 triplets → 9+0 arrangement.
10-second revision
| Concept | Recall |
|---|---|
| Cell | Basic structural + functional unit |
| ProkaryoteprokaryoteAn organism whose cells lack a membrane-bound nucleus and membrane-bound organelles. | No membrane-bound nucleus |
| EukaryoteeukaryoteAn organism whose cells contain a membrane-bound nucleus and organelles. | Membrane-bound nucleus |
| RER | Protein |
| SER | Lipid |
| Golgi | Modify + package |
| LysosomelysosomeA membrane-bound vesicle containing hydrolytic enzymes for intracellular digestion. | Digest |
| MitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration. | ATP |
| ChloroplastchloroplastA plastid containing chlorophyll where photosynthesis occurs. | Photosynthesis |
| RibosomeribosomeA non-membranous structure made of rRNA and proteins where protein synthesis occurs. | Protein synthesis |
| Cilia/flagella | 9 + 2 |
| Centriole | 9 + 0 |
Active recall — don't just reread
Close the notes and answer these without looking:
Who first observed a live cell?
Who discovered the nucleusThe nucleusThe nucleus is a double membrane-bound organelle containing the cell's genetic material (DNA) and controlling all cellular activities.?
What are the two statements of modern cell theory?
What is the defining difference between prokaryotes and eukaryotes?
Which prokaryoteprokaryoteAn organism whose cells lack a membrane-bound nucleus and membrane-bound organelles. lacks a cellA cellA cell is the smallest structural and functional unit of living organisms capable of independent existence and performing all essential life processes. wall?
What are plasmids?
Why is the plasma membraneThe plasma membraneThe plasma membrane is a thin, flexible, selectively permeable barrier that encloses the cytoplasm and regulates entry and exit of substances. selectively permeable?
What is the difference between RER and SER?
What is the function of Golgi?
Why are mitochondriamitochondriaDouble-membrane organelles that generate most cellular ATP through aerobic respiration. called semiautonomous?
What are grana?
What are thylakoids?
Where are 70S ribosomes found?
What is the 9+2 arrangement?
What is the arrangement in a centriole?
What is the difference between lysosomesLysosomesMembrane-bound vesicles containing hydrolytic enzymes (acid hydrolases) that digest worn-out organelles, foreign particles, and macromolecules. and vacuoles?
What is the function of nuclear pores?
What are plasmodesmataplasmodesmataCytoplasmic connections that pass through plant cell walls and link adjacent cells.?
What is the function of the cytoskeletoncytoskeletonA network of protein filaments that supports cell shape, organisation, and movement.?
What is the relationship between cell structure and cell function?
| SELF-CHECK If you cannot answer these without looking, you don't yet know the chapter. |
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