unit 2: cell structure
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Questions and Answers

What is a key feature of prokaryotic cells?

  • They contain histones with their DNA.
  • They contain membrane-bound organelles.
  • They always exist as unicellular organisms. (correct)
  • They have a true nucleus.

Prokaryotic DNA is associated with proteins called histones.

False (B)

What is the region where prokaryotic DNA is located called?

nucleoid region

Prokaryotic cells are thought to have evolved from __________ cells.

<p>primitive eukaryotic</p> Signup and view all the answers

Match the following characteristics with prokaryotic or eukaryotic cells:

<p>Always unicellular = Prokaryotic Has a true nucleus = Eukaryotic Microscopic size = Both Contains membrane-bound organelles = Eukaryotic</p> Signup and view all the answers

Which of the following statements regarding cells is true?

<p>All living organisms are composed of cells. (B)</p> Signup and view all the answers

Cells can originate from non-living materials.

<p>False (B)</p> Signup and view all the answers

What are the two main types of microscopes mentioned?

<p>Light microscope and Electron microscope</p> Signup and view all the answers

The magnification of light microscopes can reach up to _______.

<p>2000x</p> Signup and view all the answers

Match the following measurement units with their equivalent sizes:

<p>1 metre (m) = 100 cm 1 centimetre (cm) = 10 mm 1 millimetre (mm) = 1000 μm 1 micrometre (μm) = 1000 nm</p> Signup and view all the answers

Which type of microscopy allows viewing details using ultraviolet or violet-blue light?

<p>Fluorescent microscopy (B)</p> Signup and view all the answers

Immunofluorescence is used to detect the presence of cellular structures without the need for antibodies.

<p>False (B)</p> Signup and view all the answers

What advantage does an electron microscope have over a light microscope?

<p>It provides higher magnification. (D)</p> Signup and view all the answers

All cells can live independently.

<p>False (B)</p> Signup and view all the answers

What are the common structures found in all cells?

<p>DNA, cytoplasm, and plasma membrane</p> Signup and view all the answers

The plasma membrane is primarily composed of _______ that form a bilayer.

<p>lipids</p> Signup and view all the answers

What is the universal genetic code made up of?

<p>64 codons</p> Signup and view all the answers

What is the role of the hydrophilic heads of lipids in the plasma membrane?

<p>To interact with surrounding water (B)</p> Signup and view all the answers

Phase-contrast microscopy requires staining of the specimen to reveal details.

<p>False (B)</p> Signup and view all the answers

What is the effect of short fatty acids or unsaturated fatty acids on membrane fluidity?

<p>They increase the fluidity of the membrane.</p> Signup and view all the answers

Match the following types of microscopy with their respective features:

<p>Brightfield = Uses visible light; specimen viewed against a light background Darkfield = Specimen appears light against a dark background Phase-contrast = Reveals detailed images without staining Fluorescent = Uses dyes that emit light under specific illumination</p> Signup and view all the answers

What allows cells to carry out specific functions?

<p>The suppression and expression of different genes (B)</p> Signup and view all the answers

All cells in an organism express the same genes.

<p>False (B)</p> Signup and view all the answers

What is the primary function of pancreatic cells in terms of gene expression?

<p>Insulin production</p> Signup and view all the answers

Eukaryotic cells have ____________ organelles, while prokaryotic cells lack them.

<p>membrane-bounded</p> Signup and view all the answers

Match the following cell types with their characteristics:

<p>Prokaryotic cells = Lack membrane-bounded organelles Eukaryotic cells = Compartmentalized with specialized tasks Stem cells = Have the potential to differentiate into various cell types Multicellular organisms = Composed of multiple specialized cells</p> Signup and view all the answers

Which statement correctly describes the cytoplasm of eukaryotic cells?

<p>It consists of many unique organelles working together. (C)</p> Signup and view all the answers

Endosymbiosis explains the development of all organelles in eukaryotic cells.

<p>False (B)</p> Signup and view all the answers

What is one evolutionary mechanism that supports the origins of eukaryotic cells?

<p>Endosymbiosis</p> Signup and view all the answers

What process do prokaryotic cells use to divide?

<p>Binary fission (A)</p> Signup and view all the answers

Eukaryotic cells lack a nuclear membrane.

<p>False (B)</p> Signup and view all the answers

What is the role of mitochondria in a cell?

<p>Aerobic respiration</p> Signup and view all the answers

Chloroplasts are responsible for __________ in plant cells.

<p>photosynthesis</p> Signup and view all the answers

What is the primary function of the cell wall in prokaryotic cells?

<p>Protects the cell from damage (D)</p> Signup and view all the answers

Match the organelle with its primary function:

<p>Mitochondria = Aerobic respiration Chloroplasts = Photosynthesis Nucleus = Genetic information storage Ribosomes = Protein synthesis</p> Signup and view all the answers

The nucleoid region contains DNA that is associated with histone proteins.

<p>False (B)</p> Signup and view all the answers

Which structure separates the interior material of organelles from the cytoplasm?

<p>Organelle membrane (B)</p> Signup and view all the answers

Bacteria can reproduce at a rate of more than 1 million new cells in fewer than 8 hours.

<p>True (A)</p> Signup and view all the answers

What type of reproduction do prokaryotic cells undergo?

<p>Binary fission</p> Signup and view all the answers

The plasma membrane is described as __________ because it controls the entry and exit of substances.

<p>selectively permeable</p> Signup and view all the answers

What are two types of cells in terms of structure?

<p>Prokaryotic and Eukaryotic</p> Signup and view all the answers

Match the following structures to their functions in prokaryotic cells:

<p>Ribosomes = Produces proteins Flagellum = Provides movement Pili = Attachment to surfaces Capsule = Protects the cell</p> Signup and view all the answers

Which of the following statements about plasmids is true?

<p>Plasmids can reproduce independently of the main chromosome (D)</p> Signup and view all the answers

Cytoplasm is involved in protein synthesis in prokaryotic cells.

<p>False (B)</p> Signup and view all the answers

What is the role of the flagellum in prokaryotic cells?

<p>Movement</p> Signup and view all the answers

The __________ region of a prokaryotic cell is where the naked DNA is located.

<p>nucleoid</p> Signup and view all the answers

What is a key characteristic of 70S ribosomes in prokaryotic cells compared to eukaryotic ribosomes?

<p>They are smaller than eukaryotic ribosomes (A)</p> Signup and view all the answers

Flashcards

Cell Theory

All living things are made of cells, cells are the basic unit of life, and cells come from pre-existing cells.

Cell as basic unit of life

The smallest unit of a living organism capable of performing all basic functions of life.

Light Microscope

A microscope that uses light to view specimens.

Electron Microscope

A microscope that uses electrons to view specimens, offering much higher magnification.

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Magnification

The process of enlarging the appearance of something.

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Micrometer (µm)

A unit of measurement equal to one millionth of a meter.

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Calculating Magnification

Determining the amount an image is enlarged using a scale bar on a drawing or microscopic image.

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Cell division

The process by which cells divide to create new cells.

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Prokaryotic cell

A type of cell without a true nucleus, meaning DNA is not enclosed by a membrane.

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Eukaryotic cell

A cell with a true nucleus—a membrane-enclosed area containing DNA.

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Nucleoid region

The area in a prokaryotic cell where the DNA is located.

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Naked DNA

DNA in prokaryotic cells that isn't associated with proteins (histones).

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Membrane-bound organelles

Specialized structures within eukaryotic cells that perform specific functions, surrounded by membranes.

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Artefacts (in microscopy)

Structural features in microscope images not part of the sample but created during its preparation.

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Fluorescent Stains

Dyes that absorb and emit specific wavelengths of light, highlighting cellular components.

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Immunofluorescence

A technique using antibodies labeled with fluorescent dyes to identify specific molecules (often proteins) within cells.

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Plasma Membrane

A lipid bilayer surrounding the cytoplasm of a cell.

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Lipid Bilayer

Two layers of phospholipids creating a barrier within the plasma membrane.

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Membrane Fluidity

The ability of the plasma membrane to change shape and reform, crucial for cell function.

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Hydrophobic Barrier

A feature of the plasma membrane that prevents the passage of water-soluble substances.

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What is Binary Fission?

A process of asexual reproduction in prokaryotic cells where a single cell divides into two identical daughter cells.

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Mitosis vs. Meiosis

Mitosis is a type of cell division that produces two daughter cells genetically identical to the parent cell, while meiosis is a type of cell division that produces four daughter cells with half the number of chromosomes of the parent cell.

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What is 'naked DNA'?

DNA in prokaryotic cells that isn't associated with proteins (histones), unlike the DNA in eukaryotic cells.

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Compartmentalization in Eukaryotic cells

The presence of membrane-bound organelles within eukaryotic cells, separating different functions and activities within the cell.

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What are Cristae?

Infoldings of the inner membrane of mitochondria. Increasing surface area for ATP production during aerobic respiration.

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What is the function of Thylakoid membrane?

Membrane system within chloroplasts where light-dependent reactions of photosynthesis take place.

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What is the difference between Granum and Stroma?

Granum is a stack of thylakoid discs within a chloroplast, while stroma is the fluid surrounding the grana, where the Calvin cycle (light-independent reactions) occurs.

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Role of Mitochondria

Mitochondria are responsible for aerobic respiration, which converts food into energy (ATP) for the cell.

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Gene Expression

The process by which cells use genetic information to create proteins and other molecules, determining their structure and function.

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Cell Differentiation

The process by which cells become specialized in structure and function, leading to different cell types within an organism.

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Endosymbiosis

A theory explaining how some eukaryotic organelles, like mitochondria and chloroplasts, originated from engulfed prokaryotic cells.

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Multicellularity

The state of being composed of multiple cells, allowing for specialized functions and complex organisms.

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Why do cells have different functions?

Cells express different genes, leading to varying protein production and ultimately different structures and functions.

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What is the importance of gene expression?

Gene expression allows cells to perform specific tasks, leading to the diversity of cell types and functions within an organism.

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Plasmid

Small, circular DNA molecules found in some prokaryotes. They can replicate independently of the main chromosome and transfer between cells.

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Cell Wall (Prokaryotic)

A rigid outer layer that surrounds the cell membrane in many prokaryotes. Provides structural support and protects the cell from bursting.

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Ribosomes (70S)

Small, round organelles responsible for protein synthesis in prokaryotic cells. They are smaller than ribosomes in eukaryotic cells.

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Pili

Short, hair-like structures on the surface of some prokaryotes. They help the cell attach to surfaces and other cells.

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Flagellum

A long, whip-like structure that helps a prokaryotic cell move. Similar to a tail.

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Capsule

A gelatinous layer that surrounds some prokaryotic cells. It protects the cell from the environment and can help the cell evade the immune system.

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Binary Fission

The simple form of cell division in prokaryotes. The DNA replicates and the cell divides into two identical daughter cells.

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Study Notes

Cell Theory

  • All living organisms are composed of cells.
  • Human bodies are made of different types of cells, each with a unique function.
  • Cells are highly complex structures.
  • Cells are produced from pre-existing cells.
  • Cell growth is a result of cell division.
  • Viruses are made of simpler subunits, but not composed of cells.
  • Genetic code is universal (the 64 codons).

Cells as Basic Units of Life

  • Cells are the basic and smallest unit of life for all living organisms.
  • Cells are the fundamental building blocks to construct an organism.

Cell Structure

  • Cells contain numerous structures.
  • Examples include:
  • Nucleus, Plasma membrane, Cytoplasm, Mitochondria, Ribosomes, Golgi apparatus, Endoplasmic reticulum, Lysosome etc.

Microscopes

  • Microscopes have high magnification and resolution.
  • Light microscopes pass light through specimens
  • Electron microscopes pass electrons through specimens, providing a higher magnification (over 100,000x).
  • Light microscopes are inexpensive and simple to operate, suitable for studying living and dead specimens.
  • Electron microscopes are expensive and complex to operate, used to study dead and fixed specimens.
  • Calculating magnification and actual size of specimens can be calculated using scale bars from images.

Relative Sizes of Cell Structures

  • Molecules are measured in nanometres (nm).
  • Cell membranes are measured in nanometres to micrometres.
  • Viruses, bacteria, organelles, and cells are measured in micrometres.

Advanced Microscopy techniques

  • Scanning electron microscope (SEM) scans the cell surface
  • Transmission electron microscope (TEM) passes electrons through a thin section of the specimen
  • Freeze-fracture is used for samples suitable for EM.
  • Cryogenic electron microscopy uses computer enhancements to create 3D images of cell protein structures.
  • Artefacts are structural features in EM images that don't belong to the original sample cells.

Light Microscopy

  • Fluorescent stains, used in UV or Violet-blue light, allow visualization of cellular components.
  • Immunofluorescence uses dyed antibodies which bind to specific targeted molecules.

Common Structures in all Cells

  • All organisms have DNA
  • Cytoplasm (mostly water)
  • Plasma membrane

Arrangement and Properties of Plasma Membrane

  • Plasma membrane forms a bilayer with hydrophobic tails inside and hydrophilic heads outside.
  • Hydrophobic interactions and interaction with water stabilize the membrane.
  • Membrane fluidity is critical for proper functioning.
  • Short fatty acid chains make the cell membrane more fluid.

Prokaryotic Cells

  • Prokaryotic cells are simpler in structure, lacking a nucleus or other membrane-bound organelles.
  • The region where DNA is stored in a prokaryotic cell is called the nucleoid.
  • Eukaryotic cells evolved from prokaryotic cells.
  • Prokaryotic DNA is naked DNA (not associated with proteins).
  • Prokaryotic cells are primarily unicellular.
  • Common components of prokaryotic cells include (e.g.) cell wall, cell membrane, cytoplasm, and ribosomes.

Prokaryotic Cellular Structure

  • Cell Wall protects the cell
  • Plasma membrane is a barrier
  • Cytoplasm contains metabolic enzymes
  • Pili structures involved in attachment
  • Flagella are used for motility
  • Ribosomes synthesize proteins
  • Nucleoid region contains the naked DNA.
  • Capsules protect the cell.
  • Plasmids are small, circular DNA molecules

Binary Fission

  • Binary fission is the asexual reproduction process in prokaryotic cells.
  • It results in two genetically identical daughter cells
  • It's a fast process (greater than 1 million new cells in less than 8 hours).

Eukaryotic Cells

  • Eukaryotic cells contain a nucleus and membrane-bound organelles.
  • They are more complex and larger than prokaryotic cells.
  • The cell contains numerous specialized structures and organelles.

Eukaryotic Organelles

  • Mitochondria are responsible for aerobic respiration.
  • Chloroplasts are involved in photosynthesis.
  • Endoplasmic Reticulum, Golgi Apparatus, Nucleus, etc
  • Nuclei contain DNA.
  • Plasma membranes form the outer barrier.
  • Cell walls are present in plant cells.

Unicellular Organisms

  • Unicellular organisms have cell membranes, important for maintaining homeostasis.
  • Vacuoles isolate and store materials.
  • Cilia or flagella allow for movement in response to changes in the environment.
  • Ribosomes and other cellular components facilitate cellular functions.

Different Types of Eukaryotic Cells

  • Differences include presence of cell walls in plants and fungi or the presence or absence of chloroplasts.

Atypical Eukaryotes

  • Some eukaryotic cells have unique structures, such as fungal hyphae or the multinucleated cells in human skeletal muscle.

Endosymbiotic theory:

  • This theory explains the origin of mitochondria and chloroplasts.
  • It proposes that these organelles were once free-living prokaryotic cells that were engulfed by a larger cell.
  • The engulfed prokaryotic cells established a mutually beneficial relationship with the host cell and evolved into organelles.

Cell Specialization and Multicellularity

  • Multicellular organisms exhibit cellular specialization of various functions and division of labor.
  • Cells differentiate during development, forming tissues, organs, and organ systems
  • Example of cell types include nerve cells, muscle cells, blood cells, etc.

Multicellular Organisms and Differentiation

  • Cells arise from existing cells.
  • Zygotes differentiate into various cell types through gene expression.
  • Differentiation creates various cell types for specific functions.

Cells to Organism organisation

  • Cell ⇒ Tissues ⇒ Organs ⇒ Organ Systems ⇒ Organism.
  • This organisation is for specific function and co-ordination

Summary of Cell Structures and Functions

  • Cells are the basic unit of all living organisms, with variation in structure and function.
  • Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells contain a nucleus and other organelles.
  • The structure and function of organelles are crucial to cell survival and the maintenance of larger organisms.
  • Differentiation allows for cell specialization and function in multicellular organisms.

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A2.2 Cell Structure PDF

Description

Explore the fundamental concepts of cell theory, the diverse structures of cells, and the tools used to study them. This quiz covers everything from the basic unit of life to the types of microscopes that reveal cellular details. Test your knowledge of cell organization and functions!

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