Biology Chapter Cell Structures
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Questions and Answers

Which of the following structures is present in animal cells but not in plant cells?

  • Centrioles (correct)
  • Golgi apparatus
  • Chloroplasts
  • Ribosomes

What is the main function of the rough endoplasmic reticulum?

  • Lipid synthesis
  • Energy production
  • Protein synthesis (correct)
  • DNA replication

Which of the following options correctly identifies the components of the cytoskeleton?

  • Microfilaments and microtubules (correct)
  • Lysosomes and peroxisomes
  • Centrioles and mitochondria
  • Nucleus and nucleolus

What is the primary function of lysosomes?

<p>Digestion of waste material (D)</p> Signup and view all the answers

Which component is responsible for the synthesis of lipids?

<p>Smooth endoplasmic reticulum (C)</p> Signup and view all the answers

What is the basic structural and functional unit of every organism?

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

Which technique can be used for the isolation of subcellular structures?

<p>Cell fractionation (D)</p> Signup and view all the answers

What type of microscope uses visible light to magnify cellular structures?

<p>Light Microscope (LM) (D)</p> Signup and view all the answers

Which of the following statements about cells is true?

<p>All cells descend from earlier cells. (A)</p> Signup and view all the answers

What is the maximum magnification capability of a light microscope?

<p>1000x (C)</p> Signup and view all the answers

What size range are most plant and animal cells typically found in?

<p>10 µm to 100 µm (A)</p> Signup and view all the answers

Which microscope is used to visualize smaller structures such as viruses?

<p>Transmission Electron Microscope (TEM) (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic of cells?

<p>Cells can survive without energy input. (B)</p> Signup and view all the answers

What type of images does a scanning electron microscope (SEM) provide?

<p>3D images of the surface of a specimen (B)</p> Signup and view all the answers

Which of the following statements about cilia is accurate?

<p>Cilia help move inhaled debris upward toward the throat. (D)</p> Signup and view all the answers

What is the primary advantage of electron microscopes over light microscopes?

<p>Electron microscopes can provide images at much higher resolutions. (A)</p> Signup and view all the answers

What method is primarily used in cell fractionation to separate cellular components?

<p>Centrifugation (C)</p> Signup and view all the answers

What is the resolution capability of a light microscope?

<p>200 nm (A)</p> Signup and view all the answers

Which term describes the process of isolating cell organelles for analysis?

<p>Cell fractionation (C)</p> Signup and view all the answers

How are organelles separated during the process of cell fractionation?

<p>Based on their size and density (B)</p> Signup and view all the answers

Which of the following is NOT a benefit of using electron microscopy?

<p>Ability to visualize live specimens (D)</p> Signup and view all the answers

What is the function of pili in prokaryotic cells?

<p>To attach to surfaces (C)</p> Signup and view all the answers

Where is the genetic material located in a prokaryotic cell?

<p>In the nucleoid region (B)</p> Signup and view all the answers

What are ribosomes primarily made of?

<p>Ribosomal RNA and protein (C)</p> Signup and view all the answers

What is the primary role of ribosomes in prokaryotic cells?

<p>To synthesize proteins (C)</p> Signup and view all the answers

Which structure serves as the outer layer of a prokaryotic cell?

<p>Capsule (C)</p> Signup and view all the answers

Where are ribosomes assembled within the cell?

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

What is the function of ribosomes in the cell?

<p>Protein synthesis (C)</p> Signup and view all the answers

What is a characteristic feature of prokaryotic cells compared to eukaryotic cells?

<p>Prokaryotic cells do not contain membrane-bound organelles (D)</p> Signup and view all the answers

Which organelle is responsible for locomotion in some prokaryotic cells?

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

What type of proteins do free ribosomes primarily synthesize?

<p>Cytosolic proteins (D)</p> Signup and view all the answers

What structure outside the plasma membrane provides support to prokaryotic cells?

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

Which of the following correctly describes bound ribosomes?

<p>They are attached to the rough endoplasmic reticulum. (C)</p> Signup and view all the answers

In prokaryotic cells, what is the main function of the plasma membrane?

<p>To selectively control the entry and exit of substances (D)</p> Signup and view all the answers

What structure regulates the entry and exit of molecules from the nucleus?

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

Which of the following statements about ribosomes is incorrect?

<p>Ribosomes are exclusively made of proteins. (B)</p> Signup and view all the answers

What is the size of a ribosome approximately?

<p>0.1 µm (B)</p> Signup and view all the answers

What is the primary feature of differential-interference-contrast microscopy?

<p>It enhances image contrast by modifying optical density differences. (D)</p> Signup and view all the answers

What is the major advantage of confocal microscopy over standard fluorescence microscopy?

<p>It provides sharper images by focusing on a single plane. (B)</p> Signup and view all the answers

What is the maximum resolution of light microscopes as stated?

<p>200 nm (D)</p> Signup and view all the answers

What limitation do most light microscopes have regarding subcellular structures?

<p>They cannot resolve organelles due to their small size. (D)</p> Signup and view all the answers

What is the function of the fluorescent dyes used in fluorescence microscopy?

<p>To absorb UV radiation and emit visible light. (C)</p> Signup and view all the answers

What type of imaging can be reconstructed using confocal microscopy?

<p>Three-dimensional structures from multi-layer images. (B)</p> Signup and view all the answers

Which of the following best describes the limitation of light magnification?

<p>It magnifies samples up to about 1000 times. (D)</p> Signup and view all the answers

What is the primary purpose of using optical modifications in phase-contrast microscopy?

<p>To increase sample contrast by enhancing density differences. (C)</p> Signup and view all the answers

Flashcards

What is a cell?

The fundamental unit of life, responsible for all biological functions within an organism.

What is cell biology?

The study of cells and their structures, using various tools like microscopes and biochemical techniques.

What is a light microscope (LM)?

A type of microscope that utilizes visible light to magnify and illuminate a specimen. It's commonly used for observing the basic structures of cells.

What is an electron microscope (EM)?

A type of microscope that utilizes a beam of electrons for enhanced magnification and resolution. It allows for observation of very fine cellular details.

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What is cell fractionation?

A technique that separates different cellular components based on their size, density, and shape. This helps scientists study individual organelles within a cell.

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How are all cells related?

The process by which cells arise from pre-existing cells, indicating a common evolutionary origin for all life.

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Why is the study of cells important?

The study of cells helps reveal the intricate workings of living organisms, providing a fundamental understanding of how life functions.

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How is cell structure related to cell function?

A cell's structure directly corresponds to its function. For example, muscle cells have a unique structure that allows them to contract and move.

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Scanning Electron Microscope (SEM)

A type of electron microscope that provides a 3D image of the surface of a specimen, revealing intricate details.

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Resolution

The ability of a microscope to distinguish between two closely spaced objects as separate entities.

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Cell Fractionation

A technique that separates cell components based on size and density, allowing the study of individual organelles.

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Centrifuge

A device used in cell fractionation to separate components by spinning at high speeds.

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Transmission Electron Microscope (TEM)

A type of electron microscope that transmits electrons through a thin slice of the specimen, revealing internal structures.

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Resolving Power

The smallest distance between two points that can be distinguished as separate entities by a microscope.

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Magnification

The ability to see very small objects, often beyond the scope of the human eye.

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Microscopy

The process of using microscopes to examine small objects and structures.

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What is Differential-interference-contrast (DIC) microscopy?

This type of microscopy enhances contrast by exaggerating differences in density, giving the image a 3D-like appearance.

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What is fluorescence microscopy?

This microscopy technique allows scientists to view the location of specific molecules within a cell by using fluorescent dyes or antibodies to tag them.

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What is Confocal microscopy?

This advanced technique uses lasers and specialized optics for 'optical sectioning' of fluorescently-stained specimens, creating a sharper image by focusing on only one plane of focus.

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What is the limitation of a light microscope (LM) in terms of resolution?

A light microscope (LM) can magnify samples up to 1000 times (1000x) their actual size. However, its resolution is limited to 0.2 µm (200 nm), meaning it can't distinguish details smaller than that.

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How does one enhance contrast in light microscopy?

Various techniques can be used to enhance contrast in light microscopy, such as staining or labeling cell components, making them more visible.

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What structures are too small to be resolved by a light microscope (LM)?

Most subcellular structures, including organelles (membrane-enclosed compartments) are too small to be resolved by a light microscope (LM) due to its resolution limitations.

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What is the advantage of using an electron microscope (EM) over a light microscope (LM)?

Electron microscopes (EM) utilize a beam of electrons, providing a much higher resolution than light microscopes (LM), allowing visualization of very fine cellular details, even smaller structures like ribosomes.

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What does cell fractionation aim to do?

Cell fractionation separates different cellular components based on their size, density, and shape, enabling scientists to study individual organelles within a cell.

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What is a nucleoid?

A region within a prokaryotic cell where the genetic material (DNA) is located, but not enclosed by a membrane.

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What are ribosomes?

Small organelles found in both prokaryotic and eukaryotic cells, responsible for protein synthesis (making proteins).

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What is a capsule?

A protective outer layer that surrounds some prokaryotic cells, providing extra protection and aiding in attachment.

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What are pili?

Hair-like appendages found on the surface of some prokaryotes, used for attachment to surfaces or other cells.

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What are flagella?

Whip-like structures used for locomotion (movement) in some prokaryotes.

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What is a cell wall?

A rigid structure that surrounds the plasma membrane of many prokaryotes, providing structural support and shape.

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What is the plasma membrane?

A thin membrane that encloses the cytoplasm of a prokaryotic cell, regulating the passage of molecules in and out of the cell.

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What is cytoplasm?

The fluid-filled space inside a prokaryotic cell that houses the cell's organelles and molecules.

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Endoplasmic Reticulum (ER)

A network of membranes within a cell, involved in protein synthesis (rough ER) and lipid synthesis (smooth ER).

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Nuclear Envelope

The membrane that surrounds the nucleus, controlling what enters and exits the nucleus.

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Nucleolus

A sphere-shaped organelle within the nucleus, responsible for making ribosomes.

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Nucleus

The control center of a cell, containing DNA and regulating cellular activities. The nucleus also houses the nucleolus and chromatin.

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Plasma Membrane

The outer boundary of the cell, regulating the passage of substances in and out.

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What is the nuclear envelope?

The nuclear envelope is a double membrane that encloses the nucleus, regulating the passage of molecules between the nucleus and the cytoplasm. It is studded with pore complexes, which allow the selective transport of molecules.

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What are pore complexes?

These are large protein complexes embedded in the nuclear envelope, acting as selective channels regulating the transport of molecules into and out of the nucleus. They are essential for maintaining the integrity of the nucleus and its communication with the cytoplasm.

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What are free ribosomes?

Free ribosomes are located in the cytoplasm and synthesize proteins that will function within the cytosol, such as enzymes involved in metabolism.

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What are bound ribosomes?

Bound ribosomes are attached to the endoplasmic reticulum (ER) and synthesize proteins destined for secretion outside the cell, for insertion into membranes, or for delivery to other organelles.

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What is the endoplasmic reticulum (ER)?

The endoplasmic reticulum (ER) is a network of interconnected membranes that extends throughout the cytoplasm of eukaryotic cells. It plays a crucial role in protein synthesis, folding, and modification, as well as lipid and steroid production.

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What is the nucleolus?

The nucleolus is a specialized region within the nucleus where ribosomes are assembled. It is rich in RNA and proteins, including ribosomal RNA (rRNA) and proteins that make up the ribosomal subunits.

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What is ribosomal RNA?

Ribosomal RNA (rRNA) is a type of RNA that is a major component of ribosomes. It helps align the mRNA and tRNA during protein synthesis, ensuring the correct sequence of amino acids in the polypeptide chain.

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Study Notes

Cell Structure and Function

  • Cells are the basic structural and functional units of all organisms
  • All organisms are made of cells
  • Cell structure is related to cellular function
  • Cells are related by descent from earlier cells
  • Techniques for studying cells include microscopy and cell fractionation
  • Microscopy is used to visualize cells and structures
  • Light microscopy uses visible light.
  • Electron microscopy uses beams of electrons
  • Transmission electron microscopy (TEM) studies internal structures.
  • Scanning electron microscopy (SEM) studies surface structures.
  • Magnification and resolution are important aspects of microscopy.
  • High resolution allows viewing of smaller details.
  • Magnification is the ratio of image size to real size.
  • Resolution is the minimum distance of two distinguishable points.
  • Contrast is the visible differences in parts of a sample.
  • Different types of microscopy methods are used for different purposes, including brightfield, phase-contrast, differential-interference-contrast, and fluorescence.
  • Confocal microscopy creates 3D images by focusing laser light.
  • Cell fractionation isolates subcellular components to determine their functions
  • Separation is based on size and density.
  • Centrifugation is used to fractionate cells into their component parts.

Cell Types and Structure

  • Two types of cells: prokaryotic and eukaryotic.
  • Prokaryotic cells (Bacteria and Archaea) are unicellular organisms.
  • Features of prokaryotic cells: lack a nucleus, lack membrane-bound organelles, and have a nucleoid region for DNA.
  • Eukaryotic cells (Protists, Fungi, Plants, and Animals) are larger and more complex with a nucleus and membrane-bound organelles.
  • Examples of unicellular eukaryotic organisms are protists.
  • Fungi can be unicellular or multicellular.
  • Plants and animals are multicellular organisms.
  • The first cells were prokaryotic. Eukaryotic cells developed later.

Comparison of Prokaryotic and Eukaryotic Cells

  • Prokaryotic cells: do not have a nucleus or membrane-bound organelles; have one chromosome.
  • Eukaryotic cells: have a nucleus, contain many membrane-bound organelles, and have many chromosomes.

Cellular Organelles

  • Organelles are the specialized compartments within a cell.

Nucleus

  • The nucleus is the genetic control center of the cell.
  • Contains DNA, the genetic material of the cell
  • DNA is organized into chromosomes within the nucleus.
  • Regions of the nucleus include the Nucleolus where rRNA is made and the Nuclear Envelope which encloses the nucleus and regulates the passage of materials.

Ribosomes

  • Ribosomes are the protein synthesis machinery of the cell.
  • Made of rRNA and protein.
  • Free ribosomes synthesize cytosolic proteins.
  • Bound ribosomes synthesize secreted or membrane proteins.

Endoplasmic Reticulum (ER)

  • The ER is a network of membranes.
  • Two types: rough ER (RER) and smooth ER (SER).
  • RER has ribosomes attached to its membrane, synthesizes and modifies proteins for secretion and insertion into the membrane.
  • SER lacks ribosomes, synthesizes lipids, metabolizes carbohydrates, stores calcium, and detoxifies poisons.

Golgi Apparatus

  • Modifies proteins and lipids received from the ER and sorts them for transport to other locations.
  • Receives proteins and lipids from the ER.
  • Modifies these products.
  • Sorts and packages the modified products into vesicles.

Lysosomes

  • Contain hydrolytic enzymes for intracellular digestion.
  • Break down waste and worn-out cell parts.
  • Functions include phagocytosis (consuming microorganisms) and autophagy (consuming damaged organelles).

Vacuoles

  • Membrane-bound sacs with diverse functions.
  • Plant cells typically contain one large central vacuole for storage, water balance, and maintaining cell turgor pressure.
  • Food vacuoles are formed by phagocytosis used for digestion.

Mitochondria

  • Site of cellular respiration.
  • Chemical energy conversion - converts chemical energy from glucose to ATP (usable chemical energy).
  • Found in nearly all eukaryotic cells.
  • Composed of two membranes: outer membrane and inner membrane with cristae.

Chloroplasts

  • Site of photosynthesis in plants and algae.
  • Contain chlorophyll, which captures light energy.
  • Converts light energy to chemical energy to make sugars.
  • Double membrane - an outer membrane and an inner membrane with thylakoids stacked into grana.

Peroxisomes

  • Specialized metabolic compartments.
  • Produce hydrogen peroxide and convert it to water.
  • Involved in detoxification.
  • Involved in fatty acid breakdown.

Proteasomes

  • Degrade short-lived or damaged proteins.
  • Target proteins for degradation using ubiquitin.

Cytoskeleton

  • A network of protein fibers throughout the cytoplasm.
  • Maintains cell shape and plays a role in cell movement and support of internal components.
  • Microfilaments, intermediate filaments and microtubules are part of the cytoskeleton and have different roles.

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Test your knowledge on the differences between animal and plant cells with this quiz. Questions cover cell structures, the functions of organelles like the rough endoplasmic reticulum, and components of the cytoskeleton. Perfect for biology students looking to reinforce their understanding of cellular biology.

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