Cells as the Basic Unit of Life
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Questions and Answers

What is one of the key principles of the unified cell theory proposed by Schleiden and Schwann?

  • All living things are composed of cells. (correct)
  • Cells operate independently without interaction.
  • All cells contain mitochondria.
  • Cells can arise spontaneously from non-living matter.

Which statement accurately reflects Rudolf Virchow's contribution to the cell theory?

  • Cells manufacture energy through cellular respiration.
  • New cells can arise from spontaneous generation.
  • Cellular division is the process by which cells arise from pre-existing cells. (correct)
  • All cells are functionally identical regardless of their type.

Which statement is most consistent with the modern version of cell theory?

  • All living organisms consist of multiple types of cells exclusively.
  • All cells are devoid of genetic material.
  • Cells are the fundamental unit of structure and function in living organisms. (correct)
  • Metabolism and biochemistry take place in the nucleus of the cell.

What role does cellular division play in the context of modern cell theory?

<p>It is the process by which cells arise from pre-existing cells. (B)</p> Signup and view all the answers

In the context of the modern cell theory, what is stated about genetic material?

<p>Cells contain both DNA and RNA, which are vital for the function of cells. (C)</p> Signup and view all the answers

Which of the following advancements helped scientists to observe cells more clearly?

<p>Advances in lenses and microscope construction. (D)</p> Signup and view all the answers

What misconception about cell origination was later disproven?

<p>Spontaneous generation can lead to cell formation. (A)</p> Signup and view all the answers

What aspect of cell theory emphasizes the chemical composition of cells?

<p>All cells are chemically the same in organisms of similar species. (B)</p> Signup and view all the answers

What shapes the overall structure of cytoplasmic organization in cells with a true nucleus?

<p>Highly structured endomembranes (A)</p> Signup and view all the answers

During which type of cell division do cells with a true nucleus undergo DNA separation?

<p>Mitosis or meiosis (A)</p> Signup and view all the answers

What is the primary distinction in DNA structure between cells with a true nucleus and those with a nucleoid region?

<p>Circular DNA vs. linear chromosomes (A)</p> Signup and view all the answers

Which of the following organelles are present in cells with a true nucleus but absent in those with a nucleoid region?

<p>Chloroplasts (C), Mitochondria (D)</p> Signup and view all the answers

How does the surface area to volume ratio primarily change as cell size increases?

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

What component of motility differs between the two types of cells described?

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

Which feature is specific to a true nucleus compared to a nucleoid?

<p>Protection of DNA by a double membrane (C)</p> Signup and view all the answers

What is a common feature of ribosomes in different types of cells?

<p>Ribosome sizes vary between cell types (D)</p> Signup and view all the answers

What is the primary reason eukaryotic cells can effectively overcome low surface-area-to-volume ratio issues?

<p>They contain numerous organelles for compartmentalization. (A)</p> Signup and view all the answers

How does compartmentalization in eukaryotic cells improve the efficiency of biochemical reactions?

<p>By localizing substrates and enzymes, reducing diffusion distance. (B)</p> Signup and view all the answers

Which of the following statements is NOT true regarding the advantages of compartmentalization in eukaryotic cells?

<p>It allows for immediate access to substrates from any part of the cell. (D)</p> Signup and view all the answers

In what way does the presence of organelles in eukaryotic cells resemble an industrial complex?

<p>Both have specialized areas for critical functions and reactions. (A)</p> Signup and view all the answers

What role does cytosol play within eukaryotic cells in relation to organelles?

<p>It offsets the low surface-area-to-volume ratio through reduced volume. (A)</p> Signup and view all the answers

Which characteristic distinguishes eukaryotic cells from prokaryotic cells?

<p>Eukaryotic cells possess a complex structure with organelles. (B)</p> Signup and view all the answers

Which statement about the diffusion process in relation to prokaryotic cells is correct?

<p>As prokaryotic cells increase in diameter, diffusion becomes less effective. (B)</p> Signup and view all the answers

Which of the following is an example of how biochemical reactions are organized in eukaryotic cells?

<p>Enzymes that work together are located in close proximity within organelles. (D)</p> Signup and view all the answers

Which of the following correctly defines a macromolecule?

<p>A very large molecule, particularly biological polymers (A)</p> Signup and view all the answers

What does polymerization refer to?

<p>The process of forming a polymer from identical units through bonding (D)</p> Signup and view all the answers

What fundamental question does the theory of evolution address?

<p>Where do living organisms come from? (A)</p> Signup and view all the answers

What was one significant contribution of Robert Hooke to cell biology?

<p>He coined the term 'cell' after observing cork tissue. (D)</p> Signup and view all the answers

Which of the following statements best describes the cell theory?

<p>Cells are the basic unit of life for all organisms. (A)</p> Signup and view all the answers

What major technological advancement has influenced cell biology since the 1600s?

<p>The development of complex microscopes (A)</p> Signup and view all the answers

Which level of biological organization is above tissues?

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

How is hereditary information typically transmitted according to scientific theories?

<p>Via cellular division and replication (D)</p> Signup and view all the answers

What is a primary mode of nutrition for plant cells?

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

Which of the following structures is absent in animal cells but present in plant cells?

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

Where is the nucleus located in animal cells compared to plant cells?

<p>On one side in plant cells and in the centre in animal cells (C)</p> Signup and view all the answers

Which organelle is more numerous in animal cells than in plant cells?

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

What type of vacuole structure is characteristic of plant cells?

<p>Few large vacuoles (C)</p> Signup and view all the answers

Which of the following is a significant role of lysosomes in animal cells?

<p>Digestion of waste materials (A)</p> Signup and view all the answers

Which organelle is responsible for the photosynthesis process found in plant cells?

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

Which of the following best describes the shape of plant cells?

<p>Square or rectangular (B)</p> Signup and view all the answers

What is the primary structural difference between eukaryotic and prokaryotic flagella?

<p>Eukaryotic flagella contain a central axoneme composed of microtubules. (C)</p> Signup and view all the answers

Which of the following accurately describes the composition of centrioles?

<p>Each centriole is composed of 9 sets of triplet microtubules. (D)</p> Signup and view all the answers

What role do vacuoles play within a cell?

<p>They store cellular waste and protect the cell from contamination. (D)</p> Signup and view all the answers

During which cellular process do centrioles give rise to spindle fibers?

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

What is the function of radial spokes in the structure of cilia and flagella?

<p>They connect peripheral microtubule pairs to central tubules. (A)</p> Signup and view all the answers

How do the sizes and numbers of vacuoles differ between animal and plant cells?

<p>Plant cells have more numerous, larger vacuoles compared to animal cells. (A)</p> Signup and view all the answers

Which feature is essential in giving mechanical resistance to the cell?

<p>Cytoskeleton matrix. (D)</p> Signup and view all the answers

What is the central part of a centriole known as?

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

Flashcards

Cell Theory

An explanation for organisms being made up of cells; supported by evidence

Cell

Box-like structures in cork tissue, studied by Hooke.

Organelle

A tiny structure in a cell performing a specific function

Molecule

Smallest particle retaining compound properties, formed by atoms bonded.

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Macromolecule

Very large molecule, often a biological polymer.

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Polymerization

Process of bonding monomers to form a polymer.

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Biological levels of organization

Organelle, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and biosphere

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Robert Hooke

Observed box-like structures and named them 'cells'.

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Modern Cell Theory Part 1

All known living things are made up of one or more cells, and all living cells arise from pre-existing cells by division, and the cell is the fundamental unit of structure and function in all living organisms

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Cell Theory's basic tenets

Cells are the basic unit of structure and function in living things,all organisms are made up of one or more cells,and new cells arise from existing cells.

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Abiogenesis

The idea that life arises from non-living matter.

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Omnis cellula e cellula

A Latin phrase meaning "All cells arise from pre-existing cells."

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Energy flow in cells

Metabolism and biochemical processes occur within cells.

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Genetic material in cells

Cells carry genetic material (DNA) that is passed to daughter cells during division.

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Chemical Composition of Cells

Cells in organisms of similar species, all cells are fundamentally similar in chemical composition.

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Prokaryotic Cell Size

Typically 1-5 micrometers in diameter.

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Eukaryotic Cell Size

Typically 10-100 micrometers in diameter.

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Prokaryotic DNA

Circular DNA located in a nucleoid region.

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Eukaryotic DNA

Linear chromosomes with histone proteins, contained within a nucleus.

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Prokaryotic Ribosomes

50S and 30S subunits.

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Eukaryotic Ribosomes

60S and 40S subunits.

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Prokaryotic Organelles

Lack membrane-bound organelles.

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Eukaryotic Organelles

Have many membrane-bound organelles.

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Plant Cell Shape

Plant cells typically have a square or rectangular shape due to the rigid cell wall surrounding them.

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Animal Cell Shape

Animal cells often have irregular or round shapes, as they lack a rigid cell wall.

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Cell Wall

A rigid outer layer present in plant cells that provides structural support and protection.

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Plasma Membrane

A thin, flexible layer present in both plant and animal cells that controls what enters and exits the cell.

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Vacuoles in Plant Cells

Large, fluid-filled sacs in plant cells that store water, nutrients, and waste products.

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Vacuoles in Animal Cells

Smaller and numerous sacs in animal cells that store various substances but not as prominently as in plant cells.

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Mitochondria in Plant Cells

Powerhouses of plant cells, fewer in number compared to animal cells, responsible for generating energy.

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Mitochondria in Animal Cells

Powerhouses of animal cells, more numerous than in plant cells, responsible for generating energy.

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Cytoskeleton

A network of protein fibers in cells that provides structure, support, and helps with movement. It's like the cell's internal scaffolding.

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Cytokinesis

The process of dividing the cytoplasm of a cell during cell division, creating two daughter cells.

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Cilia & Flagella

Hair-like projections on cells, cilia are short and flagella are long, both used for movement.

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Axoneme

The core structure of cilia and flagella, containing microtubules arranged in a 9+2 pattern.

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Basal Body

Centriole-like structures from which cilia and flagella grow.

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Centriole

Tiny, cylindrical structures in cells, made up of microtubules and involved in cell division.

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Vacuole

Fluid-filled sacs within cells, mainly for storage of water, nutrients, and sometimes waste.

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Plant vs. Animal Vacuoles

Plant cells have large, central vacuoles for storage and support, while animal cells have smaller vacuoles.

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Surface-area-to-volume ratio

The ratio of a cell's surface area to its volume.

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Why is a small cell better?

Small cells have a higher surface-area-to-volume ratio. This allows for efficient diffusion of molecules in and out.

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Organelle function

Organelles compartmentalize a eukaryotic cell, increasing efficiency and reducing diffusion distances.

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Incompatible reactions

Organelles separate incompatible reactions, preventing interference and promoting efficiency

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Chemical reactions become more efficient

Organelle organization concentrates substrates and enzymes, speeding up reactions

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Eukaryotes vs. Prokaryotes

Eukaryotic cells have organelles, allowing for compartmentalization, specialization, and greater efficiency.

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Eukaryotic cytosol volume

The cytosol in eukaryotes is a smaller fraction of the total cell volume due to organelles.

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Study Notes

Cells as the Basic Unit of Life

  • Organisms are living entities composed of one or more cells.
  • Cells have five fundamental characteristics: organisms share a suite of five fundamental characteristics.
  • Cells are membrane-bound units that regulate the passage of materials between the interior and exterior.
  • Replication is the primary goal of every organism.
  • Organisms evolve over time.
  • Organisms process genetic information (genes).
  • Organisms respond to environmental stimuli to maintain stable internal conditions.
  • Organisms need energy to survive and reproduce.
  • Examples include plants absorbing sunlight, while animals ingest food.
  • Atoms bond to form molecules.
  • Molecules assemble into macromolecules.
  • Cells are the simplest level of organization in living things. (one or more cells).
  • A single organelle is a complex assembly of macromolecules.
  • The biosphere represents the highest level of organization for living things.

Cell Theory

  • The cell is the fundamental unit of structure and function for all living things.
  • All organisms are made up of one or more cells.
  • Cells arise from other cells.
  • Cells have the following additional characteristics: Cells carry genetic material passed to daughter cells during cellular division; cells are essentially the same in chemical composition; energy flow (metabolism and biochemistry) occurs within cells.

Biological Levels of Organization

  • The biological levels of organization range from the simplest (atom) to the most complex (biosphere): organelle, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and biosphere.
  • Atoms bond to form molecules
  • Molecules combine to form macromolecules.
  • Macromolecules join together to form organelles.
  • Organelles are the basic unit of living things

Cell Size and Function

  • Most cells are between 1 and 100 µm in diameter.
  • The smallest cells are bacteria (mycoplasmas).
  • Typical bacteria are 1–5 µm in diameter.
  • Eukaryotic cells are typically 10–100 µm in diameter.
  • Surface area to volume ratio—a smaller cell has a higher ratio, promoting efficient exchange with the environment.

Prokaryotic vs. Eukaryotic Cells

  • Prokaryotes generally are much smaller than eukaryotes.
  • Prokaryotic DNA is not enclosed within a membrane-bound nucleus but is contained in a region called the nucleoid.
  • Eukaryotic DNA is enclosed within a membrane-bound nucleus.
  • Eukaryotic cells are compartmentalized into a larger number of distinct organelles.

Eukaryotic Cell Structures and Functions

  • Plasma membrane:
    • A boundary between the cell's contents and the environment.
    • It is selectively permeable, regulating the passage of substances into and out of the cell.
    • It contains proteins that act as channels, pores, or carriers.
  • Endoplasmic reticulum (ER):
    • A network of membranes that transports material throughout the cell.
    • Rough ER: studded with ribosomes; involved in protein synthesis
    • Smooth ER: lacks ribosomes; involved in lipid synthesis and detoxification
  • Mitochondria:
    • Powerhouses of the cell; sites of aerobic respiration.
    • Have a double membrane.
    • The inner membrane is folded into cristae, increasing the surface area for ATP production.
  • Ribosomes:
    • Sites of protein synthesis.
    • Composed of RNA and proteins.
    • Found in all cells (prokaryotes and eukaryotes).
  • Golgi apparatus:
    • Modifies, sorts, and packages proteins and lipids for secretion or use within the cell
    • Membrane-bound sacs
  • Lysosomes:
    • Contain digestive enzymes (breaks down waste, cell death).
  • Nucleus:
    • Contains the cell's genetic material (DNA).
    • Enclosed by a double membrane (nuclear envelope).
    • Contains the nucleolus, where ribosomes are assembled. Nucleolus
  • Nucleus:
    • Cell's control center
    • Contains DNA in the form of chromosomes
    • Regulates the cell's activities
  • Vacuoles:
    • Fluid-filled sacs for storage.
    • Large in plant cells, helping maintain turgor pressure.
  • Chloroplasts (plant cells only):
    • Site of photosynthesis.
    • Contain chlorophyll.
  • Cytoskeleton:
    • Provides shape and support.
    • Composed of protein fibers. (microfilament, microtubules, intermediate filaments).
  • Cytoplasm
    • Fluid inside the cell, contains all the organelles

Cilia and Flagella

  • Motile appendages projecting from the cell surface.
  • Cilia are shorter and more numerous.
  • Flagella are longer and fewer.
  • Microtubules are organized in a 9+2 arrangement.

Centrosomes and Centrioles

  • Involved in cell division.
  • Composed of centrioles, which are microtubule-organizing centers.

Plastids (plant cells only)

  • Double-membrane-bound organelles
  • There are three types of plastids: leucoplasts, chromoplasts, and chloroplasts.

Cell Size in Relation to Function

  • Cell size is constrained by the ratio of surface area to volume.
  • A smaller surface area-to-volume ratio limits the exchange of materials needed to support larger cells. This is why cells divide, to maintain optimal function.

Cell Structures in Relation to Function

  • The different organelles in cells have specialized roles.
  • Their composition and structure are related to their specific functions.

Effects of Solutions on Cells

  • Hypertonic solution: higher solute concentration. Water moves out of the cell causing it to shrivel
  • Hypotonic solution: lower solute concentration. Water moves into the cell causing it to swell and potentially burst
  • Isotonic solution: equal solute concentration. Water moves in and out of the cell at equal rates

Food Preservation Using Osmosis and Diffusion

  • Methods using high salt or sugar concentrations to prevent bacterial growth.
  • Low pH (acidity): an alternate method for preserving food.

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