Biology Chapter: Cell Structures and Functions

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Questions and Answers

Which of the following is NOT a characteristic of prokaryotic cells?

They contain organelles with specialized functions (correct)

They can be free-living single cells

DNA is not enclosed within a membrane

They are often part of multicellular organisms

Which of the following components is most abundant in a cell?

Proteins

Lipids

Nucleic acids

Water (correct)

What is the primary role of transport proteins in the cell membrane?

To facilitate energy processing within the cell

To provide structural support to the cell

To serve as a barrier that prevents all molecules from entering

To allow selective passage of specific molecules (correct)

During evolution, what two processes are involved in natural selection?

Random variation and selective propagation Signup and view all the answers

Which element is NOT one of the six elements that compose cells?

Iron Signup and view all the answers

Which of the following statements about eukaryotic cells is true?

Their DNA is partitioned in a membrane-bound nucleus Signup and view all the answers

Which of the following is a function of the cell membrane?

Separate the internal environment from the external environment Signup and view all the answers

Which type of microorganism is characterized as having no cellular structure?

Virus Signup and view all the answers

What role do mitochondria and chloroplasts play in cells?

They produce energy for the cell Signup and view all the answers

Which of the following is a method by which cells reproduce?

By division into two daughter cells Signup and view all the answers

Which of the following statements correctly describes the flow of genetic material?

Polynucleotide → DNA → Polypeptide. Signup and view all the answers

What component is NOT a fundamental building block of all cell membranes?

Nucleotides Signup and view all the answers

Which structure is unique to bacterial cells compared to eukaryotic cells?

Cell wall made of peptidoglycan Signup and view all the answers

Which of the following components of eukaryotic cells is correctly described?

Cilia are appendages in eukaryotic cells. Signup and view all the answers

What is a key feature of RNA among self-replicating molecules?

RNA can catalyze biochemical reactions. Signup and view all the answers

Which statement accurately describes the bacterial cell size compared to eukaryotic cells?

Bacterial cells have a diameter ranging from 0.1-5.0 µm. Signup and view all the answers

Who is credited with the discovery of the cellular world through the use of microscopes?

Robert Hooke Signup and view all the answers

Which statement regarding prokaryotic cell structures is correct?

Prokaryotic cells have a nucleoid instead of a nucleus. Signup and view all the answers

Which of the following is NOT one of the three domains of life?

Plantae Signup and view all the answers

What type of organism thrives in high salinity environments?

Halophiles Signup and view all the answers

Which type of virus is known to specifically attack bacterial cells?

Bacteriophage Signup and view all the answers

What is the primary energy source for phototrophs?

Sunlight Signup and view all the answers

Which type of stem cells can differentiate into all types of cells?

Totipotent stem cells Signup and view all the answers

What is the role of the protein coat in viruses?

Providing protection and aiding entry into host cells Signup and view all the answers

Which statement best describes the concept of reductionism in biology?

Breaking down complex processes into simpler components for analysis Signup and view all the answers

What is the primary difference between organotrophs and autotrophs?

Organotrophs rely on organic materials, while autotrophs utilize inorganic materials. Signup and view all the answers

At what stage of development is a zygote in humans?

After fertilization and before cell division Signup and view all the answers

What is a characteristic of thermacidophiles?

They prefer sulfur-rich, high-temperature environments. Signup and view all the answers

Which of the following terms describes the flow of energy through an ecosystem?

Energy transformation Signup and view all the answers

Which statement accurately describes the structure of proteins?

Proteins consist of 20 different amino acids that form their unique structure. Signup and view all the answers

What role do nucleic acids play in cells?

They store hereditary information and carry coding for protein synthesis. Signup and view all the answers

Which of the following describes the composition and function of lipids?

Lipids serve as important energy sources and make up cell membranes. Signup and view all the answers

What is the correct sequence for the organization of genetic material in cells?

Nucleotide > Nucleosome > Chromatin > Chromosome > Genome. Signup and view all the answers

Which of the following functions is associated with the cytoskeleton?

Changing shape and enabling movement of the cell. Signup and view all the answers

What is one potential outcome of a genetic mutation?

Mutations in the genome can be beneficial, neutral, or harmful. Signup and view all the answers

Which of the following substances is primarily used to store glucose for energy in plants?

Starch. Signup and view all the answers

What process allows cells to reproduce their genetic information?

Mitosis. Signup and view all the answers

Which structural level of protein organization is characterized by the folding of polypeptide chains into specific shapes?

Tertiary structure. Signup and view all the answers

What is the role of ATP in a cell?

Provides the energy necessary for various cellular processes. Signup and view all the answers

Study Notes

Order of Cells

Cells are the simplest form of life and reproduce by dividing in two.
Higher organisms are cellular cities where groups of cells perform specialized functions.
Cells carry out a number of complex tasks including:
- Order: They exhibit a high degree of order and complexity.
- Evolutionary Adaptations: They evolve over time to adapt to their environment.
- Regulation: They regulate their internal environment to maintain homeostasis.
- Response to Homeostasis: They respond to changes in their environment.
- Energy Processing: They obtain and use energy.
- Reproduction: They reproduce to create new cells.
- Growth and Development: They grow and develop over time.

Cells

Cells are small membrane-bounded compartments filled with concentrated aqueous solutions of chemicals.
Lipids are fatty acids composed of carbon, hydrogen, and oxygen.
Proteins are composed of amino acids and provide structural support.

Modern Cell Theory

Cells are the fundamental unit of life.
Cells arise from pre-existing cells through division.
Cells contain DNA that is passed from cell to cell during division.
Cells are composed of six elements: carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.
Energy flow in living organisms occurs at the cellular level.
The plasma membrane is selectively permeable, allowing specific molecules to pass in and out.
Transport proteins in the cell membrane facilitate the selective passage of molecules.
Each transport protein is specific to a particular molecule.

Major Components of a Cell

Water is the most abundant molecule in cells.
Nucleic acids (DNA and RNA) store and transmit genetic information.
Other important components include proteins, carbohydrates, lipids, and organelles.

Organelles

Organelles are orderly arrangements of molecules that perform specific functions.
Mitochondria produce energy in animal cells.
Chloroplasts produce energy in plant cells.

Different Types of Cells

Prokaryotic Cells:
- DNA is not separated from the cytoplasm.
- Bacteria and archaea are examples of prokaryotes.
- Some prokaryotes are free-living, while others are part of multicellular organisms.
Eukaryotic Cells:
- DNA is enclosed within a membrane-bound nucleus.
- Plants, animals, fungi, and protists are examples of eukaryotes.
Similarities between Prokaryotic and Eukaryotic Cells:
- Contain chromosomes
- Use DNA as genetic material
- Have ribosomes
- Contain cytoplasm
- Have a plasma membrane
- Possess vacuoles

Types of Microorganisms

Bacteria
Fungi
Viruses
Prions
Parasites
Protozoans

The Evolution of the Cell

Natural selection involves two processes:
- Random variations in genetic information are passed from one generation to the next.
- Variations that are beneficial for survival and reproduction are selected for.

From Molecules to the First Cells

Organic molecules found in cells include amino acids, sugars, purines, and pyrimidines.
DNA, RNA, and proteins are composed of hydrogen, carbon, nitrogen, oxygen, sulfur, and phosphorus.
Amino acids and nucleotides associate to form polymers.
Polynucleotides are self-replicating molecules and can undergo natural selection.
RNA can catalyze biochemical reactions.
The flow of genetic material is from polynucleotide to DNA to polypeptide.
DNA is the hereditary material.
Friedrich Wohler synthesized urea in the 1800s.
There are twenty different types of amino acids.
Phospholipids are the fundamental building blocks of all cell membranes.
They have a hydrophilic head and a hydrophobic tail.
Proteins are polypeptides, DNA and RNA are polynucleotides, and carbohydrates are polysaccharides.
The nucleus is enclosed by an outer and inner nuclear membrane and is surrounded by cytoplasm.

How are cells studied?

Microscopes are used to study cells.
Electron microscopes provide higher magnification, resolution, and detail compared to light microscopes.
Robert Hooke discovered cells using a microscope.

Classifications of Living Things: Domains of Life

There are three domains of life:
- Bacteria: Domain and Kingdom
- Eukaryota: Kingdoms: Fungi, Plants, Animals, Protists
- Archaea: Domain and Kingdom

Prokaryotic Cell Structure

Appendages:
- Pili
- Flagella
- Axial Filaments
Cell Envelope:
- Capsule (glycocalyx)
- Outer membrane (bilayer with phospholipids and lipopolysaccharides)
- Inner layer: phospholipids
- Outer layer: lipopolysaccharides
Cell Wall:
- Peptidoglycan
Periplasm:
- Space between the cell membrane and the peptidoglycan cell wall
Plasma/Cell Membrane:
- Encloses the cytoplasm
- Composed of membrane lipids and proteins
- Contains cholesterol
DNA in Nucleoid:
- Not enclosed in a membrane
Cytoplasm:
- The intracellular fluid
Size:
- Bacteria cells are much smaller than eukaryotic cells (0.1-5.0 μm diameter).
- E.coli weighs approximately 25 × 10⁹.
- The total weight of bacteria in the human body is estimated to be 1-1.5 kg.
- There are approximately 5 × 10³⁰ bacteria on Earth, weighing around 10² kg.

Eukaryotic Cell Structure

Appendages:
- Cilia
- Flagella
Cell Walls:
- Composed of cellulose or chitin (only in plants)
- Animal cells do not have cell walls
Plasma/Cell Membrane:
- Encloses the cytoplasm
- Composed of membrane lipids and proteins
- Contains cholesterol
Glycocalyx:
- A carbohydrate-rich layer on the cell surface
Cytoplasm:
- The intracellular fluid
Nucleus:
- Contains the DNA
Ribosomes:
- Involved in protein synthesis
Membrane-bound organelles:
- Specialized structures within the cell
Size:
- Eukaryotic cells are much larger than bacteria (10-100 μm).

Archaea vs. Bacteria

Halophiles:
- "Salt-loving" archaea that require high salt concentrations for survival.
- Chemoheterotrophic (consume organic compounds for energy).
Thermacidophiles:
- "Heat and acid-loving" archaea that thrive in hot, acidic environments.
- Example: Sulfur-producing archaea at 80°C and pH < 2.
Methanogens:
- "Methane-producing" archaea that live in oxygen-free environments.
- Autotrophic (produce their own food).

Single-celled Organisms Reproduction

Sexual Reproduction:
- Meiosis, a process that produces gametes (sex cells).
Asexual Reproduction:
- Budding, a process of cell division that results in a daughter cell.
- Mitosis, a process of cell division that produces two identical cells.

Viruses

Ultimate parasites:
- Viruses require a host cell to grow and reproduce.
- They transport their genetic material by infecting a host cell.
Size:
- Viruses are much smaller than cells (100 nm).
Composition:
- A protein coat encloses the genetic material.
Functions of the protein coat:
- Protects the virus from the environment.
- Allows the virus to enter the host cell.
Example:
- Bacteriophage: A virus that attacks bacteria.

We Develop From A Single Cell: The Zygote

Zygote:
- Formed by the union of an egg and sperm.
- Contains the instructions for building the human body.
- Approximately 200 micrometers in diameter.
- A zygote contains approximately 60-100 trillion (10¹²) cells.
Embryonic Stem Cells (ES):
- Cells with the potential to develop into all cell types in the body.
Totipotent Stem Cells:
- Can differentiate into all cell types.
Pluripotent Stem Cells:
- Can differentiate into many cell types.
Organization of Cells:
- Cells are organized from simple to complex:
  - Atoms
  - Simple molecules
  - Chain molecules
  - Molecular structures
  - Cells
  - Organs
  - Organisms
  - Population
  - Ecosystem
Reductionism:
- Studying the parts of a system to understand the system as a whole.
Ecosystem Dynamics:
- Cycling of nutrients
- Flow of energy

Energy Conversion

Work requires a source of energy.
Energy can be stored in different forms: light, chemical, kinetic, and thermal.
Energy exchange involves energy transformations.
Energy flows through an ecosystem, entering as light and exiting as heat.
Calorie: The amount of heat needed to raise the temperature of 1 gram of water by 1°C.
Joule: The amount of energy required to apply a one-newton force over a distance of one meter.

Primary Sources of Energy in Organisms

Organotrophs:
- Feed on other living things or organic chemicals.
- Examples: animals, fungi, gut bacteria (consumers).
Inorganotrophs:
- Feed on non-living things.
- Examples: autotrophs (producers).
  - Phototrophs: Use sunlight as their energy source. (plants, algae)
  - Chemoautotrophs: Use energy from chemicals in rocks (lithotrophic).
Decomposers:
- Break down dead organisms.
Metabolic fuels:
- Organisms obtain energy from food sources like sugars, proteins, lipids, vitamins, and minerals.
Mitochondria:
- The "power plants" of cells.

Small Molecules of the Cell and Their Functions

Water:
- Interacts with water and biomolecules.
- Most abundant biological medium.
- Small and fast molecule.
- Polar and dipolar, allowing the formation of hydrogen bonds.
- Cohesive, resulting in surface tension.
- Moderates temperature.
- Expands when frozen.
- Versatile solvent.
Small molecules:
- Carry energy (ATP).
- Transmit signals (hormones and neurotransmitters).
- Link into macromolecules (covalently).
Macromolecules:
- Large molecules with the same bonds (IVOT lipids).
Proteins:
- Provide cell structure and perform most cellular tasks.
- Composed of twenty different amino acids.
Carbohydrates:
- Used as fuel, strengthen plant cell walls, and store glucose for energy.
- Composed of monosaccharides (e.g., glucose).
Lipids:
- Important energy source and components of cell membranes.
- Composed of long fatty chains.
Nucleic acids (DNA/RNA):
- Store hereditary information and carry protein coding from DNA to protein synthesizing machinery.
- Composed of a sugar and a phosphate group joined by covalent and non-covalent bonds.
The Genome:
- The complete set of DNA packaged into chromosomes.
- Replicated during cell division (linear).
- Mutations can be beneficial or harmful.
- Nucleotide > nucleosome > chromatin > chromosome > genome
Monomers and Polymers:
- Monomers (small molecules) join together to form polymers through repeated chemical linkage reactions.
- Cells produce three main types of macromolecules: polysaccharides, proteins, and nucleic acids.
- Proteins and nucleic acids exhibit greater information complexity.
Protein Structure:
- Primary, secondary, tertiary, and quaternary structures.

What Cells Can Do

Separated from the external environment by the plasma/cell membrane.
Produce energy (ATP).
Produce their own external environment (extracellular matrix proteins, gap junctions).
Change shape and move (cytoskeleton filaments).
Send and sense information (external and internal signals transmitted, receptors).
Grow and divide (mitosis and meiosis).
Die (apoptosis - programmed death).

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Test your knowledge of prokaryotic and eukaryotic cells with this quiz. Explore important concepts such as cell membranes, transport proteins, and cellular processes. Challenge yourself with questions on natural selection, cell reproduction, and key cellular components!