Biology Chapter: Cell Types and Microscopy

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Questions and Answers

What is the main structural difference between prokaryotic and eukaryotic cells regarding their DNA?

Prokaryotic cells have DNA that floats in the cytoplasm in a single loop called the nucleoid, while eukaryotic cells contain DNA within a membrane-bound nucleus.

Identify two types of microscopes used to study cell structure and their primary differences.

Light microscopes magnify specimens using light and allow for live viewing, whereas electron microscopes use electron beams for much higher magnification and resolution but cannot view live specimens.

What are organelles, and how do they differ in prokaryotic and eukaryotic cells?

Organelles are specialized structures within a cell that perform specific functions; they have no membrane in prokaryotic cells, while in eukaryotic cells, organelles are membrane-bound.

Describe the average size and structure of prokaryotic cells.

Prokaryotic cells are small and simple, averaging around 0.1-5 µm in size. Signup and view all the answers

What is the function of the nucleus in eukaryotic cells?

The nucleus controls and regulates the activities of the cell and contains the cell's DNA, which is essential for genetic information storage and processing. Signup and view all the answers

How do transmission and scanning electron microscopes differ in their imaging methods?

Transmission electron microscopes pass electrons through a specimen to produce 2D cross-sections, while scanning electron microscopes bounce electrons off the surface to produce 3D images of the specimen's topography. Signup and view all the answers

What is the significance of the plasmid in prokaryotic cells?

Plasmids are small, circular DNA molecules in prokaryotic cells that can carry genes beneficial for survival, such as antibiotic resistance. Signup and view all the answers

Explain the total magnification calculation in microscopy.

Total magnification is calculated by multiplying the eyepiece lens magnification by the objective lens magnification. Signup and view all the answers

What defines heterotrophs and what organisms fall under this category?

Heterotrophs are organisms that cannot make their own food, including animals, fungi, and some bacteria. Signup and view all the answers

How do chemotrophs obtain energy?

Chemotrophs obtain energy by utilizing inorganic substances such as iron and sulfur, and can survive without sunlight. Signup and view all the answers

What are the main functions of carbohydrates in living organisms?

Carbohydrates serve as important energy sources and are involved in the structure of cells. Signup and view all the answers

What role do lipids play in biological systems?

Lipids function as energy storage molecules and are important for membrane structure and signaling. Signup and view all the answers

What process converts glucose into ATP, and where does it occur in eukaryotic cells?

Cellular respiration converts glucose into ATP and occurs in the mitochondria. Signup and view all the answers

What are the by-products of aerobic respiration?

The by-products of aerobic respiration are carbon dioxide and water. Signup and view all the answers

Describe the light-dependent reactions of photosynthesis.

Light-dependent reactions use sunlight to split water, releasing oxygen while producing ATP and NADPH. Signup and view all the answers

What happens during the Krebs cycle?

During the Krebs cycle, pyruvate is converted to acetyl CoA, generating NADPH and ATP. Signup and view all the answers

What is the lock and key model in relation to enzyme activity?

The lock and key model suggests that a substrate fits precisely into the active site of an enzyme. Signup and view all the answers

How does temperature affect enzyme activity?

Temperature affects enzyme activity by having optimal rates at around 37 degrees Celsius, with deviations causing denaturation. Signup and view all the answers

What is denaturation in terms of enzyme structure?

Denaturation is a permanent structural change in an enzyme that renders it unable to function. Signup and view all the answers

Explain the significance of nucleic acids in cells.

Nucleic acids, including DNA and RNA, are essential for storing and transmitting genetic information. Signup and view all the answers

What is anaerobic respiration and when does it occur?

Anaerobic respiration occurs in the absence of oxygen, typically when immediate energy is needed. Signup and view all the answers

What are two examples of organic compounds?

Two examples of organic compounds are carbohydrates and proteins. Signup and view all the answers

What role does the nucleolus play in the cell?

The nucleolus is responsible for the production of ribosomes. Signup and view all the answers

How does the structure of the cell membrane contribute to its function?

The cell membrane's phospholipid bilayer allows it to be semi-permeable, controlling the passage of substances. Signup and view all the answers

What is the primary function of mitochondria in cells?

Mitochondria produce energy needed for cellular activities through cellular respiration. Signup and view all the answers

What distinguishes the rough endoplasmic reticulum from the smooth endoplasmic reticulum?

The rough ER is covered in ribosomes and is involved in protein synthesis, while the smooth ER is involved in lipid synthesis. Signup and view all the answers

Which type of transport requires energy and involves moving materials against their concentration gradient?

Active transport requires energy to move materials against their concentration gradient. Signup and view all the answers

Explain the process of osmosis.

Osmosis is the movement of water molecules across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration. Signup and view all the answers

What function do lysosomes serve in a cell?

Lysosomes contain digestive enzymes that break down waste materials and cellular debris. Signup and view all the answers

Define facilitated diffusion.

Facilitated diffusion is the passive movement of molecules across a cell membrane down the concentration gradient via a channel or carrier protein. Signup and view all the answers

What is the role of chloroplasts in plant cells?

Chloroplasts are the sites of photosynthesis, converting light energy into chemical energy. Signup and view all the answers

How do channel proteins assist in the movement of substances across the cell membrane?

Channel proteins allow large and polar particles, such as sugars and amino acids, to pass through the membrane. Signup and view all the answers

What is the significance of the surface area to volume ratio for cellular efficiency?

A large surface area to volume ratio allows for more efficient exchange of materials with the environment. Signup and view all the answers

What are autotrophs and how do they obtain energy?

Autotrophs are organisms that can produce their own food, typically using sunlight to convert carbon dioxide and water into glucose. Signup and view all the answers

Describe the process of endocytosis.

Endocytosis is the process by which a cell takes in substances from its external environment by engulfing them with its cell membrane. Signup and view all the answers

Study Notes

Cell Types and Structure

Prokaryotes: Single-celled organisms without a nucleus or membrane-bound organelles; examples include bacteria and archaea.
Eukaryotes: Organisms with one or more cells that contain a membrane-bound nucleus and organelles; examples include animals, plants, fungi, and protists.
Prokaryotic cells feature a cell membrane, cell wall, cytoplasm, ribosomes, and a nucleoid with a circular chromosome.
Eukaryotic cells are larger and complex, ranging from 10-100 µm, and have more specialized structures.

Microscopy Technologies

Light Microscopes: Magnification of up to 1000x, resolution greater than 200 nm, can view live specimens, generally more affordable.
Electron Microscopes: Magnification up to 100,000x, resolution around 10 nm, only black & white images, cannot view live specimens, more expensive.
Types of Electron Microscopes:
- Transmission Electron Microscopes (TEM): Produce high-definition 2D cross-sections by passing electrons through specimens.
- Scanning Electron Microscopes (SEM): Bounce electrons off specimen surfaces to show topography.

Organelles and Their Functions

Nucleus: Controls cellular activities, contains DNA, involved in gene expression and replication.
Nucleolus: Site of ribosome production.
Cytoskeleton: Provides shape, structure, and facilitates movement of organelles.
Ribosomes: Sites of protein synthesis, found in cytoplasm or attached to rough ER.
Endoplasmic Reticulum (ER): Transport system; smooth ER synthesizes lipids and detoxifies chemicals, while rough ER is involved in protein synthesis.
Golgi Apparatus: Modifies, stores, and packages proteins; vesicles transport molecules to and from it.
Lysosomes: Contains digestive enzymes for waste breakdown (cell's garbage disposal).
Mitochondria: Powerhouses that produce energy through cellular respiration; double-membrane bound.
Chloroplasts: Site of photosynthesis in plant cells, containing chlorophyll (double-membrane bound).
Cell Wall: Protective barrier found in plant and bacterial cells; located outside cell membrane.
Cell Membrane: Semi-permeable membrane that controls substance passage in and out of the cell.
Vacuoles: Store substances such as water, food, and wastes; larger in plant cells than in animal cells.
Centrioles: Assist in cell division; found only in animal cells.

Membrane Structure: Fluid Mosaic Model

Comprised of a phospholipid bilayer with embedded proteins and molecules.
Semi-permeable, allowing selective passage of nutrients and waste.
Phospholipids: Hydrophilic heads and hydrophobic tails create a barrier for certain molecules.
Cholesterol stabilizes phospholipid arrangement, facilitating nonpolar molecule passage.

Transport Mechanisms

Diffusion: Passive movement of molecules from high to low concentration.
Osmosis: Movement of water across a semi-permeable membrane due to solute concentration gradients.
Facilitated Diffusion: Utilizes channel or carrier proteins for passive molecular transport.
Active Transport: Movement against concentration gradients requiring energy (ATP).
Endocytosis: Engulfing of substances into the cell.
Exocytosis: Expulsion of substances from the cell.

Surface Area to Volume Ratio

Larger surface area to volume ratios promote efficient exchange of materials.
Concentration gradients enhance diffusion efficiency.
Material characteristics (size, polarity, and solubility) affect exchange rates.

Biochemical Compounds in Cells

Key Elements: 96% of cell mass consists of carbon, hydrogen, oxygen, and nitrogen, essential for organic compounds.
Autotrophs: Organisms that produce their own food using sunlight (e.g., plants).
Heterotrophs: Organisms that cannot produce their own food (e.g., animals, fungi).
Organic Compounds: Based on carbon structures, including carbohydrates, lipids, proteins, and nucleic acids.
Inorganic Compounds: Water, salts, and carbon dioxide can either contain carbon or not.

Photosynthesis and Cellular Respiration

Photosynthesis: Conversion of CO2 and water into glucose and oxygen using sunlight; occurs in chloroplasts with two stages - light-dependent and light-independent reactions.
Cellular Respiration: Breakdown of glucose for ATP; occurs in mitochondria and can be aerobic (with oxygen) or anaerobic (without oxygen).
Aerobic Respiration: Involves glycolysis, Krebs cycle, and electron transport chain; produces 36 ATP from one glucose.
Anaerobic Respiration: Produces only 2 ATP from glucose; common in yeast.

Enzyme Action and Factors Affecting Activity

Enzymes: Proteins that act as catalysts to speed up reactions, specific to substrates.
Lock and Key Model: Enzyme active sites exactly fit specific substrates.
Factors Influencing Enzyme Activity:
- Temperature: Optimal at 37°C; temperatures too high cause denaturation.
- pH: Enzymes have optimal pH ranges; deviation slows reaction rates.
- Substrate Concentration: Higher amounts increase reaction rates until saturation is reached.

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Description

Test your knowledge on cell types, including prokaryotes and eukaryotes, as well as the microscopy technologies used to study them. This quiz covers the fundamental structures of cells and the differences between light and electron microscopes.