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Questions and Answers

What component of the cell membrane is primarily responsible for its fluidity?

Cholesterol (correct)

Glycoproteins

Proteins

Phospholipids

Which protein type is specifically involved in identifying 'self' from 'non-self' in a cell?

Channel proteins

Cell recognition proteins (correct)

Receptor proteins

Carrier proteins

During osmosis, what would happen in a hypotonic environment to an animal cell?

The cell would shrink.

The cell would swell and possibly burst. (correct)

The cell would remain unchanged.

The cell would undergo plasmolysis.

Which type of transport across the cell membrane requires a protein but no energy?

Facilitated diffusion Signup and view all the answers

What role do junction proteins play in cellular structures?

Joining cells together Signup and view all the answers

How does the cell membrane's selectively permeable nature benefit the cell?

Helps maintain homeostasis by regulating what enters and exits Signup and view all the answers

What type of molecules can generally pass through the cell membrane easily by simple diffusion?

Small and non-polar molecules Signup and view all the answers

Which proteins are responsible for transporting specific molecules or ions across the cell membrane?

Channel proteins Signup and view all the answers

What is the primary function of a dissecting or stereomicroscope?

To magnify whole specimens up to 40X Signup and view all the answers

Which of the following statements about light microscopes is true?

They utilize multiple objectives for varied magnification. Signup and view all the answers

What factor limits the size of cells concerning their surface area and volume?

The volume of a cell increases faster than its surface area. Signup and view all the answers

How does resolution differ from magnification in microscopy?

Resolution refers to clarity, while magnification refers to size. Signup and view all the answers

Which statement is NOT one of the basic premises of cell theory?

Cells can arise spontaneously from non-living matter. Signup and view all the answers

What is a key advantage of fluorescent imaging in microscopy?

It provides a clearer background contrast against the specimen. Signup and view all the answers

What is the significance of a larger surface-area-to-volume ratio in cells?

It improves the efficiency of nutrient and waste exchange. Signup and view all the answers

Which of the following best describes prokaryotic cells?

They lack a true nucleus and membrane-bound organelles. Signup and view all the answers

What is the primary advantage of using confocal microscopes?

They allow focusing on one layer of a slide at a time. Signup and view all the answers

Which of the following best characterizes the scanning electron microscope?

It scans the surface of objects using electrons. Signup and view all the answers

Which of the following statements is true regarding prokaryotic cells?

They have a simpler structure than eukaryotic cells. Signup and view all the answers

Which of these is NOT a characteristic of eukaryotic cells?

They lack organelles. Signup and view all the answers

What is the function of the Golgi apparatus in a cell?

Processing and packaging proteins for secretion. Signup and view all the answers

Which structure is responsible for producing energy in eukaryotic cells?

Mitochondria Signup and view all the answers

What role does the glycocalyx serve in prokaryotic cells?

Facilitates adherence to surfaces and prevents desiccation. Signup and view all the answers

Which of the following pairs correctly differentiates between prokaryotic and eukaryotic cells?

Prokaryotic cells lack a nucleus, eukaryotic cells contain one. Signup and view all the answers

Study Notes

Cell Theory

All organisms are composed of cells
Cells are the basic unit of structure and function in organisms
Cells only come from pre-existing cells

Cell Size and Surface Area to Volume Ratio

Cells range in size, but most are microscopic
As a cell grows, its volume increases faster than its surface area
A large surface-area-to-volume ratio is essential for cells to exchange nutrients and waste efficiently.

Microscopy

Dissecting or stereoscopes:
- Magnification: 10-40X
- Used for whole specimens
Light or compound microscopes:
- Magnification: 40X-1000X
- Used with slides
- Objectives: Scanning (4X), Low Power (10X), High Power (40X), Oil Immersion (60X-100X)
- Working distance decreases with higher magnification
Confocal microscopes:
- Allow focusing on a single layer of a slide without interference from other layers.
Transmission and Scanning Electron Microscopes:
- Use electrons to scan through (transmission) or over (scanning) the surface of an object.
- Scanning electron microscopes magnification range: 20X-30,000X.
- Transmission electron microscopes magnification range: Up to 10,000,000X.

Prokaryotic Cells

No membrane-bound nucleus or organelles
Shapes:
- Bacillus: Rod-shaped
- Spirilla: Spiral-shaped
- Coccus: Spherical
Cell envelope:
- Plasma membrane (phospholipid bilayer)
- Cell wall: Provides stability
- Glycocalyx (capsule or slime layer): Adhesion and prevents drying out
DNA storage:
- Plasmids
- Nucleoid
External Structures:
- Flagella: Movement
- Fimbriae: Adhesion
- Conjugation pili: DNA transfer
Differences from Eukaryotic Cells:
- Lack of a nucleus and other membrane-bound organelles
- Different DNA storage

Eukaryotic Cells

Contain a membrane-bound nucleus and other membrane-bound organelles
Organelles:
- Increase efficiency by compartmentalizing cellular functions
Endosymbiotic Theory:
- The theory that mitochondria and chloroplasts originated from free-living prokaryotes that were engulfed by eukaryotic cells.
- Evidence:
  - Mitochondria and chloroplasts have their own DNA.
  - They have ribosomes similar to those found in prokaryotes.
  - They reproduce independently of the cell.
Differences between animal and plant cells:
- Plant cells have chloroplasts, cell walls, and large central vacuoles, which are not found in animal cells.
- Animal cells have lysosomes, which are typically not found in plant cells.

Cell Structures and Functions

Nucleus:
- Contains chromatin (DNA)
- Surrounded by the nuclear envelope with nuclear pores.
Endoplasmic Reticulum:
- Rough ER:
  - Ribosomes attached to the surface.
  - Protein synthesis and modification.
- Smooth ER:
  - Lacking ribosomes.
  - Lipid synthesis, detoxification, calcium storage
Golgi Apparatus:
- Processes and packages proteins and lipids.
- Modifies and sorts molecules.
Lysosomes:
- Contain digestive enzymes.
- Break down waste products and cellular debris.
Vacuoles:
- Storage compartments for water, nutrients, and waste products.
- Larger in plant cells, important for turgor pressure.
Chloroplasts:
- Found in plant cells.
- Site of photosynthesis.
Mitochondria:
- The "powerhouse" of the cell.
- Site of cellular respiration.
- Produce ATP (energy).
Cytoskeleton:
- Network of protein filaments that provides support and structure to the cell.
- Responsible for cell movement, shape, and organelle transport.
Cell Membrane:
- Fluid-mosaic model:
- Flexible and proteins move around within the membrane.
- Composition:
- Phospholipids, proteins, cholesterol, glycolipids, and glycoproteins.
- Protein Functions:
- Channel proteins: Transport molecules freely.
- Carrier proteins: Transport molecules specifically.
- Cell recognition proteins: Identify "self" from "non-self".
- Receptor proteins: Bind signal proteins and trigger cellular responses.
- Enzymatic proteins: Catalyze chemical reactions.
- Junction proteins: Connect cells together.
- Selective permeability:
- Allows some molecules to pass through, but not others.
- Structure on either side of the membrane
- Cytoskeleton on the inside
- Extracellular matrix on the outside
- Both provide structure to tissues.

Passive Transport

Movement across the membrane that does not require energy.
Diffusion:
- Movement of molecules down their concentration gradient (high to low).
- Small and non-polar molecules can diffuse through the membrane.
Facilitated Diffusion:
- Movement of molecules down their concentration gradient through channel or carrier proteins.
- Requires no energy.
Osmosis:
- Diffusion of water across a membrane.
- Water moves to try to equalize the solute concentration on both sides of the membrane.
- Hypotonic environment: - More solute inside the cell. - Water moves into the cell. - Could cause the cell to swell and burst. - In plant cells, it helps maintain turgor pressure.