Week 2 Content

Question 1

What are the principal parts of a cell?
Plus draw a cell

Answer 1

The principal parts of a cell include:
* Cell membrane (plasma membrane)
* Cytoplasm
* Nucleus
* Ribosomes
* Endoplasmic reticulum (ER)
* Golgi apparatus
* Lysosome
* Mitochondria
* Cytoskeleton

Question 2

What is the structure and function of the cell membrane?

Answer 2

Structure:

Made up of a lipid bilayer, consisting of two layers of phospholipids.

Function:

○ Physical isolation: Separates the intracellular environment from the extracellular environment.

○ Exchange regulation: Controls what enters and exits the cell (semipermeable).

○ Sensitivity: Detects environmental changes using protein receptors.

○ Structural support: Maintains the cell shape and contributes to tissue and organ structure.

Question 3

What is the structure and function of the cytoplasm?

Answer 3

Structure:

The cytoplasm consists of cytosol (intracellular fluid) and organelles.

Function:

○ Contains nutrients, proteins, ions, and waste.

○ The cytosol differs from the extracellular fluid in ion concentration (e.g., higher potassium in the cytosol, higher sodium outside).

○ Organelles perform specific functions for cell maintenance and activity.

Question 4

What is the structure and function of the cytoskeleton?

Answer 4

Structure:

Composed of microtubules, intermediate filaments, and microfilaments (actin filaments).

Function:

○ Provides cell shape and strength.

○ Facilitates movement and supports the position of organelles.

○ Microtubules assist in cell division and intracellular transport.

○ Microfilaments interact with myosin to produce movement (e.g., muscle contraction).

Question 5

What is the structure and function of the nucleus?

Answer 5

• Structure:

○ Surrounded by the nuclear envelope.

○ Contains nuclear pores for chemical exchange with the cytoplasm.

○ The fluid inside is called nucleoplasm, which has a network of filaments (nuclear matrix).

• Function:

○ Holds the DNA, the genetic material.

○ DNA is organized into chromosomes (23 pairs in somatic cells).

○ The nucleus is the control center of the cell, directing protein synthesis and cellular activities.

Question 6

What is the structure and function of ribosomes?

Answer 6

Structure:

Small, non-membranous organelles made of RNA and proteins.

Function:

○ Ribosomes are the sites of protein synthesis.

○ Found either floating freely in the cytoplasm or attached to the endoplasmic reticulum.

Question 7

What is the structure and function of the endoplasmic reticulum (ER)?

Answer 7

Structure:

A network of tubules and sacs, with two types:

○ Rough ER (with ribosomes)
○ Smooth ER (without ribosomes)

Function:

○ Rough ER: Synthesizes and modifies proteins.

○ Smooth ER: Synthesizes lipids and detoxifies chemicals.

Question 8

What is the structure and function of the Golgi apparatus?

Answer 8

Structure:

A series of flattened membrane-bound sacs (cisternae).

Function:

○ Modifies, sorts, and packages proteins and lipids for transport within or outside the cell.

○ Forms vesicles for secretion or storage.

Question 9

What is the structure and function of lysosomes?

Answer 9

Structure:
Membrane-bound vesicles containing digestive enzymes.

Function:
○ Breaks down waste materials, cellular debris, and foreign substances.

○ Plays a role in apoptosis (programmed cell death).

Question 10

What is the structure and function of mitochondria?

Answer 10

• Structure:
  Membrane-bound organelles with an outer membrane and a highly folded inner membrane (cristae).
• Function:
  ○ The powerhouse of the cell, generating ATP through cellular respiration.

○ Involved in energy production, metabolism, and regulation of cell death.

Question 11

What is the function of ribosomes?

Answer 11

• Ribosomes are responsible for protein synthesis.
• They translate RNA into amino acids, forming protein chains.
• Ribosomes consist of a small and large subunit made of protein and RNA.
• When protein production is not required, the subunits separate to “turn off” the ribosome.

Question 12

Describe the structure and function of the Endoplasmic Reticulum (ER).

Answer 12

• The ER is a tubular network beginning at the nuclear envelope.
• Rough ER (RER): Studded with ribosomes. Modifies proteins (e.g., adding carbohydrates/lipids).
• Smooth ER (SER): Lacks ribosomes. Involved in lipid and carbohydrate production, detoxification, and storage/transport of molecules.

Question 13

What is the role of the Golgi apparatus?

Answer 13

• Modifies and packages proteins and enzymes for secretion.
• Packages enzymes in vesicles for use in the cytosol.
• Maintains the cell membrane by providing vesicles that deliver new material to the membrane.
• Golgi vesicles can be secretory, membrane renewal, or lysosomes.

Question 14

What is the function of lysosomes?

Answer 14

• Lysosomes contain digestive enzymes that break down debris, dead organelles, and pathogens.
• They protect the cell by isolating these enzymes.
• After digestion, the contents are either reused or secreted from the cell.

Question 15

Describe the structure and function of mitochondria.

Answer 15

• Mitochondria have two membranes: an outer membrane and a highly folded inner membrane.
• The inner membrane creates a large surface area for enzymes involved in ATP production.
• Mitochondria are the major site for ATP production, through processes like the citric acid cycle and electron transport chain.

Question 16

What are the characteristics of a phospholipid bilayer?

Answer 16

• Made up of two layers of phospholipid molecules.
• Hydrophilic heads face outward (toward the water), and hydrophobic tails face inward (away from water).
• The bilayer regulates the passage of substances into and out of the cell, allowing lipid-soluble molecules to diffuse across but preventing polar molecules from doing so without assistance.

Question 17

How do proteins and carbohydrates contribute to the structure and function of the cell membrane?

Answer 17

• Proteins:

○ Integral proteins span the membrane (transmembrane) and play roles in transport, cell signaling, and cell recognition.

○ Peripheral proteins are on the inner or outer surface, often involved in signaling or structural support.

• Carbohydrates:

○ Carbohydrates form glycoproteins, glycolipids, and proteoglycans that extend beyond the membrane.

○ They contribute to cell recognition, protection, lubrication, and help cells adhere to each other or extracellular materials.

Question 18

Why is the cell membrane more permeable to lipid-soluble substances and small molecules than to large water-soluble substances?

Answer 18

• The phospholipid bilayer is hydrophobic, allowing lipid-soluble (non-polar) molecules to dissolve and pass through more easily.
• Large, polar molecules cannot pass through without assistance from proteins because the hydrophilic heads block them from moving freely across.

Question 19

What are the mechanisms that facilitate the transport of substances across cell membranes?

Answer 19

• Diffusion: Movement of molecules from high to low concentration, requiring no energy.
• Osmosis: Diffusion of water across a membrane to equalize solute concentrations.
• Facilitated Diffusion: Passive transport using carrier proteins or channels for larger or polar molecules.
• Active Transport: Movement of molecules against their concentration gradient using energy (ATP).
• Endocytosis: Process of taking substances into the cell by vesicle formation (e.g., receptor-mediated, pinocytosis, phagocytosis).
• Exocytosis: Process of expelling substances from the cell using vesicles.

Question 20

What are the effects of isotonic, hypertonic, and hypotonic solutions on cells?

Answer 20

• Isotonic Solution: Solute concentration is equal inside and outside the cell. No net water movement occurs.
• Hypertonic Solution: Solute concentration outside the cell is higher. Water moves out of the cell, causing it to shrink.
• Hypotonic Solution: Solute concentration outside the cell is lower. Water moves into the cell, causing it to swell, and possibly burst.

Question 21

What factors influence the rate of diffusion?

Answer 21

1. Distance: Shorter distances speed up diffusion.
2. Molecule Size: Smaller molecules diffuse faster.
3. Temperature: Higher temperatures speed up diffusion.
4. Concentration Gradient: A greater difference in concentration increases the rate.
5. Electrical Forces: Can influence diffusion of charged molecules.

Question 22

What is facilitated diffusion?

Answer 22

• A type of passive transport where carrier proteins or channels assist polar or large molecules in moving across the membrane, down their concentration gradient, without using energy.

Question 23

What is primary active transport?

Answer 23

• Active transport that moves molecules against their concentration gradient, requiring energy (usually ATP).
• Example: Sodium-potassium pump, which exchanges sodium ions (Na+) out and potassium ions (K+) in.

Question 24

What is vesicular transport?

Answer 24

• Involves the use of vesicles to move materials into (endocytosis) or out of (exocytosis) the cell.
• Endocytosis: Includes receptor-mediated endocytosis (molecules bind to receptors), pinocytosis (fluid intake), and phagocytosis (solid material intake).
• Exocytosis: Secretion of materials from the cell via vesicles.

Question 25

What is carrier-mediated transport?

Answer 25

* Transport that uses proteins to move molecules across the cell membrane. * Facilitated Diffusion: A passive process where carrier proteins assist the movement of large or polar molecules down their concentration gradient. * Active Transport: A process where energy is used to move molecules against their concentration gradient.

Question 26

What is metabolism?

Answer 26

Metabolism is the collective set of chemical reactions that occur in the body, including both catabolism (the breakdown of complex molecules) and anabolism (the synthesis of complex molecules).

Question 27

What is the difference between catabolism and anabolism?

Answer 27

* Catabolism is the breakdown of complex molecules into simpler molecules, releasing energy. * Anabolism is the synthesis of complex molecules from simpler ones, requiring energy.

Question 28

Why do cells need to synthesize new organic components?

Answer 28

Cells need to synthesize new organic components for processes like maintenance and repair of cellular structures, growth, secretions (e.g., hormones or mucus), and to store nutrients for emergencies.

Question 29

What is the role and importance of ATP in the cell?

Answer 29

ATP (Adenosine Triphosphate) stores energy from food in its covalent bonds and provides energy for cell processes like movement, intracellular transport, and endocytosis. It is essential for maintaining cellular functions.

Question 30

What is the difference between aerobic and anaerobic respiration?

Answer 30

* Aerobic respiration occurs in the mitochondria and requires oxygen to produce ATP. * Anaerobic respiration occurs in the cytosol and does not require oxygen, but produces less ATP and results in the formation of lactic acid or pyruvate.

Question 31

Where does aerobic respiration occur in the cell?

Answer 31

Aerobic respiration occurs in the mitochondria, which is known as the powerhouse of the cell.

Question 32

What is the function of glycolysis in cellular respiration?

Answer 32

Glycolysis is the first stage of cellular respiration and occurs in the cytosol. It breaks down glucose into pyruvate and produces 2 ATP molecules. It is anaerobic and does not require oxygen.

Question 33

What happens after glycolysis if oxygen is not available?

Answer 33

If oxygen is not available, the product of glycolysis, pyruvate, is converted into lactic acid (in muscle cells) or ethanol (in yeast) through fermentation.

Question 34

What is the Krebs cycle and where does it occur?

Answer 34

The Krebs cycle (also called the Citric Acid Cycle) occurs in the mitochondria, and it processes pyruvate to produce energy carriers (NADH, FADH2) and 2 ATP molecules.

Question 35

What are NADH and FADH2, and why are they important?

Answer 35

NADH and FADH2 are electron carriers produced during the Krebs cycle. They transport electrons to the electron transport chain, where they are used to generate ATP.

Question 36

What is the electron transport chain (ETC), and where does it occur?

Answer 36

The electron transport chain occurs in the inner membrane of the mitochondria. It transfers electrons through a series of enzymes, which generates a large amount of ATP (32 molecules per glucose molecule).

Question 37

What is oxidative phosphorylation?

Answer 37

Oxidative phosphorylation refers to the production of ATP in the electron transport chain, where electrons are transferred to generate energy, which is then used to add a phosphate group to ADP, forming ATP.

Question 38

How much ATP is generated from each stage of cellular respiration?

Answer 38

* Glycolysis: 2 ATP * Krebs cycle: 2 ATP * Electron transport chain: 32 ATP In total, approximately 36 ATP molecules are generated from one molecule of glucose.

Question 39

Why does anaerobic glycolysis produce less ATP than aerobic respiration?

Answer 39

Anaerobic glycolysis produces only 2 ATP per glucose molecule because it does not utilize the electron transport chain or the Krebs cycle, both of which generate much more ATP.

Question 40

Why are the terms "shred," "burn," and "melt" often used inaccurately to describe exercise and fat loss?

Answer 40

These terms are more fitting for describing kitchen processes than exercise. Fat loss involves complex metabolic processes, not a simple "burning" or "melting" effect. It's the oxidation of fat molecules for energy that helps with weight loss, not direct combustion.