LEC 3; Human Cell Structure, Transport, and Function: A Comprehensive Review

What are the three main parts of a cell?

1. Plasma (cell) membrane 2. Cytoplasm (including cytosol and organelles) 3. Nucleus (including chromosomes and genes)

What is the structure of the plasma membrane?

The plasma membrane is a flexible yet sturdy phospholipid bilayer containing proteins and cholesterol.

What are the two main types of membrane proteins?

Integral (transmembrane) proteins and peripheral proteins.

What is the function of membrane proteins?

They help determine many functions of the cell membrane and vary between different cell types.

What does the Fluid Mosaic Model describe?

It describes membranes as fluid structures where lipids and proteins move easily within the bilayer.

How does cholesterol affect membrane fluidity?

Cholesterol stabilizes the membrane and reduces its fluidity.

What is the permeability of plasma membranes?

Plasma membranes are selectively permeable, allowing small, nonpolar, uncharged molecules to pass freely.

What are the mechanisms of passive transport?

1. Simple diffusion 2. Facilitated diffusion (helped by membrane proteins) 3. Osmosis (movement of water across a semipermeable membrane)

What is osmosis?

The movement of water across a semipermeable membrane from an area of high water concentration to low water concentration.

What is active transport?

The movement of molecules against their concentration gradient, requiring ATP.

What is the Na-K pump?

A mechanism of active transport that moves sodium and potassium ions across the plasma membrane.

What is vesicular transport?

A method by which macromolecules pass through the plasma membrane using vesicles.

What happens to a cell in a hypotonic solution?

Water moves into the cell, causing it to expand and potentially lyse.

What happens to a cell in a hypertonic solution?

Water moves out of the cell, causing it to shrink.

What is the role of the cytoplasm in a cell?

It contains cytosol and organelles, providing a medium for biochemical processes.

What are the inputs and outputs of cellular respiration?

Inputs: Glucose and oxygen; Outputs: Carbon dioxide, water, and ATP.

What is transcription?

The process of copying a segment of DNA into RNA.

What is translation?

The process of synthesizing proteins from RNA.

What is the significance of the phospholipid bilayer?

It forms the fundamental structure of the plasma membrane, providing a barrier and facilitating selective permeability.

What is facilitated diffusion?

The process of transporting molecules across the plasma membrane with the help of membrane proteins.

What is the difference between simple diffusion and facilitated diffusion?

Simple diffusion occurs directly through the membrane, while facilitated diffusion requires membrane proteins.

What are organelles?

Specialized structures within the cytoplasm of a cell that perform specific functions.

What is the function of the nucleus?

It houses chromosomes and genes, controlling cellular activities and gene expression.

What is a hypertonic solution?

A solution that has a higher solute concentration than another solution, causing water particles to move out of the cell and potentially leading to crenation.

What is an isotonic solution?

A solution that has the same solute concentration as another solution, resulting in no net movement of water particles and maintaining constant concentration on both sides of the cell membrane.

What is a hypotonic solution?

A solution that has a lower solute concentration than another solution, causing water to move into the cell.

What occurs to red blood cells in a hypertonic solution?

Red blood cells lose water and may undergo crenation.

What occurs to red blood cells in a hypotonic solution?

Red blood cells gain water, which may lead to swelling and possible lysis.

What is the function of the sodium-potassium pump?

It moves sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, using energy from ATP.

What are the two components of the cytoplasm?

Cytosol (intracellular fluid) and organelles (specialized structures with specific functions).

What are the three types of protein fibers in the cytoskeleton?

Microfilaments, intermediate filaments, and microtubules.

What is the role of the cytoskeleton?

It provides structure and support for the cell, maintains cell shape, promotes cellular movement, and aids in cell division.

What is the function of centrioles?

They organize the cytoskeleton and play a role in cell division.

What is the difference between cilia and flagella?

Cilia move fluid over the cell's surface, while flagella move the cell through a fluid.

What is the primary function of ribosomes?

They are involved in protein synthesis, assembling amino acids into proteins.

How are proteins synthesized using ribosomes?

Information in DNA is transcribed to RNA, which ribosomes use to build proteins.

What are the two distinct sections of the endoplasmic reticulum (ER)?

Rough ER and Smooth ER.

What is the function of rough ER?

It is studded with ribosomes and is the site of protein synthesis.

What is the function of smooth ER?

It synthesizes phospholipids and steroid hormones, regulates calcium concentration, metabolizes carbohydrates, and breaks down toxins.

What happens to water particles in an isotonic solution?

There is no net movement of water particles; the concentration remains constant on both sides of the cell membrane.

What is crenation?

The process where cells shrink due to loss of water in a hypertonic solution.

What is the significance of the sodium-potassium pump in cellular function?

It helps maintain the electrochemical gradient essential for various cellular processes.

What is the structure of ribosomes?

Ribosomes consist of a large subunit and a small subunit.

What are the main functions of the Smooth Endoplasmic Reticulum (Smooth ER)?

Synthesizes fatty acids and steroids, inactivates or detoxifies drugs, participates in carbohydrate metabolism, and stores calcium ions.

What is the primary role of the Rough Endoplasmic Reticulum (Rough ER)?

Synthesizes proteins, glycoproteins, and phospholipids, with ribosomes producing proteins for export to the Golgi apparatus and plasma membrane.

What happens to proteins as they move through the Golgi Complex?

Proteins are modified and packaged at the cis face and then transported in vesicles from the trans face to their destination.

What is the function of lysosomes?

Contain digestive enzymes to recycle cell components and can fuse with other vesicles to digest their contents.

How do peroxisomes differ from lysosomes?

Peroxisomes are smaller, contain enzymes that oxidize organic substances, and are associated with metabolism, while lysosomes contain digestive enzymes.

What is the primary function of mitochondria?

Site of cellular respiration, producing ATP to fuel cellular activities.

What is the structure of a mitochondrion?

Composed of two lipid bilayer membranes with various molecules along the inner membrane that produce ATP.

What is the role of the nucleus in a cell?

Contains hereditary units called genes, which are arranged along chromosomes made of long strands of DNA.

What is the process of transcription in protein synthesis?

Information in DNA is copied into an mRNA molecule, which can leave the nucleus.

What occurs during translation in protein synthesis?

The mRNA is read by the ribosome to build a protein.

What distinguishes different cell types in terms of protein production?

Different genes in the DNA are transcribed and translated in each cell type, leading to the production of different proteins.

What are the four steps of cellular respiration?

1. Glycolysis (in cytosol), 2. Transition Reaction (in mitochondria), 3. Citric Acid Cycle (in mitochondria), 4. Electron Transport Chain (in mitochondria).

What is the net ATP yield from glycolysis?

2 ATP (4 produced but 2 used).

What is produced during the transition reaction of cellular respiration?

2 NADH and 2 CO2, along with 2 Acetyl CoA.

How many ATP are produced in the Citric Acid Cycle per Acetyl CoA?

1 ATP per Acetyl CoA, with a total net yield of 2 ATP from 2 Acetyl CoA.

What is the total ATP yield from the Electron Transport Chain?

32 ATP.

What is the total ATP produced from one glucose molecule during cellular respiration?

36 ATP.

What is fermentation and how efficient is it?

Fermentation is the breakdown of glucose without oxygen, generating 2 ATP, which is very inefficient.

What are the phases of mitosis?

Prophase, Prometaphase, Metaphase, Anaphase, Telophase/Cytokinesis.

What distinguishes meiosis from mitosis?

Meiosis is the cell division of gametes and consists of two rounds: Meiosis I and Meiosis II.

What is the importance of the plasma membrane?

It regulates the transport of substances in and out of the cell and maintains the cell's integrity.

Where does glycolysis occur?

In the cytosol.

What is the net ATP produced from glycolysis?

2 ATP.

What are the products of glycolysis?

2 pyruvates, 2 NADH, and a net of 2 ATP.

What happens during the transition reaction?

Each pyruvate is converted to Acetyl CoA, producing 1 NADH and 1 CO2.

What is the net NADH produced in the transition reaction?

2 NADH (1 per pyruvate).

What is produced in the citric acid cycle per Acetyl CoA?

1 ATP, 3 NADH, 1 FADH2, and 2 CO2.

What is the purpose of the plasma membrane?

To protect the cell and regulate transport of substances in and out.

What is mitosis?

Cell division of somatic (non-reproductive) cells.

What is meiosis?

Cell division that produces gametes.

What are the stages of meiosis?

Meiosis I and Meiosis II.

What is the role of NADH in cellular respiration?

It acts as an electron carrier.

What is the difference between flagella and cilia?

Flagella are longer and usually fewer in number, while cilia are shorter and more numerous.

What are the inputs of cellular respiration?

Oxygen and glucose.

What are the outputs of cellular respiration?

Carbon dioxide, water, and ATP.

What is the significance of the electron transport chain?

It uses electrons from NADH and FADH2 to produce ATP.