Cell Structure and Function

These flashcards cover key concepts from the lecture on cell structure and function, including microscopy techniques, organelle functions, differences between cell types, and the role of biological molecules.

What are the distinguishing features between light microscopes and electron microscopes?

Light microscopes have poor resolution due to long wavelengths of light; electron microscopes have high magnification and resolution.

What is the main function of the eyepiece graticule in light microscopes?

To measure the size of the object viewed under the microscope.

What are the four main types of sample preparations for microscopy?

1. Dry mount, 2. Wet mounts, 3. Squash slides, 4. Smear slides.

What is the primary function of the nucleus in cells?

Site of DNA replication and transcription.

What are the two types of electron microscopes, and how do they differ?

Transmission electron microscope (TEM) produces 2D images by passing electrons through thin specimens; scanning electron microscope (SEM) produces 3D images by scattering electrons off the specimen's surface.

What is the function of ribosomes?

Site of protein synthesis.

What is the structure and function of mitochondria?

Mitochondria have a double membrane; they are the site of aerobic respiration and ATP production.

What are the main components of the plasma membrane?

Phospholipid bilayer with embedded proteins, carbohydrates, and cholesterol.

What role do lysosomes play in a cell?

They contain digestive enzymes to hydrolyze phagocytic cells and break down worn-out organelles.

How do prokaryotic cells differ from eukaryotic cells?

Prokaryotic cells are smaller, lack membrane-bound organelles, and have circular DNA free in the cytoplasm.

What is the significance of the double helix structure of DNA?

It provides stability and facilitates replication using both strands as templates.

What process allows water molecules to move across a membrane?

Osmosis, which is the movement of water from a higher to a lower water potential.

What is ATP and its role in cells?

Adenosine triphosphate (ATP) is the primary energy carrier in cells, essential for metabolic processes.

Define the term 'monomer' and give examples.

Monomers are smaller units that bond to form larger molecules, e.g., glucose (monosaccharide) and amino acids.

What is the role of enzymes in biochemical reactions?

Enzymes act as catalysts to lower the activation energy, speeding up reactions.

What is the primary function of the Golgi apparatus?

To modify, package, and transport proteins and lipids.

Describe the function of guard cells in plants.

They control the opening and closing of stomata to regulate water loss by transpiration.

What is the importance of cholesterol in the cell membrane?

Cholesterol stabilizes membrane fluidity and prevents leakage of ions and water.

What is the difference between competitive and non-competitive inhibitors?

Competitive inhibitors bind to the active site of an enzyme, while non-competitive inhibitors bind to an allosteric site, changing the enzyme's shape.

How do specialized cells differ in structure and function?

Specialized cells have unique structures tailored to their specific functions, such as erythrocytes for oxygen transport and neutrophils for immune response.

What are stem cells, and why are they significant?

Stem cells are undifferentiated cells capable of self-renewal and specialization, important for research and regenerative medicine.

What is the function of the Rough Endoplasmic Reticulum (RER)?

It is coated with ribosomes and is responsible for the synthesis and transport of proteins.

What is the role of the Smooth Endoplasmic Reticulum (SER)?

It is involved in the synthesis and processing of lipids, cholesterol, and steroid hormones.

Describe the structure and function of chloroplasts.

They have a double membrane and contain thylakoids stacked into grana; they are the site of photosynthesis in plant cells.

What is the formula for calculating magnification?

Magnification = \frac{Image\ size}{Actual\ size} or M = \frac{I}{A}.

What is the function of the cytoskeleton?

A network of fibers (microfilaments and microtubules) that provides mechanical strength, aids in transport, and enables cell movement.

Define facilitated diffusion.

The passive movement of molecules or ions across a membrane via specific transmembrane proteins, such as channel or carrier proteins.

What is active transport?

The movement of substances across a cell membrane against a concentration gradient, requiring energy in the form of ATP.

What is the primary component and function of the plant cell wall?

It is made of cellulose and provides structural support, protection, and prevents the cell from bursting when it becomes turgid.

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids have no double bonds between carbon atoms (C=C), whereas unsaturated fatty acids contain one or more double bonds.

What is the function of centrioles?

They are involved in the assembly and organization of spindle fibers during cell division (mitosis and meiosis).

Define 'resolution' in the context of microscopy.

The ability to distinguish between two separate points that are very close together as distinct objects.

What is the function of the nucleolus?

A sub-section of the nucleus responsible for the synthesis of ribosomal RNA (rRNA) and the assembly of ribosomes.

Describe the structure of a phospholipid molecule.

It consists of a hydrophilic (polar) phosphate head and two hydrophobic (non-polar) fatty acid tails.

What are the primary functions of flagella and cilia?

1. Flagella: Primarily used for cell locomotion (e.g., in sperm cells).
2. Cilia: Used to move substances across the cell surface (e.g., clearing mucus in the trachea).

Explain the 'induced-fit' model of enzyme action.

The active site of the enzyme changes its shape slightly to become perfectly complementary to the substrate as the complex forms, putting strain on the substrate's bonds.

Distinguish between channel proteins and carrier proteins in facilitated diffusion.

Channel proteins form water-filled pores for specific ions to pass through; carrier proteins bind to specific molecules and undergo a conformational change to transport them across the membrane.

Why must specimens for electron microscopy be placed in a vacuum?

To prevent air molecules from scattering the electron beam, which would degrade the image quality.

What is the role of the nuclear envelope and nuclear pores?

The nuclear envelope is a double membrane that separates the nucleus from the cytoplasm; nuclear pores allow the transport of large molecules, such as mRNA and ribosomes, out of the nucleus.

What are the key differences between prokaryotic and eukaryotic DNA?

1. Prokaryotic DNA: Circular, not associated with proteins (naked), and found in the cytoplasm as a nucleoid or plasmids.
2. Eukaryotic DNA: Linear, associated with histone proteins, and contained within a membrane-bound nucleus.

What are the three chemical components of an ATP molecule?

1. Adenine (a nitrogenous base)
2. Ribose (a pentose sugar)
3. Three phosphate groups