Lecture Notes: Cells and Transport Across the Cell Membrane

A comprehensive set of practice flashcards covering cell structure, organelles, and membrane transport mechanisms as described in the lecture notes.

What are the three main components of a cell?

Plasma membrane, cytoplasm, and nucleus.

What two fluid compartments does the plasma membrane separate?

Intracellular fluid (inside the cell) and extracellular fluid (outside the cell).

What does it mean that the plasma membrane is selectively permeable?

It determines which substances can pass through the membrane.

Describe the structure of the phospholipid bilayer.

Two hydrophobic tails oriented inward and a hydrophilic head oriented outward.

Name the major molecular components of the plasma membrane and their roles.

Phospholipids form the bilayer; cholesterol stabilizes the membrane; integral proteins span the membrane and act as channels/receptors; peripheral proteins associate temporarily; carbohydrates on the outer surface aid in cell recognition.

What is the difference between integral and peripheral proteins?

Integral proteins are permanently embedded within the membrane (often spanning it); peripheral proteins are temporarily associated with the membrane.

Where are carbohydrates located in the plasma membrane and what is their function?

On the outer surface, attached to proteins or lipids; they help cells recognize each other.

What is cytoplasm and what is cytosol?

Cytoplasm is the internal cell region containing cytosol, a jelly-like fluid with water, ions, and proteins; cytosol surrounds organelles.

What organelle generates most of the cell's ATP?

Mitochondria.

What is the function and structure of mitochondria?

Function: generate most of the cell’s energy (ATP). Structure: double-malled membrane with cristae; matrix inside.

What is the lysosome and its function?

A small membrane-bound organelle with digestive enzymes; breaks down old or unwanted molecules and organelles.

What do peroxisomes do?

Break down toxins and fatty acids; detoxify harmful molecules; abundant in liver and kidney; contain oxidases and catalases.

What is the function and location of ribosomes?

Produce proteins; can be free in the cytoplasm or attached to rough endoplasmic reticulum.

What is the rough endoplasmic reticulum (RER)?

A network of membrane sacs with ribosomes on the surface; synthesizes proteins for membranes or secretion.

What is the Golgi apparatus responsible for?

Receives proteins from the rough ER, modifies, sorts, and packages them for destination; composed of cisterns.

What are the three major pathways for newly synthesized proteins after the Golgi?

Pathway A: exocytosis (contents released outside); Pathway B: vesicle membrane becomes part of the plasma membrane; Pathway C: vesicles become lysosomes.

What is the function of the smooth endoplasmic reticulum (SER)?

Synthesis and breakdown of lipids (including steroids from cholesterol); detoxification of lipid-soluble drugs; stores Ca2+.

What are the three cytoskeletal filament types?

Microfilaments, intermediate filaments, microtubules.

What are the main functions of cytoskeletal filaments?

Maintain cell shape, enable cell movement, and anchor/guide movement of organelles.

What are centrioles and centrosomes and their role?

Centrioles are small organelles in the centrosome; they guide chromosome movement during mitosis.

What is the nucleus and what does it contain?

The nucleus contains DNA that controls cell activities and provides instructions for protein synthesis.

How many chromosomes do human somatic cells have?

46 chromosomes (23 pairs); sex cells have 23 chromosomes.

What is the nuclear envelope and what are nuclear pores?

The nuclear envelope surrounds the nucleus; nuclear pores allow materials to move between the cytosol and the nucleus.

What is the nucleolus?

A region within the nucleus responsible for ribosome production.

What is a concentration gradient?

A difference in the concentration of a substance between two areas; substances move from high to low concentration down the gradient, without energy.

Differentiate simple diffusion and osmosis.

Simple diffusion moves lipid-soluble solutes and gases directly through the bilayer down their concentration gradient; osmosis is the diffusion of water across the membrane, either through a channel protein or the bilayer.

What is facilitated diffusion?

Transport of water-soluble substances across the bilayer using a channel or carrier, down their concentration gradient.

What is active transport?

Movement of substances against their concentration gradient that requires energy (usually ATP) via transport proteins.

What is vesicular transport and what are its two main forms?

Transport of large numbers of molecules via vesicles; exocytosis (vesicles fuse with the membrane to release contents) and endocytosis (uptake into the cell).

What is endocytosis and its subtypes?

Endocytosis is the uptake of materials into the cell via vesicles; subtypes include phagocytosis (cell eating).

What is phagocytosis and which cells perform it?

A specialized type of endocytosis where large particles are ingested by phagocytes (e.g., macrophages).