bio unit 3

Flashcards covering Cell Theory, Cell Organelles, Cell Membrane, Passive Transport (Diffusion, Osmosis, Tonicity), and Active Transport (Protein Pumps, Bulk Transport) based on the provided lecture notes.

What are cells?

Cells are the primary building blocks of life that come in all shapes and sizes, mostly observed under a microscope.

Who named the tiny compartments 'cells' after observing thin slices of cork in 1665?

Robert Hooke

Who observed single-celled organisms, which he called animalcules, swimming in pond water in 1674?

Antonie van Leeuwenhoek

Which German scientist proposed in 1838 that plants are made of cells?

Matthias Schleiden

Who concluded that all animals are made of cells, observing structural similarities with plant cells?

Theodor Schwann

Who reported in 1855 that all cells come from preexisting cells, modifying Schwann’s spontaneous formation claim?

Rudolf Virchow

What is the Cell Theory?

A set of statements or principles that explain a phenomenon, repeatedly tested, widely accepted, and used to make predictions, which can be updated with new evidence.

What is the first statement of the Cell Theory?

All organisms are composed of cells.

What is the second statement of the Cell Theory?

Cells are the smallest structure that performs the functions of life (the basic unit of life).

What is the third statement of the Cell Theory?

All cells come from preexisting cells.

What are the four common components found in all cells?

All cells are enclosed with a cell membrane, contain ribosomes, are filled with cytoplasm, and contain DNA (genetic material).

Define a prokaryotic cell.

A cell type that existed before the evolution of a nucleus; it lacks a true nucleus and other membrane-bound organelles.

Define a eukaryotic cell.

A cell with a true nucleus, where DNA is protected, and containing many membrane-bound organelles.

What are key characteristics of prokaryotic cells?

Belong to Kingdoms Bacteria & Archaea, always unicellular, tiny (1-10 µm), ancient (evolved 3.5 bya), simple, no membrane-bound organelles (only ribosomes), and DNA is loose in the cytoplasm (nucleoid region) with plasmids.

What are key characteristics of eukaryotic cells?

Belong to Kingdoms Plants, Animals, Fungi & Protists, mostly multicellular, larger (10-100 µm), more modern (evolved 1.4 bya), complex with many compartments, have many membrane-bound organelles (and ribosomes), and DNA is protected in the nucleus.

What is an organelle?

A 'mini organ' inside a cell that carries out a specific function.

What is the function of the cell membrane (plasma membrane)?

It forms an outside boundary for all cells, is made of a phospholipid bilayer, and controls what enters and leaves the cell (semipermeable).

What is the function of the cell wall?

It provides support, shape, and protection; it is rigid and found in all plant cells and almost all bacteria.

What is cytoplasm?

The space inside the cell, including organelles, filled with cytosol.

What is cytosol?

The jelly-like fluid in the cytoplasm, consisting mainly of water.

What is the function of a ribosome?

It synthesizes proteins and is not a membrane-bound organelle, found attached to the rough ER or free-floating in the cytoplasm.

What is the function of the Rough ER?

It has ribosomes attached to its surface and folds, modifies, and transports proteins.

What is the function of the Smooth ER?

It has no ribosomes, makes lipids (fats), and breaks down drugs and alcohols.

What is the function of the Nucleus?

It contains genetic information (DNA) needed to make proteins and protects the cell's DNA.

What is the function of the Nucleolus?

It is a dense region of the nucleus where ribosomes are made.

What is the function of the Golgi apparatus?

It processes, sorts, and delivers proteins out of the cell.

What is the function of a vesicle?

It is a small, membrane-bound sac that transports materials around the cell.

What is the function of a mitochondrion?

It converts sugars into ATP (cellular energy) through a series of chemical reactions.

What is the function of a chloroplast?

It is the site of photosynthesis in plant cells and some protists, converting solar energy into chemical energy (glucose).

What is the function of a lysosome?

It contains digestive enzymes to break down damaged or worn-out cell parts and defends against bacteria and viruses, being numerous in animal cells.

What is the function of a vacuole?

It is a fluid-filled sac for storage, numerous in animal cells, and acts as a large central vacuole in plants for water storage, helping them survive dry periods.

What is the function of a flagellum?

It is a whip-like appendage that extends from some cells, allowing for cell movement (e.g., in sperm, bacteria, protozoa).

How is the total magnification of an object calculated when using a microscope?

Total magnification is calculated by multiplying the ocular lens magnification by the magnification of the objective lens being used.

What are the three main functions of the cell membrane?

It forms a boundary between the cell and its outside environment, controls the passage of materials in and out of the cell, and maintains the cell’s homeostasis.

What is a phospholipid composed of?

A phospholipid consists of a glycerol, two fatty acids (nonpolar tails), and a phosphate group (polar head).

What do hydrophilic and hydrophobic mean in the context of a phospholipid?

Hydrophilic means 'attracts/loves water' (the polar head), and hydrophobic means 'repels/hates water' (the nonpolar tails).

Describe the structure of a phospholipid bilayer.

It is made of two phospholipid layers where polar heads interact with the watery environment inside and outside the cell, while nonpolar tails avoid water, pointing inward.

What is the fluid mosaic model?

It describes the cell membrane as a 'mosaic' of phospholipids, proteins, cholesterol, and carbohydrates that can move laterally or flip-flop, making the membrane flexible and fluid, not rigid.

What is selective permeability?

It is the property of the cell membrane that allows certain molecules or ions to pass through by either active or passive transport, enabling the cell to maintain homeostasis.

What is the function of transport proteins?

They allow molecules to move into and out of the cell.

How does a protein channel work?

It provides a hydrophilic channel with a pore for small polar molecules and charged ions to pass through the hydrophobic portion of the membrane.

What is the role of a carrier protein?

It undergoes a shape change to move a molecule to the other side of the cell membrane, providing passage for larger polar molecules (like glucose and amino acids) and charged ions, and can be used in active or passive transport.

What is the function of marker proteins, and what is a glycoprotein?

Marker proteins identify the cell to other cells (like fingerprints for the immune system); a glycoprotein is a marker protein labeled with a carbohydrate chain.

What is the function of receptor proteins, and what is a ligand?

Receptor proteins receive chemical signals and perform an action in response; a ligand is the small molecule (like a hormone or neurotransmitter) that acts as the messenger and binds to the receptor.

What is the difference between membrane receptors and intracellular receptors?

Membrane receptors receive chemical signals from outside the cell and initiate a response within the cell, while intracellular receptors bind to a ligand that crosses the membrane to initiate a response inside the cell.

What is the function of cholesterol in the cell membrane?

Cholesterol (a lipid) is embedded in the nonpolar tails of the phospholipid bilayer, stabilizing the membrane and embedded proteins, helping maintain fluidity, and reducing solidification at lower temperatures.

What is a concentration gradient?

The difference in the concentration of a substance between two areas, where materials naturally flow from an area of high concentration to an area of low concentration.

What is diffusion?

The movement of molecules in a fluid or gas from a region of higher concentration to a region of lower concentration, resulting from the natural motion of particles.

What is dynamic equilibrium?

The state when an equal number of molecules are moving through the membrane in both directions, resulting in equal amounts of solutes and movement on both sides.

What is passive transport?

Membrane transport that does NOT require energy input from a cell, where molecules naturally diffuse from high to low concentrations (down/with the concentration gradient).

What are the three types of passive transport?

Simple Diffusion, Facilitated Diffusion, and Osmosis.

Describe simple diffusion.

It is the diffusion of small, nonpolar molecules (like lipids, CO2, O2) directly through the cell membrane from high to low concentration, requiring no energy or protein.

Describe facilitated diffusion.

It is the diffusion of polar molecules and charged ions through transport proteins (channel or carrier proteins) from high to low concentration, requiring no energy.

What is osmosis?

The diffusion of water molecules across a semipermeable membrane from high to low concentration, requiring no energy, where water always moves towards the higher concentration of solute.

What is tonicity?

The ability of an extracellular solution to make a cell gain or lose water through osmosis, determined by the concentration of solutes in the surrounding fluid.

What happens to a cell in a hypertonic solution?

A hypertonic solution has a higher concentration of solutes than the cell, causing water to flow out of the cell and making it shrink or even die.

What happens to a cell in an isotonic solution?

An isotonic solution has the same concentration of solutes as the cell, causing water to move equally into and out of the cell, so the cell’s size remains the same.

What happens to a cell in a hypotonic solution?

A hypotonic solution has a lower concentration of solutes than the cell, causing water to move into the cell, making the cell grow/swell and potentially burst (lysis).

What is plasmolysis and in what environment does it occur?

Plasmolysis occurs when a plant cell loses too much water, causing the plasma membrane to shrink away from the rigid cell wall, potentially leading to cell death. This happens in a hypertonic environment.

What is turgor pressure and how does it relate to plant rigidity?

Turgor pressure is the force that pushes the plasma membrane of a plant cell against its cell wall, allowing plants to maintain rigidity. A cell lacking turgor pressure is described as flaccid (limp).

What is active transport?

Membrane transport that requires energy input (ATP) from a cell.

What are the two types of active transport?

Active Transport (using protein pumps) and Bulk Transport.

How does active transport using protein pumps work?

Molecules are pushed from low to high concentrations (against the concentration gradient) using protein pumps powered by ATP energy.

What is bulk transport?

The movement of a larger substance into or out of the cell using vesicles, both requiring energy because the cell membrane changes shape.

What are the three types of bulk transport?

Phagocytosis, Pinocytosis, and Receptor-Mediated Endocytosis.

What is phagocytosis?

The process by which a cell engulfs large particles or whole cells (cell 'eating'), used as a defense mechanism or to obtain food.

What is pinocytosis?

The process by which a cell engulfs small amounts of extracellular fluid (cell 'drinking'), also taking in dissolved molecules.

What is receptor-mediated endocytosis?

The process by which a cell engulfs extracellular particles only if they bind to a specific receptor, allowing for specific, targeted substances to be brought into the cell (e.g., how viruses enter animal cells).