Chapter 2 Cells

Appstate A&P

What are the 3 major parts of a generalized/composite cell?

Nucleus, cytoplasm, and plasma membrane.

What is the main role of the nucleus?

It contains genetic information and acts as the gene-containing control center of the cell.

What is the cytoplasm?

The cellular material between the plasma membrane and the nucleus.

What is the plasma membrane?

The membrane forming the cell's boundary between the intracellular and extracellular environments.

What does “intracellular” mean?

Inside the cell.

What does “extracellular” mean?

Outside the cell.

What are major functions of the plasma membrane?

It forms a barrier, controls entry and exit of substances, participates in transport, and contains proteins with many specialized roles.

What does selectively permeable mean?

The membrane permits some substances to cross more easily than others and therefore controls what enters and leaves the cell.

What helps stabilize the plasma membrane?

Cholesterol.

Why is the plasma membrane called a fluid mosaic?

Membrane proteins move within a fluid membrane, creating constantly changing patterns.

What are the 2 broad categories of membrane proteins listed?

Integral proteins and peripheral proteins.

What are integral membrane proteins?

Proteins associated deeply with the membrane, often extending through the phospholipid bilayer.

What are peripheral membrane proteins?

Proteins associated more loosely with a membrane surface rather than spanning the bilayer.

What functions can membrane proteins perform?

Ion channels, carriers/transporters, receptors, enzymes, linkers, and cell identity markers.

What do membrane ion channels do?

Provide pathways for specific ions to cross the membrane.

What do carrier or transporter proteins do?

Help move particular substances across the membrane.

What do membrane receptors do?

Bind specific signaling molecules and allow the cell to respond to signals.

What is the basic structure of the plasma membrane?

A phospholipid bilayer containing proteins and cholesterol.

What forms the surfaces of the phospholipid bilayer?

Water-soluble/hydrophilic phospholipid heads.

What forms the interior of the phospholipid bilayer?

Water-insoluble/hydrophobic phospholipid tails.

Why do the phospholipid heads face the watery environments?

The heads are water soluble.

Why do the phospholipid tails point inward?

The tails are water insoluble and avoid contact with water.

What types of substances can readily interact with/pass through the lipid region of the membrane?

Lipid-soluble substances.

What are the 2 major categories of membrane transport?

Passive transport and active transport.

Does passive transport require ATP?

No.

Does active transport require cellular energy/ATP?

Yes.

What are the passive processes listed in the slides?

Simple diffusion, facilitated diffusion, and osmosis.

What are the active processes listed in the slides?

Active transport, endocytosis, and exocytosis.

What is simple diffusion?

Movement of substances from an area of higher concentration to an area of lower concentration without assistance.

Does simple diffusion move with or against the concentration gradient?

With the concentration gradient: high → low.

What is a concentration gradient?

A difference in the number/concentration of particles between two regions.

What substances are listed as examples of simple diffusion?

Oxygen, carbon dioxide, and lipid-soluble substances.

Does simple diffusion require a carrier protein?

No. It is unassisted.

Does simple diffusion require ATP?

No.

What is facilitated diffusion?

Passive movement across a membrane from high to low concentration with help from a channel or carrier protein.

Why is facilitated diffusion needed?

Some substances cannot pass directly through the lipid bilayer and need membrane proteins to cross.

What molecules are listed as examples using facilitated diffusion?

Glucose and amino acids.

What are the 2 membrane routes listed for facilitated diffusion?

Protein carriers and water-filled protein channels.

Does facilitated diffusion require ATP?

No.

Simple diffusion vs. facilitated diffusion?

Both move high → low and require no ATP. Simple diffusion is unassisted; facilitated diffusion uses a membrane protein.

What is osmosis?

Movement of water across a selectively permeable membrane.

Toward what type of region does water move during osmosis according to the slides?

Toward the region with a higher concentration of solutes.

Does osmosis require ATP?

No.

What is osmotic pressure/tonicity according to the slides?

The ability of osmosis to generate enough pressure to move a volume of water.

What happens to osmotic pressure as the concentration of nonpermeable solutes increases?

Osmotic pressure increases.

What does isotonic mean?

Same osmotic pressure.

What does hypotonic mean?

Lower osmotic pressure.

What does hypertonic mean?

Higher osmotic pressure.

Isotonic vs. hypotonic vs. hypertonic?

Isotonic = same osmotic pressure; hypotonic = lower; hypertonic = higher.

What happens to a cell in an isotonic environment in the tonicity diagram?

The cell maintains its normal general shape because osmotic pressures are balanced.

What happens to water relative to a hypertonic region?

Water tends to move toward the region with the higher concentration of nonpermeable solutes.

What is active transport?

Movement of substances across the membrane using carrier proteins and cellular energy, often from lower concentration to higher concentration.

Does active transport move with or against the concentration gradient?

Against the gradient: low → high.

What substances are listed as examples of active transport?

Sugars, amino acids, sodium ions, potassium ions, and others.

What is primary active transport?

Transport that directly uses ATP and transport proteins to move substances against their concentration gradient.

What is the example of primary active transport emphasized in the slides?

The Na+/K+ ATPase pump.

What does the Na+/K+ ATPase pump do according to the slide?

Moves 3 Na+ out of the cell for every 2 K+ moved into the cell.

How many Na+ move OUT with the Na+/K+ pump?

3 Na+.

How many K+ move IN with the Na+/K+ pump?

2 K+.

What is vesicular transport?

Active transport of large substances in membrane-bound vesicles.

What is endocytosis?

Bringing material INTO the cell by forming vesicles.

What is exocytosis?

Removing/releasing material FROM the cell using vesicles that fuse with the plasma membrane.

What is phagocytosis?

A type of endocytosis that engulfs particles such as molecules or bacteria; the slides call it “cell eating.”

What is pinocytosis?

A type of endocytosis involving uptake of extracellular fluid/water; the slides call it “cell drinking.”

Memory trick for endocytosis vs. exocytosis?

ENDO = enter/in. EXO = exit/out.

Memory trick for phagocytosis vs. pinocytosis?

Phagocytosis = cell eating. Pinocytosis = cell drinking.

Passive vs. active transport?

Passive = no ATP and generally moves down a gradient. Active = requires cellular energy and can move substances against a gradient or through vesicles.

What is cytosol?

The largely water-based fluid portion of the cytoplasm containing dissolved proteins, salts, sugars, and other solutes.

What are cytoplasmic organelles?

Specialized cellular structures that serve as metabolic machinery and perform specific functions needed for homeostasis.

What are inclusions?

Stored or accumulated chemical substances in the cytoplasm, such as glycogen granules and pigments.

What is a mitochondrion?

A double-membrane organelle that provides most of the cell's ATP through aerobic cellular metabolism.

What are cristae?

Shelf-like folds of the mitochondrial inner membrane.

What is the main function of mitochondria?

ATP production.

Why are mitochondria often called the “energy house” of the cell?

They produce most cellular ATP through aerobic metabolism.

What unusual genetic feature do mitochondria have?

They contain their own DNA and RNA.

What are ribosomes?

Small granules made of protein and rRNA.

What is the main function of ribosomes?

Protein synthesis.

What do free ribosomes synthesize?

Soluble proteins.

What do membrane-bound ribosomes synthesize?

Proteins that will be incorporated into membranes or processed through the endomembrane system.

What is the endoplasmic reticulum?

A large network of interconnected tubes and membranes enclosing spaces called cisternae.

What does “reticulum” mean?

Network.

With what membrane is the ER continuous?

The nuclear membrane/envelope.

What are the 2 varieties of ER?

Rough ER and smooth ER.

Why does rough ER look “rough”?

Its external surface is studded with ribosomes.

What is the major function of rough ER?

It manufactures secreted proteins and contributes to synthesis of integral membrane proteins and phospholipids.

Why is rough ER called a “membrane factory” in the slides?

It participates in production of membrane proteins and phospholipids used in cell membranes.

What distinguishes smooth ER from rough ER?

Smooth ER lacks the ribosome-studded appearance of rough ER and consists of looping tubules.

What does smooth ER do in the liver?

Participates in lipid and cholesterol metabolism, glycogen breakdown, and detoxification of drugs.

What does smooth ER do in the testes?

Participates in synthesis of steroid-based hormones.

What does smooth ER do in skeletal and cardiac muscle?

Stores and releases calcium.

Rough ER vs. smooth ER?

Rough ER has ribosomes and is heavily involved in protein/membrane production. Smooth ER lacks surface ribosomes and is involved in lipid metabolism, detoxification, steroid synthesis, and calcium storage depending on cell type.

What is the Golgi apparatus?

A series of stacked, flattened membranous sacs.

What is the main function of the Golgi apparatus?

Modification, concentration, and packaging of proteins.

What analogy do the slides use for the Golgi apparatus?

A post office.

Why is the Golgi like a post office?

Products arrive from the ER, are processed/sorted, packaged into vesicles, and sent to designated locations.

How do proteins get from the ER to the Golgi?

Transport vesicles from the ER fuse with the Golgi apparatus.

What happens after proteins move through the Golgi?

Secretory/transport vesicles leave the Golgi and move to designated parts of the cell.

What is the cis face of the Golgi in the diagram?

The “receiving” side that accepts transport vesicles arriving from rough ER.

What is the trans face of the Golgi in the diagram?

The “shipping” side from which new vesicles leave.

What is the cytoskeleton?

The cell's internal “skeleton” or scaffolding made of dynamic rods and filaments.