Chapter 3&4 anatomy

Cells

Are the building blocks of all plants & animals

Cells

Are the smallest functioning units of life

Cells

Are produced through division of pre-existing cells

Each cell

Maintains homeostasis

Human body cells

Maintain anatomical structures and perform physiological functions as different as running & thinking

Cytology

The study of the structure & function of cells

Light microscopy

Magnifies cellular structures about 1000 times (500x for high school)

Light microscopy disadvantage

Cannot see structures inside the cell

Light microscopy examples

Onion cells, bacteria, and paramecium

Electron microscopy

Has much higher magnification (up to the millions) and can see organelles

Electron microscopy examples

TEMs – mitochondria; SEMs – pollen grain surface

Extracellular fluid

The water medium surrounding the body; found outside the cell membrane (not all cells have one)

Cell shapes

Not all cells are circular

Cytosol

Fluid found inside the cell membrane

Cytosol contents

ions, proteins (enzymes), salts, and water (≈70%)

Phospholipid bilayer

The fundamental structure of the plasma membrane

Plasma membrane function #1

Physically isolates the inside of the cell from the outside surroundings

Plasma membrane function #2

Regulates the exchange of substances into and out of the cell

Plasma membrane function #3

Sensitive to the outside environment

Receptors (plasma membrane)

Located within the membrane; determine the amount and type of substances inside & outside the cell

Plasma membrane function #4

Provides structural support through specialized connections between neighboring cells

Lipids

Major component of the cell membrane

Phospholipid

Molecule forming the primary component of all cell membranes, creating a selectively permeable bilayer enclosing the cell and its organelles

Hydrophilic

“Water-loving” (attracted to water)

Hydrophobic

“Water-hating” (repelled by water)

Phospholipid bilayer reason

Because there is water inside and outside the cell, two layers (a bilayer) of phospholipids are needed

Phosphate heads

Face the outsides of the cell membrane; polar and in contact with water

Fatty acid tails

Face the inside of the cell membrane; nonpolar and away from water, making the membrane impermeable to most substances

Polar substances

Cannot cross the nonpolar fatty acid tails

Nonpolar substances

Cannot cross the polar phosphate heads

Exceptions to permeability

Oxygen & CO₂ (small and nonpolar) and Cholesterol (stabilizes phospholipids)

Transmembrane proteins

Proteins that span across the entire cell membrane

Channel proteins

Open fully, allowing many substances to cross at once

Carrier proteins

Open partially, carrying only a few substances at a time

Glycoproteins

Proteins with carbohydrate chains attached; aid in cell recognition, signaling, immune response, and structural support

Examples of glycoproteins

Antibodies, cell surface receptors

Glycolipids

Lipids with carbohydrate chains attached; help with cell recognition, communication, and membrane stability

Examples of glycolipids

ABO blood group

Permeability

The property that determines whether substances can cross a membrane

Passive transport

Movement of substances from an area of higher concentration to lower concentration; no ATP required

With gradient

Movement downhill, with concentration gradient (no ATP)

Against gradient

Movement uphill, against concentration gradient (requires ATP)

Diffusion

Passive movement of small, nonpolar molecules (like O₂ & CO₂) from high to low concentration; no ATP and no membrane protein required

Examples of diffusion

Oxygen (O₂) and Carbon dioxide (CO₂)

Osmosis

Movement of water (H₂O) from an area of higher free water concentration to lower free water concentration; no ATP, requires membrane protein (aquaporin)

Hypertonic solution

Solution with a higher solute concentration

Hypotonic solution

Solution with a lower solute concentration

Isotonic solution

Both sides have equal solute concentrations

Equilibrium

When solute concentrations are equal on both sides of a permeable membrane

RBC in hypertonic solution

Water leaves the RBC → cell shrinks (crenation)

RBC in hypotonic solution

Water enters the RBC → cell swells and bursts (hemolysis)

Active transport

Movement of substances against concentration gradient, requires ATP and a membrane protein

Examples of active transport

H⁺ pump, Na⁺/K⁺ pump

Vesicular transport

Substances move in or out of the cell without crossing the membrane, using vesicles; requires ATP

Endocytosis

Type of vesicular transport that brings substances into the cell

Phagocytosis

“Cell eating”; brings in large substances (e.g., WBC engulfing bacteria)

Pinocytosis

“Cell drinking”; brings in small, non-specific substances

Receptor-mediated endocytosis (RME)

Selective endocytosis where specific molecules bind to receptors, forming coated vesicles that bring them into the cell

Examples of RME

Cholesterol and iron transport

Exocytosis

Functional reverse of endocytosis; vesicle fuses with plasma membrane and releases contents outside the cell

Function of exocytosis

Fuses with the plasma membrane and discharges contents into the extracellular environment

Cytosol

The intracellular fluid of the cell; contains nutrients, ions, soluble & insoluble proteins, and waste products

Cytosol vs. extracellular fluid

Cytosol composition differs from the extracellular fluid surrounding most body cells

Organelles

Internal structures that perform specific functions essential for cell structure, maintenance, and metabolism

Membrane-enclosed organelles

Nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, peroxisomes

Function of organelle membranes

Membranes isolate organelles from the cytosol

Proteasomes

Non-membranous organelles; large protein complexes that break down and recycle damaged, misfolded, or unneeded proteins tagged with ubiquitin

Cytoskeleton

Internal protein framework of threadlike filaments and hollow tubules that give the cytoplasm strength and structure

Major cytoskeletal elements

Microfilaments, intermediate filaments, and microtubules

Microfilaments

Thinnest cytoskeletal filaments made of actin; support cell shape, enable movement, and aid in endocytosis/exocytosis

Intermediate filaments

Rope-like cytoskeletal filaments that provide mechanical strength and stabilize organelles and cell structure

Microtubules

Hollow tubes made of tubulin; provide tracks for intracellular transport, form the mitotic spindle, and give structure to cilia and flagella

Microvilli

Finger-like projections of the plasma membrane that increase surface area for absorption and secretion

Centrioles

Cylindrical structures made of microtubule triplets; organize the mitotic spindle and aid in cell division

Cilia

Short, hair-like extensions of the plasma membrane that move fluids, mucus, or substances across the cell surface

Flagella

Long, whip-like projections that enable cell motility (e.g., sperm tail)

Endoplasmic reticulum (ER)

Network of membranous sacs and tubules involved in synthesis, folding, and transport of proteins and lipids

Rough ER

Studded with ribosomes; synthesizes and modifies proteins

Smooth ER

Lacks ribosomes; synthesizes lipids, metabolizes carbohydrates, and detoxifies harmful substances

Golgi apparatus

Flattened membrane stacks that (1) modify and package secretions, (2) renew/modify the plasma membrane, and (3) package enzymes for use in the cytosol

Lysosomes

Membrane-bound vesicles containing hydrolytic enzymes that digest and recycle macromolecules, organelles, and pathogens (autolysis)

Peroxisomes

Small, enzyme-filled organelles that break down fatty acids and detoxify harmful substances

Mitochondria

Double-membrane organelles that produce ATP through aerobic respiration and help regulate cell metabolism

Mitochondrial energy production

Involves glycolysis (cytosol) → pyruvate oxidation → citric acid cycle → oxidative phosphorylation (ETC & ATP synthesis) to generate ATP

Nucleus

The control center of the cell that stores DNA and directs cellular activities

Nuclear envelope

Double membrane surrounding the nucleus that separates it from the cytoplasm

Nuclear pores

Protein complexes in the nuclear envelope that regulate transport of molecules (e.g., RNA, proteins) between the nucleus and cytoplasm

Nucleoli

Dense structures within the nucleus where RNA is synthesized and ribosomal subunits are assembled

rRNA

RNA component of ribosomes that helps catalyze protein synthesis

Chromosomes

Condensed, threadlike structures of DNA and protein that carry genetic information

Chromatin

Loosely packed DNA and proteins in the nucleus; exists as euchromatin

DNA polymerase

Enzyme that synthesizes new DNA strands by adding nucleotides during DNA replication

Ribosomes

Tiny, non-membranous structures composed of rRNA and proteins; site of protein synthesis. Found free in cytosol or attached to rough ER.

Vesicles

Small membrane-bound sacs that transport materials between organelles (e.g., from ER → Golgi → membrane).

Vacuoles

Larger storage vesicles that store water, nutrients, or waste; more prominent in plant cells.

Centriole pair (centrosome)

Area near the nucleus that contains centrioles; organizes microtubules and plays a key role in cell division.

Cytoplasmic inclusions

Non-membranous storage materials like glycogen granules, lipid droplets, or pigment granules found in the cytoplasm.

Cytoplasmic inclusions

Non-membranous storage materials like glycogen granules, lipid droplets, or pigment granules

Centrosome / Centrioles

Organize microtubules and help in cell division