unit 2 biol 2401

Cytology

Study of cells.

Microscopy

Using a microscope to view small structures invisible to the naked eye.

Light microscope magnification range

Typically 40x to 1000x.

Transmission electron microscope (TEM)

Produces 2D images.

Scanning electron microscope (SEM)

Produces 3D images.

Plasma membrane

Outer barrier separating the cell from its environment; controls entry and exit.

Nucleus

Control center of the cell that houses DNA.

Cytoplasm contents

Cytosol, organelles, and inclusions.

Cytosol

Fluid portion of the cytoplasm.

Organelles

Specialized structures performing specific cell functions.

Inclusions

Temporary stored materials (e.g., pigments, nutrients).

Function of organelle membrane

Separates organelle contents from cytosol; allows specific reactions.

Non-membrane-bound organelles

Made of protein; not surrounded by a membrane (e.g., ribosomes, cytoskeleton).

General functions of cells

Maintain integrity/shape, obtain nutrients, and dispose of wastes.

Plasma membrane composition

Equal parts lipids and proteins by weight.

Phospholipids

Form the main structure of the plasma membrane.

Cholesterol

Strengthens and stabilizes the plasma membrane.

Glycolipids

Help form the glycocalyx for cell recognition.

Integral membrane proteins

Span the entire membrane.

Peripheral membrane proteins

Attached to the membrane surface.

Membrane protein functions

Transport, receptor, enzyme, identity marker, and cell adhesion.

Passive transport

No energy required; moves down the concentration gradient.

Active transport

Requires energy (ATP); moves against the concentration gradient.

Diffusion

Movement of molecules until equilibrium is reached.

Potassium ion concentration

Higher inside the cell.

Sodium ion concentration

Higher outside the cell.

Simple diffusion

Movement of small, nonpolar molecules (O₂, CO₂, lipids).

Channel-mediated diffusion

Movement through protein channels.

Carrier-mediated diffusion

Movement using carrier proteins.

Osmosis

Diffusion of water across a selectively permeable membrane.

Primary active transport

Energy comes directly from ATP.

Sodium-potassium pump

Moves 3 Na⁺ out and 2 K⁺ in using ATP.

Symporter

Moves two substances in the same direction.

Antiporter

Moves substances in opposite directions.

Exocytosis

Vesicle fuses with plasma membrane to release materials.

Endocytosis

Cell takes in materials using vesicles.

Phagocytosis

Cell “eating” solid materials.

Pinocytosis

Cell “drinking” liquids.

Resting membrane potential (RMP)

Electrical charge difference across the plasma membrane.

Ion that determines RMP

Potassium (K⁺).

Glycocalyx

Cell recognition and protection coating.

Channel-linked receptors

Open ion channels in response to ligand binding.

Ribosomes

Make proteins.

Ribosomes attached to rough ER

Make proteins for secretion or membranes.

Free ribosomes

Make proteins that stay in the cytosol.

Rough endoplasmic reticulum (RER)

Modifies and packages proteins.

Smooth endoplasmic reticulum (SER)

Synthesizes lipids, detoxifies, stores calcium.

Transport vesicles

Move proteins from ER to Golgi apparatus.

Golgi apparatus

Modifies, sorts, and packages proteins/lipids.

Secretory vesicles

Transport substances to plasma membrane for exocytosis.

Autophagy

Recycling of worn-out organelles.

Autolysis

Self-destruction of a damaged cell.

Mitochondria

Produce ATP; increase in number as energy demand rises.

Cytoskeleton

Provides shape, movement, and transport within the cell.

Tight junctions

Prevent substances from passing between cells.

Hemidesmosomes

Anchor cells to the basement membrane.

Gap junctions

Allow small molecules and ions to pass between cells.

Transcription

Making RNA from DNA.

Messenger RNA (mRNA)

Carries genetic information from nucleus to ribosome.

Transfer RNA (tRNA)

Brings amino acids to the ribosome.

Ribosomal RNA (rRNA)

Forms part of the ribosome.

Steps of transcription

Initiation, elongation, termination.

Product of transcription

mRNA.

Translation

Process of making a protein from mRNA.

Location of translation

Ribosome.

Steps of translation

Initiation, elongation, termination.

Product of translation

Protein.

Mitosis

Cell division producing two identical cells.

Meiosis

Cell division producing gametes with half the chromosomes.

Cell cycle phases

Interphase and mitotic phase.

DNA replication

Unwind

Prophase

Chromosomes condense and spindle forms.

Metaphase

Chromosomes line up in the middle.

Anaphase

Sister chromatids separate to opposite poles.

Telophase

New nuclei form around separated chromosomes.

Cytokinesis

Division of the cytoplasm.

Apoptosis

Programmed cell death.

Mitotic phase order

Prophase - Metaphase - Anaphase - Telophase.

Cellularity

Tightly packed cells with little space.

Avascularity

No blood vessels; nutrients diffuse through tissues.

Extensive innervation

Many nerves for sensory input.

High regeneration capacity

Fast repair and replacement of damaged cells.

Physical protection

Shields from injury, dehydration, and pathogens.

Selective permeability

Controls what enters and exits the body.

Secretions

Produces and releases substances like mucus or hormones.

Sensations

Detects stimuli such as touch, temperature, and pain.

Simple epithelium

One cell layer; allows absorption, filtration, secretion.

Stratified epithelium

Multiple layers; provides protection.

Pseudostratified epithelium

Appears layered but all cells touch basement membrane.

Simple squamous epithelium

Gas exchange; found in lungs and blood vessels.

Simple cuboidal epithelium

Secretion and absorption; found in glands and kidneys.

Simple columnar epithelium

Absorption and secretion; found in stomach and intestines.

Ciliated pseudostratified columnar epithelium

Moves mucus; found in respiratory tract.

Keratinized stratified squamous epithelium

Protection; found in the skin.

Nonkeratinized stratified squamous epithelium

Moist protection; found in mouth, esophagus, and vagina.

Transitional epithelium

Stretches; found in urinary bladder.

Glands

Structures that make and release secretions.

Endocrine glands

Secrete hormones into the bloodstream.