Cell Theory, Structure, and Function Overview

Robert Hooke

Coined the term 'cell' after observing cork tissue under a microscope and noting small compartments.

Anton van Leeuwenhoek

Observed bacteria and protozoa using a handcrafted lens microscope and called them 'animalcules'.

Cell Theory

1) All living things are made of cells, 2) The cell is the smallest unit of life, and 3) All cells come from pre-existing cells.

Schleiden and Schwann

Proposed that all living things are composed of cells.

Surface area-to-volume ratio

Small size of cells maintains a high surface area-to-volume ratio, allowing efficient nutrient uptake and waste removal.

Resolution in microscopy

The smallest distance between two objects where they can still be distinguished as separate.

Types of microscopes

Light microscopes and electron microscopes.

Light microscope

A microscope using light and glass lenses. Types include bright field, fluorescence, and confocal microscopy.

Electron microscope

A microscope using an electron beam and electromagnets. Types include transmission EM, scanning EM, and freeze fracture microscopy.

Compartmentalization in eukaryotic cells

The organization into membrane-bound organelles, allowing different environments and specialized functions within one cell.

Cell fractionation

A method to isolate organelles by breaking cells, centrifuging the contents, and separating parts by density for analysis.

Ribosomes in prokaryotes and eukaryotes

Both are composed of two subunits, lack membranes, and synthesize proteins.

Differences in ribosomes

Prokaryotic ribosomes float in the cytoplasm; eukaryotic ribosomes may be free or attached to the ER or inside organelles.

Functions of the nucleus

Stores DNA, is the site of DNA replication, and regulates gene transcription.

Nucleolus

A region in the nucleus where ribosomes are assembled from RNA and proteins.

Nucleoplasm

The substance within the nucleus excluding the nucleolus, including the liquid matrix and dissolved molecules.

Nuclear envelope

A double membrane with pores that regulate the movement of molecules between the nucleus and cytoplasm.

Chromatin

DNA-protein complex that condenses into chromosomes during cell division.

Nuclear lamina

A protein mesh that supports nuclear shape and anchors chromatin to the envelope.

Endomembrane system

Includes plasma membrane, nuclear envelope, ER, Golgi apparatus, and lysosomes.

Endomembrane System

Plasma membrane, nuclear envelope, ER, Golgi apparatus, and lysosomes.

Vesicles

Small membrane-bound sacs that transport substances between components of the endomembrane system.

Rough ER

It is studded with ribosomes on its outer surface.

Functions of the rough ER

Synthesizes proteins, modifies them, and packages them for delivery via vesicles.

Smooth ER

It lacks ribosomes and has a tubular structure.

Functions of the smooth ER

Detoxifies small molecules, degrades glycogen, synthesizes lipids and steroids, and stores calcium ions.

Golgi apparatus components

Flattened membrane sacs (cisternae) and small vesicles.

Functions of the Golgi apparatus

Modifies, sorts, and packages proteins; synthesizes polysaccharides; and processes proteins into functional fragments.

Regions of the cisternae in the Golgi

Cis (receives vesicles), Medial (modifies proteins), Trans (sends proteins to final destinations).

Primary lysosomes

From the Golgi apparatus; they contain digestive enzymes.

Function of lysosomes

Digest food, waste, and damaged cell parts in an acidic environment.

Phagocytosis

The process where cells engulf particles into a phagosome, which fuses with a lysosome for digestion.

Autophagy

The breakdown and recycling of cell's own components by lysosomes.

Tay Sachs disease

A lysosomal storage disorder caused by defective enzymes, leading to lipid accumulation and early death.

Proteasome

A protein complex that degrades denatured or unwanted proteins through proteolysis.

Peroxisomes

Organelles that break down toxic byproducts using enzymes; found in both prokaryotes and eukaryotes.

Glyoxysomes

Specialized peroxisomes in plants that convert lipids into carbohydrates for seedling growth.

Lorenzo's Oil

A treatment for peroxisome-related disorders involving neurological and liver issues.

ALD (Adrenoleukodystrophy)

A genetic disorder where peroxisomes cannot break down long-chain fatty acids, leading to severe symptoms.

Plasma membrane

A phospholipid bilayer with proteins, regulating transport, communication, and adhesion.

Cytoplasm

The fluid inside cells (cytosol) containing dissolved molecules and site of many biochemical reactions.

Mitochondria

Generate ATP from fuel molecules via cellular respiration.

Membranes and components of mitochondria

Inner membrane (cristae), outer membrane, and matrix with enzymes, DNA, and ribosomes.

Mitochondria

Store calcium, perform beta-oxidation, synthesize some amino acids/heme, and regulate apoptosis.

Mitochondrial replication

By binary fission, similar to prokaryotes.

Plastids

Plant and algal organelles including chloroplasts, chromoplasts, and leucoplasts.

Chloroplasts

Sites of photosynthesis; contain thylakoids (grana) and stroma with DNA and ribosomes.

Chromoplasts

Plastids that contain pigments for red, orange, and yellow coloration.

Leucoplasts

Plastids that store starch and fats.

Vacuoles

Storage organelles in plants/protists for waste, toxins, turgor pressure, pigments, and digestion.

Contractile vacuoles

Organelles in freshwater protists that expel excess water.

Cytoskeleton

A network of fibers supporting cell shape, movement, and transport.

Components of the cytoskeleton

Microfilaments, intermediate filaments, and microtubules.

Microfilaments

Actin filaments that aid in movement and shape, including muscle contraction.

Intermediate filaments

Rope-like proteins that provide strength and anchor cells.

Microtubules

Tubulin structures forming internal scaffolds and tracks for motor proteins.

Microtubule doublet

Two microtubules joined in a 9+2 array for movement in cilia and flagella.

Flagella and cilia

: long, few, for swimming; : short, many, for movement via power strokes.

Centrioles

Structures that help form the mitotic spindle in cell division.

Dynein

A motor protein that slides microtubule doublets past each other.

Nexin

A protein that links microtubules and prevents sliding, causing bending of cilia.

Kinesin

A motor protein that moves vesicles along microtubules.

Cell function experimental approaches

Inhibition (blocking a process) and mutation (disabling a gene or structure).

Extracellular structures

Cell-secreted structures like walls or matrices outside the plasma membrane.

Plant cell walls

Made of cellulose fibers embedded in polysaccharides and proteins.

Plasmodesmata

Channels between plant cells lined with plasma membrane for transport and communication.

Extracellular matrix (ECM)

A network of collagen and proteoglycans that supports animal tissues, helps with signaling, and guides cell movement.

Osteogenesis imperfecta

A collagen-related genetic disorder causing brittle bones due to ECM defects.

Prokaryotic vs. eukaryotic cells

Prokaryotes lack organelles and a nucleus, are smaller, and have simpler structure; eukaryotes have complex compartmentalization.

Similarities between prokaryotic and eukaryotic cells

Both have membranes, DNA, ribosomes, and can reproduce.

Endosymbiosis theory

Theory that mitochondria and plastids originated from engulfed prokaryotes in early eukaryotic cells.