Cell Structure Revised by Bryant Wong

Cell Theory  All organisms are composed of one or more cells  Cells are the smallest living things  Cells come from other cells

Does Size Really Matter  Yes  Surface area to volume ratio Surface Area to Volume Video

Microscopes  Resolution: the minimum distance two points can be apart and still be distinguished as two separate items  Light Microscope< Compound Microscope< Electron Microscope< Scanning Electron Microscope <Transmission Electron Microscope Descriptions of Microscopes Descriptions of MicroscopesDescriptions of MicroscopesDescriptions of Microscopes

What do all cells have?  Centrally located genetic material  Cytoplasm  Plasma membrane  Chromosomes (carry genes)  Ribosomes (make proteins)  Cytosol

Eukaryotic cells have internal membranes that compartmentalize their functions  The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic  Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells  Protists, fungi, animals, and plants all consist of eukaryotic cells

Prokaryotic Cells

Plant Cell

Animal Cell

Peptido…who?  Archeabacteria lack peptidoglycan  Gram Positive Vs Gram Negative

Comparing Prokaryotic and Eukaryotic Cells  Prokaryotic cells  Have no nucleus  DNA is in an unbound region called the nucleoid  Lack membrane-bound organelles

Comparing Prokaryotic and Eukaryotic Cells  Eukaryotic Cells  Have DNA in a nucleus that is bounded by a membranous nuclear envelope  Have membrane-bound organelles  Generally much larger than prokaryotic cells  The logistics of carrying out cellular metabolism sets limits on the size of cells

Eukaryotes  Archeabacteria seem to be more related to eukaryotes than prokaryotes….what might this imply?

The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes  The nucleus contains most of the DNA in a eukaryotic cell  Ribosomes use the information from the DNA to make proteins

Organelles  Nucleus Nucleus  Ribosomes Ribosomes  Organelles of the endomembrane system Organelles of the endomembrane system Organelles of the endomembrane system

The Nucleus: Genetic Library of the Cell  The nucleus contains most of the cell’s genes and is usually the most conspicuous organelle  The nuclear envelope encloses the nucleus, separating it from the cytoplasm

Ribosomes: Protein Factories in the Cell  Ribosomes are particles made of ribosomal RNA and protein  Ribosomes carry out protein synthesis in two locations:  In the cytosol (free ribosomes)  On the outside of the endoplasmic reticulum (ER) or the nuclear envelope (bound ribosomes)

The endomembrane system regulates protein traffic and performs metabolic functions in the cell  Components of the endomembrane system:  Nuclear envelope  Endoplasmic reticulum Endoplasmic reticulum Endoplasmic reticulum  Golgi apparatus Golgi apparatus Golgi apparatus  Lysosomes Lysosomes  Vacuoles Vacuoles  Microbodies Microbodies  Plasma membrane  These components are either continuous or connected via transfer by vesicles  The endomembrane system is a complex and dynamic player in the cell’s compartmental organization

The Endoplasmic Reticulum: Biosynthetic Factory  The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells  The ER membrane is continuous with the nuclear envelope  The are two distinct regions of ER:  Smooth ER, which lacks ribosomes  Rough ER, with ribosomes studding its surface

Smooth ER  Functions  Synthesizes lipids  Metabolizes carbohydrates  Stores calcium  Detoxifies poison

Rough ER  Functions  Has bound ribosomes  Produces proteins and membranes, which are distributed by transport vesicles  Membrane factory for the cell

The Golgi Apparatus: Shipping and Receiving Center  The Golgi apparatus consists of flattened membranous sacs called cisternae  Functions  Modifies products of the ER  Manufactures certain macromolecules  Sorts and packages materials into transport vesicles

Lysosomes: Digestive Compartments  A lysosome is a membranous sac of hydrolytic enzymes  Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids  Lysosomes also use enzymes to recycle organelles and macromolecules, a process called autophagy

Vacuoles: Diverse Maintenance Compartments  Vesicles and vacuoles (larger versions of vacuoles) are membrane- bound sacs with varied functions  A plant cell or fungal cell may have one or several vacuoles

Vacuoles  Food vacuoles are formed by phagocytosis  Contractile vacuoles, found in many freshwater protists, pump excess water out of cells  Central vacuoles, found in many mature plant cells, hold organic compounds and water

Microbodies  Enzyme bearing membrane enclosed vesicles  Peroxisomes- catalyze the removal of electrons associated with hydrogen atoms  Glyoxysomes- in plants convert fats into carbohydrates

Mitochondria and Chloroplasts  Involved in energy metabolism  Both contain their own DNA and protein synthesis machinery…what does this say?  Both surrounded by a double membrane  Arrived in the cells by endosymbiosis

Mitochondria  Metabolize sugar to generate ATP Crista

Chloroplasts  Use light to generate ATP

Fibers of The Cytoskeleton  Microfilaments- 2 protein chains loosely twined  Microtubules- largest- hollow tubes  Intermediate filaments

What is the function of the cytoskeleton fibers?  Modulate cell shape  Permit cell movement  Move materials within the cytoplasm  Kineson moves towards the outside of the cell  Dynein moves towards the inside of the cell

Extracellular Structures and Cell Movement  Actin fillaments allow some cells to crawl, forward movement achieved by myosin  Cilia and Flagella- 9+2 structure (fundamental component of eukaryotic cells)

Cell Wall  Provide Protection and Support  Found in plants, fungi and protists  Plants and protists made of cellulose  Fungi made of chitin  Primary walls, middle lamella, some have secondary walls

Extracellular Matrix (ECM)  Animals lack cell walls so they have ECM to protect them  Glycoproteins  Collagen  Elastin  Fibronectin  Integrins

Real Life Application  Organelles keep the cell alive and the cells keep organisms alive.  We inherit mitochondria from our mother.  Organelle discoveries suggest that all cells had a common ancestor. We all evolved from the same thing. Bacteria, eukaryotes, and archaea all had a primitive organelle consisting of little polyphosphate. Researchers can track evolutionary history.

 Relate surface area and volume with cell size and how it effects the cell.