Unit 2 : Cells
Characteristics of Living Cells
All living things grow and develop
All living things have one or more cells
All living things reproduce
All living things use energy
All living things have DNA
All living things sense and respond to stimuli
Cell Theory
All living things have one or more cells
The cell is the basic unit of life
All cells come from other pre-existing cells
Notable Scientists
Robert Hooke—first to discover cells, named them “cells”
Anton von Leeuwenhoek—discovered many single cell organisms. discovered that not only plants have cells
Matthias Schleiden—determined that all plants are made of cells
Theodor Schwann—determined that all animals have cells
Rudolph Virchow—determined that all cells come from other pre-existing cells
Eukaryotic Cell Structures & Organelles
Cell Membrane—thin, flexible protective barrier that covers the cell’s surface and acts as a barrier; determines what goes in and out of the cell. all cells have a cell membrane
Nuclear Envelope—double membrane surrounding the nucleus. defines and protects the nucleus. all eukaryotes have a nuclear envelope
Centriole—one of two structures that make up a centrosome. participates in cell division. only animal cells have centrioles
Centrosome—structure located near the nucleus that forms the spindle during cell division. made up of two centrioles. only animal cells have centrosomes
Nucleoplasm—fluid material inside the nucleus. all eukaryotes have nucleoplasm
Endomembrane System—all organelles whose membranes are physically continuous or are transferred in segments as vesicles. includes the nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vesicles, and vacuoles. all eukaryotes have an endomembrane system
Mitochondria—organelle in all eukaryotes (including plants) that converts the energy stored in glucose into energy stored in ATP does the process of cellular respiration. all eukaryotes have mitochondrias
Lysosome—small organelles filled with hydrolytic enzymes that break down materials that are not needed by the cell. only animal cells have lysosomes. plant cells do not have them because they cant store wastes in the large central vacuole.
Cytoplasm—the fluid and most of the organelles in a cell EXCEPT the nucleus. all cells have cytoplasms
Cytosol—the fluid inside the cell. all cells have cytosol
Cytoskeleton—network of fiber extending throughout the cytoplasm that organizes the structures and activities of the cell.
Types of Cytoskeletons
Microfilaments—smallest fibers; maintains cell shape; forms the cleavage furrow during cytokinesis
Intermediate Filaments—medium sized fibers; contributes to cell shape
Microtubules—largest fibers; involved in cell division (separates the chromatids) and motility
Free Ribosome—makes proteins. free ribosomes make proteins that will be used within the cell. they float freely in the cytoplasm. all cells (prokaryotes and eukaryotes) have free ribosomes
Bound Ribosome—makes proteins. bound ribosomes make proteins that will either be in the cell membrane or will be secreted from the cell. they are attached to the rough endoplasmic reticulum. all eukaryotes have bound ribosomes
Nucleolus—dense region in the nucleus where ribosome production begins. all eukaryotes have nucleoli
Golgi Apparatus—warehouse for receiving, sorting, shipping, modifying, and storing proteins that will be secreted from the cell. all eukaryotes have the golgi apparatus
Smooth Endoplasmic Reticulum—folded membranes that do NOT have ribosomes attached. has various functions depending on the cell type. functions include: production of lipids, metabolizing carbohydrates, detoxifying drugs and poisons, and storing calcium ions. all eukaryotes have a smooth endoplasmic reticulum
Rough Endoplasmic Reticulum—folded membranes where ribosomes attach if the ribosome is making a secreted protein. newly made proteins are threaded in the RER where they fold and may get carbohydrates attached. the RER transports the proteins as they are being made. all eukaryotes have a rough endoplasmic reticulum.
Nuclear Pore—small holes in the nuclear envelope that eukaryotes use to move some materials in and out of the nucleus. all eukaryotes have nuclear pores
Vesicles—transport sacs that move materials throughout the cell. vesicles bud off of the rough endoplasmic reticulum to deliver material to the Golgi Apparatus and vesicles also bud off of the Golgi Apparatus to deliver material to the cell membrane. vesicles can also move materials into the cell during endocytosis. all eukaryotes have vesicles
Vacuole—sac-like structures that store materials such as water, salts, proteins, and carbohydrates. all eukaryotes have vacuoles. animals have small, temporary vacuoles. plants have large, permanent central vacuoles.
Phospholipid Structure
phosphate group (“head”)—hydrophilic
lipid (“tail”)—hydrophobic
Types of Microscopes
Compound Light Microscopes
Benefits: uses light, cheap, easy to use, can view living specimens
Limitations: magnification is limited, can’t see very small objects
Scanning Electron Microscope
Benefits: uses electrons, allows us to see the 3D surface of an object.
Limitations: expensive, requires a lot of training, specimens are killed
Transmission Electron Microscope
Benefits: uses electrons, allows us to see the internal structures of a cell.
Limitations: expensive, requires a lot of training, specimens are killed
Types of Cells
Eukaryotic—cells with membrane bound organelles, may be multicellular or unicellular.
Prokaryotic—cells without membrane bound organelles, all prokaryotes are unicellular.
Plant Cell Structures & Functions
Large Central Vacuole—large, sac like structure in plant cells that stores water and other inorganic materials. contributes to turgor pressure (pressure that allows plant cells to be rigid)
Chloroplasts—organelles that performs photosynthesis, converting sunlight, carbon dioxide, and water into glucose
Cell Wall—rigid structure outside of a plant cell membrane that gives extra support and protection to the plant cell.
Prokaryote Structure
Nucleoid Region—non-membrane bounded region in a prokaryotic cell where DNA in concentrated
Ribosomes—produces proteins (NOT membrane bound and NOT technically organelles. ribosomes are subcellular structures that ALL cells have)
Capsule—sticky layer of sugars or proteins that surrounds the cell wall, protecting the cell and enabling it to adhere to various surfaces.
Cell Membrane—thin, flexible protective barrier that covers the cell’s surface and acts as a barrier; determines what goes in and out of the cell. all cells have a cell membrane
Cell Wall—rigid structure outside of the cell membrane that gives the prokaryote protection from pressure. almost all prokaryotes have cell walls.
Flagellum—motility structure
Plasmid—extrachromosomal DNA; carries accessory genes
Endosymbiont Theory—a theory about where mitochondria and chloroplasts come from. the theory is that an ancient ancestor to the eukaryote engulfed and oxygen-using prokaryote, forming an endosymbiont. over time, eukaryotic cells became dependent on the eukaryote for nutrients and protection.
Evidence: mitochondria and chloroplasts are both double membrane bound, they both have their own DNA and ribosomes, and they can both divide independently from the nucleus.
Organelle—any membrane enclosed structure with specialized functions in the cytoplasm of a eukaryotic cell.
Homeostasis—maintenance of a stable internal environment
Chromosome—discrete units of DNA and the associated proteins. eukaryotes have linear chromosomes stored in the nucleus. prokaryotes have a single, circular chromosome in the nucleoid region.
Chromatin—granular, loose form of DNA present in a resting cell. individual chromosomes cannot be seen (but they are present…they just haven’t condensed. the chromatin condenses into individual chromosomes during cell division)
Apoptosis—programmed cell death initiated by lysosomes.
Contractile Vacuole—some unicellular eukaryotes do not have cell walls and could burst due to osmosis of water into the cell. contractile vacuoles pump water out of the unicellular eukaryotes.