Chapter 3 Flashcards
Cells
Electron microscopy
-requires specimen to be killed, chemically fixed, and placed in vacuum,
-only produce black and white (false color can be added later)
-more expensive than light microscopy
-used to view parts of the cells, and viruses, which are smaller and require more magnification
Light microscopy
-can view living organisms
-can view in color
-used to view the entire cell
-less magnification then electron microscopes
-transmit light through cells
-must be transparent enough, or you can’t see through it
-can be used to see living cells
2 types of light microscopy
-compound scope
-confocal scope
Light microscopy: compound scope
-2 or more lenses to focus visible light through a specimen
-up to 1600X magnified and resolves objects 200 nanometers apart
Light microscopy: confocal scope
-enhances resolution by focusing a laser through a lens to the object
-fluorescent dyes can be attached to different molecules
-emitted light passes through a pinhole to a detector
-only scan 1 tiny part of a specimen at a time
Cell
-smallest unit of life that can function independently
-all organisms are made of one or more cells
-cells weren’t discovered until microscopes were invented, because most of them are too small to see without a microscope (most cells are less than 0.1 mm in diameter)
Cell theory was first invented in…
The mid-1800’s, after it became possible to study cells using microscope
Early cell theory (first 2)
1.) all organisms are made of one or more cells
2.) the cell is the structural and fundamental unit of life
Early cell theory (one after the first 2)
3.) all cells come from preexisting cells
Additional cell ideas in modern theory
4.) all cells have the same basic chemical composition
5.) all cells use energy
6.) all cells contain DNA that is duplicated and passed on as each cell divides
2 types of electron microscopy
-TEM microscopy
-SEM microscopy
TEM microsopy
-Transmission Electron Microscope
-allows us to view internal cell structures
-transmits a beam of electrons right through the cells
-50 million times magnification
-high resolution, 2D image
-resolves objects less then 1 angstrom (10 to the -10th power meters) apart
-internal features of specimen
SEM microscopy
-Scanning Electron Microscope
-reveals details on cell’s surfaces
-bounces electrons off the surface of the cells
-external features of specimen
-lower resolution than TEM, 3D image
-250,000X magnification
-resolve objects 1-5 nanometers apart
Cells can vary in size
-bacteria and archaea cells are about 10X smaller in diameter than most plant and animals cells
-frog eggs are about 10X larger than most plant and animal cells
-thousands of bacteria cells would fit in 1 human cells
All cells share common features
-regardless of size, all cells have DNA, RNA, proteins, ribosomes, cytoplasm, and a cell membrane (aka plasma membrane
-the all carry out chemical reactions needed to sustain life, such as cellular respiration and protein synthesis
Bacteria and archaea have different compositions of…
-cell walls
-cell membranes
-flagella
-also different key DNA sequences
Nucleus and membrane-bounded organelles are found in…
Eukaryotic cells, not prokaryotic cells
Smaller cells have more…
Surface area relative to their volume
-high surface area allows the cell to quickly exchange materials with its surroundings (make the exchanges efficient)
-ex. oxygen from the air must quickly enter your lungs
Nucleoid
The part of a prokaryotic cell where DNA is located (not bounded by a membrane)
Life is classified into 3 domains
Prokaryotic
-domain bacteria
-domain archaea
Eukaryotic
-domain eukarya
Prokaryotes
The most ancient forms of life
-small, simple in structure, lack of nucleus
-bacteria and archaea are the 2 domains of prokaryotes
Eukaryotes
Evolved billions of years are prokaryotes
-larger, more complex, with many internal parts including a nucleus and other membranous organelles
-protists, fungi, plants, and animals
Nucleus
A membrane-bounded sac that contains DNA in a eukaryotic cell
Domain bacteria
-prokaryotic
-no nucleus
-no membrane bounded organelles
-membrane chemistry: fatty acids
-typical cell size: 1-10 um
-some are used to make pharmaceuticals
Domain archaea
-prokaryotic
-no nucleus
-no membrane bounded organelles
-membrane chemistry: non fatty acids
-typical cell size: 1-10 um
Domain eukarya
-eukaryotic
-nucleus present
-membrane bounded organelles present
-membrane chemistry: fatty acids
-typical cell size: 10-100 um
Anatomy of a bacteria cell
-ribosomes, cytoplasm, enzymes, and DNA
-prokaryotic
-lack membrane bound organelles
-their ribosomes and DNA are free in the cytoplasm
Ribosome
A structure built of RNA and protein where the mRNA anchors during protein synthesis
-manufactures proteins
-2 globular subunits composed of RNA and protein
Cell membrane
The boundary of a cell
-consisting of proteins embedded in a phospholipid bilayer (aka plasma membrane)
Cells can adapt to have a higher surface area by…
Being elongated, flattened, spiral, or highly folded shapes to increase surface area to volume ratio
Anatomy of an animal cell
-eukaryotic
-they have many different membrane bounded organelles
Anatomy of a plant cell
-eukaryotic
-they have most of the same membrane bounded organelles as animal cells
-they also have a large central vacuole, cell wall, and chloroplast (as animal cells don’t have those)
Eukaryotic cells divide the labor into…
-cell membrane
-organelles involved in protein production
-organelles involved in protein localization
-organelles involved in cellular digestion
-energy related organelles
-the cytoskeleton
Phospholipid bilayer
Double layer of phospholipids that forms in water
-forms a majority of cell’s membranes
-amphipathic
-selectively permeable to lipids and small, nonpolar molecules (some substances can pass through)
Cell wall
A rigid boundary surrounding cells of many prokaryotes, protists, plants, and fungi
-2 main components of a plant cell wall are cellulose and lignin
-cellulose, hemicellulose, pectin and many types of proteins
-protects cell
-provides shape to cell
-connects adjacent cells
DNA
Nucleic acid that stores the cell’s genetic information
RNA
Nucleic acid that participates in the production of proteins
Cytosol
The fluid portion of the cytoplasm
Functions of a cell membrane
-forms a barrier between the cell and the outside world
-regulates passage of substances in and out of cell
-helps maintain homeostasis
Cell membranes are composed of…
Phospholipid bilayers
-because of their chemical structure, phospholipids spontaneously form bilayers when they are surrounded by water
-1 head and 2 tails
Phospholipids are made of…
-a molecule of glycerol
-a phosphate group
-2 fatty acids
Amphipathic
Molecules that have both polar and nonpolar regions
-hydrophilic heads: polar bonds, which are attracted to water
-hydrophobic tails: nonpolar bonds, which repel water
Cytoplasm
The watery mixture that occupies much of the cell’s volume
-in eukaryotic cells, in consists of all materials, including organelles, between the nuclear envelope and cell membrane
-pH 7
Fluid mosaic
2D structure of moveable phospholipids and proteins that form biological membranes
-the combination of phospholipids and proteins form a fluid mosaic
Endoplasm definition
Within the cytoplasm
Reticulum definition
Network
rER
Rough endoplasmic reticulum
-ribosome studded portion of the ER where secreted proteins are synthesized
-produces proteins that are destined for secretion from the cell
sER
Smooth endoplasmic reticulum
-lack ribosomes on the outside or organelle
-portion of the ER that produces lipids and detoxifies poison and drugs
Cell membranes contain proteins
-membranes proteins are embedded throughout the bilayer
Different functions of membrane proteins
1.) transport proteins
2.) enzymes (chemical reactions to slowly sustain life)
3.) recognition proteins (helps body recognize its own cells/ attack unfamiliar cells)
4.) adhesion protein (help cells stick to each other)
Capsule
Protective layer around some bacteria and fungi
Carbohydrates protrude outward from the cell membrane
-chains of sugars are attached to some of the proteins and phospholipids in cell membranes
-they play roles in cell to cell communication
Cell membranes contain steroids
-the membrane steroids keep the membrane at the right level of fluidity (not too soft and not too stiff)
-cholesterol is an example of a membrane steroid
Cell membranes are fluid mosaic
-the membrane is neither a solid nor a liquid (it’s more like Jell-O)
-in the membrane, the phospholipids re constantly moving and switching places
Dividing labor: protein production
The nucleus controls protein production
-nucleus contains DNA, which specifies the “recipe” for the proteins
-it also contains the nucleolus, which synthesis ribosomes
RNA is synthesized in the nucleus
Messenger RNA (mRNA) matches the sequence of DNA
-mRNA carries the protein “recipe” through a nuclear pore in the 2 layered nuclear envelope
RNA binds to a ribosome
-RNA moves from the nucleus out to a ribosome, where the protein is synthesized
2 different locations of ribosomes
-floating in the cytosol
-attached to the rER
Endoplasmic reticulum
ER
-interconnected, membranous tubules and sacs in eukaryotic cells
Nucleus
Perforated sac containing DNA, proteins, and RNA
-surrounded by a double membrane
-the organelle that contains most of a eukaryotic cell’s DNA
-separates DNA from rest of cell
-site of first step in protein synthesis
mRNA
Messenger RNA
Nuclear pore
A hole in the nuclear envelope
Nuclear envelope
2 membranes bounding a cell’s nucleus
Nucleolus
Structure within a nucleus where components of ribosomes are assembled
-produces ribosome subunits
Proteins are synthesized in ribosomes
-free floating ribosomes synthesis proteins that will function in the cytosol
-ribosomes attached to the rER synthesize proteins the function inside of organelles or may be secreted outside of the cell
Parts of the endomembrane system
-nuclear envelope
-endoplasmic reticulum
-Golgi apparatus
-lysosomes
-vacuoles
-cell membrane
Endomembrane system
Eukaryotic organelles the exchange materials in transport vesicles
-moves molecules around
Vesicle
Membrane bounded sacs that transport materials within a cell (like a bubble)
Proteins that are secreted
-different parts of the endomembrane system work together to secrete proteins, moving them outside of the cell
-mammary glands cells produce proteins and secrete then in order to make milk for baby mammals
Proteins enter the rER
-secreted proteins move from ribosomes into the rER, where they are modified and folded into their exact 3D shape
-the proteins exit the rER in the bubbles of the membrane called transport vesicles
Proteins move from the rER into the golgi apparatus
The vesicles leaving the rER fuse with the golgi apparatus
Golgi apparatus
A stack of flat, membrane sacs that act as a “processing center”
-enzymes in the Golgi apparatus also manufacture and attach carbohydrate to proteins or lipids, forming “name tags” recognized by the immune system
Lysosome
Organelle in eukaryotic cell that buds from Golgi apparatus and enzymatically dismantles molecules, food, debris, bacteria, and worn-out cell parts
-sac containing hydrolytic enzymes, surrounded by a single membrane
-some transport vesicles leaving the Golgi apparatus carry enzymes that catalyze hydrolysis reactions
-these vesicles fuse with lysosomes, where cellular digestion of large molecules occurs
-rarely in plant cells
Lysosome membrane pH
4.8 pH
Proteins leave the Golgi apparatus in…
Transport vesicles
-the transport vesicles then fuse with the cell membrane
-the contents of the vesicles expelled to the outside of the cell
Peroxisome
Membrane bounded sac that contains enzymes, often forming visible proteins crystals
-surrounded by a single membrane
-break down fatty acids and dispose of toxic chemicals
-they originate in the ER
-aid in digestion and oxidizes certain toxic molecules
-also eliminates hydrogen peroxide
Mitochondria
(singular: mitochondrion) Organelles that houses the reaction of cellular respiration in eukaryotic cells
-2 membranes: inner membrane is folded into enzyme studded cristae
-contains DNA and ribosomes
-only inherited from the female parent
-almost all eukaryotic cells have mitochondria
-extracts energy from food, converts sugar’s energy into a form of energy that a cell can use for work
Cristae
(singular: crista) Folds of inner mitochondrial membrane along with many of the reactions of cellular respiration occurs
Chloroplast
Organelle housing the reaction of photosynthesis in eukaryotic plant cells
-2 membranes enclosing stacks of membrane sacs
-contain photosynthetic pigments and enzymes
-contains DNA and ribosomes
-plastids that carry out photosynthesis
-other plastids store pigment or food
-inside plant cells and some protists
-convert energy from sunlight into sugar, which is food for the cell
Central vacuole
Membrane bounded storage sac in a plant cell containing enzymes, acids, water soluble pigments and other solutes
-surrounded by a single membrane
-90% of some plant cell’s volume
-cellular digestion occurs in large central vacuoles, which also helps regulate the size and water balance of plant cells
-produces turgor pressure
-recycles plant cell content
-contains pigment
Matrix
The space inside a mitochonrion
Stroma
The space inside a chloroplast
Thylakoids
Flattened sacs of internal membranes in chloroplasts
-these are the sites for the chemical reaction of photosynthesis
-the sugar then travels to the mitochondria, which extracts the energy used for the cellular process
Cytoskeleton
A network of protein tracks and tubules found in eukaryotic cells
-transports organelles within a cel
-maintain cell shape
-structural basis for flagella and cilia
-connects adjacent cells
4 functions of a cytoskeleton
1.) structural function
2.) aids in cell division
3.) organelle transport
4.) cell movement
3 major components of a cytoskeleton
1.) microfilaments
2.) intermediate filaments
3.) microtubules
-they all work together
Microfilaments
Smallest component of the cytoskeleton
-needed for cell contraction and changes in cell shape
-composed of actin proteins
-7nm
-long rod
Intermediate filaments
Medium component of the cytoskeleton
-forms a strong scaffold for mechanical strength
-have varied protein composition
-also binds some cells together
-10 nm
Microtubules
Largest component of the cytoskeleton
-act as “trackways” for moving organelles and vesicles
-composed of tubulin proteins
-23 nm
-hollow tube
-also makeup structures called cilia and flagella that protrude out from cells
Flagella
Long, whip-like, tail-like appendages that cells use for mobility
-from microtubules
-single or in pairs
-longer than cilium
-sperm cells use flagella
Cilia
One of many short, moveable protein projections extending from a cell (kind of like fringe)
-from microtubules
-airways need cilia to push particles like dust out of the respiratory tract
Dynein
Motor proteins to generate movement
-inside cilia and flagella, microtubules slide against each other with the help of motor proteins called dynein
-as a result, the cilium or flagellum bends
“Recycling centers” of cells
-lysosomes
-peroxisomes
-vacuoles
Centrosome
Part of the cell that organizes microtubules
4 functions of a cell wall
1.) provide mechanical strength
2.) regulate volume
3.) prevent cells from bursting
4.) role in cell specialization
Plasmodesmata
(single: plasmodesma) channels (tunnels) that pass through the plant cell wall
-plant cells communicate through this
-nutrients and biochemicals travel through these channels to adjacent cells
Cells stick together to communicate
-cells in multicellular organisms must constantly communicate with each other in order for tissues to function properly
-proteins and carbohydrates protruding from animal cells are crucial for cell communication
3 different types of juctions
1.) GAP junction
2.) tight junction
3.) anchoring/adhering junctions
GAP junctions
Form channels between the membranes of 2 animal cells, allowing the exchange of substances (materials can move through directly and rapidly)
-(plasmodesmata is a plant cell analogy)
-also allows cytoplasm to flow between cells
-ex. muscles cells in heart and digestive tract
Tight junctions
Seal spaces between animal cells by fusing cell membranes
-like sewing machine stitches
-proteins fuse the membranes to adjacent cells
-allow sheets of cells to form a leak proof barrier (prevent fluid to flow past cells)
-ex. cells in inner lining of stomach and small intestine
Anchoring/adhering junctions
Connect adjacent animal cell membranes in 1 spot
-connects cells to extracellular matrix
-proteins react inside cells and bind to the cytoskeleton, for added mechanical strength
-ex. cells in outer layer of skin
All components of chloroplasts
-stroma
-thylakoids
-DNA
-photosynthesis
-pigments
-ribosomes
Bacteria can sense magnetic fields
Magnetosomes orient bacteria to earth’s magnetic field lines
-this allows bacteria to swim through water, easily adjusting to their optimal oxygen concentration
