Chapter 6 Flashcards
What is magnification?
The ratio of an object’s image size to its real size
What is resolution?
The measure of clarity of the image; or the minimum distance of two distinguishable points
What is contrast?
Visible differences in brightness between parts of the sample
What can light microscopes (LM) magnify to?
About 1,000x
What does a scanning electron microscope do?
Send a beam of electrons onto a specimen, and generates a 3-D image (ish)
What does a transmission electron microscope do?
Send a beam of electrons through a specimen
What is cell fractionation?
Takes cells apart and separates major organelles from each other
How do you fractionate cells?
With a centrifuge, different organelles drop to the bottom of a test tube with different speeds and gravitational speed
What domains consist of prokaryotic cells?
Archaea and Bacteria
What are the types of cells? (broad)
Prokaryotic and Eukaryotic
What are the basic features of all cells?
Plasma membranes
Semifluid substances (cytosol/cytoplasm) Chromosomes (DNA/genes)
Ribosomes (make proteins)
What are the defining characteristics of prokaryotes?
No nucleus, DNA in an unbound region called the nucleoid
No membrane bound organelles
Cytoplasm bound by plasma membrane
Eukaryotic defining characteristics?
DNA in a nucleus that is bound by a double membrane
Membrane bound organelles
Cytoplasm in the region between the plasma membrane and nucleus
Generally much larger than prokaryotes
What sets the size limit on cells?
Metabolic requirements; surface area to volume; volume grows more proportionally than surface area
What is a plasma membrane composed of?
A phospholipid bilayer; hydrophilic heads to the outside on each side and the hydrophobic tails inside
What is the nucleus?
Contains most of the DNA and genes in a eukaryotic cell
Ribosomes use information from DNA to make proteins
What are the parts of the nucleus?
Nuclear envelope
Nucleolus
Chromatin
What are nuclear lamina?
Structures on the nuclear side of the envelope that are composed of proteins that maintains the shape of the nucleus
What are nuclear pores?
They regulate entry/exit of molecules from the nucleus
What is the nuclear envelope?
Encloses the nucleus, separating nucleus from cytoplasm, and is a double membrane (two phospholipid bilayers)
What is DNA organized into?
Discrete units called chromosomes
What does chromatin do?
Condenses to form discrete chromosomes as a cell prepares to divide
What are chromosomes?
Each one contains one DNA molecule associated with proteins called chromatins
What is the site of ribosomal RNA synthesis?
The nucleolus (within nucleus)
What are ribosomes?
Complexes made of ribosomal RNA and protein
Where are ribosomes located/build proteins?
In the cytosol (free ribosomes)
On the outside of the endoplasmic reticulum or nuclear envelope (bound ribosomes)
What does the endomembrane system consist?
Nucelar envelope
ER
Golgi apparatus
Lysosomes
Vacuoles
Plasma membranes
What is the endoplasmic reticulum?
It is continuous with the nuclear envelope
Has two distinct regions: Smooth and Rough
Also accounts for more than half the total membrane in eukaryotic cells
What is the surface differences between rough ER and smooth ER?
Smooth ER lacks ribosomes embedded in its walls
Rough ER has surfaces with ribosomes embedded in them
What does the Smooth ER do?
Synthesize lipids
Detoxify drugs and poisons
Stores calcium ions
What does the Rough ER do?
Ribosomes secrete glycoproteins (proteins covalently bonded to carbohydrates)
Distributes transport vesicles, secretory proteins surrounded by membranes
A membrane factory for the cell
What is the Golgi apparatus?
Consists of flattened membranous sacs called cisternae
Modifies products of the ER
Manufactures certain macromolecules
Sorts and packages materials into transport vesicles
What are the sides of the Golgi apparatus?
Cis face: “Receiving” side of Golgi apparatus
Trans face: “shipping” side of Golgi apparatus
What is a lysosome?
A membranous sac of hydrolytic enzymes that digest macromolecules
Work best in acidic environment inside the lysosome
Hydrolytic enzymes and lysosomal membranes made by rough ER and transferred to G.A
What do lysosomes do?
Some cells engulf others by phagocytosis, forming food vacuoles
A lysosome fuses with the vacuole and digests the contents
Lysosomes use enzymes to recycle the cell’s own organelles and macromolecules, called autophagy
What are vacuoles?
Large vesicles derived from the ER and G.A
Performs a variety of functions in different kinds of cells
What are the kinds of vacuoles?
Food vacuoles formed by phagocytosis
Contractile vacuoles are found in freshwater protists, and pump excess water out of cells
Central vacuoles are found in mature plant cells, and contain a solution called sap
What does a central vacuole do?
It’s the plant’s main repository of inorganic ions, which includes potassium and chloride
Also plays a major role in plant cell growth (turgor pressor)
What does the mitochondria do?
The sites of cellular respiration (metabolic process that uses oxygen to generate ATP)
Endosymbiont theory
Enveloped in double membrane
Contains free ribosomes and circular DNA molecules
Grows and reproduces somewhat independently in cells
What are chloroplasts?
The site of photosynthesis in photosynthetic cells
Enveloped by a double membrane
Contains free ribosomes and circular DNA molecules
Grows and reproduces somewhat independently in cells
Characteristics of mitochondria?
Found in nearly all eukaryotic cells
Smooth outer membrane, inner membrane folded into cristae
Inner membrane in two compartments: intermembrane space and mitochondrial matrix
Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix
Characteristics of chloroplasts?
Contain green pigment chlorophyll
Contains enzymes and other molecules that function in photosynthesis
Found in leaves and other green organs of plants and in algae
What do chloroplasts contain?
Thylakoids, which are membranous sacs that are stacked to form grana (um)
Stroma, which is the internal fluid
It is also part of a group of plant organelles called plastids
What are peroxisomes?
Specialized metabolic compartments bound by a single membrane
Contain enzymes that remove hydrogen atoms from various substances and transfer them to oxygen; forms hydrogen peroxide
What do the peroxisomes do?
Some use oxygen to break fatty acids into smaller molecules for fuel for respiration
In livers, they detoxify alcohol and other harmful compounds
Glyoxysomes in fat storing tissues of plant seeds convert fatty acids to sugar to feed the emerging seedling
What is the cytoskeleton?
A network of fibers extending throughout the cytoplasm
Its composed of three types of molecular structures: microtubules, microfilaments, intermediate filaments
What does the cytoskeleton do?
Organizes the cell’s structures and activities, anchoring organelles
Helps to support the cell and maintain its shape
Interacts with motor proteins to produce cell motility- which cells use to travel along tracks provided by cytoskeleton
What are microtubules?
Thickest of the three cytoskeleton components; hollow tubes
Made of tubulin polymers, a dimer
What do microtubules do?
Helps maintain cell shape
Helps with cell motility
Chromosome movements in cell division
Organelle movements
What are microfilaments?
Two intertwined strands of actin
Made of actin proteins
What do microfilaments do?
Help maintain cell shape
Changes in cell shape
Muscle contractions
Cytoplasmic streaming (plant cells)
Cell motility
Cell division (animal cells)
What are intermediate filaments?
Fibrous proteins coiled into cables
Can be one of several different proteins, including keratins
The “permanent” one out of the three
What do intermediate filaments do?
Helps maintain cell shape
Anchorage of nucleus and certain other organelles
Formation of nuclear lamina
What are centrosomes/centrioles?
Animal cells: microtubules grow out from a centrosome near the nucleus, which has a pair of centrioles with nine triplets of microtubules arranged in a ring
What do cilia/flagella do?
Microtubules control the beating of flagella/cilia
Many unicellular protists locomote with them, but multicellular cells can have them as well
Motile cilia are in larger numbers on cell surfaces; flagella are limited to only a few or one
Commonalities between cilia and flagella?
A group of microtubules sheathed in an extension of the plasma membrane
Nine doublets of microtubules are arranged in a ring with two single microtubules in the center
Basal body that anchors the cilia/flagella
Motor proteins called dynein that drive the bending movements of the structures
What is dynein?
A motor protein that walks along microtubules
The movements of the “feet” cause the microtubules to bend instead of slide, because the tubules are held in place
What are the differences of microfilaments in motile structures?
They contain the protein myosin along with actin
What is cytoplasmic streaming?
A circular flow of cytoplasm within cells that is driven by actin protein interactions
Characteristics of cell walls in plant cells?
Prokaryotes, fungi, and some protists have them as well
Cell walls protect the plant cell, maintain shape, and prevent excessive uptake of water
Made of cellulose fibers embedded in other polysaccharides and protein
Layers of a cell wall?
Primary cell wall
Middle lamella
Secondary cell wall
What is the primary cell wall?
It is a relatively thin and flexible wall, the membrane that is secreted first during the cell’s “infancy”
What is the middle lamella?
A thin layer between primary walls, and contains polysaccharides called pectins
What is a secondary cell wall?
Found in some cells; is added between the plasma membrane and the primary cell wall
What is the extracellular matrix (ECM)?
Animal cell equivalent of cell walls
Made of glycoproteins like collagen, proteoglycans, and fibronectin
Fibronectin and other proteins bind to receptor proteins in the plasma membrane called integrins
What does the ECM do?
Can regulate a cell’s behavior by communicating with a cell through integrins
Can influence the activity of genes in the nucleus
Mechanical signaling may occur through cytoskeleton changes that trigger chemical signals in the cell
What are cell junctions?
Neighboring cells in tissues/organs/systems adhere, interact, and communicate through direct physical contact
What are plasmodesmata?
Channels that connect plant cells
Water and small solutes (sometimes proteins and RNA) can pass from cell to cell
What are the types of cell junctions?
Tight junction
Desmosomes
Gap junctions
What are tight junctions?
Membranes of neighboring cells are pressed together and prevent leakage of extracellular fluid (skin)
What are desmosomes?
Also called anchoring junctions, they fasten cells together into strong sheets (heart cells)
What are gap junctions?
Also called communicating junctions, they provide cytoplasmic channels between adjacent cells
What are some of the embedded proteins in a cell’s membrane?
Proton pump
Calcium channel
Aquaporin
Receptor
