Chapter 6-Lecture Notes Flashcards
All organisms are made of _____________
cells
The cell is the simplest collection of matter
that can be alive
All cells are related by their descent from earlier cells
Cells can differ substantially from one another but share common features
Cells are usually too small to be seen by the naked eye we use
Microscopy
In a l\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ visible light is passed through a specimen and then through glass lenses Lenses refract (bend) the light, so that the image is magnified
light microscope (LM),
Three important parameters of microscopy
________________ the ratio of an object’s image
size to its real size
_____________ the measure of the clarity of the image, or the minimum distance of two distinguishable points
____________________ visible differences in brightness between parts of the sample
Magnification,
Resolution,
Contrast,
Light microscopes can magnify effectively to about_______________________________
Various techniques enhance contrast and enable cell components to be stained or labeled
1,000 times the size of the actual specimen
The resolution of standard light microscopy is too low to study_________________, the membrane-enclosed structures in eukaryotic cells
organelles
Two basic types of electron microscopes (EMs) are used to study subcellular structures
_____________________ focus a beam of electrons onto the surface of a specimen, providing images that look 3-D
___________________ focus a beam of electrons through a specimen
TEMs are used mainly to study the internal structure of cells
Scanning electron microscopes (SEMs)
Transmission electron microscopes (TEMs)
provide sharper images of three-dimensional tissues and cells
New techniques for labeling cells improve resolution
Confocal microscopy and deconvolution microscopy
takes cells apart and
separates the major organelles from one another
Cell fractionation
Centrifuges fractionate cells into their
component parts
_____________have
internal membranes that compartmentalize
their functions
Eukaryotic cells
Only organisms of the domains Bacteria and Archaea consist of
prokaryotic cells
Protists, fungi, animals, and plants all consist of
eukaryotic cells
The basic structural and functional unit of every organism is one of two types of cells:
prokaryotic or eukaryotic
Basic features of all cells
Plasma membrane
Semifluid substance called cytosol
Chromosomes (carry genes)
Ribosomes (make proteins)
Prokaryotic cells are characterized by having
No nucleus
DNA in an unbound region called the nucleoid
No membrane-bound organelles
Cytoplasm bound by the plasma membrane
Eukaryotic cells are characterized by having
DNA in a nucleus that is bounded by a membranous nuclear envelope
Membrane-bound organelles
Cytoplasm in the region between the plasma membrane and nucleus
Eukaryotic cells are generally much larger than prokaryotic cells
is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell
plasma membrane
has internal membranes that partition the cell into organelles
The basic fabric of biological membranes is a double layer of phospholipids and other lipids
Plant and animal cells have most of the same organelles
A eukaryotic cell
layers in prokaryotic cells
plasma membrane
cell wall
capsule
contains most of the cell’s genes and is usually the most conspicuous organelle
The nucleus
The nuclear membrane is a double membrane; each membrane consists of a
lipid bilayer fluid mosaic
encloses the nucleus, separating it from the cytoplasm
The nuclear envelope
The nuclear size of the envelop is lined by the ________ , which is composed of proteins and maintains the shape of the nucleus
nuclear lamina
n the nucleus, DNA is organized into discrete units called
chromosomes
Each chromosome is composed of a single DNA molecule associated with proteins
The DNA and proteins of chromosomes are together called
chromatin
Chromatin condenses to form discrete __________________ as a cell prepares to divide
chromosomes
is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis
Ribosomes: Protein Factories
The nucleolus
Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane
The endomembrane system consists of
These components are either continuous or connected via transfer by
vesicles
accounts for more than half of the total membrane in many eukaryotic cells
The endoplasmic reticulum (ER)
two types smooth and rough ER
Smooth ER,
Rough ER,
which lacks ribosomes
whose surface is studded with ribosomes
The smooth ER
Synthesizes lipids
Metabolizes carbohydrates
Detoxifies drugs and poisons
Stores calcium ions
The rough ER
Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates)
Distributes transport vesicles, secretory proteins surrounded by membranes
Is a membrane factory for the cells
Has bound ribosomes, which secrete _____________________(proteins covalently bonded to carbohydrates)
glycoproteins
Distributes _______, secretory proteins surrounded by membranes
transport vesicles
——————————— consists of flattened membranous sacs called cisternae
Functions of the Golgi apparatus
Modifies products of the ER
Manufactures certain macromolecules
Sorts and packages materials into transport vesicles
The Golgi apparatus
________________________ is a membranous sac of hydrolytic enzymes that can digest macromolecules
Lysosomal enzymes work best in the acidic environment inside the lysosome
Hydrolytic enzymes and lysosomal membranes are made by rough ER and then transferred to the Golgi apparatus for further processing
A lysosome
Some types of cell can engulf another cell by _________________ this forms a food vacuole
A lysosome fuses with the food vacuole and digests the molecules
phagocytosis;
Some types of cell can engulf another cell by
——————————; this forms a food vacuole
A lysosome fuses with the food vacuole and digests the molecules
phagocytosis
are large vesicles derived from the ER and Golgi apparatus
Vacuoles
are the sites of cellular respiration, a metabolic process that uses oxygen to
generate ATP
Mitochondria
found in plants and algae, are the sites of photosynthesis
Peroxisomes are oxidative organelles
The Evolutionary Origins of Mitochondria and Chloroplasts
Mitochondria and chloroplasts have similarities with bacteria
Chloroplasts,
suggests that an early ancestor of eukaryotes engulfed an oxygen-using nonphotosynthetic prokaryotic cell
The endosymbiont theory s
They have a smooth outer membrane and an inner membrane folded into
cristae
Chloroplast structure includes
Thylakoids, membranous sacs,
stacked to form a granum
Stroma, the internal fluid
The chloroplast is one of a group of plant organelles, called plastids
membranous sacs,
Thylakoids,
is one of a group of plant organelles, called plastids
The chloroplast
stacked to form a ___________
_______________________ the internal fluid
geranium
Stroma,
are specialized metabolic compartments bounded by a single membrane
Peroxisomes produce hydrogen peroxide and convert it to water
Peroxisomes
perform reactions with many different functions
How peroxisomes are related to other organelles is still unknown
Peroxisomes
is a network of fibers extending throughout the cytoplasm
It organizes the cell’s structures and activities, anchoring many organelles
The cytoskeleton
The cytoskeleton
It is composed of three types of molecular structures
Microtubules
Microfilaments
Intermediate filaments
The cytoskeleton helps to support the cell and maintain its shape
It interacts with motor proteins to produce motility
Inside the cell, vesicles can travel along tracks provided by the cytoskeleton
________________ are the thickest of the three components of the cytoskeleton
___________________ also called actin filaments, are the thinnest components
______{___________are fibers with diameters in a middle range
Microtubules
Microfilaments,
Intermediate filaments
___________________ are hollow rods about 25 nm in diameter and about 200 nm to 25 microns long
Functions of microtubules
Shaping the cell
Guiding movement of organelles
Separating chromosomes during cell division
Microtubules
In animal cells, microtubules grow out from a
—————————–near the nucleus
In animal cells, the centrosome has a pair of _______________ each with nine triplets of microtubules arranged in a ring
centrosome
centrioles,
Microtubules control the beating of ________________________microtubule-containing extensions that
project from some cells they differ in their beating patterns
flagella and cilia,
_____________________ that anchors the cilium or flagellum
A motor protein called _________________ which drives the bending movements of a cilium or flagellum
A basal body
dynein,
__________________are solid rods about 7 nm in diameter, built as a twisted double chain of
actin subunits
The structural role of microfilaments is to bear tension, resisting pulling forces within the cell
They form a 3-D network called the _____________ inside the plasma membrane to help support the cell’s shape
Bundles of microfilaments make up the core of microvilli of intestinal cells
Microfilaments
cortex just
that function in cellular motility contain the protein myosin in addition to actin
In muscle cells, thousands of actin filaments are arranged parallel to one another
Thicker filaments composed of myosin interdigitate with the thinner actin fibers
Microfilaments
is a circular flow of cytoplasm within cells
This streaming speeds distribution of materials within the cell
In plant cells, actin-myosin interactions and sol-gel transformations drive cytoplasmic streaming
Cytoplasmic streaming
___________________ range in diameter from
8–12 nanometers, larger than microfilaments
but smaller than microtubules
They support cell shape and fix organelles
in place
Intermediate filaments r
____________________ are more permanent cytoskeleton fixtures than the other two classes
Intermediate filaments
is an extracellular structure that distinguishes plant cells from animal cells
cell wall
The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water
Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein
Prokaryotes, fungi, and some unicellular eukaryotes also have cell walls
Plant cell walls may have multiple layers
Primary cell wall: Relatively thin and flexible
Middle lamella: Thin layer between primary walls of adjacent cells
Secondary cell wall (in some cells): Added between the plasma membrane and the primary
cell wall
Relatively thin and flexible
Primary cell wall:
Thin layer between primary walls of adjacent cells
Middle lamella:
Added between the plasma membrane and the primary
cell wall
Secondary cell wall (in some cells):
Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM)
The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin
are channels that perforate plant cell walls
Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell
Plasmodesmata
3 types of cell junctions are common in epithelial tissues
Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells
membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid
At tight junctions,
) fasten cells together into strong sheets
Desmosomes (anchoring junctions
(communicating junctions) provide cytoplasmic channels between adjacent cells
Gap junctions
The Cell: A Living Unit Greater Than the Sum of Its Parts
Cells rely on the integration of structures and organelles in order to function
For example, a macrophage’s ability to destroy bacteria involves the whole cell, coordinating components such as the cytoskeleton, lysosomes, and plasma membrane
