Chapter 6 Flashcards
All organisms are made of
cells
The cell is the
simplest collection of matter that can live.
They have the 7 qualities of life
Cell structure is correlated to
cellular function
All cells are related by their
descent from earlier cells.
Though usually too small to be seen by the unaided eye,
cells can be complex
Scientists use microscopes to
visualize cells to small to see with the naked eye
In a Light Microscope (LM),
visible light passes through a specimen and then through glass lenses
Lenses refract (bend) the light, so that
the image is magnified
Three important parameters of microscopy
Magnification
Resolution
Contrast
Magnification
the ratio of an object’s image size to its real size
Resolution
the measure of the clarity of the image, or the minimum distance of two distinguishable points.
(how clear you can see the image and magnify it)
Contrast
visible differences in parts of the sample
Light Microscopes (LMs) can magnify to about
1,000 times the size of the actual specimen
Various techniques enhance
contrast and enable cell components to be stained or labeled
Most subcellular structures, including organelles,
are too small to be resolved by a Light Microscope (LM)
Organelles
membrane-enclosed compartments
Two basic types of Electron Microscopes (EMs) that are used to study subcellular structures
Scanning Electron Microscopes (SEMs)
Transmission Electron Microscopes (TEMs)
Scanning Electron Microscopes (SEMs)
focus a beam of electrons onto the surface of a specimen, providing images that look 3-D.
-Allows you to see the surface!!
SURFACE (SSS)
Transmission Electron Microscopes (TEMs)
focus a beam of electrons through a specimen
-allows you to see the little things inside
internal ultrastructures
-Disadvantage: only dead specimen
Cell fractionation
takes cells apart and separates the major organelles from one another
-so you can study just the parts you’re interested in.
It starts out slow and short spins, then it ends up with fast and long spins
Centrifuges fractionate cells into
their component parts
Cell fractionation enables scientists to
determine the functions of organelles
Biochemistry and cytology help correlate
cell function with structure
The order the organelles fall out during Cell fractionation
- nucleus
- mitochondria and chloroplast
- microsomes
- ribosomes
The basic structural and functional unit of every organism is one of two types of cells:
prokaryotic or eukaryotic
Prokaryotic Cells
Domain Bacteria and Domain Archaea
Eukaryotic Cells
Kingdoms:
plants, animals, fungi, protists (protista)
Basic features of ALL cells
plasma membrane
semifluid substance called cytosol
chromosomes (carry genes. DNA)
ribosomes (make proteins)
Every cell needs to be able to
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
The plasma membrane is a
selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell
The general structure of a biological membrane is a
double laye of phospholipids
Metabolic requirements set upper limits on the size of
cells
Eukaryotic cells?
The surface area to volume ratio of a cell is
critical
As the surface area increases by a factor of n^2,
the volume increases by a factor of n^3
Small cells have a greater surface area relative
to volume.
this is how eukaryotic cells can be so big
Cells need enough surface area for their
work, metabolism.
All of the membranes are put together into a eukaryotic cell and that is what
makes the surface area so big
A eukaryotic cell has internal membranes that partition the cell into
organelles
Organelles participate in
metabolism (enzymes built into their membranes)
Organelles provide
local environments for specific reactions
Plant and animal cells have most of the same
organelles
In animal cells but not plant cells
lysosomes
centrioles
flagella (in some plant sperm)
In plant cells but not animal cells
chloroplasts
central vacuole and tonoplast
cell wall
plasmodesmata
The nucleus contains most of the
DNA in a eukaryotic cell
The genetic instructions are
how a cell know what to do
Ribosomes use the information from the DNA to
make proteins
The nucleus and the ribosomes work
together in eukaryotic cells
Nucleus function
hold the DNA
Ribosomes function
make proteins
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
The nuclear membrane is a
double membrane. (it folds back over)
- membrane is continuous at the pores
- pore complexes line the pore
Pores regulate the entry and exit of molecules from the
nucleus
The shape of the nucleus is maintained by the
nuclear lamina, which is composed of protein
Nucleus job
hold DNA
In 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
chromosomes as a cell prepares to divide
The Nucleolus (not a membranous organelles) is located within the
nucleus and is the site of ribosomal RNA (rRNA) synthesis
The nucleolus is where we
put together ribosomes
The nucleolus is located within the
nucleus
the dense region
Nucleolus function
make RNA to make ribosomes
Ribosomes are particles made of
ribosomal RNA and protein
-site of protein synthesis
Ribosomes carry out protein synthesis in two locations
in the cytosol
and
on the outside of the endoplasmic reticulum or the nuclear envelope
The ribosomes that carry out protein synthesis in the cytosol are
free ribosomes-they float around free
-proteins for use in the cytosol
The ribosomes that carry out protein synthesis on the outside of the endoplasmic reticulum or the nuclear envelope are
bound ribosomes- they are physically stuck to the thing. they will have proteins that end up outside the membrane.
-proteins for membranes, packages, or secretion
Ribosomes function
make proteins (important!!!)
Endomembrane system
a series of physically connected structures
Components of the Endomembrane system
1st- Nuclear Envelope 2nd- Endoplasmic Reticulum 3rd- Golgi Apparatus 4th- Lysosomes 5th- Vacuoles 6th- Plasma Membrane
-The components go through the endomembrane system through this order
The components of the endomembrane system are either continuous or connected via transfer by
vesicles
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
There are two distinct regions of ER
Smooth ER, which lacks ribosomes
Rough ER, surface is studded with ribosomes
Functions of Smooth ER
-synthesizes lipids
(sex hormones, steroids, etc.)
-metabolizes carbohydrates
-detoxifies poison (liver) (alcohol)
(increased use leads to higher tolerance)
-stores calcium (takes the calcium and holds it inside if you want to get cells attention, let the calcium out.
Smooth ER detoxifies alcohol but when
you havent drank alcohol in awhile, you wont have enough smooth ER anymore to get the alcohol out and detoxify
Functions of Rough ER
- Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates. (proteins with sugar on them))
- distributes transport vesicles, proteins surrounded by membranes
- is a membrane factory for the cell
- makes proteins=main purpose/job
glycoproteins
proteins covalently bonded to carbohydrates.
proteins with sugar on them.
The Golgi apparatus 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 (then pops off?)
- –Cis face (near ER)
- –Trans face (far side)
It ships and packages.
Modifies, packaging, and shipping.
A lysosome is a
membranous sac of hydrolytic enzymes that can digest macromolecules
Lysosomal enzymes can hydrolyze
proteins, fats, polysaccharides, and nucleic acids
Lysosomal enzymes work best in
the acidic environment inside the lysosome
Lysosomes=
digestive
animal cells only.
its a vesicle with digestive enzymes. (package)
Some types of cell can engulf another cell by
phagocytosis; this forms a food vacuole
2 ways lysosomes function
- A lysosome fuses with the food vacuole and digests the molecules
- Lysosomes also use enzymes to recycle the cell’s own organelles and macromolecules, a process called autophagy
- digest food
- recycle used up old orangelles
Vacuoles
plants only
A plant cell or fungal cell may have one or several
vacuoles, derived from endoplasmic reticulum and Golgi apparatus
Food vacuoles are formed by
phagocytosis
Contractile vacuoles,
found in many freshwater protists, pump excess water out of cells.
-vacuoles fill up with water and before they explode, they pump the water out
Central vacuoles,
found in many mature plant cells, hold organic compounds and water
vacuoles look like an
empty spot in a cell
The endomembrane system is a
complex and dynamic player in the cell’s compartmental organization
Proteins destined for secretion are synthesized on the
inside of the endomembrane system.
secreted in the inside, proteins end up outside cell??
Mitochondria
are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP.
Cells make ATP
Chloroplasts,
found in plants and algae, are the sites of photosynthesis
important functionals
Peroxisomes are
oxidative organelles
-moving electrons around in interactions
Mitochondria and chloroplasts are NOT part of
the endomembrane system
Mitochondria and chloroplasts have similarities with bacteria
- Enveloped by a double membrane
- Contain free ribosomes and circular DNA molecules
- Grow and reproduce somewhat independently in cells
- 2 membranes on outside
- has its own DNA and ribosomes
- do what they want when they want. independent.
The Endosymbiont theory
- An early ancestor of eukaryotic cells engulfed a nonphotosynthetic prokaryotic cell, which formed an endosymbiont relationship with its host
- The host cell and endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion
- At least one of these cells may have taken up a photosynthetic prokaryote, becoming the ancestor of cells that contain chloroplasts
(this helps us describe why we have mitochondria and chloroplasts.
Chloroplast function
photosynthesis
mitochondria function
cellular respiration, make ATP
Mitochondria are in nearly all
eukaryotic cells
Mitochondria have a
smooth outer membrane and an inner membrane folded into cristae
(the folds/loopy thing)
The inner membrane creates two compartments:
intermembrane space and mitochondrial matrix
Some metabolic steps of cellular respiration are catalyzed in the
mitochondrial matrix
Cristae present a large surface area for enzymes that
synthesize ATP
anything that is a eukaryote has a
mitochondria.
this is because they all need to make energy
Parts of mitochondria
outer membrane, inner membrane, intermembrane space, cristae, matrix, DNA, ribosomes
Chloroplasts contain the green pigment
chlorophyll, as well as enzymes and other molecules that function in photosynthesis
Chloroplasts are found in
leaves and other green organs of plants and in algae
Chloroplast structure includes
- Thylakoids, membranous sacs, stacked to form a granum. (a single membrane sac)
- Stroma, the internal fluid (the dense goopy stuff)
granum- a bunch of thylakoids together
The chloroplast is one of a group of plant organelles, called
plastids
DNA and ribosomes are in the
stroma in the chloroplast
Parts of Chloroplast
outer membrane, inner membrane, intermembrane space, thylakoid, granum, stroma, DNA, ribosomes
Peroxisomes are
specialized metabolic compartments bounded by a single membrane
(a sac with hydrogen peroxide in it surrounded by a single membrane
Peroxisomes produce
hydrogen peroxide and convert it to water
-Oxygen is used to break down different types of molecules (oxidation)
Peroxisomes perform reactions with
many different functions
How peroxisomes are related to other organelles is
still unknown
-They do not bud off the endomembrane system
The cytoskeleton is a
network of fibers extending throughout the cytoplasm
(a series of tubes, lines, and building blocks that help a cell retain its shape
The cytoskeleton organizes the cell’s
structures and activities, anchoring many organelles
The cytoskeleton helps to
support the cell and maintain its shape
The cytoskeleton interacts with
motor proteins to produce motility
Inside the cell, vesicles can travel along
“monorails” provided by the cytoskeleton
Recent evidence suggests that the cytoskeleton may
help regulate biochemical activities
roles of the cytoskeleton
support and motility
Three main types of fibers make up the cytoskeleton
microtubules
microfilaments
intermediate filaments
Microtubules
, are the thickest of the three components of the cytoskeleton
(big)
Microfilaments
, also called actin filaments, are the thinnest components
small
termediate filaments
are fibers with diameters in a middle range
medium
Microtubules functions
- Shaping the cell
- Guiding movement of organelles
- Separating chromosomes during cell division
Centrosomes
Centrioles
Cilia/Flagella
In many cells, microtubules grow out from a
centrosome near the nucleus
The centrosome is a
“microtubule-organizing center”
In animal cells, the centrosome has a pair of
centrioles, each with nine triplets of microtubules arranged in a ring
plants don’t have
centrioles
centrioles are made of
microtubules.
they have a 3/9 pattern which creates the centriole
Microtubules control the
beating of cilia and flagella, locomotor appendages of some cells
Cilia and flagella share a common structure
- A core of microtubules sheathed by the plasma membrane
- A basal body that anchors the cilium or flagellum
- A motor protein called dynein, which drives the bending movements of a cilium or flagellum (the back and forth flapping movement)
basal body looks identical to centriole structure, but
they have different functions
cilia/flagella have a
2/9/2 pattern
How dynein “walking” moves flagella and cilia
- Dynein arms alternately grab, move, and release the outer microtubules
- Protein cross-links limit sliding
- Forces exerted by dynein arms cause doublets to curve, bending the cilium or flagellum
motor proteins interact with
microtubules to get movement of cilia and flagella
Microfilaments (Actin Filaments) are
solid rods
The structural role of microfilaments is
to bear tension, resisting pulling forces within the cell
Microfilaments
form a 3-D network called the cortex just inside the plasma membrane to help support the cell’s shape
Microfilaments that function in cellular motility contain the protein
myosin in addition to actin
microfilaments are how are
muscles move.
Microfilaments interaction with anysoin, 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
Localized contraction brought about by actin and myosin also drives
amoeboid movement
Pseudopodia (cellular extensions) extend and
contract through the reversible assembly and contraction of actin subunits into microfilaments
Cytoplasmic streaming 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
Intermediate filaments support
cell shape and fix organelles in place
Intermediate filaments are more
permanent cytoskeleton fixtures than the other two classes
-stable
Most cells synthesize and
secrete materials that are external to the plasma membrane
These extracellular structures include
- Cell walls of plants
- The extra cellular matrix (ECM) of animal cells (plants dont have)
- Intercellular junctions (how 2 cells join and communicate)
These structures help provide connections between adjacent cells, determine cell shape, and transmit information
-important- we need all of this!
The cell wall is
an extracellular structure that distinguishes plant cells from animal cells
Prokaryotes, fungi, and some protists also have
cell walls.
(but made of different things)
fungi cell wall- chitin
plant cell wall- cellulose
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
Plant cell walls may have multiple layers
primary cell wall
middle lamella
secondary cell wall
plasmodesmata
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
Plasmodesmata are
channels between adjacent plant cells
how they talk to eachother
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
ECM proteins bind to
receptor proteins in the plasma membrane called integrins
Functions of the extracellular matrix (ECM)
- Support
- Adhesion
- Movement
- Regulation
Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact
Intercellular junctions facilitate this contact
There are several types of intercellular junctions
Plasmodesmata -found in plant cells only
Tight junctions -found in animal cells only
Desmosomes -found in animal cells only
Gap junctions -found in animal cells only
Plasmodesmata are
channels that perforate plant cell walls
Through plasmodesmata,
water and small solutes (and sometimes proteins and RNA) can pass from cell to cell
At tight junctions,
membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid
tight junctions
pressed together tightly so there is no gap
Desmosomes (anchoring junctions) fasten cells together into
strong sheets
Gap junctions (communicating junctions) provide cytoplasmic channels between
adjacent cells
gap junctions
tubes between cells that allow things to get from one to another
desmosomes
one cell is anchored and allows everything to act as a unit instead of individual cells
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
The Cell:
A Living Unit Greater Than the Sum of Its Parts
