Chapter 6 - Cells and structures Flashcards
All organisms are…?
all organisms are made of cells
the cell is the simplest collection of matter that can live
Cells are?
the organisms basic units of structure and function
what is the light microscope (LM)?
Visible light is passed through the specimen and then through glass lenses. The lenses refract (bend) the light in such a way that the image of the specimen is magnified as it is projected into the eye, onto photographic film or digital sensor, or onto a video screen
what are the two important parameters in microscopy?
- magnification
2. resolve
what is magnification?
magnification in microscopy is the ratio of an object’s image size to its real size
what is resolution?
resolution is a measure of the clarity of the image; its the minimum distance two points can be separated and still be distinguished as two points
who discovered cells?
Robert Hooke
what is the electron microscope (EM)?
forces a beam of electrons through the specimen or onto its surface
what is cell ultrastructure?
used to refer to a cells anatomy by an electron microscope
what are the two types of electron microscopes (EM)?
- Scanning electron microscope (SEM)
2. Transmission electron microscope (TEM)
what is an SEM microscope?
it is useful for detailed study of the surface if a specimen, it has great depth of field, which results in an image that appears 3D
what is a TEM microscope?
used to study internal ultrastructure of cells, the image is created by the pattern of transmitted electrons . It uses electromagnets as lenses
what is a disadvantage of electron microscopy?
the methods used to prepare the specimen kills the cells , it can also specimen preparation can introduce artifacts, structural features seen in micrographs that do not exist in the living cells
what is cell fractionation?
the goal of cell fractionation is to take cells apart and separate the major organelles from one another
what is a centrifuge?
can spin test tubes holding mixtures of disrupted cells at various speeds to separate them
what is a cystol?
semifluid substance in which organelles are found
what is a prokaryotic cell?
the DNA is concentrated in a region called the nucleoid, nut no membrane separates this region from the rest of the cell
what is the cytoplasm?
the entire region between the nucleus and the plasma membrane
eukaryotic cells are generally?
eukaryotic cells are generally a lot bigger than prokaryotic cells. size is a general aspect of cell structure that relates to function
what is the plasma membrane?
functions as a selective barrier that allows sufficient passage of oxygen, nutrients, and wastes to service the entire volume of the cell
what is the flagellum?
organelle present in some animal cells; composed of membrane enclosed microtubules
what is a centrosome?
regions where the cell’s microtubules are initiated; in an animal cell, contains a pair of centrioles (plant cells don’t have centrioles)
what is the cytoskeleton?
reinforces cell’s shape, functions in cell movement components are made of protein (microfilaments, intermediate filaments, and microtubules)
what is microvilli?
projections that increase the cells surface area
what is peroxisome?
organelle with various specialized metabolic functions; produces hydrogen peroxide
what is the mitochondrion?
organelle where cellular respiration occurs and most ATP is generated
what are lysosomes?
digestive organelle where macromolecules are hydrolyzed
what is the golgi apparatus?
organelle active in synthesis, modification, sorting, and secretion of cell products
what are ribosomes?
non-membranous organelles (small brown dots) that make proteins in cytoplasm or bound to rough ER or nuclear envelope
what is the nucleus?
the nucleus consists of 3 parts
- nuclear envelope
- nucleolus
- chromatin
what is the nuclear envelope?
double membrane enclosing the nucleus; perforated by pores; continuous with ER
what is the nucleolus?
non-membranous organelle involved in production of ribosomes; a nucleus has or more nucleoli
what is chromatin?
material consisting of DNA and proteins; visible as individual chromosomes in a dividing cell
what is a cell wall?
only in plant cells; outer layer that maintains the cells shape and protects cell from mechanical damage; made of cellulose, other polysaccharides and proteins
what is a plasmodesmata?
only in plant cells; channels through cell walls that connect the cytoplasm of adjacent plant cells
what is chloroplast?
only in plant cells; photosynthetic organelle; converts energy of sunlight to chemical energy stored in sugar molecules
what is the nuclear lamina?
a netlike array of protein filaments that maintain the shape of the nucleus by mechanically supporting the nuclear envelope
what are free and bound ribosomes?
free ribosomes: are suspended in the cytosol
bound ribosomes: are attached to the outside of the endoplasmic reticulum or nuclear envelope
what is the endomembrane system?
carries out a variety of tasks in the cell
what are vesicles?
sacs made of membrane
what is the endoplasmic reticulum (ER)?
is such an extensive network of membranes that it accounts for more than half the total membrane in many eukaryotic cells
what are the two distinct regions of the ER?
- The smooth endoplasmic reticulum (SER)
2. The rough endoplasmic reticulum (RER)
what is the smooth endoplasmic reticulum SER?
is named this because its outer surface lacks ribosomes, is responsible for various metabolic processes like the synthesis of lipids, metabolism of carbohydrates, and detoxification of drugs and poisions
what is the rough endoplasmic reticulum RER?
has ribosomes that stud the outer surface of the membrane, many types of specialized cells secrete proteins produced by ribosomes attached to the RER
what are glycoproteins?
proteins that have carbohydrates covalently bonded to them
what are transport vesicles?
vesicles in transit from one part of the cell to another
what is phagocytosis?
engulfing smaller organisms or other food particles
what are contractile vacuoles?
pump excess water out of the cell, thereby maintaining the appropriate concentration of salts and other molecules
what is the central vacuole?
prominent organelle in older plant cells; functions include storage, breakdown of waste products, hydrolysis of macromolecules; enlargement of vacuole is a major mechanism of plant growth
what is the tonoplast?
membrane enclosing the central vacuole
what is the cristae?
The outer membrane of the mitochondria is smooth, but the inner membrane is convoluted, with infoldings called cristae
what is the mitochondrial matrix?
which is enclosed by the inner membrane, contains many different enzymes as well as mitochondrial DNA and ribosomes
what are thylakoids?
inside the chloroplast is another membranous system in the form of flattened, interconnected sacs
thylakoids are stacked like poker chips, each stack is called a GRANUM
- the fluid outside the thylakoid is the STROMA
what is actin?
it is a globular protein
what is myosin?
myosin acts as a motor protein by means of projections that walk along the actin filaments
what are microtubules function?
maintenance of cell shape, cell motility, chromosome movements in cell division
what are microfilaments (actin filaments) function?
changes in cell shape, muscle contraction, cytoplasmic streaming, cell division (cleavage furrow formation)
what are intermediate filaments function?
anchorage of nucleus and certain other organelles, formation of nuclear lamina
what is the primary cell wall?
a young plant cell first secretes a relatively thin and flexible wall
what is the middle lamella?
between primary walls of adjacent cells, a thin layer rich in sticky polysaccharides called pectins
what is the secondary cell wall?
other plant cells add a secondary cell wall between the plasma membrane and the primary cell wall
What is the extracellular matrix of the Animal cells (ECM)?
although animal cells lack walls akin to those of plant cells, they do have an elaborate extracellular matrix
- the main ingredient of the ECM are glycoproteins secreted by the cells
what is collagen?
the most abundant glycoprotein in the ECM, it forms strong fibres outside the cells
