Chapter 6 - A Tour of the Cell Flashcards
The cell is the…
simplest collection of matter that can be alive
Cells are an organism’s basic units of…
structure and function
Light Microscope
visible light is passed through the specimen and then through the glass lenses
Magnification
the ratio of an objects image size to its real size
Resolution
a measure of image clarity, it is the minimum distance two points can be separated and still be distinguished as separate points
Electron microscope
focuses a beam of electrons through the specimen or onto its surface
Scanning electron microscopes
useful for studying the topography of a specimen
Transmission electron microscopes
used to study the internal structure of cells
Biochemistry
the study of chemical processes of cells
Cell fractionation
technique that takes cells apart and separates major organelles and other subcellular structures from one another
- centrifuge spins test tubes holding mixtures of disrupted cells
- the resulting forces cause a fraction of the cell components to settle to the bottom of the tube, forming a pellet
Cytosol
semifluid substance within the membrane of a cell
Plasma membrane
functions as a selective barrir that allows passage of enough oxygen, nutrients, and wastes to service the entire cell
As a cell increases in size…
its volume increases faster than its surface area
A eukaryotic cells has extensive and elaborate,,,
internal membranes. Each type of membrane has a unique combination of lipids and proteins for its specific functions
Nucleus
contains most of the genes in a Eukaryotic cell
Nuclear envelope
double membrane that separates the nucleus from the cytoplasm, perforated by pores
Nuclear lamina
a netlike array of protein filaments that maintains the shape of the nucleus
DNA and associated proteins are organized into…
chromosomes
Each chromosome contains…
one long DNA molecule associated with many proteins, called chromatin
Nucleolus
region of densely stained fibers inside the nucleus
-rRNA is synthesized and assembled with proteins to from ribosomal subunits
The nucleus directs protein synthesis by…
synthesizing mRNA according to instructions provided by the DNA
Ribosomes
containing rRNA and proteins carry out protein synthesis
Free ribosomes
synthesize proteins that function within the cytosol
Bound ribosomes
are attached to the outside of the endoplasmic reticulum or the nuclear envelope
-synthesize proteins that are destined for insertion into membranes, for packaging within certain organelles such as lysosomes or for export from the cell
Endomembrane system
includes the nuclear envelope, ER, golgi apparatus, lysosomes, various kinds of vesicles and vacuoles, and the plasma membrane
Tasks of the endomembrane system
synthesis of proteins, transport of proteins into membranes and organelles orout of the cell, metabolism and movement of lipids, and detoxification of poisons
Endoplasmic reticulum
includes a network of membranous tubules and sacs called cisternae that separate the internal compartment of the ER from the cytosol
Smooth ER
rich in enzymes, synthesis of lipids, metabolation of carbs, detoxification, and storage of calcium ions
Rough ER
especially abundant in cells that secrete proteins that are produced by ribosomes attached to rough ER
MEMBRANE FACTORY FOR THE CELL
Most secretory polypeptides are…
glycoproteins
Golgi apparatus
center of receiving, sorting, shipping, and manufacturing
-consists of flattened membranous sacs- cisternae
Cis face (golgi)
receives material
Trans face
where golgi products that are secreted depart from
Lysosome
membranous sac of hydrolytic enzymes that many eukaryotic cells use to digest macromolecules
- some lysosomes arise by budding from trans face of the golgi
- carry out intracellular digestion
Lysosomes play a role in autophagy…
recylcing the cell’s organelles and macromolecules
Food vacuoles
formed by phagocytosis and fuse with lysosomes
Contractile vacuoles
found in freshwater potists, pump excess water out of the cell
Tonoplast
membrane surrounding the vacuolein plant cells
In plants and fungi, vacuolues carry out…
enzymatic hydrolysis, like animal lysosomes do
Mitochondria
are the sites of cellular respiration
- have a smooth outer membrane and a convoluted inner membrane with infoldings called cristae
- the inner membrane encloses the mitochondrial matrix, a fluid-filled space
Chloroplasts
found in plants and algae, are the sites of photosynthesis
-contain the green pigment chlorophyll
Endosymbiont theory
states that an early ancestor of eukaryotic cells engulfed an oxygen-using non-photosynthetic prokaryotic cell
The number of mitochondria is correlated with…
the cell’s level of aerobic metabolic activity
Stroma
fluid-filled space inside the innermost membrane of a cholorplast. in it floats membranous sacs called thylakoids
Amylopasts
colorless organelles that store starch (amylose)
Chromoplasts
store pigments for fruits/flowers
Peroxisomes
contain enzymes that transfer hydrogen atoms to oxygen, producing hydrogen peroxide as a byproduct
- some use oxygen to break fatty acids down
- contain enzymes that convert H2O2 to water
Cytoskeleton
a network of fibers extending throughout the cytoplasm that provides a mechanical support and maintains the cell’s shape
- provides anchorage for many organelles/enzymes
- plays a major role in cell motility
- made of microtubules, microfilaments, and intermediate filaments*
Motor proteins
bring about movements of cilia and flagella
Microtubules
- thickest
- hollow rods constructed from a globular protein called tubulin
- shape and support the cell
- serve as tracks to guide motor proteins
- in many animal cells, microtubules grow out from a centrosome near the nucleus
Within the centrosome is a pair of centrioles, each with…
nine sets of triplet microtubules arranged in a ring
The cilium or flagellum is anchored in the cell by a…
basal body structurally similar to a centriole
-each outer doublet has pairs of large protruding motor proteins called dyneins
Microfilaments or actin filaments
- thin solid rods
- structural role in the cytoskeleton is to bear tension
- important in cell motility, especially in muscles cells
In plant cells, actin-myosin interactions drive cytoplasmic streaming…
which creates a circular flow of cytoplasm within cells
Intermediate filaments
- larger than microfilaments but smaller than microtubules
- built from a particular molecular subunit belonging to a family of proteins whose members include keratin
- more permanent fixtures of the cytoskeleton
Cell wall
-in plants
extracellular structure of plant cells that distinguishes them from animal cells: protects cell, maintains shape, prevents excessive water intake
-basic design of cell wall consists of cellulose
Primary cell wall
relatively thin and flexible wall secreted by a young plant cell
Middle lamella
- between the primary walls of adjacent cells
- thin layer with sticky polysaccharides called pectins
- glues adjacent cells together
When a plant stops growing…
it strengthens its wall by secreting hardening substances into the primary wall or by adding a secondary cell wall
Extracellular matrix (ECM)
-primary constituents are glycoproteins (especially collagen fibers) embedded in a network of proteoglycans
In many cells, fibronectins in the ECM connect to…
integrins, cell surface receptor proteins that span the membrane and bind on their cytoplasmic side to proteins attached to microfilaments of the cytoskeleton
ECM can…
- regulate cell behavior
- influence the activity of genes
Plant cells are perforated with plasmodesmata…
channels that connect cells, allows cytosol to pass between
Tight junctions
the plasma membranes of neighboring cells are very tightly pressed against each other
Desmosomes (anchoring junctions)
function like rivets, fastening cells together into strong sheets
Gap junctions (communicating junctions)
provide cytoplasmic channels from one cell to an adjacent cell (similar to plasmodesmata in plants)
