Biology lecture Flashcards
(27 cards)
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 or into a camera
3 imp. Parameters in microscopy
Magnification- ratio of an objects image size to its real size .
Resolution- a measure of the clarity of the image ; it is the minimum distance two points can be separated and still be distinguished as separate points.
Contrast- the difference in brightness between the light and dark areas of an image this includes staining or labeling cell components to stand out visually.
Electron microscope (EM)
Focused a beam of electrons through the specimen or onto its surface .
Resolution - inversely related to the wavelenght of the light (or electrons) a microscope uses for imaging ,and electrons beams have much shorter wavelengths than visible light.
Disadvantage - methods used to prepare the specimen kill the cells.
Scanning electron microscope (SEM)
Useful for detailed study of the topography of a specimen .
The electron beam scans the surface of the sample ,usually coated with a thin film of gold. The beam excites electrons on the surface ,and these secondary electrons are detected by a device that translates the pattern of electrons into an electronic signal sent to a video screen.
The result is an image of the specimens surface that appears 3 dimensional .
Transmission electron microscope (TEM)
Used to study the internal structure of cells .
TEM aims an electron beam through a very thin section of the specimen ,much as light microscope aims light through a sample on a slide.
Specimen has been stained with atoms of heavy metals ,which attach to certain cellular structures ,thus enhancing the electrons density of some parts of the cell more than others.Electrons passing through the specimen are scattered more in the denser regions ,so fewer are transmitted .
Microscopes are the most important tools of CYTOLOGY & BIOCHEMISTRY
Cytology- the study of cell structure.
Biochemistry- the study of the chemical processes (metabolism) of cells.
Cell fractionation
Technique for studying cell structure and function .
Enables researchers to prepare specific cell components in bulk and identify their functions ,a task not usually possible with intact cells.
Prokaryotic cell Ex: of domains and what it is and DNA found ..
Ex: Bacteria and Archaea
DNA concentrated in a region that is not membrane enclosed called the nucleoid
Eukaryotic cell Ex: of domains and what it is and DNA found ..
Ex: Protosts,fungi, animals and plants
DNA is an organelle called the nucleus which is bounded by a double membrane .
Interior of cell is called cytoplasm refers only to the region between the nucleus and plasma membrane .
Within the cytoplasm of a eukaryotic cell suspended in cytosol ,are a variety of organelles of specialized cells form and function.
Nucleus houses most of the cells DNA
. Nucleus-Contains most of the genes .
Ribosomes -use information from the DNA to make proteins
Nucleus envelope- encloses the nucleus separating its contents from the cytoplasm.
Nuclear envelope double membrane. Two membranes each a lipid bilayer with associated proteins .
Intricate protein structure Pore Complex - lines each pore and plays an imp. role in the cell by regulating the entry and exit of proteins and RNA .
Nuclear side of envelope is lined by Nuclear Lamina -a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope.
Within the nucleus ,the DNA is organized into discrete units called Chromosomes ,structures that carry the genetic information.
The complex of DNA and proteins making up chromosomes is called Chromatin.
A prominent structure within the non-dividing nucleus is the NUCLEOLUS which appears through the electron microscope as a mass of densely stained granules and fibers adjoining part of the chromatin
what Ribosomes are?
Two cytoplasmic locales that ribosomes build :
Are complexes made of ribosomal RNA and protein ,are the cellular components that carry out protein synthesis
Two cytoplasmic locales : FREE RIBOSOMES suspended in cytosol while
FREE RIBOSOMES -> most proteins function within the cytosol; ex’s are enzymes that catalyze the first steps of sugar breakdown .
BOUND RIBOSOMES are attached to the outside of the endoplasmic reticulum or nuclear envelope .
BOUND RIBOSOMES ->Make proteins that are destined for insertion into membranes, for packing within certain organelles such as lysosomes,or for export from the cell (secretion).
Endomembrane system
Includes the nuclear envelope,the endoplasmic reticulum ,golfi apparatus ,lysosomes and various kinds of vesicles and vacuoles and the plasma membrane .
Endoplasmic reticulum (ER) Endoplasmic means “within the cell “ Reticulum means “ little net”
what it is
An extensive network of membranes that it accounts for more than half the total membrane in many eukaryotic cells .
The ER. separates the internal compartment of the ER ,called the ER lumen (cavity) or cisternal space from the cytosol.
Smooth ER -outer surface lacks ribosomes
Rough ER- studded with ribosomes on the outer surface of the membrane and thus appears rough through the electron microscope.
Functions :
Smooth ER : functions in diverse metabolic processes,which vary with cell type.
These processes include synthesis of lipids, metabolism of carbohydrates ,detoxification of drugs and poisons ,and storage of calcium ions.
Enzymes of smooth ER are imp in the synthesis of lipids,including oils,steroids ,and new membrane phospholipids .
Other enzymes of the smooth ER help detoxify drugs and poisons ,especially in liver cells .Detoxification usually involves adding hydroxyl groups to drug molecules ,making them more soluble and easier to flush from the body.
Also stores calcium ions .
In muscle cells ,for ex the smooth er membrane pumps calcium ions from the cytosol into the ER lumen.
Rough ER functions : aids in synthesis of secretory and other proteins from bound ribosomes ; adds carbohydrates to proteins to make glycoproteins ; produces new membrane.
Most secretory proteins are GLYCOPROTEINS: proteins with carbohydrates covalently bonded to them .The carbohydrates are attached to the proteins in the ER lumen by enzymes built into the ER membrane.
Golgi apparatus :shipping and receiving center
We can think of the golgi as warehouse for receiving ,sorting ,shipping ,and even some manufacturing .
Products of the ER such as proteins are modified and stored then sent to other destinations.
Consists of flattened membraneous sacs- cisternae- looking like a stack of pita bread .
The two sides of a golgi are cis and trans act as the receiving and shipping departments of golgi apparatus.
Cis= same side ,located near the ER
Transport vesicles move material from the ER to the golgi apparatus .
Trans= opposite side ,gives rise to vesicles that pinch off and travel to other sites.
Products of the endoplasmic reticulum are usually modified during their transit from the cis to the trans region of the golgi apparatus .
Golgi function: modification of proteins ,carbohydrates on proteins and phospholipids ; synthesis of many polysaccharides ; sorting of golgi Products ,which are then released in vesicles.
Lysosome :digestive compartment
What is a lysosome: a membraneous sac of hydrolytic enzymes that many eukaryotic cells use to digest (hydrolyze) macromolecules
Lysosome Function : breakdown of ingested substances ,cell macromolecules ,and damaged organelles for recycling .
Phagocytosis - amoebas and many other unicellular eukaryotes eat by engulfing smaller organisms or food particles.
Autophagy - lysosomes also use their hydrolytic enzymes to recycle the cells own organic mayerial.
Vacuoles def. & variety of functions in diff kinds of cells
Vacuoles are large vesicles derived from the endoplasmic reticulum and golgi apparatus .
Function- digestion ,storage ,waste disposal ,water balance ,plant cell growth and protection.
Food vacuoles - formed by phagocytosis
Contractile vacuoles - pump excess water out of the cell ,thereby maintaining a suitable concentration of ions and molecules inside the cell .
plants - small vacuoles can hold reserves of imp organic compounds such as the proteins stockpiled in the storage cells in seeds.
Central vacuole - mature plant cells contain central vacuole which develops by the coalescence of smaller vacuoles . Plays a major role of growth of plants cells which enlarge as the vacuole absorbs water enabling the cell to become larger with a minimal investment in new cytoplasm.
Mitochondria and chloroplasts change energy from one form to another .
Mitochondria -sites of cellular respiration, the metabolic process that uses oxygen to drive the generation of ATP by extracting energy from sugars ,fats, and other fuels.
Chloroplast found in plants and algae , are the sites of photosynthesis. This process in chloroplasts converts solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from carbon dioxide and water.
Peroxisome
Peroxisome - contains enzymes that transfer hydrogen atoms from certain molecules to oxygen ,producing hydrogen peroxide (H2O2) as a by product ; h2O2 is converted to water by another enzyme.
Similarities btw mitochondria and chloroplasts
Endosymbiont theory -which states that an early ancestor of eukaryotic cells engulfed an oxygen using non photosynthetic prokaryotic cell.
Eventually, the engulfed cell formed a relationship with the host cell in which it was enclosed becoming an endosymbiont (a cell living within another cell) .
Mitochondria: Chemical Energy Conversion
Each of the two membranes enclosing the mitochondrion is a phospholipid bilayer with a unique collection of embedded proteins .
The outer membrane is smooth ,but the inner membrane is convoluted ,with infoldings called CRISTAE.
The inner membrane divides the mitochondrion into two internal compartments.
The first is the inter-membrane space, the narrow region btw the inner and outer membranes. The second compartment ,the MITOCHONDRIAL MATRIX ,is enclosed by the inner membrane. The matrix contains many different enzymes as well as the mitochondrial DNA and ribosomes.
Chloroplasts: Capture of Light Energy
Contain the green pigment chlorophyll .
Inside the chloroplast is another membraneous system in the form of flattened ,interconnected sacs called THYLAKOIDS .
Some regions ,thylakoids are stacked like poke chips ;each stack is called GRANUM,plural GRANA.
Fluid outside the thylakoids is the STROMA ,which contains the chloroplast DNA and ribosomes as well as many enzymes.Membrane of the chloroplast divide the chloroplast space into 3 compartments :
The inter-membrane space ,the stroma, and the thylakoid space.
Chloroplast is a specialized member of a family of closely related plant organelles called PLASTIDS.
1.Type of Plastid
AMYLOPLAST ,colorless organelle that stores starch (amylose) particularly in roots and tubers.
2.Type of Plastid
CHROMOPLAST, which has pigments that give fruits and flowers their orange and yellow hues.
Peroxisomes: Oxidation
Is a specialized metabolic compartment bounded by a single membrane.
Peroxisomes contain enzymes that remove hydrogen atoms from certain molecules, molecules and transfer them to oxygen (O2) producing hydrogen peroxide (H2O2)
Peroxisomes grow larger by incorporating proteins made in the cytosol and ER, as well as lipids made in the ER and within the peroxisome itself.
The cytoskeleton is a network of fibers that organizes structures and activities in the cell . And its role .
Cytoskeleton- a network of fibers extending throughout the cytoplasm.
The cytoskeleton plays a major role in organizing the structures and activities of the cell.
Roles of cytoskeleton: Support & Motility
Give mechanical support to the cell and maintain its shape.
Cytoskeleton provides anchorage for many organelles and even cytosolic enzyme molecules.
Cell motility includes both changes in cell location and more limited movements of cell parts .
CELL MOTILITY- requires the interaction of the cytoskeleton with motor proteins.
Cytoskeleton and motor proteins work together with plasma membrane molecules to allow whole cells to move along fibers outside the cell.
Inside the cell, vesicles and other organalles often use motor protein “feet” to “walk” to their destinations along a track provided by the cytoskeleton.
The cytoskeleton also manipulates the plasma membrane, bending it inward to form food vacuoles or other phagocytic vesicles.
Three types of fibers that make up the cytoskeleton .
Microtubules ,the thickest .
Structure: hollow tubes
Diameter: 25nm with 15nm lumen
Protein subunits : tubulin, a dimer consisting of a-tubulin and B-tubulin.
Main functions: Mantainenance of cell shape; cell motility ; chromosome movements in cell division; organalle movements.
Microfilaments (Actin filaments) ,the thinnest
Structure: 7nm
Protein subunits: Actin
Main functions: Maintenance of cell shape ; changes in cell shape ; muscle contraction ; cytoplasmic streaming (plant cells) ; cell motility ;cell division (animal cells)
Intermediate filaments ,are fibers with diameters in a middle range .
Structure: Fibrous proteins coiled into cables
Diameter: 8-12nm
Protein subunits: One of several different proteins (such as keratins)
Main functions: Maintenance of cell shape; anchorage of nucleus and certain other organelles ; formation of nuclear lamina.
