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USC / Biology / BIOL 101 / How does magnification affect the quality of an image?

How does magnification affect the quality of an image?

How does magnification affect the quality of an image?


School: University of South Carolina
Department: Biology
Course: Biological Principles
Professor: Alan white
Term: Fall 2017
Tags: Cell, DNA, tumors, cellcycle, Mitosis, and Meiosis
Cost: 50
Name: Introduction to Biology Second Exam Study Guide
Description: These notes cover chapters 5, 6, 7, & 8 which will all be on our second exam on March 7.
Uploaded: 02/26/2018
14 Pages 146 Views 3 Unlocks

BIO Second Exam Chapters 5, 6, 7, 8  

How does magnification affect the quality of an image?

Chapter 5 – Cell Structure  

∙ Cells and Microscope  

o Unicellular – Bacteria & Archaea  

o Multicellular – Plants & Animals  

∙ Light Microscope

o Visible light passes through a specimen and then  through glass lenses, which magnifies the image  o Quality of an image depends on 3 characteristics  Magnification – ratio of object’s image size to  its real size  

 Resolution – measure of the clarity  

∙ Minimum distance of two distinguishable  


 Contrast – visible differences in parts of the  sample  

o Can magnify up to about 1,000 times  

o Staining specimens with dyes to enhance contrast o Organelles are too small to be seen  

What are examples of membrane-bound organelles?

 Can only be seen by an electron microscope ∙ 4 basic features common to all cells (Prokaryotic &  Eukaryotic)

o Plasma membrane

o DNA  

o Cytoplasm  

o Ribosomes  

∙ Eukaryotic Cells

o Nucleus which contains most of the DNA  

o Other membrane-bound organelles  

 Mitochondria, Golgi bodies, and Endoplasmic  reticulum  

o Examples: Protists, Fungi, Animals, and Plants

∙ Prokaryotic Cells  

o Lack a nucleus  

o DNA in an unbound region called nucleoid  Don't forget about the age old question of How does history threats affect internal validity?

o No membrane-bound organelles  

What are the two forms of endoplasmic reticulum?

o Examples: Bacteria & Archaea  

∙ Nucleus  

o Contains most of the DNA  

o Enclosed by a nuclear envelope  

 Separates it from the cytoplasm  

 Double membrane  

∙ Each membrane consists of a lipid bilayer 

o DNA and proteins form genetic material called  chromatin  

 Condenses to form chromosomes during cell  division  

∙ Ribosomes

o Particles made of ribosomal RNA and protein  o Carry out protein synthesis in two locations If you want to learn more check out What kind of process is vertical sorting?

 Cytosol (free ribosomes)

 On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)

∙ The Endoplasmic Reticulum  

o 2 different forms  

 Rough ER – rough surface because of  

ribosomes studded on its surface  

∙ Makes proteins 

 Smooth ER – smooth surface due to lack of  


∙ Synthesizing lipids

∙ Detoxifying poison  

∙ Metabolizing Carbohydrates  

∙ Storing Calcium  


∙ Golgi Apparatus  

o Processing and packaging of the molecules that  were made in the ER, takes place Don't forget about the age old question of What are the 7 types of crimes?

o Modifying products of the ER  

o Making certain macromolecules  

o Sorting & packaging materials into transport  vesicles  

∙ Vacuoles

o Central vacuole

 Biggest organelle found inside the cells of  

mature plants  

∙ 80% of the volume

 Storage of water & Organic compounds

 A compartment for waste disposal  We also discuss several other topics like What is the purpose of psychological testing?

 Pigments to attract pollinators  

 Toxins to deter Herbivores  

∙ Plasma Membrane  

o Allows passage of oxygen & nutrients into the cell  and of waste material out of the cell

o Only a selective few can pass through

o Double layer of phospholipids

∙ Mitochondria  

o Where respiration takes place

o Smooth outer membrane

o Inner membrane folded into cristae 

 Ridges that present a large surface area for  enzymes that synthesize ATP  

∙ Serves as an energy molecule 

∙ Has the potential to react with water and  

release energy stored in it’s bonds  


∙ Chloroplast  

o Sites of photosynthesis 

o Contain green pigment – chlorophyll  

o Found in leaves and other green organs of plants  and in algae  

o 3 important components  

 Thylakoids

∙ Membranous sacs

 Granum

∙ Stacked up thylakoids

 Stroma  

∙ Fluid inside chloroplast

∙ Cytoskeleton  If you want to learn more check out What does the constitution of the united states say?

o Network of fibers found in cytoplasm 

 Microtubules  

∙ Thickest of the three

 Microfilaments

∙ Thinnest components  

 Intermediate Filaments We also discuss several other topics like What do lysosomes contain?

∙ Fibers in a middle range  

o Support & maintenance of cell shape

o Anchoring organelles

o Helping chromosome movement during cell division o Cell motility (locomotion via structures like cilia &  flagella)

∙ Extracellular Structures

o Cell walls of plants

o The extracellular matrix (ECM) of animal cells o Intercellular junctions, in both plants and animals o The structures found outside the cells serve various  functions such as

 Protection

 Communication between cells

 Transport of substances in and out of cell  


∙ Cell walls of plants

o Found in plants  

o Absent in animal cells

o Protects the plant cell

o Maintains shape  

o Prevents excessive uptake of water  

o Made of cellulose fibers embedded in other  

polysaccharides and protein  

∙ ECM  

o Made of glycoproteins (Carbs and proteins)  

o Support the cells structure  

o Cell to Cell adhesion

o Movement of substances across cell

o Regulate intercellular communication

∙ Intercellular Junctions

o Tight junctions – formed from cells pressing  


 Prevents leakage of extracellular fluid

 Found in the stomach lining to prevent the  

stomach acid from seeping into the stomach  

o Desmosomes – Fasten cells together by interlocking  joints 

 Found in skin to resist tear and strain  

o Gap junctions – Communication channels in an  animals cell for the movement of water and solutes  between adjacent cells

o Plasmodesmata – Communication channels in plant  cells for movement of water and solutes between  adjacent cells

Chapter 6 – Structure & Function of DNA  

∙ DNA – Nucleic Acid  

o Deoxyribonucleic acid (DNA)

o Ribonucleic Acid (RNA)  


∙ DNA directs synthesis of messenger RNA (mRNA) and,  through mRNA, controls protein synthesis  

∙ Protein synthesis occurs in ribosomes  

∙ DNA is located in the Nucleus and double helix  ∙ Nucleic acids are polymers called polynucleotides  o Made of monomers called nucleotides

 Consists of a Nitrogenous base, A pentose  

sugar, A phosphate group  

∙ 5 Nitrogenous Bases

o Adenine (A) – Found in both DNA & RNA  

o Guanine (G) – Found in both DNA & RNA  

o Cytosine ( C ) – Found in both DNA & RNA  

o Thymine (T) – Found only in DNA 

o Uracil (U) – Found only in RNA 

∙ 2 Sugars

o Deoxyribose : only DNA

o Ribose : only RNA  

∙ Phosphate group: Po4 – Both DNA and RNA  ∙ AT, TA, GC, CG  

∙ RNA single strand 

o A, U, G & C

∙ DNA to RNA to Protein  

∙ Gene expression : process by which DNA makes mRNA  (by transcription) and mRNA makes Protein (by  translation)  

∙ Sequence of bases along a DNA or mRNA polymer is  unique for each gene  

∙ RNA is the intermediate between DNA and the proteins  for which they code  

∙ Transcription  

o RNA synthesis is catalyzed by RNA (an enzyme)  o RNA follows base-pairing rules  

o DNA that is transcribed called transcription unit  o RNA is close cousin of DNA  


∙ 3 stages of Transcription

o Initiation – RNA polymerase bind to a promoter  region on DNA & initiate the process of transcription o Elongation – Transcription progresses by following  the base pairing rule  

o Termination – The process of transcription stops when the Polymerase reaches the end of  

Transcription unit  

∙ Codons = mRNA triplets after Transcription  

o The flow of information from DNA to protein is  based on an intermediate mRNA triplet code called  CODON 

o Codon : an mRNA base triplet formed after  

transcription of DNA (AAG, UAA, AGU)  

o Total of 64 codons  

 61 of these code for an amino acid 

∙ 1 (AUG) is a START Codon – required to  

start the translation process

 Other 3 (UAA, UAG, UGA) stop codons do not  code for an amino acid  

o During translation, these mRNA base triplets are  read by Ribosomes  

o Each codon specifies the addition of one of 20  amino acids  

∙ 3 stages of Translation  

o Initiation – begins at start codon AUG 

o Elongation – During the elongation stage, each  codon read by Ribosome bring in an Amino acid o Termination – Termination occurs when a stop codon in the mRNA reaches the ribosome 


Chapter 7 – Cell Cycle & Tumors  

∙ Cell Cycle  

o Eukaryotic cell cycle consists of 2 cycles 

 Interphase: cell growth & replication phase  ∙ 3 sub phases: G1 phase, S phase, G2  


∙ S phase – Synthesis/replication of DNA  

 Mitotic (M) phase: cell division phase  

∙ 2 sub phases

o Mitosis & cytokinesis  

∙ Cell cycle control system  

o Regulated by both internal and external signals   Act upon specific checkpoints in the cell cycle   Determined whether or not a cell is to go  

ahead into its next phase  

∙ Checkpoints  

o G1, G2, & M  

o G1 is most important  

o If cell receives a “go-ahead” signal it continues to  the S phase and undergoes replication (synthesis)  of DNA  

o If it does not receive a “go-ahead” it will exit the  cycle and go into a nondividing (quiescent) state  called the G0 phase

∙ Internal signals

o Cyclin-CDK complexes act as an internal signal to  the cell  

o Makes the cell go into its next phase  

o If Cyclin-CDK does not form the cell does not go  onto next phase 

∙ External signals

o Growth factors


 Stimulates the cells to grow  

 Signals them to go to the next phase and  

eventually die  

o Density-dependent inhibition  

 Absence of density signals the cell to continue  dividing  

 When enough density is reached because of  overcrowding, the cells pick up the signal and  

stop dividing  

o Anchorage Dependence  

 Cells need to have an Anchor 

∙ Medium or surface on which cells attach in

order to grow

 Such substratum provides an attachment  

ground for cells to grow and divide  

 Absence of anchor (substratum) prevents cell  growth and division from taking place  

∙ Loss of Cell Cycle Control System  

o Cell fails to arrest itself even when signals suggest it to do so 

o Cell continues to go through the phases & continues to grow & divide even if its receiving a stop signal  Bad affects on the cells which affects the  

tissues & organs and eventually the entire  


o Cancer cells  

 Do not exhibit any density-dependent inhibition  Continue to grow and divide even when they  are overcrowded and tightly packed together  

 Do not exhibit any anchorage dependence

 Remain uninhibited even when the growth  

factors are absent  

 Some are highly evolved and complex and  

would not require a supply of growth factors  


from the environment for any number of  


∙ Can make their own growth factors and  

don’t need any from an external source  

∙ They may convey a growth factor’s signal  

without the actual presence of the growth  


∙ They may have cell cycle control system  

which eliminates the need for a signal  

from the growth factor  

∙ Loss of Cell Cycle Controls in Cancer Cells  

o Transformation – normal cell converted to a  

cancerous cell  

o Cancer cells form masses of abnormal cells called  tumors 

o Benign tumor – abnormal cells remain at the  original site, the lump  

o Malignant tumor – if the abnormal cells leave the  original site & start invading surrounding tissues  ∙ Metastasis of the Tumor  

o If malignant tumor continues to grow it will spread  to the rest of the body by using either blood or  lymph as a medium  

 Metastasis of the tumor  

∙ It will form secondary tumors at these new


Refer to the textbook for pictures of the examples of the  growth and metastasis of a tumor, lung cancer, colon cancer,  and breast cancer 

Chapter 8 – Mitosis & Meiosis  


∙ Cell division: the continuity of life is based on the  reproduction of cells

o Nucleus division + Cytoplasm division  

o Nucleus division: Mitosis or Meiosis

o Cytoplasm division: Cytokinesis  

∙ Genome: all the DNA in a cell  

∙ Chromatin: DNA molecules in a cell packed with proteins o During cell division, chromatin comes together and  condenses into Chromosomes 

 Every eukaryotic species has a unique number of chromosomes in their cell (humans = 46)  

∙ Diploid cell (2n) – 2 sets of chromosomes  

o Humans – 2n=46  

∙ Gamete: sperm or egg 

o Contains a single set of chromosomes (haploid – n)  Humans haploid number (n) = 23  

∙ 4 cells to know in regards to Cell Division

o Somatic cells: all body cells except Gametes and  Germ Cells 

 Diploid cells  

o Germ Cells: diploid cells found ONLY in GONADS (Testis & Ovary)  

o Gametes: Reproductive cells  

 Haploid (sperm, egg)  

o Zygote: Diploid cells formed from fertilization of  Sperm & egg 

∙ Homologous chromosomes: two chromosomes in each  pair  

o Each pair includes one chromosome from each  parent 

o Similar (same length and carry genes controlling  the same inherited characters)  

∙ Sister Chromatids: identical chromosomes (carbon copy) 11

∙ Mitosis: cell division that produces identical daughter  cells 

o Happen in Somatic cells (46) and gives rise to  somatic cells 

o 5 phases

 Before prophase the DNA & Protein exist as  Chromatin  

 Prophase: chromosomes first become visible  ∙ Chromatin condenses into tightly packed  

structures (Chromosomes)  

 Metaphase: chromosomes are all lined up in  the middle 

 Anaphase: sister chromatids separate & move  toward opposite ends of the cell  

 Telophase: genetically identical daughter  

nuclei are at opposite ends of the cell &  

nuclear division is complete  

∙ Cytokinesis is underway by late telophase

∙ Meiosis: produces unique cells called gamete (sperm or  egg)  

o Happens in Germ cells(46) and gives rise to  Reproductive cells (sperm or egg, 23)  

o 2 sets of cell divisions  

 Result in 4 daughter cells 

∙ Have only half as many chromosomes as  

the parent cell  

o Meiosis 1  

 Prophase 1  

∙ Crossing over takes place – exchanges  

DNA between homologous Chromosomes  

& contributes to Genetic variation  

 Metaphase 1  


 Anaphase 1  

 Telophase 1 – the first nuclear division is  


o Meiosis 2  

 Go through the same steps  

 Anaphase – the non identical sister chromatids separate & move toward opposite ends of cell

 Telophase 2 – 2nd nuclear division is complete  o Each daughter cell is genetically distinct from the  others and from the parent cell  

o Responsible for most of the genetic variation &  occurs by two mechanisms

 Independent assortment of chromosomes  

∙ Each pair of chromosomes assorts itself  

independent of the other pairs  

∙ The number of possible combinations  

when chromosomes assort independently  

is 2n where n is the haploid number  

 Crossing over

∙ Produces Recombinant chromosomes –  

combine genes inherited from each  


∙ Genetic variation by combining DNA from  

two parents into a single chromosome 

∙ Fertilization: union of gametes  

o Egg is called a zygote – has 1 set of chromosomes from each parent  

 Produces somatic cells by Mitosis and develops into an adult  

 At sexual maturity, the ovaries and testes start to undergo Meiosis to produce haploid  


∙ Gametes are produced by Meiosis  


o Results in one set of chromosomes in

each gamete  


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