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85 terms

MCDB 1A

STUDY
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Cell Size
limited by diffusion
Surface to Volume Ratio
Must be high enough to sustain life's processes
Diversity of Life is due to:
Evolution by Natural Selection: Adaptations- structural, physiological or behavioral traits that enhance an organisms ability of survival and reporduction
Three Domains of Living Organisms:
Bacteria, Archaea and Eukaryotes
Unicellular
single cell structures, small, have limited functions and must remain small due to limited functions.
Multi cellular
can attain large size, can adopt many shapes and has greater functional capabilities
Prokaryotic cells
NO nucleus. Small mostly bacteria with many different shapes. ALWAYS unicellular
Prokaryotic Components
Nucleoid, Ribosomes, Cell Walls, Fagella
Nucleoid
Dark Region in the cell containing DNA and protein (bacterial DNA is one long circular plasmid), not membrane bound
Ribosomes
Protein synthesis, free in cytoplasm/ cytocol process is called translation
Cell Walls
outside the plasma membrane ex. peptidoglycan
Flagella
Complex protein structure used for swimming
Eukaryotic cells
Contain membrane bound organelles. Ex: plant, animal, fungi
1) Nucleus
-contains DNA wound on histone proteins, condensing forming chromosomes
-site of DNA replication, transcription and mRNA processing
-Nucleolus- dark region in nucleus, site of fRNA synth and ribosome assembly
- nuclear Envelope: double membrane surrounding nucleus, continuous with the ER
- nuclear pore: complex structure with many protein, highly regulates what goes in and out of nucleus
2) Ribosome
- site of protein synthesis (translation)
- may be free in cytoplasm or embedded in the Rough Endoplasmic Reticulum (RER)
3) Mitochondria
- site of cellular respiration (breakdown of glucose for ATP)
- double membrane
- inner membrane= electron transport chain with proton pump
- matrix= site of citric acid cycle, DNA, ribosomes
- outer membrane= forms the intermembrane space for the proton gradient
4) Plastid: plants and protists
a) Chloropast
- site of photosynthesis, harvest light energy into glucose
- double membrane w/thylakoids, grana( stack of circular disks) , stroma ( the individual stacks)
b) Peroxisomes: detoxifying organelle, collects toxins like hydrogen peroxide
c) Glyoxysomes: plants only, converts lipids to carbohydrates
5) Vacuoles: Plants and protists
- large membrane bound, filled with water, waste, toxic compounds, anthocyanains, enzymes
- responsible for the turgor pressure of plant cells (makes plant cells crisp/full of water)
6) Lysosomes
(bud from the golgi)
- contain digestive enzymes to break down large molecules, may fuse with phagosome to become a secondary lysosome where food particles are digested
7) Rough endoplasmic reticulum (RER)
- flattened membrane channels, embedded with ribosomes, proteins translated here enter the lumen (inside) of the ER for further processing
8) Smooth endoplasmic reticulum
- flattened membrane channels, lipid synthesis, breakdown(hydrolysis) of glycogen, modification of small molecules like drugs and pesticides.
9) Golgi apparatus
- recieves, modifies, sorts and sends out proteins bound in vesicles
-:cis" closest to ER and recieves proteins in vesicles
- "trans" furthest from er an sends vesicles to plasma membrane.
Cell Membranes
...
Fluid Mosaic model
lipid bilayer: composed of cholesterol, proteins (integral/peripheral) forms by self assembly.
Transport Across membranes
Simple diffusion: small, uncharged molecule, non polar pass through membrane, no ATP or proteins needed
Ex: osmosis
Facilitated diffusion
no ATP (passive) polar molecules can pass through channel (proteins example) ion channel, gated, wopen when stimulated by a ligand or voltage
Active Transport
Move against concentration gradient, requires energy
(uniport, symports, antiports)
1) primary active trasport- uses ATP directly to move molecules (sodium- potassium pump)
2) secondary active trasnport: uses concentration gradient of ion (usually from primary active transport)
Large/ Multiple Molecules
too large to diffuse or fit through proteins so they form whole vesicles
( endocytosis vs exocytosis)
CEll Junctions
adherence or communication between cells
Tight junctions
seal cells and prevents substance from moving between cells
desmosomes
provide mechanical support
gap junctions
facilitate communication and transport between adjoining cells
Cytoskeleton
creates shape and structure for cell and provides movement
Microfilaments
1) cellular movement/shape
2) protein : actin- plus and minus ends. rapidly grow and shorten
intermediate filaments
made of fibrous proteins(keratin) stabilize structure
microtubules
a) rigid internal skeleton for cells
b) protein: tubulin, plus and minus ends
c)unique 9+2 arrangment creates cilla, flagella and basal bodies
Chromosomes/thecellcycle/cell division
Key terms: cytokinesis, binary fission, chromatin, chromosome, chromatid, centromere, cohesion, histone, nucleosome, nuclear envelope, kinetochore, centrioles, centrosome, spindle poles, spindle microtubules, cleavage furrow, contractile ring, cell plate, crossing over, non disjunction, polyploid, aneuploidy.
cytokinesis
the process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells. Occurs in the late stages of mitosis. and sometimes in meiosis
Binary fission
(Prokaryotes) two separate cells are produced. asexual reproduction. All cells produced are genetically identical. DNA is replicated and then attached to different parts of cell membrane
Chromatin
the combination of DNA and proteins that make up the contents of the nucleus of a cell. Primary Functions: package DNA into a small volume to fit in cell, strengthen DNA to allow itosis and meiosis and prevent DNA damage. Controls gene expression and DNA replication. ONLY found in eukaryotes.
chromosome
an organized structure of DNA and protein found in cells. Coiled DNA containing genes, regulatory elements and nucelotide sequences.
chromatid
one of the two copies of DNA making up a duplicated chromosome which are joined at their centromeres for the process of cell division.
centromere
the part of a chromsome that links sister chromatids During mitosis spindle fibers attach to the centromere vis the kinetochore. Main role: to act as the site of assembly of the kinetochore.
cohesin
a protein complex that regulates the separation of sister chromatids during cell division.
histone
highly alkaline proteins found in eukaryotic cell nuclei. Function: package and order the DNA into structural units called nucleosomes.
nucleosome
the basic unit of DNA packaging in eukaryotes consisting of a segment of DNA would in sequence around eight histone protein cores. The DNA acts like a thread on a spool. Keeps the DNA compacted in the nucleus.
nuclear envelope
double lipid bilayer that encloses the genetic material in eukaryotic cells. Serves as the physical barrier sperating the contents of the nucleus from the cytoplasm. Contain nuclear pore which facilitate and regulate the exchange of materials (Proteins and RNA) between the nucleus and the cytoplasm
kinetochore
protein structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart.
centrioles
cylindrically shapred cell structure, composed of nine triplets of microtubules. Functions: involved in organization of the mitotic spindle and in completion of cytokinesis. Important part of centrosomes. play a crucial role in the spatial arrangement of a cell
centrosome
an organelle that serves as the main microtubule organizing center. (MTOC) of an animal cell. Also a regulator of cell cycle progression.
spindle poles
subcellular structure that segregates chromosomes between daughter cells during cell division. composed mainly of microtubules. Microtubules attach to chromosomes through kinetochores. two poles form on either end of the nucleus
spindle microtubules
the microtubules that reach out and pull the chromsomes to either pole
cleavage furrow
the indentation of the cell's surface that begins the progession of cleavage. This leads to cytokinesis and the final splitting of the membrane between the two daughter cells.
contractile ring
made of myosin II and actin filaments, constricts the cell membrane to form the cleavage furrow. Mechanical agent of cytokinesis. Is necessary to force the split between the daughter cells
cell plate
Involves the delivery of golgi derived and endosomal vesicles carrying cell wall and cell membrane components to the plane of cell division. Forms the cell wall betweeen the two daughter cells following cell division
crossing over
the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes. Occurs during prophase 1 in meiosis in a process called synapsis. Results in new combinations of genes that are genetically diverse
non disjunction
In mitosis: the failure of sister chromatids to separate during and after mitosis

In meiosis: the failure of homologous chromosomes to segregate or to seprate during and after meiosis
polyploid
a cell having more than twice the haploid number of chromosome. containing more than two paired sets of chromosomes. refers to a numerical change in the whole set of chromosomes
aneuploidy
an abnormal number of chromosomes. Having an extra or missing chromosome. Causes birth defects including down's syndrome. Refers to a numerical change in part of the chromosome set
The cell cycle
involves many repitions of cellular growth and reproduction.
Interphase
made up of three distinctive parts: the G1 phase, the S Phase and the G2 Phase
G1 Phase
follows mitosis and is the period in which the cell is synthesizing its structural proteins and enzymes to perform its functions.
S phase
DNA within the nucleus replicate. Each chromosome is copied so by th end of the S phase two DNA molecules exist for each one
G2 Phase
The cell prepares for Mitosis. Proteins organize themselves to form a series of fibers called the spindle which helps chromosome movement.
Mitosis
Occurs in somatic (non sex) cells. chromosome numbers stay the same. Both are diploid.
Prophase
DNA condenses so sister chromatids are visible, mitotic spindle begins to form
prometaphase
nuclear envelope disappaears, chromosomes (sister chromatids) begin to line up vertically
metaphase
sister chromatids aligned at equatorial plate
Anaphase
sister chromatids separate to opposite poles
telophase
spindle breaks down, chromosomes uncoil, nuclear envelope reforms; resulting in two daughter nuclei
Meiosis
Sex cells, chromosomes number reduced by half 2n-> n to make haploid cells ( for gametes) each parent contributes a gamete
IMPORTANT diff between mitosis and meiosis
Anaphase 1: homologous pairs separate to create haploid cells ( sister chromatids are still attached)
Prophase1: synapsis and crossing over occur to create genetic diversity in gametes
Mitosis results in two genetically identical diploid cells (2n)
Meiosis results in: four genetically varied haploid cells (n)
Gametogenesis
production of gametes
Oogenesis
egg/ova formation. Germ cells undergo mitosis to create primary oocytes(2n)
- primary oocytes undergoes meiosis 1 to create the secondary oocyte(n) and the first polar body
- secondary oocyte undergoes meiosis II to create ootid which develops into the egg/ova
- all divisions are uneven resulting in three polar bodies which are degraded
Spermatogenesis
- germ cells divide by mitosis to create primary spermatocytes (2n)
- meiosis 1 create two haploid secondary spermatocytes (n)
- Meiosis 2 creates four haploid spermatids (connected by cytoplasmic bridge) these develop into sperm
Cytoplasmic bridges
thin strand of cytoplasm linking cells- developing sperm
zygote
the initial cell formed when two gamate cells are joined by means of sexual reproduction. Earliest developmental stage of the embryo
jelly coat
jelly substance that surrounds the egg
vitelline envelope
membrane outside of the plasma membrane forming a fibrous mat over a sea urchin egg. becomes the fertilization membrane
hermaphorditic
an organism that has reproductive organs associated with both sexes
cumulus cells
a cluster of cells that surround the oocyte both in the ovarian follicle and after ovulation. must be penetrated by the spematozoa in order for fertilization to occur
zona pellucida
the strong membrane that forms around an ovum as it develops in the ovary. the membrane remains in place during the egg's travel through the fallopian tube. In order for a sperm to fertilize an egg the sperm must penetrate the zona. If it is fertilized it diasppears so that the egg can be implanted in the uterus
acrosomal reaction
when a sperm fuses with a plasma membrane and then penetrates the female egg in order to fertilize it. the reaction occures in the acrosome of the sperm as it approaches the egg. In the head of the sperm enzymes are released that break through the eggs membrane allowing the sperm to access the egg.
Fertilization
union of the haploid sperm and haploid egg to create a diploid zygote.
There are four steps to fertilizationg
1) recognition of sperm and egg
2) activation of sperm: either the jelly coat or zona pellucida initiate the acrosomal reaction on the sperm, this helps the sperm reach the egg plasma membrane
3) plasma membrane fuse between the egg and sperm
4) additional sperm are blocked from reaching the egg( fast block is done through cell depolarization and slow block is through cortical granule release
5) activation of egg
6) nuclei fuse