مذكرة مراجعة الأحياء الصف 11 Elite الفصل الثاني

مذكرة مراجعة الأحياء الصف 11 Elite الفصل الثاني

3.5 Metabolism

Not started Study

 Substrates like the end product Of glycolysis (pyruvate) exist continuously affected by changes in cellular and environmental conditions

Degradative reactions Catabolism (break down molecules) must be dynamically balanced with constructive reactions Anabolism

Eg : this breakdown adds to metabolic pool of pyruvate

. Catabolic (breakdown of fat) occur when insufficient carbohydrate present

. When energy needs to be stored as fat } pyruvate is taken from the pool

The dynamic balance of catabolism + anabolism essential to optimal cellular function

 If only anabolism is working we will gain fat

Catabolisrn (break dow•n I respiration)

glucose break down during cellular respiration

Fats

1. Fat (used as energy source)

breakdown to = glycerol + 3fatty acid

2. Glycerol converted to pyruvate }

enter glycolysis

. Fatty acids converted to ( 2 carbon acetyl COA) ) enter the citric acid cycle

. 18 Carbon fatty acid results in ( 9 acetyl COA)

 Sun is the ultimate source of energy for producing carbohydrate in the Chloroplasts

 Ultimate goal of cellular respiration in a mitochondrion is the conversion of carbohydrate energy into that of ATP molecules

I. Energy flows from the sun (through chloroplasts) to carbohydrate

. (Through mitochondria) to ATP rnolecules

 flow of energy maintain biological organization at all levels from molecules to organisms to ultimately the biosphere

 Some energy lost with each Chemical transformation

 Solar energy captured by plants (lost as heat)

All life depends on continual input of solar energy

 aerobic organisms utilize the carbohydrate + oxygen (produced by Chloroplasts) } to generate energy within mitochondria to stay alive

C02 produced by mitochondria retum to chloroplasts } to be used in the manufacture of carbohydrates + producing oxygen (as byproduct) Chloroplasts + mitochondria } are instrumental

 Allow the flow’ Of energy through living organisms Permitting a cycling of chemicals ‘etabolism

. Some cells must die for the organism to take tadpol becomes a frog  the tail as cxcurs

. Freed from one another as a result of

if abnormal cell (could tk:ome cancerous . cell infected with a virus)

Death through apoptosis prevents a tumor from developing and helps limit the spread of viruses

Gl checkpoint

 Bcxiy produce of new red blood cells + skin cells + cells that line your respiratory and digestive tracts

 ensures that the conditions are right for making the commitment to divide } by evaluating growth signals to determining the availability for nutrient + assessing the integrity of DNA Failure ) the cell cycle enter Go or go through

Evaluating growth Signal •

 Signaling molecules (hormones) sent from nearby cells or distant to encourage/ discourage cells from entering the cell cycle

 Signals cause the cell to enter Go or to complete Gl Growth signals cause cyclin dependent kinase (CDK) to add phosphate (P)to RB protein ) major regulator of G I Normal : (CDK is not he Cell Cycle rntøin) bond with

Not normal : ( CDK is present) the Shane Chan 

} nucleosome Nucleosome : each bead joined by DNA

 String is compacted by folding into a zigzag structure } shortening DNA strand

HI appears to mediate coiling process

. The fiber loops back + forth into radial loops

Euchromatin : loosely coiled represents the active chromatin containing genes that are being transcribed

 DNA of euchromatin accessed by RNA polymerase + other factors (needed to promote transcription)

Regulating the level of compaction of DNA is important method of controlling gene expression in the cell

. Heterochromatin : dark stained fiber within the nucleus of the cell represent more highly compacted form of chromosome

Heterochromatin considered inactive chromatin because the genes contained on it are infrequently transcribed

. Protein scaffold helps further condense the chromosome into a form that is characteristic of metaphase chromosomes

Metaphase plate : imaginary plane that is perpendicular it indicates the future axis and passes through this circle Of cell division

Polar spindle fibers : nonattached spindle fibers reach beyond the metaphase plate and overlap

M checkpoint delays the start of anaphase until

Kinetochores of each chromosome are attached to spindle fibers

 Chromosomes are aligned along the metaphase plate

4. Anaphase

• shortest phase Of mitosis

I. 2 sister chromatids separate at the centomere — result with

 daughter chromosomes Daughter chromosomes (with centromere + single chromatid Of a single double helix) pulled to the opposite poles

. spindle fibers disassemble at the region of kinetchores

daughter chromosomes move toward the spindle poles

spindle poles are moving farther apart tEcause the polar spindle fibers are sliding past one another }

Microtubule proteins (as the motor molecules kinesin and dynein) involved in the sliding process ‘Itosis and cytokinesis

Cytokinesis in Plant Cells

 cytokinesis in plant cells involves the building of new cell walls between the daughter cells

 cytokinesis is visible when a small flattened disk appears between the two daughter plant cells

1. Golgi apparatus produces vesicles

. Vesicles move along the microtubules to the region of the disk

. more vesicles arrive and fuse the cell plate become visible

Cell plate : newly formed plasma membrane that expands outward until it reaches the old plasma membrane and fuses with this membrane

. New membrane releases molecules that form the new plant cell wall Cell wall : primary call walls are strengthened but the addition of cellulose fibrils

. The space between the daughter cells becomes filled with middle lamella which stick the primary cell walls together

5.2 Genetic Variation

Not started Study

uses Of meiosis

. Keeping chromosome number constant between generation

. Increase genetic diversity of the population

Genetic Recombination

Crossing over : exchange of genetic material between nonsister chromatids of bivalent during meiosis I

 in human : 2-3 crossovers occur between the nonsister chromatids during meiosis

synapsis : homologues line up side by side and nucleoprotein lattice appears between
them

d. Following meiosis II daughter chromosomes have a new combination Of genetic material due to crossing over (occurred between nonsister chromatids during meiosis l)

. (a) homologues line up Side by Side = nucleoprotein lattice appears between them

nucleoprotein lattice holds the bivalent together (DNA of duplicated chromosomes of each homologue pair iS aligned)

2. crossing over occur

3. nucleoprotein lattice breaks down

. (b) homologues temporarily held together by chiasmata

sing (1) + chiasma(3) regions where the nonsister chromatids are attached

 chiasmata indicate where crossing over has occurred

 exchange of color represents the exchange of genetic material

. exchange of genetic information between the nonsister chromatids

. homologues separate } distributed to different daughter cells

After meiosis II daughter chromosomes have a new combination of genetic material due to crossing over ( occurred between nonsister chromatids during meiosis l)

 the members of a homologous pair can carry slightly different instructions or alleles } for the same genetic traits due to a swapping of genetic material during crossing over ) the chromatids held together by a centromere are no longer identical

 when the Chromatids separate during meiosis II some Of the daughter cells receive daughter chromosomes with recombined alleles

due to genetic recombination the offspring have a different set of alleles and. different genes than their parents } this increases the genetic variation of the Offspring

Independent Assortment of Homologous Chromosomes

 homologous chromosome pairs separate independently I randomly

 Homologous align at metaphase plate (maternal / paternal homologous oriented toward either pole

All possible chromosome orientation for a cell that. contain 3 pairs of homologous chromosomes

 result with 8 combinations of maternal + paternal chromosomes in the resulting gametes } due to independent assortment Of homologous

Significance of Genetic Variation

 human with 23 pair of chromosome = the possible chromosomal combination in gametes 2″23

 the variation that results from meiosis is enhanced by fertilization (union of male +
female gametes)

 The chromosomes donated by the parents are combined (2A23)2 different chromosome combinations in the zygote ) this number shows that no crossing over

 When crossing over occurs it will result with (4A23)2 genetically different zygotes for every couple

Crossing over can occur several times in each chromosome

The staggering amount of genetic variation achieved through meiosis is particularly important to the long term survival of species } because it increases genetic variation within a population

 process of sexual reproduction brings genetic recombinations among members of a population

 Asexual reproduction passes on exactly the same combination Of chromosomes and genes

 Asexual reproduction my be advantageous some offspring may have a better chance Of survival and reproductive success than others