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3.11: End of Chapter Content

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    Image Description

    Figure 3.2: Two cells drawn with openings so the inside organelles can be viewed and labeled. The eukaryotic cell is square shaped with a thick cell membrane around the outside. DNA is inside a circular membrane-enclosed nucleus. Labeled arrows point to different shaped membrane-enclosed organelles and ribosomes (represented by small dots). The prokaryotic cell has a capsule shape and a flagellum (tail). The thick cell wall is labeled, as is the cell membrane underneath it. DNA is loosely coiled in the nucleoid, ribosomes are represented by small dots.

    Figure 3.3: Two cells are depicted with different shaped organelles inside them. The plant cell is square with a thick cellulose cell wall outside the cell membrane. The cytoplasm inside holds many chloroplasts (green ovals), two mitochondrion (brown ovals with wavy lines inside), and a circular nucleus containing loose DNA strands. A large permanent vacuole (empty space) is shown. The animal cell is round, with a thin cell wall. The cytoplasm holds different shaped organelles including a few mitochondria and a circular nucleus containing loose DNA strands.

    Figure 3.4: The phospholipid bilayer is constructed of two sheet-like layers of lipid molecules. The individual lipid molecules have hydrophobic tails and hydrophilic heads. The tail-side of the two sheets form the middle of the bilayer, with the heads forming the outsides of the bilayer.

    Under the bilayer are filaments of the cytoskeleton (drawn as thick wavy lines). Imbedded in the phospholipid bilayer are:

    • Glycoproteins: proteins with carbohydrate attached,
    • Glycolipid: lipid with carbohydrate attached,
    • Peripheral membrane proteins (fit in only one layer),
    • Integral membrane proteins (that extend all the way through the bilayer),
    • Cholesterol (small molecules in only one layer), and
    • Protein channels (hat extend all the way through the bilayer)

    Figure 3.5: A three-dimensional cell is partly opened to expose various labeled organelles. These include:

    • A sphere shaped nucleus containing a smaller sphere shaped nucleolus,
    • Ribosomes depicted as small dots,
    • Rough endoplasmic reticulum shown as long thin membranes outside of the nucleus,
    • Smooth endoplasmic reticulum near the rough ER,
    • Mitochondria shown as small oval organelles with a wavy membrane inside. Some have microtubules (lines) extending from them.
    • Tube like centrioles,
    • Golgi body appearing as a stacked membrane, and
    • Lysosomes appear as small dots outside the nucleus.

    Figure 3.9: The DNA double helix is shown wound around nucleosomes. Each nucleosome is made of clustered spherical histones and the DNA wraps around it twice. The DNA wound around nucleosomes resembles “beads on a string.” Many wrapped and condensed nucleosomes form chromatin fiber, which are further wound into an X-shaped chromosome.

    Figure 3.12: Original (template) DNA extends from an X shaped chromosome, and its two strands are separated at the replication fork by helicase (an enzyme depicted as a triangle). The bottom original template strand has DNA polymerase moving away from the replication fork to create a new lagging strand DNA by adding free nucleotides. On the upper strand of original DNA, DNA polymerase works toward the replication fork, adding free nucleotides to build the leading strand.

    Figure 3.15: This pie chart shows the proportion of time spent in each cell phase. The shortest phases are the mitotic phases (mitosis followed by cytokinesis) which lead to the formation of two daughter cells. This is followed by a long cell growth (G1, interphase), DNA synthesis (S, interphase), and cell growth (G2, interphase), before returning to the mitotic phase.

    Figure 3.17: Image depicts protein synthesis as divided into three phases, and shows the molecules involved at each phase, and that are used to help create the following document. First, in transcription, DNA (double stranded) is used as a template to create pre-mRNA (single stranded). Second, in RNA processing (also called splicing), pre-mRNA is modified to form a shorter mature mRNA. Lastly, in translation, mature mRNA is used as instructions to link together spherical amino acids in a chain, or protein.

    Figure 3.18: The single-stranded structure of RNA is shown with a backbone of sugar-phosphates in a helical shape and nucleobases are shown as rungs on a ladder. On the left side of the figure, the chemical structure of each nucleobase is depicted: cytosine (C), guanine (G), adenine (A), and uracil (U).

    Figure 3.19: A stretch of double stranded DNA is depicted in the process of transcription. The two strands are pulled apart in the middle, the top strand forms the template strand. RNA polymerase (a bubble shaped enzyme) sits on the template strand and adds free nucleotides to a growing RNA transcript. The DNA template strand reads ATGACGGATCAG… and the RNA strand is complementary and contains uracil (U; UACUGCCUAGUC…).

    Figure 3.20: At the top of the diagram, sections of a gene (DNA) are labeled: a promoter region followed by alternating sections of exons (filled in with horizontal lines) and introns (vertical lines). In the middle of the diagram, the pre mRNA transcription contains copies of the alternating exon and intron portions with lines drawn in. The bottom strand (mature mRNA) shows the introns removed and the exons (all horizontal lines) connected.

    Figure 3.21: A roughly circular ribosome sits on a mRNA strand and facilitates the transfer of amino acids (dots) carried by tRNA to a growing amino acid (peptide) chain. Amino acids appear as different colored dots on a string. Their abbreviations and full names are listed.

    • alanine— ala
    • arginine— arg
    • asparagine— asn
    • aspartic acid— asp
    • cysteine— cys
    • glutamine— gln
    • glutamic acid— glu
    • glycine— gly
    • histidine— his
    • isoleucine— ile
    • leucine— leu
    • lysine— lys
    • methionine— met
    • phenylalanine— phe
    • proline— pro
    • serine— ser
    • threonine— thr
    • tryptophan– trp
    • tyrosine— tyr
    • valine— val

    Figure 3.22: Accessible full text RNA codon to amino acid table

    Figure 3.26: Grid illustration of the pollen of a purple-flowered pea plant (heterozygous genotype of capital B and lowercase b) mixing with the pistol (also a heterozygous genotype of capital B and lowercase b) could create combinations of genotypes: two capital B alleles (purple flower), capital B and lowercase B alleles (purple flower), or two lower case b alleles (white flower).

    Figure 3.28: A grid format uses images of circles for the red blood cells, covered with smaller shapes, to depict antigens on blood types. Shapes that fit against the antigen shapes like puzzle pieces depict antibodies that can bind antigens.

    For ABO blood types:

    • A has circular (A) antigens on the cell, and V-shaped antibodies capable of binding B antigens.
    • B has triangular (B) antigens on the cell, and moon-shaped antibodies capable of binding A antigens.
    • AB has circular (A) and triangle (B) antigens. No corresponding antibodies.
    • O has no antigens, and both V-shaped and moon-shaped antibodies capable of binding A and B antigens.

    For Rh Blood types:

    • Rh+ has rectangular (Rh) antigens on the cell. No corresponding antibodies.
    • Rh- has no specific antigens, and box-shaped antibodies capable of binding Rh antigens.

    Figure 3.29: A 3×3 Punnett-square grid showing the genotypes that result when the different ABO blood type alleles come together. A, B, and O constitute both the row and column headers. The cells are the resulting genotype (two combined alleles).

    Top row: AA, AB, AO

    Middle row: AB, BB, BO

    Bottom row: AO, BO, OO

    Figure 3.34: Two images each show DNA wrapped around a series of histones. The top image shows DNA wrapped around seven tightly clustered histones. Many methyl groups (small dots) are on the DNA and on histone tails. A portion of the DNA tucked between two histones is highlighted as a gene and labeled “DNA inaccessible, gene inactive”. Text reads: Methylation of DNA and histones causes nucleosomes to pack tightly together. Transcription factors cannot bind the DNA, and genes are not expressed. The bottom image shows DNA wrapping around three widely spaced histones, with a highlighted active gene (where the DNA is accessible between two histones). Acetyl groups are attached to histone tails. Text reads: Histone acetylation results in loose packing of nucleosomes. Transcription factors can bind the DNA and genes are expressed.

    This page titled 3.11: End of Chapter Content is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Hayley Mann (Society for Anthropology in Community Colleges) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.