HUMAN ANATOMY AND PHYSIOLOGY LAB REPORT
I.
INTRODUCTION
Living organisms, such as humans, possess differences that makes them
distinctive from others. Yet, these organisms do have their similarities found in the
smallest living unit of their bodies called the cell. Cell is vital feature of a life form
for it determines the body’s structure, functions, and processes. The cell’s
systematic operations may not be seen fully by the naked eye, but it is still essential
to recognize and understand its intricate elements that takes place within the body.
II.
OUTLINE
o Cell Structure
- All cells have a plasma (cell) membrane, cytoplasm, and deoxyribonucleic acid
(DNA).
- The plasma membrane acts as the barrier between the cell’s intracellular
environment from its extracellular environment.
- DNA is the material within the nucleus that contains our genes.
- [Eukaryotic cells]
® contain organelles
® commonly found in plants and animals
- [Prokaryotic cells]
® lack a nucleus and organelles
® commonly unicellular (e.g., bacteria).
- [Organelles]
® “little organs” that have distinctive properties and functions
® Nucleus stores DNA that determines the cell’s processes.
® Chromatin is formed when DNA and proteins are mixed.
® Chromosome is formed when chromatins condense.
® Nucleolus is the production site of ribosomes.
® Ribosomes is responsible for protein synthesis; these can wander
freely (free ribosomes) or attach to endoplasmic reticulum.
® [Endoplasmic reticulum (ER)]
o transports cellular materials
o Rough ER have ribosomes attached to it while smooth ER does
not.
® [Golgi apparatus]
o collects proteins and other materials that exited ER via vesicles
o folds proteins into useful forms or coat them with additional
components (e.g., lipid or carbohydrates)
® Vacuoles is the “storage”.
® Lysosomes is the “garbage collector”; consume defective or worn-out
cell parts through their enzymes that decomposes cellular waste.
® Mitochondrion is the “powerhouse”; it produces adenosine
triphosphate (ATP) molecules which supply energy for cell operations.
® Cytoskeleton shapes the cell; it includes microfilaments (thread-like
proteins) and microtubules (thin hollow tubes).
o DNA Transcription and Translation
- DNA contains the instructions for protein synthesis and where gene is located.
- RNA-coding region begins with promoter and ends in terminator.
- [Gene expression]
® occurs when the encoded ribonucleic acid (RNA) is used for protein
synthesis
® separated into two processes called transcription and translation.
- [Transcription]
® happens in the cell’s nucleus
® DNA is a template with RNA polymerase to create messenger RNA
(mRNA)
® three stages:
o Initiation
Þ promoter region serves as a binding site for RNA polymerase
Þ gene expression is regulated by permitting or blocking RNA
polymerase access to the promoter region
o Elongation
Þ RNA polymerase moves the template DNA as
complementary bases link up
Þ RNA polymerase connects nucleotides to the developing
three prime end of the RNA
o Termination
Þ mRNA transcript is finished
Þ RNA polymerase separates DNA and mRNA
® mRNA contains both protein-coding exons and non-coding introns.
- [Before mRNA can be used in translation]
® Introns splicing
o Non-coding introns is deleted and modified 5’ cap and 3’ poly-A
tail is inserted
o Carried out by spliceosome
® Spliceosome
o Made up of proteins and RNA
o Eliminates intron segments and combines neighboring exons
o Forms a mature mRNA that may exit the nucleus via a nuclear
pore and enter the cytoplasm to initiate translation
- [Codons]
® Three-letter codes that groups the nitrogenous bases
® 64 codons included in genetic code
® Mostly code for specific amino acids
® 4 special codons: 1 – for start, 3 – for stop
- [Translation]
® happens in the cell’s cytoplasm
® mRNA’s stored information creates polypeptide as it binds to the small
ribosomal subunit before the start codon.
® The anticodon sequence of transport RNA (tRNA) determines the kind
of amino acid it transports to the ribosome.
® three stages:
o Initiation
Þ initiator tRNA binds to the start codon
Þ the large ribosomal subunit attaches to form the translation
complex
o Elongation
Þ individual amino acids are delivered to the mRNA by a tRNA
through a complementary base pairing of mRNA codons and
tRNA anticodons
Þ A site of the large ribosomal subunit
§ has a charged tRNA attached to it
Þ P site
§ development of a peptide bond between its amino
acid and the tRNA’s amino acid
Þ E site
§ exit point of uncharged tRNA
Þ will proceed until a stop codon is achieved
o Termination
Þ A site at a stop codon
§ has a binding release factor
Þ P site
§ discharge of the polypeptide from the tRNA
Þ Entire complex disintegrates and can reassemble to restart
the process from initiation
® (goal) to create polypeptides fast and precisely
- [Proteins]
® needed for the normal functioning of the body
® involved in a variety of physiological processes including digestion,
transcription, and translation
o Cell Division
- [Sexual reproduction]
® occurs when two gametes unite to form an embryo that is genetically
unique from the parent organisms
- [Interphase]
o G1 – cells grow larger
o S – cell duplicates its DNA
o G2 – DNA is proofread by enzymes
- [Mitosis]
® begins the cell division
® phases:
o Prophase
Þ nuclear membrane dissolves and DNA thickens
Þ spindle fibers appear on cell’s end and develop toward DNA
chromosomes
o Metaphase
Þ spindle fibers attach to the centromeres and align them in the
middle
o Anaphase
Þ spindle fibers separate the chromosomes toward the
opposite sides of the cell
o Telophase
Þ two new nuclei are formed
Þ Cytokinesis – cell divides into two
- [Meiosis]
® process where gametes are formed with germline cells
® divisions:
o Meiosis I
Þ one parent germline cell = two daughter cells
Þ DNA of the daughter cells is half of the parent cell’s DNA
o Meiosis II
Þ formation of four haploid cells with only one copy of each
chromosome
® Meiosis I phase:
o Prophase I
Þ the duplicated sister chromatids are joined together and stay
fused at the centromere
Þ each pair of homologous chromosomes undergoes synapsis
to form two pairs of sister chromatids
Þ [recombination/crossing over] chromosomal material is
exchanged between the sister chromatids pair
Þ sister chromatids for each chromosome are non-identical
o Metaphase I
Þ synapsed chromosomes align at the equator of the cell
Þ chromosomes align randomly
o Anaphase I
Þ homologous chromosomes separate, migrate, and pair up at
the cell poles
Þ sister chromatids remain attached at their centromeres
o Telophase I & Cytokinesis
Þ the cell splits into two daughter cells to undergo Meiosis II
® Meiosis II phase:
o Prophase II
Þ chromosomes condense, nucleus envelope collapse, and the
spindle apparatus forms
Þ no synapsis of homologous chromosomes or crossing over
o Metaphase II
Þ Chromosomes align randomly at the equator of the cell
o Anaphase II
Þ sister chromatids are separated as microtubules shorten
Þ cell’s ends are pulled farther as microtubules lengthen
o Telophase II
Þ nuclear membrane changes and the cytoplasm is divided
into two haploid daughter cells
o Cytokinesis
Þ division of cytoplasm into two daughter cells
- Began with two cells, ends with four cells called gametes
- Two gametes may fuse to form a diploid embryo that grows through many
cycles of mitosis
III.
CONCLUSION
Cells are a primary building block of all living creatures. No organism on
Earth is known to have ever lived without cells. However small they are
microscopically, they add up to make organisms look and behave in their
spectacular assorted ways, from the myriads of species on this planet to the
complexities of human beings.