Zoology: Cellular Basis of Life

• NU Lipa offers a Zoology course focused on the cellular basis of life

Learning Objectives

• Review the history of the cell.
• Classify the different types of cells.
• Discuss the functions of cells.
• Characterize parts of an animal cell.
• Analyze cellular processes.

Review on the History of the Cell

• It involves cell theories

Classification of Cells

• Includes prokaryotes and eukaryotes

Function of Cells

• Discusses their functions

Different Parts of the Animal Cell

Cellular Processes

• Discusses the cell cycle and cell transport

Cell Theory

• The cell represents the basic functional and structural unit of life
• Is vital, playing a role in biological activities
• Includes membrane-bound organelles, with individual functions to keep the cell alive and active

General Cell Types

• Prokaryotic cells are without a true nucleus
• Eukaryotic cells have a true nucleus
• Escherichia coli under an electron microscope represents a prokaryotic cell
• CD1 cerebral cortex stained with green and blue fluorescent stain in mice represents a eukaryotic cell

Prokaryotic Cells

• Lacks a true, membrane-bound nucleus
• Considered "before nucleus"
• Independent, single-celled organisms such as bacteria and cyanobacteria
• Small in size with simple internal structures
• Contain a nucleoid region with DNA
• Some have flagella, pili, or fimbriae

Eukaryotic Cells

• Possess a true nucleus that houses DNA in chromosomes
• Possess organelles for cell processes
• Have a network of minute filaments and tubules for cell shape and movement
• All protists, fungi, plants, and animals have Eukaryotic Cells

Cell Function

• Dependent on its structural characteristics and the nature of proteins present
• Cell structure and function are closely related to each other
• Generalized cell functions include the movement of substances across the membrane include the cell division to make new cells, and protein synthesis

Animal Cell Parts

• Nucleus
• Endoplasmic Reticulum
• Cell membrane
• Organelles
• Cytoplasm
• Ribosomes

Parts and Functions of Animal Cell

Cell Membrane

• Protects the cell
• Controls molecule transportation
• Gives the cell its shape
• Helps with adhesion to form tissues and communication

Cytoplasm and Cytoskeleton

• The cytoplasm holds water and nutrients
• The cytoskeleton provides structural rigidity and helps movement

Nucleus

• Stores genetic information
• The Nucleus is responsible for communication with the ribosome to perform protein synthesis

Ribosomes

• Are responsible for protein synthesis

Smooth Endoplasmic Reticulum

• Responsible for Lipid synthesis, the secretion of steroid hormones & the metabolism of the carbohydrates

Rough Endoplasmic Reticulum

• Responsible for protein synthesis with the attachment of ribosomes

Golgi Apparatus

• Packages proteins for transportation

Vacuoles

• Responsible for food, water, and waste storage
• In plants it regulates turgor pressure

Lysosomes

• Responsible for Digestion of waste & obsolete materials
• Response to foreign bodies
• Cell repair & Apoptosis

Peroxisome

• Responsible for Lipid synthesis (including bile acids)
• Break down of hydrogen peroxide

Mitochondria

• Considered the "Powerhouse of the cell"
• Produces energy (ATP synthesis)

Cell Cycle

• The Cell Cycle is a series of stages to grow and divide
• As a cell replicates its chromosomes to grows and prepares for divison

Interphase

• Made up of three phases: G1, S, & G2

M Phase

• Separates the copied chromosomes to form two full sets, called Mitosis
• The cell divides into two new cells via Cytokinesis
• The M Phase the shortest phase in the Cell Cycle

Phases of the Cell Cycle

• G1 is for the primary growth phase
• S is for synthesis in DNA replication
• G2 is the secondary growth phase
• M is for mitosis
• C is for cytokinesis

G1 Phase

• The cell grows and prepares for division by making metabolic changes

S Phase

• The cell makes copies of its chromosomes, making each one has two sister chromatids

G2 Phase

• The cell checks the duplicated chromosomes and prepares for division by making metabolic changes

M Phase

• Separates the copied chromosomes to form two full sets
• The chromosomes are maximally condensed and aligned in a plane called the metaphase plate
• Sister chromatids split apart at the centromere and move toward the centrosome
• The cell elongates and the chromosomes decondense
• The cell pinches into two to form two daughter cells

Cell Growth Checkpoint

• Happens toward the end of growth phase 1 (G1)
• Checks whether the cell is big enough and has the proper proteins for the synthesis phase
• If not then it will have a resting period, or G0 phase, until cells divides

DNA Synthesis Checkpoint

• Takes place during synthesis phase (S)
• Sees if the DNA has been replicated correctly
• If true then continuous division of cells into Mitosis (M) is possible

Mitosis Checkpoint

• Happens during the mitosis phase (M)
• Sees if the mitosis is complete
• The the cell with divide, and the cycle repeats

Cell Division

• Derives from pre-existing cells
• New cells are produced for growth to replace damaged or old cells
• Cell division differs among prokaryotes and eukaryotes

Mitosis

• Division of the nucleus, aka karyokinesis
• Occurs only in eukaryotes
• Consists of 4 stages
• Does not occur in some cells

Gray Matter

• Crucial for brain function & composed of neuron cell bodies
• Does not regenerate

White Matter

• Composed of myelinated axons
• Regenerates to a limited extend

Mitosis - Early Prophase

• The chromatin in the nucleus condenses
• The mitotic spindle forms from fibers in the cytoskeleton or centrioles

Mitosis - Late Prophase

• The nuclear membrane and nucleolus break down
• Chromosomes continue to condense and become clearly visible
• Spindle fibers called kinetochores attach to the centromere of each chromosome
• The spindle finishes forming between the poles

Mitosis - Prophase

• Centrioles form and move toward opposite ends of the cell
• The Nuclear membrane dissolves
• Spindle fibers from each centriole attach to each sister chromatid at the kinetochore

Mitosis - Metaphase

• Chromosomes attached to the kinetochore fibers, move to the center of the cell
• The Chromosomes then align at the center

Mitosis - Anaphase

• Occurs Rapidly
• Sister chromatids are pulled apart/separation

Mitosis - Telophase

• Sister chromatids are already at the opposite poles
• Spindle fibers disassemble
• A Nuclear envelope forms
• A Nucleolus appear
• Cytokinesis occurs
• Chromosomes reappear as chromatin

Mitosis - Cytokinesis

• In animal cells, this happens through cleavage
• A Cleavage furrow is generated, a shallow groove
• The cell is then pinched into two

Mitosis - Daughter Cells

• Daughter cells are identical to one another
• Must grow in size to mature
• Consist of the same number of chromosomes as the parent cell
• Used for growth and repair
• Are diploid (2n)

Cancer

• Uncontrollable division causes tumors
• An oncogene is a mutated gene that becomes cancer
• Before an oncogene becomes mutated, it is called a proto-oncogene
• Has a potential to cause cancer (regulating normal cell division.)

Brain Tumor

• Impact mental health causing difficulties
• Anxiety and depression occur due to the location, size & rate of growth

Cell processes and Fertilization

• Most people think of development on the day of birth
• Development begins when sperm and egg unite & both influence & are influenced by an ever-changing environment
• Meiosis is the cell division from sperm and egg cells unite

Meiosis

• Involves reduction division where chromosome number is reduced by one half, diploid to haploid (2N to N)
• Daughter cells have the haploid (N) number of chromosomes instead of the diploid (2N) number from mitosis
• Ensures fertilization results in a diploid (2N) individual
• Forms gametes (eggs and sperm cells)
• The creation of sperm cells is spermatogenesis
• The creation of egg cells is oogenesis
• The haploid sperm and egg are brought together (1n) to create diploid zygote (2n)
• Meiosis consists of 2-part cell divisions
• Produces gametes with one copy of each chromosome

Stages of Meiosis I - Prophase I

• Homologous chromosomes become paired
• Crossing over occurs

Stages of Meiosis I - Metaphase I

• Homologous pairs of chromosomes align along the equator of the cell

Stages of Meiosis I - Anaphase I

• Homologs separate and move to opposite poles

Stages of Meiosis I - Telophase I

• Nuclear envelopes reassemble
• The Spindle disappears
• Cytokinesis divides cell into two