Agenda for the day

1. Types of cells – Somatic vs. Gamete2. Steps of the cell cycle3. Mitosis – defined4. Mitosis lab

Focus for the day

• Today, we will discuss the importance of mitosis and how it relates to cell reproduction.

• I will sequence the steps of the cell cycle, particularly mitosis, using a laboratory exercise.

Cells

Living cells are divided into two types: Eukaryotic (Plant & Animal cells)

Prokaryotic (Bacteria)

WHAT’S THE DIFFERENCE?

Prokaryotic Cells

• Prokaryotic cells do not have a membrane bound nucleus. Instead, their genetic material is in a circular loop in a region referred to as the nucleoid.

Prokaryotic These cells are simple in structure No structured nucleus Exist as single-celled organisms Bacteria is both helpful and harmful to us and the

environment. Example: Bacterial cells

Structure:

PROKARYOTIC

Capsule (bacterial cells only)Cell wallChromosomesCytoplasmFlagellum (bacterial cells only)Inner membraneOuter membranePili (bacterial cells only)Ribosomes

• Members of the kingdoms Archaebacteria (ancient bacteria) and Eubacteria (true bacteria) have prokaryotic cells.

• Most bacteria come in one of three basic shapes: spirilla (spiral), bacilli (rod), and cocci (round).

Unique parts of the bacterial cell Capsule - Protects the bacterial cell and serves as a barrier

against phagocytosis by white blood cells. Flagellum – “Mobility”. Flagella are long appendages which rotate

by means of a "motor" located just under the cytoplasmic membrane. Bacteria may have one, a few, or many flagella in different positions on the cell.

Pili - These hollow, hair-like structures allow bacteria to attach to other cells.

BACTERIAL CELL(PROKARYOTIC)

• More complicated organisms have cells which have more structural integrity with a defined nucleus.

• Members of the kingdoms Protista, Fungi, Plantae (plants), and Animalia (animals) all have eukaryotic cells.

Eukaryotic These cells tend to be larger than the cells of bacteria

(prokaryotic) Have a defined nucleus Found in organisms made up of many cells

Example: Plant and Animal cells

Structure:

EUKARYOTIC

Cell MembraneCell Wall (plant cells only)CentrosomeCentriole (animal cells only)Chloroplast (plant cells only)CytoplasmCytoskeletonCytosolGolgiLysosome

MitochondriaNucleusNucleolusPeroxisomeReticulumRibosomesRough Endoplasmic Secretory VesicleSmooth Endoplasmic Vacuole

Unique parts of the plant cell Cell wall – a feature of plants cells that functions like stiff

lattice-like wall which helps plant cells maintain their structure and shape

Chloroplast – a feature of plant cells that allows plants to do photosynthesis and make their own glucose from sunlight, water and carbon dioxide

PLANT CELL(EUKARYOTIC)

SimilaritiesDESCRIPTION

Bacterial Cells Plant Cells Animal Cells

1. DNA/ Chromosomes Yes Yes Yes2. Cell membrane Yes Yes Yes3. Structures to produce energy for cell- Cell Respiration

No-occurs near cell

membrane

Yes- in organelle called

mitochondrion

Yes- in organelle called

mitochondrion

4. Structures that make proteins and enzymes for the cell

Yes-poly- (many)

ribosomes

Yes- endoplasmic

reticulum (organelle)

Yes- endoplasmic

reticulum (organelle)

5. Cytoplasm Yes Yes Yes

SIMILARITIES

DifferencesDESCRIPTION

Bacterial CellsPlant Cells

Animal Cells

1. Cell Wall Yes Yes No2. Nucleus-nuclear membrane No Yes Yes3. Fimbria-DNA transfer Some No No4. Vacuoles No Yes Yes

5. Chloroplasts (organelles) (for photosynthesis)

Yes-blue-green bacteria has a green pigment that makes its

own food.

Yes No

6. Flagella-mobility Yes No No7. Capsule Some No No

DIFFERENCES

Types of cells in the body

• 1. Somatic Cells

• 2. Gametes

Somatic Cells

• Somatic cells can be defined as any cells other than gametes, germ, or undifferentiated stem cell which make up the entire body.

• Somatic stem are natural cells which are found in the bodies of all multicellular organisms.

• Somatic cells are undifferentiated and are not dedicated to a particular type of tissue permanently.

Somatic cells perform two major functions:

• Replacing dying cells, especially in the epidermis where the requirement is continuous

• Repairing the damaged tissue, mostly when the body has faced the onslaught of trauma and disease

Gametes• Gametes, also known as germ cells or sex

cells, are spermatozoon (sperm cells) or ovum (egg cells) which result from the process of meiosis.

• They are haploid, meaning that each cell contains only half of the complement of chromosomes and genetic material needed to encode (and essentially create) an individual.

• Two gametes merge to produce a single diploid cell, the zygote, which will contain the complete number of chromosomes needed for life.

Haploid Vs. Diploid

• Haploid = n

• Diploid = 2n

• Diploid cells (2N) have two complete sets of chromosomes (one from the mom and one from the dad). The body cells of animals are diploid.

• Haploid cells have one complete set of chromosomes. In animals, gametes (sperm and eggs) are haploid.

Diploid HaploidExamples Spermatogonium cell Human sex cells (sperm and

ova).

Organisms Humans and most animal cells are diploid organisms.

Algae and fungi are examples of organisms that are mostly haploid during their life cycle. Male bees, wasps, and ants are also haploid.

Cell Division and Growth During the process of reproduction, haploid cells (male and female) unite to form a diploid zygote, which divides by mitosis to give rise to more diploid cells.

Haploid cells are the result of the process of meiosis, a type of cell division in which diploid cells divide to give rise to haploid germ cells.

About: Diploid cells contain two complete sets of chromosomes

Haploid cells have half the number of chromosomes (n) as diploid – i.e., a haploid cell contains only one complete set of chromosomes.

Specialized cells

Epithelial, Muscle, and Bone cells

• Epithelial cells are attached to one another. Special devices (intercellular junctions, tonofilaments) provide for structural integrity of the epithelium. There are several types of cell junctions.

Cell Junctions:

• Adhering junctions• Tight (occluding) junctions• Gap junctions

Muscle cells

• 1. Skeletal muscle

• 2. Cardiac muscle

• 3. Smooth muscle

• http://www.youtube.com/watch?v=PJDrR3sZPZU

Bone Cells

• Osteoclasts are large cells that dissolve the bone. They come from the bone marrow and are related to white blood cells.

• Osteoblasts are the cells that form new bone. They also come from the bone marrow and are related to structural cells. They have only one nucleus. Osteoblasts work in teams to build bone.

• Osteocytes make up the structure of existing bone. They also come from osteoblasts.

• http://www.youtube.com/watch?v=78RBpWSOl08

Cell Differentiation

• Cell differentiation is the development of a generic cell into a cell with a specific function, which is directed by various triggers.

• This differentiation is essential for cell renewal and embryonic development; it occurs numerous times in the development of a single-celled zygote into a multi-cellular organism with many different cell types.

• It is also essential for cellular turnover, the continuous maintenance of most multi-cellular organisms.

• Through differentiation, a cell drastically changes its size, shape, membrane potential, metabolic activity, and responsiveness.

What is (and is not) mitosis?

Mitosis is nuclear division plus cytokinesis, and produces two identical daughter cells during

prophase, **prometaphase, metaphase, anaphase, and telophase. Interphase is often included in

discussions of mitosis, but interphase is technically not part of mitosis, but rather encompasses stages G1, S,

and G2 of the cell cycle.

**Prometaphase is often times considered part of prophase.

The Cell CycleG1 phase: Metabolic changes prepare the cell for division. At a certain point (the restriction point) the cell is committed to division and moves into the S phase.S phase: DNA synthesis replicates the genetic material. One chromosome now consists of two sister chromatids.G2 phase: Metabolic changes assemble the cytoplasmic materials necessary for mitosis and cytokinesis.M phase: A nuclear division (mitosis) followed by a cell division (cytokinesis).

Interphase

• Interphase consists of the G1, S, and G2 phase.

Cell Division

• Mitosis

• Mitosis is the division of a SOMATIC cell

Mitosis

• can be defined as nuclear division plus cytokinesis. The process produces two identical daughter cells through prophase, prometaphase, metaphase, anaphase, and telophase.

Prior to Mitosis (G2)

The cell is engaged in metabolic activity and preparing for mitosis (the next four phases that lead up to and include nuclear division). Chromosomes are not clearly discernible in the nucleus, although a dark spot called the nucleolus may be visible. The cell may contain a pair of centrioles (or microtubule organizing centers in plants) both of which are organizational sites for microtubules.

ProphaseChromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nucleolus disappears. Centrioles begin moving to opposite ends of the cell and fibers extend from the centromeres. Some fibers cross the cell to form the mitotic spindle.

Prometaphase

The nuclear membrane dissolves, marking the beginning of prometaphase. Proteins attach to the centromeres creating the kinetochores. Microtubules attach at the kinetochores and the chromosomes begin moving.

Metaphase

Spindle fibers align the chromosomes along the middle of the cell nucleus. This line is referred to as the metaphase plate. This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome.

Anaphase

The paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Motion results from a combination of kinetochore movement along the spindle microtubules and through the physical interaction of polar microtubules.

Telophase

• Chromatids arrive at opposite poles of cell, and new membranes form around the daughter nuclei. The chromosomes disperse and are no longer visible under the light microscope. The spindle fibers disperse, and cytokinesis or the partitioning of the cell may also begin during this stage.

Cytokinesis In animal cells,

cytokinesis results when a fiber ring composed of a protein called actin around the center of the cell contracts pinching the cell into two daughter cells, each with one nucleus. In plant cells, the rigid wall requires that a cell plate be synthesized between the two daughter cells.

Mitosis

• https://www.youtube.com/watch?v=C6hn3sA0ip0

Oreo Lab Instructions

• In groups of 3:• You will get 6 oreo cookies, 3 toothpicks, and

some sprinkles.• Determine which color sprinkles represent the

mitotic structures inside the cell. You will need to modify the sprinkles to represent smaller structures (like centrioles). The filling represents the cytoplasm.

• Each oreo represents a stage of the cell cycle: IPMATC

Meiosis

Meiosis

• Meiosis is a process which stands alone, separate from the cell cycle, even though the process of mitosis occurs within meiosis. This process (unlike mitosis), is necessary for sexual reproduction and results in a total of four daughter cells, each of which are different from the parent cell.

• The cell's chromosomes replicate and form pairs in meiosis. In a process called crossing over, each pair exchanges chromosomal material to enhance genetic variation. The cell then follows division steps similar to mitosis to form two daughter cells. These two daughter cells, in turn, undergo cell division to create a total of four new sex cells, each with only half the chromosomal makeup of the parent cell, and each with the unique assortment of genetic information.

• So when a male sex cell and a female sex cell combine during sexual reproduction, a new cell with the normal number of chromosomes is created. This new cell will divide repeatedly by mitosis until a complete new individual is formed.

Prophase 1

• DNA replication precedes the start of meiosis I. During prophase I, homologous chromosomes pair and form synapses, a step unique to meiosis. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent.

• Chromosomal condensation allows these to be viewed in the microscope. Note that the bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent.

Prophase 1

Prometaphase 1

• The nuclear membrane disappears. One kinetochore forms per chromosome rather than one per chromatid, and the chromosomes attached to spindle fibers begin to move.

Metaphase 1

• Bivalents, each composed of two chromosomes (four chromatids), align at the metaphase plate. The orientation is random, with either parental homologue on a side. This means that there is a 50-50 chance for the daughter cells to get either the mother's or father's homologue for each chromosome.

Anaphase 1

• Chiasmata separate. Chromosomes, each with two chromatids, move to separate poles. Each of the daughter cells is now haploid (23 chromosomes), but each chromosome has two chromatids.

Telophase 1

• Nuclear envelopes may reform, or the cell may quickly start meiosis II.

Prophase 2

Metaphase 2 and Anaphase 2

Telophase 2 and Cytokinesis

Meiosis

• http://www.youtube.com/watch?v=qCLmR9-YY7o

Organism Levels

• 1. Chemical Level: The smallest microscopic units of matter that have the properties of an element. They combine with covalent bonds to form molecules such as molecular oxygen (O2), glucose (C6H12O6), or methane (CH4).

• 2. The Cellular Level: The smallest unit of life. Cells have various sizes, shapes, and properties that allow them to carry out specialized functions.

• 3. Tissue Level: A tissue is a group of cells having a common structure and function. There are four types of tissue: muscle, epithelia, nervous, and connective.

• Connective: Fibrous, nonliving: gives shape to organs and holds them in place

• Muscle: Most active tissue – smooth, skeletal, cardiac

• Nervous: Central and peripheral• Epithelial: provides a barrier of protection

• 4. Organ Level: Two or more tissues working for a common function develop an organ. All four tissue types combine to form skin, the largest organ in the body, or the cochlea in the ear, the smallest organ of all.

• 5. Organ System Level: Organs work together for a common function. The organ systems include the integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic, respiratory, digestive, urinary, and reproductive systems.

• 6. Organismal Level: The organismal level (whole animal), includes all the organ systems that work together to maintain homeostasis.