The Cell and cell division The cell is the smallest structural and functional unit of life – Cell activities are dictated by their specific structures/organelles Cells become specialized to do their job better  leads to structural modifications – differ in size, shape, subcellular components, and functions BIOL 105 Lab 2--The Cell/Cell Division1

All cells have some common structures and functions Human cells have three basic parts: – Plasma membrane—flexible outer boundary – Cytoplasm—intracellular fluid containing organelles – Nucleus—control center BIOL 105 Lab 2--The Cell/Cell Division2

Plasma Membrane Bilayer of phospholipids and proteins – Has small amount of cholesterol and glycolipids – Head is a phosphate group which faces extra and intra-cellularly; is hydrophilic (and polar) – Tail is lipids; are hydrophobic (and nonpolar) – Allows for an aqueous environment inside and outside the cell but creates a barrier between the cell and its surroundings Plays a dynamic role in cellular activity Separates intracellular fluid (ICF) from extracellular or interstitial fluid (ECF) Is selectively permeable; determines what can come into and leave cell BIOL 105 Lab 2--The Cell/Cell Division3

Cell Reproduction: Process by which a cell divides and duplicates its genetic information Includes 2 stages: 1.Interphase: period of a cell’s life when it carries out its normal metabolic activities and grows; o chromosomes appear as chromatin (chromosomes +proteins called histones) o Nuclear membrane is intact and visible as are the nucleoli BIOL 105 Lab 2--The Cell/Cell Division4

2.Mitotic phase –DNA and nuclear division into 2 daughter cells Is subdivided into four stages: --Prophase -- Anaphase --Metaphase -- Telophase – Mitotic phase is essential for body growth and tissue repair BIOL 105 Lab 2--The Cell/Cell Division5

Prophase—divided into 2 stages Chromosomes become visible, each with two chromatids joined at a centromere DNA has replicated, but has not formed condensed structure of chromosome. They remain as loosely coiled chromatin; copies of chromatin remain attached to each other. chromatin Centrosomes separate, act as areas of growth of 2 “spindles” which migrate toward opposite poles of cell. Mitotic spindles (microtubules) form (from centrosomes) and push centrosomes toward opposite ends of cell Nuclear membrane is still intact to protect DNA molecules from mutation. BIOL 105 Lab 2--The Cell/Cell Division6

Figure 3.33 Late Prophase BIOL 105 Lab 2--The Cell/Cell Division7 Nuclear envelope breaks up so the spindle can interact with chromosomes. Metaphase Centromeres of chromosomes (called spindles) are aligned at opposite poles of cell Chromosomes line up at middle of the cell, called metaphase plate or equator or equatorial plate Anaphase Separated sister chromatids are pulled along behind centromeres and move to opposite cell ends.sister chromatids centromeres Are pulled by kinetochores

Telophase and Cytokinesis Begins when chromosome movement stops Two sets of chromosomes uncoil to form chromatin New nuclear membrane forms around each chromatin mass Nucleoli reappear Spindle disappears Cytokinesis—division of cytoplasm so 2 new daughter cells are formed – Actually begins at end of Anaphase – Ring of actin microfilaments contracts to form a cleavage furrow and pinches apart so 2 daughter cells form BIOL 105 Lab 2--The Cell/Cell Division8

LABWORK 1. ID and describe the parts of the cell. 2. Identify the different stages of mitosis on microscope slides. 3. Describe process of DNA replication and mitosis. 4.Study process of mitosis models. [cell models] 5.Be able to identify interphase and each stage of mitosis on models and slides. BIOL 105 Lab 2--The Cell/Cell Division9