CHAPTER 2.2: CELLS PART 1: A tour of the Cell

Anatomy of the Cell Cells are not all the same All cells share general structures All cells have three main regions Nucleus Cytoplasm Plasma membrane Figure 3.1a

The Nucleus Control center of the cell - F Contains genetic material (DNA) - F Three regions - D Nuclear envelope (membrane) - D Nucleolus - D Chromatin - D

The Nucleus Figure 3.1b

The Nucleus Nuclear envelope (membrane) Barrier of the nucleus - F Consists of a double membrane - D Contains nuclear pores that allow for exchange of material with the rest of the cell - D

The Nucleus Nucleoli Nucleus contains one or more nucleoli - D Sites of ribosome assembly - F Ribosomes migrate into the cytoplasm through nuclear pores - F

The Nucleus Chromatin Composed of DNA and protein - F Present when the cell is not dividing - D Scattered throughout the nucleus - D Condenses to form chromosomes when the cell divides - F

Plasma Membrane Barrier for cell contents - F Double phospholipid layer - D Hydrophilic heads Hydrophobic tails Also contains proteins, cholesterol, and glycoproteins - D

Plasma Membrane Figure 3.2

Plasma Membrane Specializations Microvilli Finger-like projections that increase surface area for absorption - F

Plasma Membrane Specializations Membrane junctions Tight junctions Impermeable junctions - D Bind cells together into leakproof sheets - F Desmosomes Anchoring junctions that prevent cells from being pulled apart - F Gap junctions Allow communication between cells - F

Plasma Membrane Specializations Figure 3.3

Membrane Transport – first page passive no energy required diffusion active requires energy sodium-potassium pump

Cytoplasm Cytoplasm is the material outside the nucleus and inside the plasma membrane – D Contains three major elements Cytosol Organelles Inclusions

Cytoplasm Contains three major elements Cytosol Fluid that suspends other elements - F Organelles Metabolic machinery of the cell “Little organs” that perform functions for the cell Inclusions Chemical substances such as stored nutrients or cell products

Cytoplasmic Organelles Figure 3.4

Cytoplasmic Organelles Mitochondria “Powerhouses” of the cell - F Change shape continuously - D Carry out reactions where oxygen is used to break down food - F Provides ATP for cellular energy - F

Cytoplasmic Organelles Ribosomes Made of protein and RNA - D Sites of protein synthesis - F Found at two locations - D Free in the cytoplasm As part of the rough endoplasmic reticulum

Ribosomes Synthesize proteins from amino acids (Translation)

Endoplasmic Reticulum Detoxifies Makes lipids Stores Ca++ SER Transports proteins RER

Cytoplasmic Organelles Golgi apparatus Modifies and packages proteins Produces different types of packages Secretory vesicles Cell membrane components Lysosomes

Pathway 3 Pathway 2 Pathway 1 Figure 3.6 Rough ER Proteins in cisterna Membrane Lysosome fuses with ingested substances Transport vesicle Golgi vesicle containing digestive enzymes becomes a lysosome Pathway 3 Pathway 2 Golgi apparatus Secretory vesicles Pathway 1 Golgi vesicle containing membrane components fuses with the plasma membrane Proteins Golgi vesicle containing proteins to be secreted becomes a secretory vesicle Secretion by exocytosis Plasma membrane Extracellular fluid Figure 3.6

Common in animals, rare in plants Stores acids & enzymes Lysosomes Common in animals, rare in plants Stores acids & enzymes Intracellular digesion Engulfs “foreign” Recycles Uncontrolled release = cell death

Cytoplasmic Organelles Lysosomes Contain enzymes that digest worn-out or nonusable materials within the cell

peroxisomes Protects the cell from its own production of H2O2 Example Secretory vesicle Protects the cell from its own production of H2O2 Example White blood cells produce H2O2 to kill bacteria Peroxisomes produce catalase, which breaks down the H2O2 catalase H2O2 H20 + ½ O2

Cytoplasmic Organelles Cytoskeleton Network of protein structures that extend throughout the cytoplasm Provides the cell with an internal framework Figure 3.7a

Cytoplasmic Organelles Cytoskeleton Three different types of elements Microfilaments (largest) Intermediate filaments Microtubules (smallest) Figure 3.7b–d

Cytoplasmic Organelles Centrioles Rod-shaped bodies made of microtubules Direct the formation of mitotic spindle during cell division

Life Cycle of a Cell Interphase – cell maintenance and growth The mitotic phase Mitosis – The division of the cell nucleus and chromosomes into two nuclei each with its own set of identical chromosomes prophase metaphase anaphase telophase Cytokinesis – the division of the cytoplasm into two parts, the final step in cell division

Mitosis prophase chromatin condenses into chromosomes, cell membrane breaks down metaphase chromosomes line up in the center of the cell anaphase centromeres are cut in half, sister chromatids pull toward centrioles telophase chromosomes “decondense,” new nuclear membrane forms

Mitosis

Cytokinesis the cytoplasm divides into two parts, the final step of cell division

Cancer cancer cell grows too much grows where it does not belong does not die when it should

Cell Diversity Figure 3.8a

Cell Diversity Figure 3.8b

Cell Diversity Figure 3.8c

Cell Diversity Figure 3.8d

Cell Diversity Figure 3.8e

Cell Diversity Figure 3.8f

Cell Diversity Figure 3.8g