Chapter 3 Anatomy of Cells

Chapter 3 Anatomy of Cells

Anatomy of Cells • Cell Structure • Cellular Components • Structure • Function

Table 3-2

The typical cell (Figure 3-1) – generic cell Varies in size; all are microscopic (Table 3-1) Varies in structure and function (Table 3-2) Functional Anatomy of Cells

Typical Cell – Fig. 3-1

Typical or Composite Cell – Fig. 3-1

Cell Structures • Plasma membrane—separates the cell from its surrounding environment • Cytoplasm—thick gel-like substance inside of the cell composed of numerous organelles suspended in watery cytosol; each type of organelle (“little organ”) is suited to perform particular functions (Figure 3-2) • Nucleus—large membranous structure near the center of the cell

Cell Membranes • Plasma membrane (Figure 3-3) • Membranous organelles – sacs and canals made of the same material as the plasma membrane

Cell Membranes • Structure – is a double layer of phospholipid molecule • Phospholipid • Heads are hydrophilic (water-loving) • Tails are hydrophobic (water-fearing) • Cholesterol molecules are scattered among the phospholipids to allow the membrane to function properly at body temperature • Membrane Proteins • Controls what moves through the membrane • Act as i.d. markers • Act as receptors

Cell Membrane • Membrane Function • To keep cellular components inside the cell and extracellular material outside the cell • Controls what moves into and out of the cell

Cytoplasm and Organelles • Cytoplasm – gel-like internal substance of cells that includes many organelles suspended in watery intracellular fluid called cytosol • Cytosol – the watery intracellular fluid • Organelles – “little organs” each have a particular structure and function • Know the function of each organelle and be able to identify it in a generalized figure of the cell

Endoplasmic Reticulum (Figure 3-5) • Function: Synthesis of proteins that will be excreted from the cell (rough ER) and synthesize lipids for the cell membrane, steroid hormones, and certain carbohydrates, removes and stores Ca2+ from the cell’s interior

Endoplasmic Reticulum • Two types of ER: • Smooth ER – do not have ribosomes attached • Synthesizes certain lipids and carbohydrates and creates membranes for use throughout cell • Removes and stores Ca++ from cell’s interior. • Rough ER – have ribosomes attached to the outer surface • Ribosomes synthesize proteins, which move toward the Golgi apparatus and then eventually leave the cell • Function in protein synthesis and intracellular transportation

Ribosomes • Function: the site of protein synthesis • Attached to rough ER or scattered in the cytoplasm • Structure: made of two pieces, a large subunit and a small subunit • Ribosomes in the endoplasmic reticulum make proteins for “export” or to be embedded in the plasma membrane; free ribosomes make proteins for the cell’s domestic use

Golgi Apparatus • Function: Synthesizes carbohydrates, processes proteins from the ER; the cell’s “post office” • Structure: cisternae stacked on one another and located near the nucleus • Processes protein molecules from the endoplasmic reticulum (Figure 3-8)

Figure 3-8. The Cell’s Protein Export System

Lysosomes • Function: Bags of digestive enzymes break down defective cell parts and ingested particles; a cell’s “digestive system” • Structure: Made of microscopic membranous sacs that have “pinched off” from Golgi apparatus

Proteasomes • Function: Hollow protein cylinders that break down abnormal/misfolded proteins and normal proteins no longer needed by the cell

Peroxisomes • Function: contain enzymes that detoxify harmful substances • Often seen in kidney and liver cells

Mitochondria • Function: A cell’s “power plant”; the site of ATP synthesis • Mitochondrial DNA: Each mitochondrion has a DNA molecule, allowing it to produce its own enzymes and replicate copies of itself

Nucleus • Definition—spherical body in center of cell; enclosed by an envelope with many pores • Function: Contains DNA (genetic code) – the “brain” of the cell, dictates protein synthesis

Nuclear Structure • Nuclear Envelope – nuclear membrane, has nuclear pores (controls entrance in and out of the cell) • Nucleoplasm – nuclear substance • Chromatin – the DNA in non-dividing cells • Nucleolous – found in the nucleus, synthesizes rRNA and combines it with protein to form ribosomes

Nucleus • Contains DNA (heredity molecules), which appear as the following: • Chromatin threads or granules in nondividing cells • Chromosomes in early stages of cell division • Functions of nucleus are functions of DNA molecules; DNA determines both structure and function of cells and heredity

Cytoskeleton • Function: acts as a framework to support the cell and its organelles; involved in cell movement; forms cell extensions

Cytoskeleton • Cell fibers – 3 types • Microfilaments • Intermediate Filaments • Microtubules

Microfilaments • Smallest cell fibers • “Cellular muscles” • Made of thin, twisted strands of protein molecules that lie parallel to the long axis of the cell • Microfilaments can slide past each other, causing shortening of the cell

Intermediate Filaments • Twisted protein strands slightly thicker than microfilaments; form much of the supporting framework in many types of cells

Microtubules • Tiny, hollow tubes that are the thickest of the cell fibers • Function: move things around in the cell

Centrosome • Also called the microtubule-organizing center (MTOC) • Plays an important role during cell division • The general location of the centrosome is identified by the centrioles

Cell Extensions • Cytoskeleton that forms projections that extend the plasma membrane outward to form tiny, fingerlike processes

Three Types of Cell Extensions • Microvilli – founds in epithelial cells that line intestines, increase surface area for absoption • Cilia – short and numerous, move substances along the surface of a cell • Flagella – involved in total cell movement; found on human sperm cells

The Big Picture • Review • Conclusions

Chapter 3 Anatomy of Cells