Chapter 2 - Objectives
Define cell, its basic activities, and its three major regions.
Describe the composition and basic functions of the plasma membrane.
Explain the different processes used to move substances across the plasma membrane.
Describe the structure and cellular
activity of each organelle: ribosomes, endoplasmic
Explain the structure of glycosomes and lipid droplets.
Describe the role of each of the
three parts of the nucleus in the control of cellular
Name specific cell types, and relate their overall shape to their specific functions.
Compare theories of cell differentiation and aging.
Overview of Cells
The cell is the basic structural and functional unit of all living things.
Major cellular regions are the plasma membrane, cytoplasm, and nucleus.
Most cell types contain each of the requisite organelles, but in differing abundances based on the cellís type and its function.
Each organelle functions like a specific division of a manufacturing plant.
The Plasma Membrane
Double layer, or lipid bilayer,
of lipid molecules (phospholipids, cholesterol, and
Separates two major fluid compartments: the intercellular fluid within the cells, and the extracellular fluid, which lies outside and between cells.
Some membrane proteins act as
receptors and are part of the bodyís cellular
The plasma membrane controls which substances can enter or leave the cell.
Small uncharged molecules pass through the lipid bilayer by diffusion.
Osmosis is the diffusion of water molecules across a selectively permeable membrane.
Facilitated diffusion is the movement of molecules down their concentration gradient, diffusing through the plasma membrane by moving through specific integral proteins.
Moving molecules across the plasma membrane against their concentration gradient is an energy-requiring process called active transport.
Movement of Large Macromolecules
Two types of vesicular transport, called endocytosis and exocytosis, move the largest macromolecules.
Three types of endocytosis occur
in cells: phagocytosis,
Hormones, low-density lipoproteins (LDLs), viruses, and some toxins enter cells by receptor-mediated endocytosis.
Exocytosis is the process by which substances move from the cytoplasm to the outside of a cell.
The three major elements of the
cytoplasm are the cytosol, organelles, and inclusions.
Cytosol is the jellylike fluid that suspends cytoplasmic elements. (p. 28)
Cytoplasmic organelles perform different cellular survival functions and compartmentalize the cellís biochemical reactions.
Ribosomes are the sites of protein synthesis as well as the RER.
Endoplasmic reticulum makes proteins (rough ER) and is the site of lipid and steroid synthesis (smooth ER).
Golgi apparatus packages and modifies proteins.
Mitochondria synthesize ATP.
Lysosomes are the sites of intracellular digestion.
Peroxisomes detoxify toxic substances.
Cytoskeleton supports cellular structures.
Centrioles act in forming cilia and flagella and organize microtubule networks during mitosis.
Inclusions are temporary structures in cells; examples are food-storage units for fats and sugars, as well as pigments.
The nucleus is the control center
of the cell; it contains the DNA that directs the cellís
The nuclear envelope surrounds the nucleus and consists of two parallel membranes separated by a fluid-filled space.
Nucleoli contain parts of several
chromosomes and assist in assembling ribosomal
Chromatin is composed of DNA and histone proteins located in the nucleus.
The DNA molecule is a double helix made up of four types of nucleotides with bases of adenine, thymine, guanine, and cytosine.
Developmental Aspects of Cells
Cell differentiation is the development of specific and distinctive features among the cell types in human body cells.
Evidence supports the theory that aging occurs because mitochondria are damaged by free radicals and/or genetically influenced processes.
THIS IS A BASIC REVIEW - JUST ENOUGH TO GIVE YOU AN IDEA OF WHY THE ANATOMY IS THE WAY IT IS. YOU WILL COVER THIS IN DETAIL IN PHYSIOLOGY. THE EXAM FOR THIS CHAPTER WILL FOCUS ON FEATURES OF THE MEMBRANE! (FLUID MOSAIC MODEL, MEMBRANE PROTEINS AND MARKERS, MEMBRANE TRANSPORT AND WHERE CELLS ARE FOUND IN THE BODY WITH THOSE FEATURES. IE: WHITE BLOOD CELLS ARE PHAGOCYTOTIC, INTESTINAL CELLS DO PINOCYTOSIS)
The cells of our bodies are all there is to us! The way that they are placed and their functions create all of the anatomy that we see. Most of the energy that our bodies use are used to maintain the lives of these 70 trillion single cellular lives! Your cells are locked in place so they cannot go out and find energy, oxygen and water. These molecules must be brought to them. In addition, our cells require very strict living conditions to thrive. Next, something has to protect all of our cells against pathogens. Animals are wonderful petri dishes for pathogens and only constant vigilance will save us from deadly infections. The last thing is to carry away waste metabolic products. These reasons are why we have 10 (plus reproductive, not vital) systems.
The Plasma Membrane - a short overview
Endocytosis and Exocytosis
Fluid Mosaic Model
Overview of Organelles