Download anatomy of the body

Cell Biology Review
Pathology 1 - Dr. Gary Mumaugh
Introduction
 The cell is the basic unit of biological organization
 Basic composition
o Protoplasm
o Cell membrane
o Organelles
 Human cells vary in size, shape and function
o From microscopic to up to two feet long
 There are 50-100 trillion cells in the human body.
 Differentiation is when cells specialize.
 There are over 260 different kinds of human cells.
 As a result of differentiation, cells vary in size and shape due to their unique function
Anatomy of a Typical Cell
The Cell Membrane
 Double phospholipid layer with embedded proteins – also called Plasma Membrane
o Protein functions of include forming channels or pores, transporters, receptor
sites for hormones
 Cell membranes are selectively permeable membranes
o Only certain substances can get through - Not everything is on the “A” list
1
Cytoplasm of the Cell
 Mostly water with chemical compounds in solution or colloid
o Solution: atoms or ions distributed in medium
 Polar compounds go into solution
 Nonpolar compounds go into colloidal suspension
The Nucleus
 All human cells have a nucleus
o Except the RBC
 Control center of the cell
 Nuclear membrane has pores to allow substances passage
 Chromatin genetic material (long threads of chromosomes) are inside nucleoplasm
 Nucleolus - site of ribosome formation
Cytoplasm
 Is the watery solution of minerals, gases, organic molecules and cell organelles that
is found between the cell membrane and the nucleus
 Cytosol is the water portion of the cytoplasm
 Many of the chemical reaction that occur in the cell happen in the cytoplasm
Endoplasmic Reticulum (ER)
 System of membranes that makes up channels
 Connects with outer nuclear and cell membranes
 Types of ER
o Rough: for protein synthesis attached ribosomes
o Smooth: fat transport and sex hormone synthesis
2
Ribosomes
 Very small structures made up of protein and ribosomal RNA
 Distributed throughout cytoplasm
 Attached to rough Endoplasmic Reticulum
 Site of protein synthesis
The Golgi Apparatus
 Secretion is the task of the Golgi apparatus
o They produce specific proteins to be used elsewhere in tissues
o To secrete a substance, small sacs of the membrane break off and fuse with
the cell membrane, releasing the substance to the outside of the cell
o This is called exocytosis
 Collection of flat saclike cisternae
 Concentration and collection of cellular compounds
 Storage warehouses of the cell
 Carbohydrate synthesis site
The Mitochondria
 Powerhouses of the cell
 The aerobic (oxygen requiring) reactions of cell respiration take place here
 The site of ATP and energy production
 Cristae - inner folds where cellular respiration occurs
 Energy requirements of cell determine cristae number
3
Lysosomes
 Digestive enzyme packages
 When WBC engulf bacteria, the bacteria are digested and destroyed by lysosomal
enzymes
 Worn out cell parts and dead cells are digested by the lysosomes
 Function
o digest stored food
o maintenance and repair of organelles
o suicide agents for old or weak cells
Centrioles
 Involved in cellular division and reproduction
 Form spindle fibers during cell division
 Guide duplicated chromosomes to daughter cells
 Centrosome - two centrioles at right angles to each other
Cilia and Flagella
 Hairlike protrusions from cell membrane
 Nine double fibrils around two single central fibrils
 Cilia move materials across cell surface
 Flagellum propels cell through a medium
Functions of Cell Organelles
 ER - Transport of materials in the cell
 Ribosomes – Site of protein synthesis
 Golgi apparatus – Cell secretion
 Mitochondria – ATP production, cell powerhouse
 Lysosomes – Digestive enzymes
 Centrioles – Cell division
 Cilia – Sweeps material across the cell surface
 Flagellum – Enables a cell to move
4
Think of the “Cell Factory”
Boss give orders to the rest of the factory (DNA in the nucleus surrounded by the
nuclear membrane). The workers (ribosomes) on the assembly line are in the factory
(cytosol) who receive orders for production from the boss’s messanger (mRNA). The
raw materials are the amino acids. When things are sent to the mailroom for outside
delivery (golgi apparatus), they are eventually shuttled to the gates of the factory
(secretory vessels).The gate of the factory controls shipment in and out (cell
membrane). The turbines provide power for the factory (mitochondria).
Movement of Materials Into and Out of Cells
 Passive (Physical) Processes
o Require no cellular energy and include:
 Simple diffusion
 Facilitated diffusion
 Osmosis
 Filtration
 Active (Physiological) Processes
o Require cellular energy and include:
 Active transport
 Endocytosis
 Exocytosis
Diffusion
 Movement of molecules from area of high concentration to low concentration
 Brownian movement - random collision of diffusing molecules
 Accelerated by increased temperature
 Gas exchange in the lungs of body tissue is an example
O2 - CO2 exchange
5
Facilitated Diffusion
 Facilitate means to help or assist
 Molecules move from an area of greater concentration to an area of lesser
concentration, but they need help
o An example is glucose, which is need for ATP production.
o Glucose can’t get through membranes by themselves, so they have a carrier
enzyme or transporter to help facilitate diffusion.
Osmosis
 Movement of water through semipermeable membrane from high water
concentration to low water concentration
 Absorption of water by the small intestines and kidney is an example
o Isotonic solution - salt concentration is the same outside the cell as inside
o Hypotonic solution - salt concentration inside cell is higher than outside cell
o Hypertonic solution -salt concentration higher outside the cell than inside
 Osmotic Pressure – ability of osmosis to generate
enough pressure to move a volume of water
 Osmotic pressure increases as the concentration
of nonpermeable solutes increases
o Isotonic – same osmotic pressure
o Hypertonic – higher osmotic pressure (water loss)
o Hypotonic – lower osmotic pressure (water gain)
Active Transport
 The movement of molecules from an area of lesser concentration to an area of
greater concentration
 Opposite of diffusion
 Requires the energy of ATP to do this
 An example in the body is sodium and potassium pumps in muscle and nerve cells
6
Filtration
 Water and dissolved materials are forced through a membrane from an area of
higher pressure to an area of lower pressure
 In the body, blood pressure is an example of this, with filtration occurring through the
capillaries
Phagocytosis and Pinocytosis
 Phagocytosis
o A moving cell engulfs something
o WBC engulfing bateria
o Think of “pacman”
 Pinocytosis
o A stationary cell engulfs something
o Kidney cells absorbing lost protein
DNA and the Genetic Code
 DNA is a double helix strand of nucleotides, looking like a spiral ladder
o The rungs of the ladder are made up of four different bases, arranged in
different orders and sequences
o These sequences are the genetic code
o The DNA of our 46 chromosomes is the genome which contains 20,000 to
30,000 genes
 If there is a mistake in the DNA, the result is genetic or hereditary disease
7
RNA and Protein Synthesis
 Protein Functions
o structure, enzymes or catalysts, immune response
 Transcription Messenger RNA copies DNA code, leaves nucleus
 Translation (tRNA) picks up amino acids
Cell Division
 Cell division is the process by which a cell reproduces itself
 Two types of cell division
o Mitosis
 One cell with the diploid number of chromosomes divides once to
form two cells, each with the diploid number of chromosomes (46)
 Stages of mitosis
 Prophase, metaphase, anaphase, telophase
 Mitosis is essential for growth and for repair and replacement of
damaged cells
 Most nerve and muscle cells seem unable to divide and their loss
may involve permanent loss of function
o Meiosis: A Reduction Division
 Reduces genetic material from diploid to haploid
 Two divisions resulting in four cells
 Occurs only in the gonads
 In women, meiosis takes place in the ovaries and is called
oogenesis
 In men, meiosis takes place in the testes and is called
spermatogenesis
 Fertilization is the egg uniting with the sperm
Tumors
 Two types of tumors:
o Benign – usually remains localized
o Malignant – invasive and can metastasize; cancerous
 Two major types of genes cause cancer:
o Oncogenes – activate other genes that increase cell division
o Tumor suppressor genes – normally regulate mitosis; if inactivated they are
unable to regulate mitosis
 Cells are now known as “immortal”
8
Cellular Metabolism
 Metabolic processes – all chemical reactions that occur in the body
o Anabolism
 Larger molecules are made from smaller ones
 Requires energy
 Anabolism provides the materials needed for cellular growth and repair
o Catabolism
 Larger molecules are broken down into smaller ones
 Releases energy
 Catabolism breaks down larger molecules into smaller ones
Control of Metabolic Reactions
 Enzymes
o Control rates of metabolic reactions
o Lower activation energy needed to start reactions
o Not consumed in chemical reactions
Factors That Alter Enzymes
 Heat
 Radiation
 Electricity
 Chemicals
 Changes in pH
Energy for Metabolic Reactions
 Energy is the capacity to change something; it is the ability to do work
 Common forms of energy:
o Heat
o Light
o Sound
o Electrical energy
o Mechanical energy
o Chemical energy
9