Transcript Structure and Function of Cells and Tissues

LATG
Chapters 6 - 7
Cells & Tissues
Organic Chemistry, Biochemistry
and Infectious Diseases
Cells
Prokaryotic = bacteria, blue-green algae
Eukaryotic = plants, animals, fungi, many unicellular
organisms
Both cell types: have DNA, are membrane bound, have
ribosomes, have similar basic metabolism
Eukaryotic cells: larger (~1000X), more complex DNA,
have a nuclear and organelle membranes, have
cytoskeleton
Cells
Cells
Cells
Cells
Plasma membrane: proteins and lipids that allows fat
soluble molecules to penetrate easily but prohibits water
soluble molecules from going across without facilitated
diffusion or active transport
Cells
Within the lipid bilayer are many types of proteins:
cell receptors, transport proteins, enzymes
Cells
Lipid soluble substances can enter and leave the cell
by passive diffusion following concentration gradients
Cells
Substances can also cross the membranes without
energy expenditure via osmosis = solvent molecules
(usually H20) move across a semi-permeable
membrane due to osmotic pressure
Hypotonic
Hypertonic
Isotonic
Cells
Facilitated or carrier-mediated diffusion occurs with
molecules that are not normally fat soluble, but become
so when combined with a carrier substance allowing
entry or exit from the cell
Cells
Active transport is the movement of substances against a
concentration or electrochemical gradient and usually
requires energy expenditure by the cell
Cells
Cells
Large molecules or entire cells can enter the host cell by
endocytosis either via pinocytosis or phagocytosis and exit
the cell via exocytosis
Cells
The nucleus is made up of DNA = deoxyribonucleic acid,
and RNA = ribonucleic acid, and is involved in cell
reproduction and metabolic activities
Nucleoli may be present in resting cells and are sites of
ribosomal RNA production
The nucleus is surrounded by a nuclear membrane
containing pores and continuous with the endoplasmic
reticulum in some areas
Cells
DNA is made up of chains of nucleotides and form the basic
element of genes which determine all of our inherited
characteristics
Nucleotides consist of a sugar molecule = deoxyribose
bonded with a phosphate group and a nitrogenous base
Nitrogenous bases can be either adenine, guanine, cytosine
or thymine
Cells
DNA is usually found in double, complementary strands that
are held together by hydrogen bonds between the
nitrogenous bases
Adenine binds with thymine, cytosine binds with guanine
When the DNA is not replicating, these strands form a spiral
or double helix
Cells
During DNA
replication, the
complementary
strands separate
and enzymes
known as
polymerases
add new bases
that are identical
to the original
opposite strand
Cells
After the DNA replicates itself, the cell is ready to divide.
At this point there is condensing down of the DNA in the
nucleus from the loosely arranged chromatin into distinct
chromosomes.
Cells
Mitosis, or cell division, produces two genetically identical
cells
Cells
DNA replicates itself, but also can produce RNA in a
process called transcription. The RNA leaves the nucleus
as a single strand
DNA areas in the nucleolus produce ribosomal RNA or
rRNA
Other RNA types are messenger (mRNA) and transfer
(tRNA)
Cells
rRNA combines with proteins to form ribosomes
Ribosomes then ‘read’ the mRNA to synthesize proteins
from amino acids in a process called ‘translation’
Cells
‘Translation’ uses rRNA, mRNA, and tRNA to create
protein molecules from amino acids
Cells
Translation occurs on the surface of the endoplasmic reticulum, a
membrane bound organelle in the cell’s cytoplasm
Cells
Electron microscope pictures
showing the rough ER and
ribosomes producing proteins
Cells
There are other organelles found within the cytoplasm:
The Golgi apparatus is found close to the nucleus and
endoplasmic reticulum. It’s job is to receive, sort and
process the biomolecules it receives from the ER and
resecrete them.
Cells
Mitochondria are used for aerobic respiration and production
of energy (ATP) for the for proper functioning of the cells
metabolic processes.
Cells
Lysosomes are full of enzymes that break down fats,
protein and carbohydrates into their smallest elements to
be used by the mitochondria for energy.
Vacuoles are often found in the cytoplasm and assist in
getting rid of water and waste products from the cell
Cells
Microtubules provide support for the cell known as
the cytoskeleton to help the cell keep its shape
and control flow of elements through the cell.
Centrioles are bundles of microtubules that
assist in separation of the chromosomes
during mitosis when they form into
mitotic spindles.
Microtubules also make up cilia and flagella that are hairlike surface projections used to move the cells themselves
or material around the outside the cells.
Tissues
Cells bound together and serving a specific function are
called tissues and include epithelium, connective tissue,
muscle tissue, and nerve tissue.
Epithelium consists of sheets of cells that have a basal
lamina and an unattached or free edge. It is typically
found lining cavities, blood vessels, gland ducts and
hollow organs.
Tissues
Epithelium serves different functions depending on its type
and location but may be for protection, absorption, secretion
or facilitate movement of substances over its free surface.
Tissues
Connective tissue is found throughout the body and contains
a variety of different cell types, depending on its location.
Dense and loose connective tissue contains fibroblasts and
collagen fibers which provide elasticity to the tissue.
Tissues
Tissues
Adipose tissue contains adipocytes which store fat for
metabolism and is primarily white. Brown fat is in many
species but the greatest amount is found in species that
hibernate and it is thought to have a role in maintaining
body temperature by producing heat.
Tissues
Cartilage contains chondrocytes that are embedded in a
semi-rigid matrix. The number of fibers and density of the
matrix determines whether it is hyaline cartilage, elastic
cartilage, or fibrocartilage.
Tissues
Bone is made up of osteocytes and ground substance that
consists of calcium phosphate. The ends of long bones
contain spongy or cancellous bone while the shaft is
compact bone that surrounds the medullary cavity
containing the bone marrow.
Tissues
The cells found within connective tissue can be fixed as
seen with fibroblasts, chondrocytes, osteocytes, and adipose
cells. They can also be wandering, usually coming from the
blood, as seen with eosinophils, neutrophils, lymphocytes,
monocytes, and mast cells.
Tissues
Muscle cells can either be smooth or striated, depending on
their function and appearance under a microscope.
Smooth muscle is found in most of the our internal organs
and exhibits involuntary rhythmic and tonic contractions.
Tissues
Striated muscle can be either skeletal muscle, that contracts
voluntarily, or cardiac muscle that contracts involuntarily.
Tissues
Nerve tissue is made up of neurons that are cells
characterized by a nucleated cell body, dendrites, and an
axon. Nerves respond to stimuli by polarizing and
depolarizing by varying the concentration of sodium and
potassium ions inside the cell.
Tissues
Many nerves are covered with a myelin sheath that speeds
the conduction of the impulses down the axon. The myelin
is made from part of an oligodendrocyte cell that wraps
around the axon and has gaps in it called nodes of
Ranvier.
Tissues
The axons end either in synapses with other nerve cells, or in
motor end plates, innervating muscle cells. The end releases
neurotransmitters which are chemicals that stimulate the next
nerve or muscle to respond.
Organic Chemistry,
Biochemistry and
Infectious Diseases
Chapter 7
Biochemistry
 The
study of chemistry within living
organisms


Inorganic molecules-water, sodium,
potassium, calcium--molecules without carbon
Organic molecules-carbohydrates, lipids,
proteins--molecules with carbon
Carbohydrates
 The
sugar family of molecules
 Found as mono-, di- and polysaccharides
 Used as energy source, supportive
structures and nucleic acids
Monosaccharides
 Glucose--the
most common simple sugar
found in biological systems


Provides energy for all body systems
Only source of energy for central nervous
system
 Galactose
and fructose are other simple
sugars commonly found
Disaccharides
 Molecules
made up of two simple sugars
 Sucrose, maltose and lactose are two
commonly found disaccarhides
 Both mono- and disaccharides are known
as simple sugars
Polysaccarhides
 Complex
molecules made up of many
(sometimes thousands) simple sugars
 Starch, cellulose and glycogen are the
majors forms in animal and plant life
 Glycogen is the major storage form for
sugars in the mammalian body, primarily in
muscle and liver
Lipids
 Fatty
molecules with multiple functions
within the mammalian body




Energy storage
Protection
Insulation
Cell membranes
Lipids
 Major



forms are
Fatty acids
Triglycerides
Steroids
Fatty Acids
 The
building blocks of most lipids
 Classified as saturated and unsaturated
fatty acids
 Some of the unsaturated fatty acids are
classified as essential--can not be made
by the body
Triglycerides
 Larger
lipid molecule composed of three
fatty acids attached to one glycerol
molecule
 Primary energy storage in the body
Steroids
 Another
type of lipid important in hormonal
balance
 Some steroids





cholesterol
cortisol
testosterone
estrogen
Vitamin D
Proteins
 Made
up of chains of amino acids
 Twenty amino acids are known

Ten of these are essential
 These
20 amino acids combine to form
over 35,000 proteins during a mammal’s
lifetime
Protein Function
 Structure--collagen
 Enzymes--lipase
 Regulatory--G
proteins
 Transport--hemoglobin
 Protective--immunoglobulins
 Hormones--insulin