What is Biology? Biology is the Science of Our Lives. Biology literally means "the study of life " "the study of life ".
Majmaah University Preparatory Year Program Colleges of Medicine
Biology Course Title: Biology for Premedical Students Course Code:
Biol. 126 Credit Hours: 3 (2+1) Prerequisites : None Required
Text(s) Campbell, N. A. and Reece, J. B. (2005). Biology (6 th
edition). Pearson Education. Inc. USA. What is Biology? Biology is
the Science of Our Lives. Biology literally means "the study of
life " "the study of life ". Some Branches of Biology O Cell
biology: The study of the cell as a complete unit, and the
molecular and chemical interactions that occur within a living
cell. O Embryology: The study of the development of embryo. O
Entomology: The study of insects O Ecology: The study of
interactions among organisms and their environment. O Microbiology:
The study of microscopic organisms (microorganisms) and their
interactions with other living things. O Parasitology: The study of
parasites and parasitism. O Anatomy: The study of form, in plants,
animals, and other organisms, or specifically in humans. Histology:
The study of cells and tissues ( a microscopic branch of anatomy).
Ethology: The study of animal behavior. Genetics : the study of
genes and heredity. O Molecular Biology: The study of biology and
biological functions at the molecular level. O Neurobiology: The
study of the nervous system. O Pathology: The study of diseases,
and the causes, processes, nature, and development of disease.
Epidemiology: The study of factors affecting the health and illness
of populations. Biochemistry: The study of the chemical reactions
required for life to exist and function, usually a focus on the
cellular level. Bioinformatics: The use of information technology
for the study, collection, and storage of genomic and other
biological data What Is Life? Growth and development Metabolism
Homeostasis Movement Response to stimuli Reproduction Evolution and
adaptation Characteristics of living things Living things have a
variety of common characteristics: Organization: Living things
exhibit a high level of organization, with multicellular organisms
being subdivided into cells, and cells into organelles, and
organelles into molecules, etc. Levels of organization 1. Biosphere
Land water atmosphere (inhabited by life). 2. Ecosystem Living
thing and non-living thing with which life interacts in particular
area (forests or oceans or deserts). 3.Community living different
species in particular ecosystem. 4.Population one species.
5.Organism one individual (Body). 6. Organs group of tissues 7.
Tissues groups of cells 8. Cells 9. Organelles 10. Molecules
Homeostasis: is the maintenance of a constant (yet also dynamic)
internal environment in terms of temperature, pH, water
concentrations, etc. Much of our own metabolic energy goes toward
keeping within our own homeostatic lim its. Adaptation: Living
things are suited to their mode of existence. O Reproduction and
heredity: -Cells must have some way of reproducing, whether that
involves asexual (no recombination of genetic material) or sexual
(recombination of genetic material). -Most living things use the
chemical DNA (deoxyribonucleic acid) as the physical carrier of the
genetic information. -Some organisms, such as retroviruses (of
which HIV is a member), use RNA (ribonucleic acid) as the carrier.
Growth and development: Even single-celled organisms grow O
Multicellular organisms pass through a more complicated process of
differentiation and organogenesis. O Energy acquisition and
release: One view of life is that it is a struggle to acquire
energy (from sunlight, inorganic chemicals, or another organism),
and release it in the process of forming ATP ( adenosine
triphosphate ). O Detection and response to stimuli ( both internal
and external). O Interactions: Living things interact with their
environment as well as each other. The various types of symbioses
(organismal interactions with each other) are examples of this.
eg;gut flora Cell Theory 1- All organisms are composed of one or
more of cells. 2- Cell is the basic unit of life. 3- The new cell
arises only from pre-existing cell. pre-existing cell. The Cell The
Organisms Basic Unit of Structure and Function
ProkaryoticProkaryotic EukaryoticEukaryotic Types of cells of cells
Micro-organisms All other forms of life Prokaryotes Generalized
Prokaryote Capsule Cell Wall Plasma Membrane Cytosol Nucleoid DNA
Flagellum Plasmid DNA Typical shapes of bacteria Most bacteria
retain a particular shape ; a few are polymorphic Bacterial Shape
and Arrangement 24 VirusesViruses Page 328 Characters of viruses O
Viruses are much smaller than bacteria. O Virus is about 20nm in
diameter. O Viruses are not cells. O A virus is a genome enclosed
in a protective coat 26 Genome ( DNA/RNA ) Protein coat () Protein
coat (capsid) Virus is a genome enclosed in a protective coat 27 A
protein shell that encloses the viral genome. It is rode-shaped,
helical, polyhedral or more complex. Capsomeres: Are the protein
units that form capsid. A- Capsid Page 329, 330 Capsomeres (
proteins ) Capsid Sometimes further rapped in a membranous envelope
(Viral envelope ), eg. Influenza virus. viral envelope Membranous
envelop ( viral envelope ) 28 viral envelopes Some viruses have
viral envelopes, membranes cloaking their capsids. These envelopes
are derived from the membrane of the host cell. Fig. 18.2c, Page
330 B- Envelop 29 Viral Genome: (Hereditary material ) Viral
genomes may consist of: - double-stranded DNA (dsDNA), -
single-stranded DNA (ssDNA), - double-stranded RNA (dsRNA), -
single-stranded RNA (ssRNA). depending on the specific type of
virus. The viral genome is usually organized as a single linear or
circular molecule of nucleic acid. four genesseveral hundred The
smallest viruses have only four genes, while the largest have
several hundred. 30 - DNA enclosed in a protein coat ( sometimes,
membranous envelop also ) - Can be crystallised Key
CharactersViruses Key Characters Viruses - Reproduced only within a
living host cell - Reproduced only within a living host cell (
obligate parasitism ). - They lack enzymes for metabolism - Have no
ribosomes for making their own proteins - Each type of virus
infects a limited range of host cells (host range ) Human cold AIDS
Most viruses of eukaryotes attack specific tissues. eg. Human cold
viruses infect only the cells lining the upper respiratory tract,
and AIDS virus binds only to certain white blood cells (Immune
system). Eu: True Karyon: Nucleus Animal Cell Plant Cell Eukaryotic
Cell 33 Eukaryotic Cells Not in plant cell: -Lysosomes -
centrosomes with centrioles - flagella Not in plant cell:
-Lysosomes - centrosomes with centrioles - flagella 34 Generalized
Cell Animal Cell Plant Cell Nucleus Golgi Mitochondria Endoplasmic
Reticulum Centrioles Chloroplasts characters Animal cell Plant cell
O Absent O One or more small O Absent O only cell membrane O
Present O One, large central vacuole O Present O cell wall and a
cell membrane O Absent Cell wall Vacuole Chloroplast Plasma
Membrane Lysosomes Centrioles Flagella All cells are surrounded by
a plasma membrane . The semi-fluid substance within the cell is the
cytosol, containing the cell organelles . All cells contain
chromosomes which have genes in the form of DNA. All cells also
have Ribosomes, tiny organelles that make proteins using the
instructions contained in genes. All cells are surrounded by a
plasma membrane . The semi-fluid substance within the cell is the
cytosol, containing the cell organelles . All cells contain
chromosomes which have genes in the form of DNA. All cells also
have Ribosomes, tiny organelles that make proteins using the
instructions contained in genes. Similarities Similarities A major
difference between prokaryotic and eukaryotic cells is the location
of chromosomes In an eukaryotic cell, chromosomes are contained in
a true nucleus ( ). In a prokaryotic cell, the DNA is concentrated
in the nucleoid ( ) without a membrane ( ) separating it from the
rest of the cell. In prokaryotic cell, DNA is a single strand ( )
or double strand ( ) DNA. But in eukaryotic cell, DNA is double
strand. A major difference between prokaryotic and eukaryotic cells
is the location of chromosomes In an eukaryotic cell, chromosomes
are contained in a true nucleus ( ). In a prokaryotic cell, the DNA
is concentrated in the nucleoid ( ) without a membrane ( )
separating it from the rest of the cell. In prokaryotic cell, DNA
is a single strand ( ) or double strand ( ) DNA. But in eukaryotic
cell, DNA is double strand. Differences Differences
