Download Cells

Cells
Cells
• The basic unit of life
• Microscopic
• Organelles
– Structures within cells that
perform different functions
but work together
• Two types
– Animal cells
– Plant cells
Animal Cell
Plant Cell
Organelles in Animal Cells
• Cell membrane
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Made of proteins and lipids
Thin, partially permeable
Controls exchange of substances in cell
Protects organelles
• Cytoplasm
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Made of water and dissolved substances
Present throughout the cell
Provides nutrients, glycogen granules
Site of chemical reactions
• Nucleus
– Controls cell activities
– Contains genetic material or DNA in chromosomes
Organelles in Animal Cells
• Mitochondrion
– Pleated membrane to increase surface area
– Contains respiratory enzymes
– Produces energy through respiration
• Vacuole
– Fluid-filled membranes
– Small, temporary with no fixed shape
– Exchange of water, minerals and stores
substances including waste
• Endoplasmic Reticulum
– Several membranes
– Make fats and proteins
– Contain ribosomes that make proteins
Organelles in Plant Cells Only
Plant cells contain all the organelles that Animal
cells contain in addition to these:
• Cell wall
– Freely permeable
– Made of cellulose
– Outside cell membrane
– Give shape and protects cell
• Chloroplast
– Contain green chlorophyll and enzymes
– Site of photosynthesis
Organelles in Plant Cells Only
• Starch grains
– Stores carbohydrates
• Vacuole
– Large, permanent with fixed shape
– Contains cell sap
– Supports cell when turgid
– Stores cell waste
• Cytoplasm
– A thin layer
Specialization
• Unicellular organisms made of one cell
– Independent of other cells
– One cell carries out functions
• Multicellular organisms made of many cells
– Each cell does a different job
– All work together and depend on each other
Specialization
• Division of Labour
– Allows organism to increase in size
– Higher productivity and efficiency
– Develop special features to carry out
specific functions
– Different functions can be performed at
the same time
• Similar or identical cells that perform a
specific function are arranged in groups to
form tissues
Cell
Tissues
• Several different kinds of tissues are grouped
to form an organ
Tissue
Organ
• Organs form larger functional units called systems
Organ
System
• Systems are grouped to form an organism
System
Organism
Bacteria
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Unicellular
Microscopic
Release toxins
Not all harmful
Cause diseases
– Tuberculosis
– Typhoid
– Cholera
Viruses
• Unicellular (smaller than bacteria)
• Need other organisms to live
• Reproduce only inside living cells
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Enter body through openings
Attach to then enter host cell
Use the host cell to copy itself
New viruses destroy and leave the
host cell and attack new host cells
• All are harmful and cause diseases
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Common cold
Influenza
AIDS
Measles
Fungi
• Very small (yeast)
or large
(mushrooms)
• Do not cause
many diseases
– Athlelte’s foot
– Ringworm
Fungi cell
Cells of the human body
Reactions
in
Cells
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Osmosis
• Movement of water particles from an area of
high water concentration to an area of low
water concentration across a selectively
permeable membrane.
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Diffusion
• Movement of molecules from a region of high
concentration to a low concentration
– In gases and liquids
– Can occur across thin, permeable membranes
• End- products of digestion diffuse from gut into blood
• Carbon dioxide and Oxygen diffuse between blood and
alveoli
• Between blood and cells
– Characteristics of surfaces for efficient diffusion
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Thin
Concentration gradient
Moist
Large surface area to volume ratio
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Importance of Diffusion and Osmosis
• To bring useful substances to organelles for
reactions to take place
– Glucose and Oxygen in Respiration
• Removal of waste products
– Carbon dioxide from respiration, urea
– These are secreted out of the cell
• Small vessicles transport substances
• Hormones are transported this way
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Active Transport
• Transport of molecules across a membrane
from a region of lower concentration to a
region of higher concentration, using energy.
– Allows cells to take up extra substances already
present in its cytoplasm .e.g liver and glucose
– Allows cell to remove extra substances present in
the cytoplasm.
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