Transcript Cells - 2011sec1lss

Cells –
the building blocks of life
What is a cell?
• Basic unit of all living things
• Fully alive
• Capable of reproduction and
respiration*
• Many chemical reactions take
place within the cell
• Contains the elements carbon,
hydrogen and oxygen
Trivia: How did the cell get its name?
• Robert Hooke
• 1665 – used the 1st microscope
ever invented to look at a thin
piece of cork
• Box-like cells reminded him of
the cells of a monastery
• What he actually saw were the
cell walls in cork tissue
Cells from cork tissue
of tree bark
Visualising Cells
• Cells are very small
• Largest cell in the human body
– human egg
0.1 mm
Unicellular organisms
• Uni – “one”
• Living things that are only made up of one cell
yeast
paramecium
amoeba
bacteria
Multicellular organisms
•
•
•
•
Multi – “many”
Plants
Animals
Human adult – 10 trillion cells!
– Are all the cells the same?
– Different sizes, shapes, functions
– Certain similar characteristics
Typical animal cell **
Nucleus
Cytoplasm
Cell
membrane
Vacuoles
Is it THAT
simple?
Structure of an Animal Cell
Animal cell
Typical animal cell **
Nucleus
Cytoplasm
Cell
membrane
Vacuoles
• Nucleus
– Controls all
chemical
reactions and
activities in the
cell, including
reproduction
and cell repair
– Contains
chromosomes
Sidetrack: Chromosomes
• http://www.youtube.com/watch?v=eOvMNOMRRm8
nucleus
chromosomes
genes on a
chromosome
each chromosome is made up of many
genes; each gene contains instructions for
a different feature of an organism
Sidetrack: Chromosomes
• Found in the nucleus
• Made of DNA (deoxyribonucleic
acid) and proteins
• Contains genes – chemical
instructions to build the cell and
control its functions
• Genes are passed down from 1
generation to another hereditary
Human cells
have 23 pairs of
chromosomes
except the
sperm and the
egg (23
individual
chromosomes)
Sex
chromosomes
Genetic Diseases
• Down’s Syndrome
– Extra chromosome in each
cell in his/her body
– 47 chromosomes instead of
46 chromosomes
– Result of unusual cell
division when egg/sperm
was made, or during
fertilisation
– Happens by chance, can
happen to anyone
Typical animal cell **
Nucleus
Cytoplasm
Cell
membrane
Vacuoles
• Cell membrane
– Thin layer around
the cell
– Allows shape of
cell to change
– Partially
permeable,
controls
movement of
materials in and
out of the cell
– Carbon dioxide,
oxygen, water
can pass through
Typical animal cell **
Nucleus
Cytoplasm
Cell
membrane
Vacuoles
• Cytoplasm
– jelly-like
substance that
fills the cell
– contains water
and many other
substances
– chemical
reactions take
place here
Typical animal cell **
Nucleus
Cytoplasm
Cell
membrane
Vacuoles
• Vacuoles
– small spaces in
the cytoplasm
containing
water, food,
waste
materials etc
– small and
numerous in
animal cells
Typical plant cell **
Vacuole
Chloroplasts
Nucleus
Cytoplasm
Cellulose cell
wall
Cell
membrane
Functions similar to that of an Animal Cell
Plant cell
Typical plant cell **
Vacuole
Cytoplasm
• Vacuole
− Single large vacuole
− Biggest part of the cell
− Filled with cell sap (contains
substances such as sugars and
salts dissolved in water)
− Cell sap keeps the cell firm by
taking in water
Typical plant cell **
Vacuole
Cytoplasm
• Vacuole
− When the plant loses water,
plasmolysis occurs
Click here to find out more
Typical plant cell **
Vacuole
Cytoplasm
• Cytoplasm
− Reduced to a thin lining
− Still contains water and other
substances, still a place for
chemical reactions
Typical plant cell **
• Chloroplasts
Chloroplasts
Cellulose cell
wall
– Tiny disc-like structures containing
a green pigment called chlorophyll
– Chlorophyll traps light energy from
the sun so that plants can make
food during photosynthesis
– Absent in animal cells
Typical plant cell **
• Cellulose cell wall
– Surrounds the plant cell
Chloroplasts
Cellulose cell
wall
– Supports the plant cell and gives it
a regular shape
– Absent in animal cells
Sidetrack: Cellulose
• Compound containing carbon,
hydrogen and oxygen
• A type of fibre
– Dietary fibre present in fruits and
vegetables
– Manufacture of cardboard and
papers (from wood pulp)
Animal Cell
Plant Cell
Does it have a
cellulose cell wall?
No
Yes
Does it have a cell
membrane?
Yes
Yes
Does it have a
nucleus?
Yes
Yes
Does it have
cytoplasm?
Yes – it fills the cell
Yes – a thin lining only
Does it have
vacuoles?
Yes – many, but small
Yes – one, or a few,
and large
Does it have
chloroplasts?
No
Present only in cells
of green plants
Shape?
Can change
Regular (doesn’t change)