cells – the building blocks of life. what is a cell? basic unit of all living things fully alive...
TRANSCRIPT
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
paramecium
amoeba bacteria
yeast
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 **
NucleusNucleus
Cell membraneCell membrane
CytoplasmCytoplasm
VacuolesVacuoles
Is it THAT simple?Is it THAT simple?
Structure of an Animal CellStructure of an Animal Cell
Animal cell
Typical animal cell **
NucleusNucleus
Cell membraneCell membrane
CytoplasmCytoplasm
VacuolesVacuoles
• 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
each chromosome is made up of many genes; each gene contains instructions for a different feature of an organism
each chromosome is made up of many genes; each gene contains instructions for a different feature of an organism
genes on a chromosome
genes on a chromosome
nucleusnucleus
chromosomeschromosomes
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
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 **
NucleusNucleus
Cell membraneCell membrane
CytoplasmCytoplasm
VacuolesVacuoles
• 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 **
NucleusNucleus
Cell membraneCell membrane
CytoplasmCytoplasm
VacuolesVacuoles
• Cytoplasm– jelly-like
substance that fills the cell
– contains water and many other substances
– chemical reactions take place here
Typical animal cell **
NucleusNucleus
Cell membraneCell membrane
CytoplasmCytoplasm
VacuolesVacuoles
• Vacuoles– small spaces in
the cytoplasm containing water, food, waste materials etc
– small and numerous in animal cells
NucleusNucleusCell
membraneCell
membrane
VacuoleVacuole CytoplasmCytoplasm
Cellulose cell wall
Cellulose cell wall
ChloroplastsChloroplasts
Typical plant cell **
Functions similar to that of an Animal CellFunctions similar to that of an Animal Cell
Plant cell
VacuoleVacuole CytoplasmCytoplasm
Typical plant cell **
• 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
VacuoleVacuole CytoplasmCytoplasm
Typical plant cell **
• Vacuole−When the plant loses water,
plasmolysis occurs
VacuoleVacuole CytoplasmCytoplasm
Typical plant cell **
• Cytoplasm− Reduced to a thin lining− Still contains water and other
substances, still a place for chemical reactions
• Chloroplasts
– 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
Cellulose cell wall
Cellulose cell wall
ChloroplastsChloroplasts
Typical plant cell **
• Cellulose cell wall– Surrounds the plant cell
– Supports the plant cell and gives it a regular shape
– Absent in animal cells
Cellulose cell wall
Cellulose cell wall
ChloroplastsChloroplasts
Typical plant cell **
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 CellAnimal Cell Plant CellPlant Cell
Does it have a Does it have a cellulose cell wall?cellulose cell wall? No Yes
Does it have a cell Does it have a cell membrane?membrane? Yes Yes
Does it have a Does it have a nucleus?nucleus? Yes Yes
Does it have Does it have cytoplasm?cytoplasm? Yes – it fills the cell Yes – a thin lining only
Does it have Does it have vacuoles?vacuoles? Yes – many, but small Yes – one, or a few,
and large
Does it have Does it have chloroplasts?chloroplasts? No Present only in cells
of green plants
Shape?Shape? Can change Regular (doesn’t change)