SBI 3C

SEPTEMBER 2012

THE BIG QUESTION

HOW DO YOU KNOW IF SOMETHING IS ALIVE??

CHARACTERISTICS OF LIVING THINGS: Stimulus and response Require energy Produce waste Grow and reproduce

THE CELL THEORY

1. All living things are made up of cells

2. The cell is the basic functional unit of living things

3. All cells come from pre-existing cells through cell division

WHAT DO CELLS DO? Cellular respiration:

In the mitochondriaglucose + oxygen energy + water + carbon dioxide

Absorption:Bring in water and nutrients into cells

Excretion:Remove waste products from cells

Biosynthesis:Make larger molecules out of smaller onesExamples:

○ Amino acids join together to make protein○ Sugar molecules join together to make carbohydrates

GENERAL STRUCTURE OF A CELL: Inside is a liquid, water-based solution

called cytoplasm Little organs (organelles) sit in the liquid Cells are surrounded by a membrane

that separates them from the outside

organellemembrane

cytoplasm

TYPES OF CELLS:

There are 2 types of cells:Animal CellsPlant Cells

ANIMAL CELLS:

PLANT CELLS:

ORGANELLES: CELL WALL:

Only in plantsFirm but porous, surrounds cells giving them

rigidity

CELL MEMBRANE:Only in animal cellsSurrounds cell and organelles in cellComposed of a bilayer (double layer) of fat (lipid)

molecules called phospholipid bilayer

NUCLEUS: Control centre of the

cellContains DNASurrounded by a porous

double membrane (nuclear envelope)

Filled with nucleoplasm (like cytoplasm)

DNA AND RNA:

DNA: double stranded, found in nucleus

RNA: single stranded, found in cytoplasm

Chemical storage of information needed to keep the cell alive and functioning properly

RNA DNA

RIBOSOMES:Used to produce proteinEither free floating in cytoplasm or attached

to membranesVery small

ENDOPLASMIC RETICULUM:System of tubes and canals that attach to the nuclear

envelopeTwo types:

○ Rough ER (RER) has ribosomes and is the site of protein manufacturing

○ Smooth ER (SER) no ribosomes and is where fat molecules are produced

GOLGI APPARATUS:

Stacks of membraneous tubes Takes proteins from the ER and

changes them Packages them into vesicles to be

released outside the cells

LYSOSOMES:Found only in animal cellsContain protein that help to digest food or

kill invading bacteria or virusesAlso kills dead or dying cells, called the

suicide sac

MITOCHONDRIA:

Shaped like a kidney bean Float in the cytoplasm Site of chemical reactions that produce

energy for the cell Powerhouse of the cell

PLASTIDS: Only in plant cells Fairly large Different types have different functions:

storage (amyloplast - stores starch)energy production(chloroplast-site of photosynthesis)

VACUOLES: Common in plant cells Large, membrane bound sac Filled with watery solution containing

dissolved sugars, proteins, minerals Pressure from water (turgor pressure)

prevents plants from wilting