Download 2.3 note full - Grade 8A/B Science

2.3: Plant and Animal Cellular Processes
Your cells are always busy!! Even if you are asleep! Materials constantly enter the cell using
diffusion or osmosis, energy always being made from sugar and converted into ATP. Organelles
are transporting this energy, building proteins, expelling waste and sending messages.
Transforming Energy
 All cellular activities like growth, repair and reproduction need ENERGY!!!
 Mitochondria provide energy to the cell by breaking down sugar and using
the energy released to create ATP, which is our cells currency for energy!
(like money)
 This process is called cellular respiration!!!!!
o Occurs in both animal and plant cells
o Reactants= sugar and oxygen gas (what you start with)
o Products= carbon dioxide and water and ATP!! (what you end with)
 Photosynthesis- production of sugar by producers using chlorophyll
contained in chloroplasts to trap the suns energy in the bonds of sugar
created
o In plants only
o Reactants= carbon dioxide, water and sun’s energy
o Products= sugar and oxygen gas (do you notice anything interesting
here??)
o Plants then break down this sugar using their own mitochondria to get
ATP for cellular processes (just like animal cells)
o So plants make their own food (called autotrophs!)
Processing and Transporting Materials
 Water, gases like oxygen gas and carbon dioxide and some nutrients can
simply move across the cell membrane- come in and out of the cell
 They move to various organelles- whichever one needs them
 Endoplasmic reticulum- makes and assembles complex proteins and passes
them on to the Golgi Apparatus for packaging and delivery
 Lysosomes (food vacuoles)- will break down food and digest it and take
care of waste
 Nucleus- controls all of these activities and carries out the orders by use of
messenger proteins
Cell Reproduction
 Cells have a lifespan and die- they need to die to keep your body healthy
 Programmed cell death is called APOPTOSIS!
 It ensures that any cell does not get too big (remember cells are small so
essential processes like diffusion and osmosis can occur quickly)
 It also ensures that the DNA contained in the nucleus of every cell stays
correct and does not accumulate too many errors (mutations)
 Amoeba are unicellular and they will live for 2 days
 Human brain cells can live for 120 days
 Skin cells live for 20 days
 This reflects on how quickly those cells can accumulate errors
 The average human body will have about 3 billion cells die every day
 Cells can die through programmed cell death because they have damages,
have not received proper nutrition or they have reached the end of their
lifespan
 All of these cells that die must be replaced
 Cells duplicate in order to replace themselves
 During cell division
o cell will copy all its DNA
o make more organelles and cytoplasm
o nucleus will split in 2
o each nucleus, along with appropriate organelles will move to 1 of
the 2 ends of cell, which are called the 2 poles
o then the cell membrane pinches off in the center to create 2
identical cells (Cleavage furrow)
 There are distinct stages to this process of cell division (mitosis), but you
will learn them later
 In a plant cell, there is no pinching in the center of the cell. A wall, called
a plate. Will begin to form in the center of the dividing cell after all the
organelles have moved to the poles.