Science 8 Name: ____________

The Discovery of Cells

Cells The basic unit of living organisms

The Cell Theory Robert Hooke in the ______ observed cork under a microscope and

named the structures he saw ________ Many scientists then studied cells. Their work is summarized in

the ____ ____________:o All organisms are made up of one or more cellso The cell is the basic unit of structure and organization of

organismso All cells come from preexisting cells

Types of microscopes ________ light microscopes: use lenses to magnify objects up to

1500 times ____________ microscope: uses a beam of electrons to magnify

objects up to 500,000 times

Two basic cell types All cells have ___________: __________ structures in a cell with a

specific function1. ___________ cells: have no _________-bound organelles

example: bacteria2. ___________ cells: have_____________-bound organelles

examples: plant and animal cells

Types of Eukaryotic Cells Plant cellso Tend to be ___________or rectangularo Examples: Trees, flowers, vegetables

Animal cellso Tend to be ___________o Examples: Animals, insects, humans

2

Organelles in eukaryotic cellsOrganelle

NameFunction Found in…

Plasma (Cell) membrane

Allows ________ to move in and out of cell

Plant & animal cells

Cytoplasm clear _______ inside a cell Plant & animal cells

Ribosome Makes ___________ Plant & animal cells

Endoplasmic reticulum (ER)

Chemical ___________ Plant & animal cells

Golgi apparatus

Sorts and transports proteins Plant & animal cells

Mitochondrion Makes usable energy for the cell Plant & animal cells

Nucleus Cell ________ center that contains the DNA [chromosomes]

Plant & animal cells

Nucleolus Inside the nucleus; Makes ribosomes

Plant & animal cells

Vacuole Stores _______, water, and waste Plant & animal cells

Cytoskeleton network of rods that _______ the cell’s shape

Plant & animal cells

Cell wall _________ and __________ the cell Plant cells only

Chloroplast Contains green chlorophyll pigment which captures sunlight to produce food

Plant cells only

Lysosome ___________ food particles, old organelles, bacteria, and viruses

Animal cells only

Centrioles Help in cell division Animal cells only

Cilia Short ________ on the outside of the cell for movement

Animal cells only

Flagella Long _______ on the outside of a cell for movement

Animal cells only

Prokaryotic cells Bacterial cells Much _________ and ____________ than eukaryotic cells Organelles include only

o a plasma membrane

3

o cell wallo capsule: extra protective layer outside the cell wallo ribosomeso single loop of DNA free in the cytoplasmo sometimes has pili: small hairs on the outside of the cell

used for movemento sometimes has ____________

The Plasma Membrane _____________what enters and leaves the cell maintains homeostasis (balancen in the cell)o Allows water, oxygen, and glucose to enter when there’s not

enougho Allows water, carbon dioxide, and waste to leave when there’s

too much selective ____________: the membrane allows some molecules, but

not all, to pass through

4

DNA

Made up of a molecule called a phospholipid o lipid with a phosphate group

Plasma _______________ is a phospholipid bilayero 2 layers of phospholipids back-to-backo Polar heads face the water inside and outside the cello Nonpolar tails hide from water inside the membrane

5

Charged and likes to be near water

Uncharged and does not like to be near water

Viruses

Virus

____ __________ organism with a _______ structure that ______ reproduce on its own

Some people think its __________, others think its _______ because it cannot reproduce on its own

It must _________ another cell to __________

Structure

Very simple and ______ – much smaller than a ________, animal, or plant cell

Different __________ can have ___________ shapes but always have the same parts

How viruses reproduce

Viruses don’t have all the ________ needed to ________ on their own

6

_______: Help the virus to attach to

host cells

Capsid:_______ coat to protect

the chromosome 1 Chromosome

(Inside the virus)

Animal Virus – the type of virus that makes people sicak

So they have to _______ other cells and use the ______ in the other cells to __________

Host cell: An ________, plant, or bacterial cell that is _______ by a virus

7

2. Virus _______ its chromosome into the host cell

3. The virus chromosome uses tools in the host cell to make more _________

4. New viruses bust out of the host cell, _______ the host cell

Chromosome

Host cell

Virus

1. Virus attaches to a host cell using its _________