Cell Structure & Function
Cell Theory• All living things are made up of cells. • Cells are the smallest working units of all
living things. • All cells come from preexisting cells
through cell division.
• Cells are small so they can exchange materials with their surroundings.
Definition of Cell
A cell is the smallest unit that is capable of performing life
functions.
Examples of CellsAmoeba Proteus
Plant Stem
Red Blood Cell
Nerve Cell
Bacteria
Two Types of Cells
•Prokaryotic
•Eukaryotic
Living cells classified into 2 different types based on internal structure
• Prokaryotic cells – little defined internal structure. Lack a clearly defined structure to house their DNA. Organisms made up of prokaryotic cells are called Prokaryotes (all bacteria, all archaeans)
• Eukaryotic cells – more complex structure. Contain many different kinds of membrane-bound structures called organelles suspended in cytosol.
Types of Cells
REVIEW• What are the main differences between
Prokaryotic and Eukaryotic cells?• List one key point from the cell theory• What is the definition of a cell?• Why does a small cell have more surface
area to volume?
Prokaryotic• Do not have
structures surrounded by membranes
• Few internal structures
• One-celled organisms, Bacteria
Prokaryotic Cells• Prokaryotic cells include the bacteria and
archaea.
• Bacterial cells have these constant features:• Outer Boundary: Cell wall• Plasma membrane• Cytoplasm: Ribosomes• Thylakoids (Cyanobacteria)• Many enzymes• Nucleoid: Chromosome (DNA only)
Eukaryotic Cells
• Eukaryotic cells have a nucleus that controls the workings of the cell.
• All cells are surrounded by a plasma membrane made of phospholipids and proteins.
Eukaryotic• Contain organelles surrounded by membranes• Most living organisms
Plant Animal
• The plasma membrane regulates what enters and exits the cell.
• Inside the plasma membrane, the nucleus is surrounded by cytoplasm.
• Cytoplasm is a semi-fluid medium.
• Plant cells have a cell wall in addition to the plasma membrane.
• Primary cell walls are made from cellulose. The secondary cell wall, which forms inside the primary wall, is formed from lignin. Its purpose is to give strength to the cell.
REVIEW• List one main difference between plant
and animal cells• Do plant and animal cells have
organelles?• What is the function of organelles?
Animal cell anatomy
“Typical” Animal Cell
Plant cell anatomy
“Typical” Plant Cell
REVIEW• What are the main similarities and
differences between plant and animal cells?
Cell PartsOrganelles
• Animal and plant cells have organelles.
• Organelles compartmentalize functions within the cell.
• The organelles of animal and plant cells are similar to each other except that centrioles are present only in animal cells, and chloroplasts are present only in plant cells.
Surrounding the Cell
Cell Membrane
• Outer membrane of cell that controls movement in and out of the cell
• Double layer
Cell Wall• Most commonly found
in plant cells & bacteria
• Supports & protects cells
REVIEW• Which structure surrounds a cell?• Briefly outline the cell theory
Inside the Cell
Nucleus
• Directs cell activities• Separated from cytoplasm by nuclear
membrane• Contains genetic material - DNA
Nuclear Membrane• Surrounds nucleus• Made of two layers• Openings allow
material to enter and leave nucleus
Chromosomes• In nucleus• Made of DNA• Contain instructions
for traits & characteristics
Nucleolus• Inside nucleus• Contains RNA to build
proteins
Cytoplasm• Gel-like mixture• Surrounded by cell membrane• Contains hereditary material
Endoplasmic Reticulum• Moves materials around
in cell• Smooth type: lacks
ribosomes• Rough type (pictured):
ribosomes embedded in surface
Ribosomes• Each cell contains
thousands• Make proteins• Found on rough
endoplasmic reticulum & floating throughout the cell
Mitochondria• Produces energy through
chemical reactions – breaking down fats & carbohydrates
• Controls level of water and other materials in cell
• Recycles and decomposes proteins, fats, and carbohydrates
Golgi Bodies• Protein 'packaging
plant'• Move materials within
the cell• Move materials out of
the cell
Cilia and flagella• Cilia and flagella - 9 + 2 pattern of
microtubules• Involved in movement (cell, eggs,
debris)
• Each cilium and flagellum has a basal body at its base.
Structure of a flagellum or cilium
Lysosome• Digestive 'plant' for
proteins, fats, and carbohydrates
• Transports undigested material to cell membrane for removal
• Cell breaks down if lysosome explodes
Vacuoles• Membrane-bound
sacs for storage, digestion, and waste removal
• Contains water solution
• Help plants maintain shape
Chloroplast• Usually found in plant
cells• Contains green
chlorophyll• Where
photosynthesis takes place
REVIEW• List 5 structures within a cell• What do golgi do?• What does the mitochondria do?• What is the function of the cytoplasm?• What is the function of the nucleus?• What does the nuclear membrane allow to happen?• What is the function of the nucleolus?• What is the function of the lysosome?• What is the function of the endoplasmic reticulum?• Why don’t animal cells contain chloroplasts?
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