Cells

Mr. Balog- Biology

Cell Theory

• All living things are composed of one or more cells

• Cells arise from pre-existing cells (cells contain the hereditary information of the organisms of which they are apart)

• The cell is the basic unit of life

Microscopes

• Light (Compound Microscope)- allows us to view Eukaryotic cells, some organelles and some bacteria

• Electron Microscope- can view all cells, viruses and small molecules

Eukaryotes vs. Prokaryotes• The difference between the two groups is the presence or

absence of a nucleus surrounded by a nuclear membrane• Prokaryotes are also much smaller

Eukaryotic Cells• All Eukaryotic cells have a defined nucleus,

cytoplasm, organelles and a cellular membrane.

Eukaryotic Cells

Cell Membrane• Every cell has some form of cell membrane that holds the cell

together. Membranes are thin, flexible, and have passageways to let materials in and out of the cell.

Membranes are found in all living organisms.

• The cell membrane regulates movement of matter into or out of the cell.

• Also called the Plasma Membrane

Fluid Mosaic Model

• The cell membrane consists of two basic parts:

i. a phospholipid bilayer (“fluid”)

ii. membrane proteins (“mosaic”)

Plasma Membrane

Plasma Membrane

• The plasma membrane of all cells is semi-permeable and selectively permeable.

• It allows for sufficient passage of oxygen, nutrients and wastes to serve the entire cell.

Cell Wall

• Found only in plants

• The thick outer wall of a plant cell

• Provides structure and support to plant

• Made up of cellulose• Plants do not have bone

Cell Wall

Nucleus

• All Eukaryotic cells have a clearly defined nucleus.

• The nucleus is defined by the nuclear membrane.

• The nuclear membrane is a double membrane.

• The nuclear membrane contains pores that allow for the movement of particles.

Nucleus

Nuclear Membrane

Function of the Nucleus• The nucleus contains all of the genetic

information of the cell, DNA.

• It controls all of the daily activities of the cell (protein synthesis) and acts like a “brain”.

• DNA is loosely organized as chromatin (DNA and proteins) unless the cell is undergoing division where the chromatin becomes more organized to form chromosomes.

Nucleolus

• A small dark shaped circle within the nucleus.

• It synthesizes the parts that make up the cells ribosomes.

Cytoplasm• Gel-like substance inside the cell• Dissolves nutrients throughout the cell• Suspends organelles so that they don’t bump into

each other

Organelles- Structure and Function

• Organelles are the different components that make up the cell

• They are like the organs of the cell, all with different structures and functions

Ribosomes

• Very very small snowman shaped organelles

• Responsible for protein synthesis• Tony Roma’s • RIBS = protein• RIBS = RIBoSomes

Endomembrane System

• The endomembrane system includes the nuclear envelope (nuclear membrane), endoplasmic recticulum, Golgi apparatus, lysosomes, vacuoles (plants) and the plasma membrane

• Each part of the endomembrane system has a different structure and function

Endomembrane System

Endoplasmic Reticulum (ER)

• Means “within the cytoplasm” and “network” in Latin.

• Endoplasmic Reticulum– long system of tubes and canals throughout

cell– provides for intracellular (inside the cell)

transport of molecules• like a subway system in a city

Rough Endoplasmic Reticulum

• When ribosomes are attached to the ER, it appears “rough”

Endoplasmic Reticulum

Endoplasmic Recticulum

Golgi Apparatus

• These folded stacks of membrane are responsible for storing, modifying, and transporting newly synthesized materials in the cell.

• Looks like a stack of pancakes

• Packages materials (proteins) for export throughout the cell or outside of the cell

Golgi Apparatus

Lysosomes

• Membrane enclosed sac of enzymes

• Digest large molecules (4 organic compounds)

• Acidic Environment

Powerhouses of the Cell

• Mitochondrion– organelle within all cells– looks like a long worm inside a sandwich bag– produces ATP (energy)– site of cellular respiration

• Chloroplast– organelle within plant cells only– captures light energy– site of photosynthesis

Mitochondrion

Mitochondrion

Chloroplasts

Plant Vs. Animal

• Plant cells and animal cells differ in a few ways.

1) Only plant cells contain chloroplasts

2) Plant cells contain a LARGE central vacuole

3) Only plant cells contain a cell wall

4) Only animal cells contain lysosomes

5) Animal cells have centrioles

Plant Vs. Animal

Cytoskeleton• Copy p. 129 chart into your notes

Cilia and Flagella

• P. 131 of your textbook

• Cilia are small and hair-like. They move in a swaying motion.

• Flagella are larger and move in a swirling motion.

Cilia and Flagella

Surface Area to Volume Ratio• Cells are restricted to a size that assures a

surface area to volume ratio that provides a sufficient membrane area to meet the transport needs of a cell.

• Explained mathematically, as surface area is squared, the volume is cubed.

• When the cell membrane can no longer provide the cell with material for life processes or rid the cell of wastes – the cell divides.

• As a cell increases in size, its volume grows faster than does its surface area (membrane).

Surface Area to Volume Ratio

Regulation of Cellular Environment• Permeable means

– any molecule may pass through the membrane

• Non-permeable means– nothing can pass through the membrane

• Semi-permeable means– only water (or your favorite molecule) can pass through

the membrane

• Selectively permeable means– only things of a certain size may pass through the

membrane.• Example is a baseball diamond’s mesh backstop

– golf balls may pass through, but basket balls may not.» The hole size is related to the particle size.

Diffusion

• Diffusion– passive (no energy is required)– the movement of anything from an area of

high concentration to an area of low concentration

• e.g. a bad fart in the corner of the classroom.

Osmosis

– passive– the movement of WATER through a semi-

permeable membrane– from an area of high water concentration to an

area of low water concentration.

Active Transport

• Active Transport– uses ATP to move (pump) molecules…

• against a concentration gradient• or with a concentration gradient but at a faster

speed than can be accounted for by simple diffusion

– e.g. seaweed near Vancouver contains 200 X the iodine concentration compared to the surrounding water.

Extreme Transport

• Endocytosis– bringing material into the cell– Pinocytosis

• Cell drinking

– Phagocytosis• Cell eating

• Exocytosis

- material leaving the cell