Larry M. Frolich, Ph.D. Biology Department, Yavapai College Cell Structure and Function Cells as fundamental living unitCells as fundamental living unit

Larry M. Frolich, Ph.D.Biology Department, Yavapai College

Cell Structure and Function

• Cells as fundamental living unitCells as fundamental living unit

• Prokaryotic and Eukaryotic CellsProkaryotic and Eukaryotic Cells

• Cell MembranesCell Membranes

• Protein synthesis (quick overview)Protein synthesis (quick overview)

• Organelles and parts of a cellOrganelles and parts of a cell


What is Life? • Life needs energy• Life reproduces• Life grows and

develops• Life maintains a

stable condition—homeostasis

• Life responds to stimulus

• Life is organized because it has evolved


Life Evolves• Life is organized

hierarchically• Evolution explains

organization at every level of hierarchy

• All living organisms or species can be understood at every level of hierarchy

• All current living species (including humans) have evolved and are evolving


• Cells are the basic and fundamental unit of life

• The first life was cellular life

• The Molecules of Life are what cells and all their internal parts are made up of

Cells are fundamental unit of life


Two types of cells• Prokaryotic cells

– Relatively Simple– Relatively Small– No organelles with Molecules of Life

distributed throughout cytoplasm– Bacteria are all prokaryotic cells

• Eukaryotic cells– More complex– Much bigger (100 x size of prokaryotic

cells)– Internally organized with membrane-bound

organelles– Multi-cellular organisms, like plants and

animals, are all made up of eukaryotic cells


Eukaryotic cell


Endosymbiotic origin of mitochondria and chloroplasts

• Eukaryotic cells evolved from fusion or integration of prokaryotic cells

• Best evidence is in bacterial or prokaryotic appearance of mitochondria and chloroplasts

• These organelles are like little bacterial cells within our cells, now fully functionally integrated

• They perform fundamental cell functions. Mitochondria process sugars to produce energy; chloroplasts make sugars by photosynthesis

• But they maintain their own DNA and genetic control


Prokaryotic cells have:

• Cell membrane• DNA molecule loose in cytoplasm• Small Ribosomes where proteins are

assembled from DNA information• Microtubule structures like flagella and

cilia• Mitochondria and chloroplasts share most

of these features, including their own independent DNA


WHAT EUKARYOTIC CELLS HAVE:

• Cell membrane• Nucleus• Mitochondria (and sometimes chloroplasts for

photosynthesis) • Larger ribosomes for protein assembly from DNA

information• Internal membranes that organize cellular spaces and

distribution of Molecules of Life within cell (“cytoskeleton”)

Eukaryotic cells (like our human cells) have:


WHAT CAN EUKARYOTIC CELLS DO?

WHAT STRUCTURES ARE INVOLVED?

Separate inside of cell from external environment and control what substances pass across membrane

Cell Membrane

Produce proteins/enzymes that catalyze chemical reactions or control movement across membrane

Nucleus (DNA), Ribosomes on rough endoplasmic reticulum

Break down sugars to form energy which is stored in phosphate bonds of ATP

Mitochondria

Organize distribution of Molecules of Life (macromolecules) and ions throughout cell

Internal membrane system and “cytoskeleton” (ER, lysosomes, vessicles, microtubules)

Move Flagella, cilia, pseudopods


A cell membrane or plasma membrane separates cell from outside world—creates ability to regulate internal environment (homeostasis)


cell membrane


What are some characteristics of the plasma membrane?

• It is a phospholipid bilayer• It is embedded with

proteins that move in space

• It contains cholesterol for support

• It contains carbohydrates on proteins and lipids

• Selectively permeable

cell membrane


What does selectively permeable mean?

• The membrane allows some things in while keeping other substances out

cell membrane


How do things move across the plasma membrane?

1. Diffusion

2. Osmosis

3. Facilitated transport

4. Active transport

5. Endocytosis and exocytosis

cell membrane


What are diffusion and osmosis?

• 1. Diffusion is the random movement of molecules from a higher concentration to a lower concentration

• 2. Osmosis is the diffusion of water molecules

cell membrane


How does tonicity change a cell?

• Hypertonic solutions have more solute than the insideof the cell and lead to lysis (bursting)

• Hypotonic solutions have less solute than the inside of the cell and lead to crenation (shriveling)

• Isotonic solutions have equal amounts of solute inside and outside the cell and thus does not affect the cell

cell membrane


What are facilitated diffusion and active transport?

• 3. Facilitated transport is the transport of molecules across the plasma membrane from higher concentration to lower concentration via a protein carrier

• 4. Active transport is the movement of molecules from a lower to higher concentration using ATP as energy; requires a protein carrier

cell membrane


What are endocytosis and exocytosis?

• 5. Endocytosis transports molecules or cells into the cell via invagination of the plasma membrane to form a vesicle

• 6. Exocytosis transports molecules outside the cell via fusion of a vesicle with the plasma membrane

cell membrane

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Larry M. Frolich, Ph.D. Biology Department, Yavapai College Cell Structure and Function Cells as fundamental living unitCells as fundamental living unit