Unit 2 – Cell Structure and Unit 2 – Cell Structure and FunctionFunction Cell Theory – Cell Theory – The concept was formally articulated The concept was formally articulated

in 1839 by Schleiden & Schwann and has remained in 1839 by Schleiden & Schwann and has remained as the foundation of modern biology. as the foundation of modern biology.

6 main components of cell theory: 6 main components of cell theory: 1.1. All known living things are made up of cells.All known living things are made up of cells.2.2. The cell is structural & functional unit of all living The cell is structural & functional unit of all living

things.things.3.3. All cells come from pre-existing cells by division. All cells come from pre-existing cells by division.

(Spontaneous Generation does not occur).(Spontaneous Generation does not occur).4.4. Cells contains hereditary information which is passed Cells contains hereditary information which is passed

from cell to cell during cell division.from cell to cell during cell division.5.5. All cells are basically the same in chemical All cells are basically the same in chemical

composition.composition.6.6. All energy flow (metabolism & biochemistry) of life All energy flow (metabolism & biochemistry) of life

occurs occurs within cells. within cells.

Types of cellsTypes of cells Two main types of cells exist: Two main types of cells exist:

prokaryotes and eukaryotesprokaryotes and eukaryotes1.1. ProkaryotesProkaryotes (pro – “before”, kary – (pro – “before”, kary –

“nucleus”)“nucleus”)• lack a membrane bound nucleuslack a membrane bound nucleus• No organelles (mitochondrion, No organelles (mitochondrion,

chloroplast, etc.chloroplast, etc.• Bacteria and cyanobacteria (monerans)Bacteria and cyanobacteria (monerans)• Primitive structurePrimitive structure• Reproduce by simple fission (division)Reproduce by simple fission (division)• Smaller than eukaryotesSmaller than eukaryotes

Types of Cells - Types of Cells - continuedcontinued

2.2. EukaryotesEukaryotes (eu – “true”, kary – (eu – “true”, kary – “nucleus”)“nucleus”)

• Plants, animals, protists, and fungiPlants, animals, protists, and fungi• Possess a nucleus and membrane Possess a nucleus and membrane

bound organellesbound organelles• Larger and more advanced than Larger and more advanced than

prokaryotic cellsprokaryotic cells• more complex cellular divisionmore complex cellular division

Questions 1-3, p 72Questions 1-3, p 721.1. How did improvements in the microscope help How did improvements in the microscope help

scientists form the cell theory?scientists form the cell theory?- Improvements allowed scientists to see cells in Improvements allowed scientists to see cells in

greater and greater detail and enabled them to greater and greater detail and enabled them to discover cells in all types of living matter.discover cells in all types of living matter.

2.2. How do prokaryotic and eukaryotic cells differ?How do prokaryotic and eukaryotic cells differ?- Eukaryotic cells have a nucleus and membrane-Eukaryotic cells have a nucleus and membrane-

bound organelles, prokaryotic cells do not.bound organelles, prokaryotic cells do not.3.3. Analyze – Today, scientists can study human Analyze – Today, scientists can study human

cells grown in petri dishes. Explain how this cells grown in petri dishes. Explain how this technique builds on the work of early scientists.technique builds on the work of early scientists.

- Once it was understood that cells were the Once it was understood that cells were the basic building block of living matter, scientists basic building block of living matter, scientists could concentrate on describing different types could concentrate on describing different types of cells and discovering the relationships of cells and discovering the relationships between cell type and cell function. One way between cell type and cell function. One way to do this is too isolate the cell itself.to do this is too isolate the cell itself.

Questions 4 &5, p72Questions 4 &5, p724.4. Compare – In what ways are cells Compare – In what ways are cells

similar to atoms?similar to atoms?- Both are basic units, or building Both are basic units, or building

blocks. The atom is the basic unit of blocks. The atom is the basic unit of matter; the cell is the basic unit of matter; the cell is the basic unit of living organisms.living organisms.

5.5. Medicine – Suppose a certain poison Medicine – Suppose a certain poison kills human cells by blocking pores in kills human cells by blocking pores in the nuclear membrane. Explain why it the nuclear membrane. Explain why it would or would not kill bacteria.would or would not kill bacteria.

- It would not kill bacteria because It would not kill bacteria because bacteria do not have a nucleus, so bacteria do not have a nucleus, so there are no nuclear pores to be there are no nuclear pores to be blocked.blocked.

Cell ComponentsCell Components 1. Cytoplasm1. Cytoplasm The The cytoplasmcytoplasm is the region outside the is the region outside the

nucleus and is the location where nutrients nucleus and is the location where nutrients are absorbed, transported, and processed are absorbed, transported, and processed including the including the cytosolcytosol (fluid soup of the cell) (fluid soup of the cell) and the organelles.and the organelles.

The cytoplasm stores the waste until proper The cytoplasm stores the waste until proper disposal can be carried out.disposal can be carried out.

Both the nucleus and the cytoplasm are Both the nucleus and the cytoplasm are collectively referred to as the collectively referred to as the protoplasmprotoplasm..

The cytoplasmic organelles are the parts of The cytoplasmic organelles are the parts of the cell found in the cytoplasm.the cell found in the cytoplasm.

2. Plasma Membrane2. Plasma Membrane (Cell membrane) (Cell membrane) The The cell membranecell membrane is the outer most edge is the outer most edge

of the cell. It is also referred to as the of the cell. It is also referred to as the plasma membraneplasma membrane..

It holds the contents of the cell in place and It holds the contents of the cell in place and regulates the movement of molecules in and regulates the movement of molecules in and out of the cell.out of the cell.

The plasma membrane is composed of a The plasma membrane is composed of a double layer of lipid molecules with protein double layer of lipid molecules with protein molecules embedded in it.molecules embedded in it.

A lipid molecule consists of two parts, a polar A lipid molecule consists of two parts, a polar head and a non-polar chain tail. The polar head and a non-polar chain tail. The polar end is end is hydrophilichydrophilic, an attraction with water, , an attraction with water, while the non-polar tail iswhile the non-polar tail is hydrophobic hydrophobic, , repels water. repels water.

Like molecules (polar / non-polar) attract Like molecules (polar / non-polar) attract while unlike molecules repel.while unlike molecules repel.

3. Nucleus3. Nucleus The The nucleus nucleus is the cell’s control centre.is the cell’s control centre. It is round and surrounded by a double It is round and surrounded by a double

membrane called the membrane called the nuclear nuclear envelopeenvelope..

The nucleus contains most of the genes The nucleus contains most of the genes (genetic material).(genetic material).

The dark region found in the nucleus is The dark region found in the nucleus is called the called the nucleolusnucleolus. .

The nucleolus is responsible for the The nucleolus is responsible for the formation of ribosomes. formation of ribosomes.

4. Mitochondria4. Mitochondria (pl) mitochondrion (s)(pl) mitochondrion (s) Tiny oval shaped organelles called Tiny oval shaped organelles called mitochondriamitochondria are are

often referred to as the “power plant” of the cell.often referred to as the “power plant” of the cell. They provide the body with needed energy through a They provide the body with needed energy through a

process called process called respirationrespiration. The equation for . The equation for respiration is: ???respiration is: ???

Mitochondria are found in both plant and animal cells.Mitochondria are found in both plant and animal cells. In respiration, chemical bond energy is converted into In respiration, chemical bond energy is converted into

other forms of energy. Mitochondria are found where other forms of energy. Mitochondria are found where energy is most often needed (muscles).energy is most often needed (muscles).

Special enzymes that assist the breaking down of Special enzymes that assist the breaking down of sugar molecules are found within the mitochondria.sugar molecules are found within the mitochondria.

When a sugar molecule is broken up, 36% of the When a sugar molecule is broken up, 36% of the energy is converted to ATP, while the remaining 64% energy is converted to ATP, while the remaining 64% is heat.is heat.

Mitochondria have two separate membranes: a smooth Mitochondria have two separate membranes: a smooth outer membrane and a folding inner membrane.outer membrane and a folding inner membrane.

The inner membrane consists of finger-like projections The inner membrane consists of finger-like projections called called cristaecristae..

5. Ribosomes5. Ribosomes Ribosomes are the organelles Ribosomes are the organelles

responsible for the synthesis of responsible for the synthesis of proteins.proteins.

They are one of the smallest organelles They are one of the smallest organelles found in the cytoplasm.found in the cytoplasm.

A ribosome is made up of two parts. A ribosome is made up of two parts. The mRNA molecule attaches between The mRNA molecule attaches between the two parts and is fed through the the two parts and is fed through the ribosome in protein synthesis.ribosome in protein synthesis.

The ribosomes are located on the The ribosomes are located on the endoplasmic reticulum (ER).endoplasmic reticulum (ER).

6. Endoplasmic Reticulum6. Endoplasmic Reticulum (ER) (ER) The ER is a series of canals that carry The ER is a series of canals that carry

material throughout the cytoplasm.material throughout the cytoplasm. The canals, composed of flattened parallel The canals, composed of flattened parallel

membranes are referred to as ER.membranes are referred to as ER. There are two types of ER:There are two types of ER: 1. 1. Smooth ERSmooth ER: No ribosomes; appear flat: No ribosomes; appear flat 2. 2. Rough ERRough ER: Has ribosomes attached to : Has ribosomes attached to

it; appears bumpyit; appears bumpy Rough ER is found mostly where enzymes Rough ER is found mostly where enzymes

are needed since the ribosomes make are needed since the ribosomes make enzymes (which are a type of protein).enzymes (which are a type of protein).

Smooth ER is found where lipids are Smooth ER is found where lipids are synthesized.synthesized.

7. Golgi Apparatus7. Golgi Apparatus The The Golgi apparatusGolgi apparatus appears like a stack appears like a stack

of pancakes, but is actually a bunch of of pancakes, but is actually a bunch of membranous sacs piled on one another.membranous sacs piled on one another.

In the Golgi apparatus, protein molecules In the Golgi apparatus, protein molecules are stored after being produced by the are stored after being produced by the ribosomes.ribosomes.

The Golgi apparatus will move to the The Golgi apparatus will move to the plasma membrane and then fuse or stick plasma membrane and then fuse or stick to it. At this point, small packages called to it. At this point, small packages called vesiclesvesicles are released out of the cell. For are released out of the cell. For more information refer to transport of more information refer to transport of molecules.molecules.

8. Lysosomes8. Lysosomes LysosomesLysosomes are vesicles containing a are vesicles containing a

variety of digestive enzymes that help variety of digestive enzymes that help break down large molecules and worn-break down large molecules and worn-out cell parts.out cell parts.

They are formed by the Golgi apparatus.They are formed by the Golgi apparatus. They play an important role in the They play an important role in the

defence mechanism of the human body defence mechanism of the human body by destroying harmful substances that by destroying harmful substances that find their way into the cell.find their way into the cell.

They also release digestive enzymes They also release digestive enzymes that break down bacteria.that break down bacteria.

9. Centrioles9. Centrioles Centrioles Centrioles are paired cylindrical are paired cylindrical

structures that play an important role structures that play an important role in cell division.in cell division.

They are responsible for separating the They are responsible for separating the chromosomes into two different cells.chromosomes into two different cells.

Are only found in animal cells.Are only found in animal cells. The centrioles are produced by the The centrioles are produced by the

centrosomes (make microtubules – centrosomes (make microtubules – centrosomes are found in both plant centrosomes are found in both plant and animal cells).and animal cells).

10. Vacuole10. Vacuole A large part of the cytoplasm in plant A large part of the cytoplasm in plant

cells is composed of a fluid-filled space cells is composed of a fluid-filled space called a called a vacuolevacuole..

The vacuole serves as a storage space The vacuole serves as a storage space for sugars, minerals, and proteins.for sugars, minerals, and proteins.

It may be referred to as a contractile It may be referred to as a contractile vacuole when it increases and decreases vacuole when it increases and decreases in size. in size.

It will change it’s size for two reasons: It will change it’s size for two reasons: 1. To change the pressure of the cell 1. To change the pressure of the cell 2. To regulate the rate of absorption of 2. To regulate the rate of absorption of mineralsminerals

11. Chloroplast11. Chloroplast Chloroplasts are the location for Chloroplasts are the location for

photosynthesis.photosynthesis. They contain a green pigment called They contain a green pigment called

chlorophyll.chlorophyll. They are not found in animal cells.They are not found in animal cells.

12. Cell Wall12. Cell Wall Most plant cells are surrounded by a Most plant cells are surrounded by a

non-living non-living cell wallcell wall.. Cell walls are composed of cellulose.Cell walls are composed of cellulose. Their main function is to protect and Their main function is to protect and

support the plant.support the plant. Some plants will have a secondary Some plants will have a secondary

cell wall that is used for additional cell wall that is used for additional support.support.

Cool Cells website:Cool Cells website:

http://www.wiley.com/legacy/collegehttp://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_/boyer/0470003790/animations/cell_structure/cell_structure.htmstructure/cell_structure.htm

Questions 1-3, p 79Questions 1-3, p 791.1. What are the functions of the cytoskeleton?What are the functions of the cytoskeleton?- The cytoskeleton supports and shapes a cell, The cytoskeleton supports and shapes a cell,

helps position and transport organelles, helps position and transport organelles, provides strength, assists in cell division, provides strength, assists in cell division, and aids cell movement.and aids cell movement.

2.2. Describe the structure of the nucleus.Describe the structure of the nucleus.- The nucleus is surrounded by a double The nucleus is surrounded by a double

membrane with pores that connect its membrane with pores that connect its interior to the cytoplasm. DNA and the interior to the cytoplasm. DNA and the nucleolus are located inside the nucleus.nucleolus are located inside the nucleus.

3.3. Explain the structure and function of the Explain the structure and function of the mitochondrion.mitochondrion.

- A mitochondrion supplies energy to a cell by A mitochondrion supplies energy to a cell by releasing the energy stored in food releasing the energy stored in food molecules. The outer membrane surrounds molecules. The outer membrane surrounds a highly folded inner membrane where a highly folded inner membrane where chemical activity occurs. It has its own chemical activity occurs. It has its own ribosomes and DNA.ribosomes and DNA.

Questions 4-6, p 79 Questions 4-6, p 79 4.4. What function does the cell wall perform in a What function does the cell wall perform in a

plant?plant?- The cell wall protects, supports, and shapes a The cell wall protects, supports, and shapes a

plant cell, and regulates what moves into the plant cell, and regulates what moves into the cell. The cell walls of multiple cells can help cell. The cell walls of multiple cells can help support the entire plant.support the entire plant.

5.5. Compare – What similarities do mitochondria Compare – What similarities do mitochondria and chloroplasts share?and chloroplasts share?

- Both membranes-bound organelles have their Both membranes-bound organelles have their own DNA and help make energy available to the own DNA and help make energy available to the cell.cell.

6.6. Compare – Describe how the endoplasmic Compare – Describe how the endoplasmic reticulum, mitochondrion, and Golgi apparatus reticulum, mitochondrion, and Golgi apparatus are structurally similar. are structurally similar.

- All are composed of membrane-enclosed All are composed of membrane-enclosed chambers. The surface area of each is greatly chambers. The surface area of each is greatly increased by folds and layers.increased by folds and layers.

Question 7, p 79Question 7, p 79

7.7. Health – Medicine, alcohol, and many Health – Medicine, alcohol, and many drugs are detoxified in liver cells. Why drugs are detoxified in liver cells. Why do you think the liver cells of some do you think the liver cells of some people who abuse alcohol and drugs people who abuse alcohol and drugs have an increased amount of smooth have an increased amount of smooth ER?ER?

- Increased amounts of smooth ER in the Increased amounts of smooth ER in the livers cells suggests that the cells have livers cells suggests that the cells have responded to increased amounts of responded to increased amounts of toxins by producing more smooth ER toxins by producing more smooth ER to handle the processing.to handle the processing.