Topic 2.3 Eukaryotic Cells

Assessment Statements 2.3.1: Draw and label a diagram of the

ultrastructure of a liver cell as an example of an animal cell

2.3.2: Annotate the diagram with the functions of each named structure

2.3.3: Identify structures from 2.3.1 in electron micrograph of liver cells

2.3.4: Compare prokaryotic and eukaryotic cells 2.3.5: State three differences between plant and

animal cells 2.3.6: Outline two roles of extracellular

components

What is a eukaryotic cell? Eukaryotic cells range in size: 5 to

100 µm (in diameter) Most noticeable organelle: nucleus

Others can be noticeable with high enough resolution

What is a eukaryotic cell? Organelles: are non-cellular

structures that carry out specific functions Organelles found in cell vary with the

type of cell Organelles bring out

compartmentalization▪ Allows chemical reactions to be separated

(important because some chemical reactions are not compatible with others)

NOT in prokaryotic cells

Organelles of Eukaryotic Cells Common organelles:

Endoplasmic Reticulum (ER) Ribosomes Lysosomes (not usually in plants) Golgi apparatus Nucleus Chloroplasts (only in plant and algal cells) Centrosomes ▪ Centrioles (type of centrosomes—not in plants)

Vacuoles

Organelles of Eukaryotic Cells Cytoplasm-not an organelle but a

region All organelles occur within The fluid part between the organelles is

referred as the cytosol

Organelles of Eukaryotic Cells Endoplasmic Reticulum

Extensive network of tubules or channels that extend almost everywhere in the cell from the nucleus to the plasma membrane▪ Enables the function of transportation of

materials throughout the internal region of the cell

Two general types▪ Smooth and Rough

Organelles of Eukaryotic Cells

Endoplasmic Reticulum (Smooth) Has no ribosomes attached to it Has many unique enzymes embedded on its

surface▪ Function:▪ Production of membrane phospholipids and cellular lipids▪ Production of sex hormones such as testosterone and

estrogen▪ Detoxification of drugs in the liver▪ Storage of calcium ions needed for contraction in muscle cells▪ Transportation of lipid-based compounds▪ To aid the liver in releasing glucose into the bloodstream

when needed

Organelles of Eukaryotic Cells Endoplasmic Reticulum (Rough)

Has ribosomes on the exterior of the channels

Ribosomes involved in protein synthesis

Function:▪ Protein development and transport

Most cells contain both types of ER with the rough being closer to the nuclear membrane

Organelles of Eukaryotic Cells

Ribosome Not have a exterior membrane Function: Protein synthesis Can be found free (in cytoplasm) or

attached (ER) Found in both Eukaryotic and

Prokaryotic cells▪ Ribosomes found in eukaryotic cells are

larger and denser then ones in prokaryotic cells

▪ All ribosomes contain 2 subunits ▪ Eukaryotic: 80S▪ Prokaryotic 70S

Organelles of Eukaryotic Cells

Lysosomes Intracellular digestive centers (come from

Golgi ) No internal structures They are sacs bounded by a single

membrane but contain as many as 40 different hydrolytic enzymes (very acidic)

Function: Fuse the old or damaged organelles from within the cell to break them down so that recycling of the components may occur▪ Also involved breakdown of materials brought into

cell by phagocytosis

Organelles of Eukaryotic Cells

Golgi Apparatus Consists of flattened sacs called

cisternae (stacked on top of eachother) Functions: in collection, packaging,

modification, and distribution of materials synthesized in cell▪ Cis side-near ER, to receive product▪ Move into the cisternae of the Golgi

▪ Trans side-product is discharged from▪ small sacs called vesicles are released from this

side These carry modified materials to wherever they

are needed inside and outside the cell

Organelles of Eukaryotic Cells

Mitochondria Rod shaped organelle that appear

throughout the cytoplasm (same size as a bacterial cell)

Has their own DNA, circular Double Membrane-Outer (smooth),

Inner (Folded into cristae)▪ Inside the inner membrane is a semi-fluid

substance called matrix▪ Inner membrane spaces-lies between the

two membranes

Organelles of Eukaryotic Cells Mitochondria-Function

The cristae provides huge internal surface area for chemical reactions to occur▪ Most chemical reactions involve the

production of usable cellular energy-ATP

Contains its own ribosomes (70S type)

Cells that have high energy requirements, such as muscle cells, have a large numbers of mitochondria

Organelles of Eukaryotic Cells Nucleus-is an isolated region where the DNA

resides Bordered by a double membrane referred to as the

nuclear envelope▪ Allows for separation for the DNA—providing an area where

DNA can carry out its functions and not be affected by the other parts of a cell

▪ DNA (genetic material) is usually found in a form of chromosomes▪ Carry all the information necessary for the cell to exist (allows for

survival)▪ DNA is only found in the form of chromatin during cellular

division (formed from histones and DNA (nucleosome)▪ Nucleosome consists of 8 histones with a DNA wrapped around them

Organelles of Eukaryotic Cells

Nucleus Usually located centrally in

the cell Most cells only contain one! Cannot reproduce without a

nucleus▪ Only found in very specialized

cells (example: blood) Nucleolus: dark area inside

the nucleus▪ Function of nucleolus:

production of ribsomes

Organelles of Eukaryotic Cells

Chloroplast Only occurs in plant and algae cells Double membrane and is about the size of a

bacterial cell▪ Contains its own DNA (circular) and 70S ribosomes

Also contains granum, thylakoid, and stroma▪ Granum-is made up of numerous thylakoids stacked

in a pile▪ Thylakoid-are flattened membrane sacs with

components necessary for absorption of light ▪ Stroma-similar to cytosol: occurs outside the grana

but within the double membrane (contains enzymes and chemicals necessary to complete photosynthesis

Organelles of Eukaryotic Cells Centrosome

Occurs in all eukaryotic cells▪ Consists of a pair of

centrioles at a right angle to one another▪ Involved in assembling

microtubules (important for movement, structure, and cell division)

▪ Plants do not have centrioles but the centrosome is located at one end of the cell close to the nucleus

Organelles of Eukaryotic Cells

Vacuoles-are storage organelles that usually form from the Golgi Apparatus Membrane bound and have many

possible functions Plant cells-occupy VERY large area inside

the cell▪ Allows an uptake of water that provides

rigidity Function: storage of number of different

substances including potential food, metabolic wastes and toxins, and water▪ Enable cells to have higher surface area to

volume ratio

Comparison of Prokaryotic and Eukaryotic cells (differences)

Prokaryotic Cells Eukaryotic CellsDNA in a ring form without protein

DNA with proteins as chromosomes/chromatin

DNA free in the cytoplasm (nucleoid region)

DNA enclosed within a nuclear envelope (nucleus)

No mitochondria Mitochondria present70S ribosome 80S ribosomeNo internal compartmentalization to form organelles

Internal compartmentalization present to form many types of organelle

Size less than 10 µm Size more than 10 µm

Comparison of Prokaryotic and Eukaryotic cells Similarities:

Both types of cells have some sort of outside boundary that always involves a plasma membrane

Both types of cell carry out all the functions of life

DNA is present in both cell types

Comparison of Plant and Animal cells (differences)

Plant cells Animal CellsExterior of cell includes an outer cell wall with a plasma membrane just inside

Exterior of cell includes only a plasma membrane. There is not cell wall

Chloroplasts are present in the cytoplasm

There are not chloroplasts

Possess large centrally located vacuoles

Vacuoles are usually not present or Very small

Store carbohydrates as starch Store carbohydrates as glycogen

Do not contain centrioles within a centrosome area

Contain centrioles within a centrosome area

Because a rigid cell wall is present, this cell type has a fixed, often angular, shape

Without cell wall, this cell is flexible and more likely to be rounded shape

Comparison of Plant and Animal cells The outermost region of various cell

types is often unique:Cell Outermost part

Bacteria Cell wall of PeptidoglycanFungi Cell wall of ChitinYeasts Cell wall of glucan and mannanAlgae Cell wall of cellulosePlants Cell wall of celluloseAnimals No cell wall: plasma membrane secretes a mixture of

sugar and proteins called Glycoproteins that form the extracellular matix

Extracellular matrix (ECM): Extracellular matrix (ECM): composed

of collagen fibers plus a combination of sugars and proteins called glycoproteins Fiber-like structures that anchor the matrix

to the plasma membrane—strengthens the plasma membrane and allows attachment between adjacent cells

ECM allows for cell to cell interaction (many researchers believe it is involved in directing stem cells to differentiate)