BIOLO

GY 11 IB

2.3: E

UKARYOTI

C CELL

S

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 micrographs of liver cell

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

EUKARYOTIC CELLS

Eu = True, karyon meaning ‘kernel’, referring to the nucleus True Nucleus

The general size of a eukaryotic cell is about 5-100 um.

The ribosomes are larger than eukaryotic cells (80S versus 70S ribosomes)

Compartmentalization allows chemical reactions to be separated increasing the efficiency of the cell

ORGANELLES

Endoplasmic Reticulum

Ribosomes

Lysosomes (not usually in plant cells)

Golgi Apparatus

Mitochondria

Nucleus

Chloroplasts (only in plant cells)

Vacuoles

ENDOPLASMIC RETICULUM

Extensive netowrk of tubules or channels that extends almost eveywhere in the cell from the nucleus to the plasma membrane

Function: transportation of materials throughout the internal region of the cellSmooth ER Rough ER

Produces membrane phospholipids and cellular lipids

Produces sex hormones (testosterone and estrogen)

Detoxifies drugs in the liver

Stores calcium ions needed for contraction in muscle cells

Transport lipid based compounds

Aid the liver in releasing glucose into the bloodstream when needed

Involved in protein development and transport (function as support for ribosomes)

RIBOSOMES

Carry out protein synthesis

Can be free in the cytoplasm or attached to the rough ER

Composed of RNA and protein

Larger and denser in eukaryotes vs prokaryotes

Composed of two subunits (80S)

LYSOSOMES

Digestive centers the arise from the Golgi apparatus

Sacs of hydrolytic enzymes the catalyze the breakdown of proteins, nucleic acids, lipids and carbohydrates

Fuse with old or damaged organelles to recycle the components

Responsible for breaking down materials brought into the cell by phagocytosis

The interior of a functioning lysosome is acidic

GOLGI APPARATUS Composed of flattened sacs called cisternae

Functions in the collection, packaging, modification, and distribution of materials synthesized in the cell

One side is always close to the rough ER (cis side) receiving products from the ER

Movement occurs to discharge the product from the opposite (trans) side. Small sacs, called vesicles, can be seen coming off the trans side carrying modified materials to wherever they are needed inside or outside the cell.

Prevalent in glandular cells that manufacture and secrete substances (ex. in the pancreas)

MITOCHONDRIA

Have their own DNA! (a circular chromosome similar to that in bacterial cells)

Double membrane – smooth on the outside, folded on the inside

Reactions within produce usuable cellular energy (ATP), where it gets its nickname ‘the powerhouse’

Produces and contains its own ribosomes (70S)

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

NUCLEUS

Isolated region housing the DNA in the form of chromosomes (strands of DNA wrapped around histones [protein])

Double membrane nuclear envelope (allows for compartmentalization – providing an area where DNA can carry out its functions and not be affected by processes occurring in other parts of the cell)

Nuclear pores in the nuclear membrane allow communication with the cell’s cytoplasm

CHLOROPLASTS

ONLY in algae and plant cells!

Double membrane, about the same size as mitochondrion

Has its own DNA (in the form of a ring) and 70S ribosomes

Grana (pile of thylakoids) + stroma (fluid containing enzymes necessary for photosynthesis)

Can reproduce independently of cell

VACUOLE

Storage organelles the usually form from the Golgi apparatus

Occupy large space in plant cells

Can store food, metabolic wastes and toxins, and water

Enable cells to have higher surface area to volume ratios

In plants, they allow an uptake of water providing rigidity

CENTROSOME

Generally contains a pair of centrioles which are involved in assembling microtubules (important in providing cell structure and allowing movement)

Important to cell division

Higher plant cells produce microtubules even though they do not have centrioles

Located at one end of the cell, close to the nucleus

Prokaryotic Cells Eukaryotic Cells

DNA in ring form without histones DNA with protein as chromosomes/chromatin

DNA free in cytoplasm (nucleoid region)

DNA enclosed in a nuclear envelope

No mitochondria Mitochondria present

70S ribosomes 80S ribosomes

No internal compartmentalization to form organelles

Internal compartmentalization present to form many types of organelle

Size = less than 10 micrometers Size = more than 10 micrometers

SIMILARITIES OF PROKARYOTIC AND EUKARYOTIC CELLS

1. Both types of cell have some sort of outside boundary that always involves a plasma membrane

2. Both types carry out all the functions of life

3. DNA is present in both cell types

Plant Cells Animal Cells

Exterior of cell includes an outer cell wall with a cell membrane just inside

Exterior of cell includes only a cell membrane

Chloroplasts present in the cytoplasm

No chloroplasts

Possess large centrally located vacuoles

Vacuoles are usually small or non existent

Store carbohydrates as starch Store carbohydrates as glycogen

Do not contain centrioles within a centrosome area

Contain centrioles within a centrosome area

Fixed, often angular shape (because of rigid cell wall)

Cell is flexible and usually round

EUKARYOTIC CELLS