Basic Cell Structure

Cells• Basic building blocks of life

• Understanding of cell morphology is critical to the study of biotechnology

Cell• Smallest living unit of an

organism

• Grow, reproduce, use energy, adapt, respond to their environment

Cell• Many cannot be seen with the

naked eye

• A cell may be an entire organism or it may be one of billions of cells that make up the organism

Cells• Divided and classified in many

ways

• One common classification method is the presence or absence of a cell necleus

Nucleus• Relatively large structure with

a cell

• Directs cell activities

• Some simple single celled organisms lack a nucleus

Nucleus• Prokaryotes – have no

nucleus

• Eukaryotes – have a nucleus

Prokaryotes• Single celled organism

• Kingdom Monera

• Lacks a cell nucleus

• Internal structure is less organized than other cells

Prokaryotes• Genetic info needed is within

the cell

• Two most common – blue green bacteria and true bacteria

Blue green bacteria

• Have ability to produce their own food like plants

• Most bacteria get their food from other sources

Prokaryotes• Less complex than eukaryotes

• Still have many of the basic internal characteristics

Common prokaryote structures• Cytoplasm

• Chromosomal material

• Cell membrane and wall

• Ribosomes

• Some have flagellum for mobility

Eukaryotes• Organism made up of cells that

have a nucleus

• May be single celled – Kingdom Protista

• May have billions of cells like plant and animal kingdoms

Eukaryotes• Single celled eukaryotes

include paramecia, euglena, and diatoms

Eukaryotes• Typically are highly organized

• Infinite number of shapes and purposes

Eukaryotes• Human body has at least 85

different cell types

• All eukaryotes have a number of structures in common

Common structures

• Organelles – smaller parts of the cell with specific funtions

• Cell membrane – acts as a gatekeeper

Cell membrane

• Controls what enters and leaves the cell

• Plants, algae and bacteria typically have a tough outer structure known as a cell wall

Cell wall• Provides additional structure and

protects the cell from pressure caused by movement of water

• Animal cells do not have walls

Cytoplasm• Organelles are surrounded by a

jelly like substance

• Primary component is water

Nucleus• Largest and most identifiable part

of the cell

Other organelles

• Ribosomes

• Mitochondria

• Golgi bodies

• Endoplasmic reticulum

Other organelles

• Lysosomes

• Vacuoles

• Chloroplasts in plants

Nucleus• Brain of the cell

• Site of much of the manipulation done in biotechnology

Nucleus• Controls activity of the cell

• Round or oval structure

• Typically found in the middle of the cell

• Appears darker than surrounding material

Nucleus• Surrounded by a membrane that

controls passage of materials in and out of the area

Nucleus• Contains DNA

• DNA is located on chromosomes

• Most organisms are diploid – have two chromosomes for each trait

Diploid• Humans – 23 pair

• Goldfish – 90 chrms, 45 pair

Cytoplasmic Organelles

• Organelles are required for proper cell function

• Ribosome – make proteins for cellular use and communication

• May be attached to endoplasmic reticulum

Endoplasmic reticulum

• Layered membraneous

• Make and transport proteins

Vacuole• Large organelle, without specific

shape

• Store waste or raw materials used in synthesis of proteins

Golgi Bodies• Golgi apparatus

• Similar to endo. Ret.

• Look like a thick elastic band that has been folded several times

Golgi Bodies• Adds modifications to unfinished

proteins

• Makes lysosomes

Lysosome• Small round

• Store enzymes that break down food into chemical compounds

• Destroy cell organelles and the cell itself

Mitochondria• Energy factories

• Rod shaped

• Change food into molecules that can be used for energy

Mitochondria• Contain DNA

• Can replicate themselves

Chlorplast• Found in plants and some other

organisms

• Contain chlorophyll

Cellular processes

• Respiration

• Osmosis

• Diffusion

• Photosynthesis

Respiration• Cells break down carbohydrates

and other molecules to produce energy

• Oxidation of glucose is one of most common forms

Respiration• Breaking down of sugar into

water, carbon dioxide, and energy

• Energy is used to do the work of the cell

Osmosis & Diffusion

• Transport of raw materials, wastes, and synthesized materials out of the cell

Diffusion• Movement of molecules,

especially gases and liquids from areas of high concentration to areas of low concentration

Osmosis• Specific type of diffusion

• Movement of water through a membrane from areas of high concentration to areas of low concentration

Equilibrium• Diffusion and osmosis happen to

enable a cell to reach equilibrium

Cellular reproduction

• Three ways

• Fission

• Mitosis

• Meiosis

Fission• Prokaryotes

• Cell grows larger and makes a second copy of its DNA

• At some point the cell membrane divides the cell by the growth of a transverse septum

Fission• Two new cells are formed as the

division grows inward from either side of the cell

• Two cells now called “daughter cells”

• Sometimes known as “binary fission”

Mitosis• Eukaryotes

• Requires 6 stages

• Interphase, prophase, metaphase, anaphase, telophase, cytokinesis

Mitosis• Creates cells that are identical to

the original cell.

• Have the entire compliment of chromosomes existing in pairs - diploid

Meiosis• Division of sex cells

• Stages of Meiosis I: Interphase I, prophase I, metaphase I, anaphase I, telophase I, cytokinesis I

Meiosis• Meiosis II

• Interphase II, prophase II, metaphase II, anaphase II, telophase II, cytokinesis II

Meiosis• Each cell receives one

chromosome from each pair randomly

• Resulting cells have half the normal number of Chromosomes - haploid