Cell Unit• Learning Goal 2: Describe cell organelles and their functions within the cell.

Prokaryotic Cells

Believed to be the first cells to evolve.

Lack a membrane bound nucleus and organelles.

Genetic material is naked in the cytoplasm

Ribosomes are only organelle.

Eukaryotic Cells

• “True nucleus”; contained in a membrane bound structure.

• Membrane bound organelles.

• Thought to have evolved from prokaryotic cells.

Prokaryotic vs. Eukaryotic

CellSize of the Cell http://learn.genetics.utah.edu/content/begin/cells/scale/

Cell Structure http://learn.genetics.utah.edu/content/begin/cells/insideacell/

Cell Wall

• The main function of the cell wall is to provide support and protection for the cell.

• Found in plant and prokaryotic cells.

• Formed from cellulose molecules.

Cytoplasm

• Location of growth, metabolism, and replication.

• Is a gel-like matrix of water, enzymes, nutrients, wastes, and gases and contains cell structures.

Ribosomes

• Translate the genetic code to assemble proteins.

• Found attached to the Rough endoplasmic reticulum or free in the cytoplasm.

Ribosome

Rough Endoplasmic ReticulumRough E.R.

Network of continuous tubes, studded with ribosomes.

Manufactures, processes, and transports proteins for export from cell.

Continuous with nuclear envelope.

Endoplasmic Reticulum

Smooth Endoplasmic ReticulumSmooth E.R.

• Similar in appearance to rough ER, but without the ribosomes.

• Contains a collection of enzymes that perform specialized tasks.

Lysosome

• Single membrane bound structure.

• Found mostly in animal cells.

• Contains digestive enzymes that break down cellular waste, old cell parts, and nutrients for use by the cell.

Lysosome

Golgi Apparatus (Complex)

• Modifies, sort, and package proteins and lipids made by the ER.

Golgi Apparatus

Mitochondria

• Membrane bound organelles that are the site of cellular respiration (ATP production)

• Powerhouse of the cell.

Mitochondria

Nucleus

• Double membrane-bound control center of cell.

• Brain of the cell.• Contains nearly all of

the cell’s DNA.

Nucleus

Parts of the nucleus: Chromatin - genetic material of cell in its non-dividing

state. Chromosomes – Condensed chromatin ready for cell

division.

Figure 2: Different levels of DNA condensation. (1) Double-strand DNA. (2) Chromatin strand (DNA with histones). (3) Chromatin during interphase with centromere. (4) Condensed chromatin during prophase. (Two copies of the DNA molecule are now present) (5) Chromosome during metaphase.

Parts of the nucleus:

Nucleolus - dark-staining structure in the nucleus that plays a role in making ribosomes

Nuclear envelope - double membrane structure that separates nucleus from cytoplasm.

Centrioles

• Found only in animal cells.

• Self-replicating• Made of bundles of

microtubules.• Help in organizing cell

division.

Cytoskeleton

Solid rods of globular proteins.

cytoskeleton offers support to cell structure.

Cell membrane

Endoplasmicreticulum

Microtubule

Microfilament

Ribosomes Mitochondrion

Section 7-2

Figure 7-11 Cytoskeleton

Chloroplast

Site of photosynthesis

Membrane bound structure.

Contains chlorophyll

Chloroplast

Vacuole

• Store water and nutrients needed by the cell.

• Help support the shape of the cell.

• Plants have a large central vacuole.

• Other types of cells have a much smaller vacuole.

Animal Vacuole

Plant Cell Vacuole

Cell Membrane

Plasma (Cell) Membrane Is a Fluid Mosaic

• The plasma membrane is a selectively semipermeable barrier– controls the passage of substances into and out of the cell.

• Fluid Mosaic composed of Phospholipids, Proteins, Cholesterol, Glycolipids, and Glycoproteins.

Phospholipid BilayerPhopholipids are the main components of membranes. They arrange themselves in abilayer, with their water-hating tails facing each other, and their water-loving heads facing the outside of the cell on one side, and the inside of the cell on the other side.

Phospholipid

Phospholipid Bilayer

Membrane Proteins Roles of

membrane proteins include:

•Structural

•Enzyme

•Transport

•Cell- recognition

Types of TransportTypes of Transport

Transport Across the MembraneDiffusion • a substance moving from an area of high concentration of

the substance to a region of low concentration of the substance until it reaches equilibrium.– This is a passive process that does not require an energy

input.

DiffusionDiffusion

DiffusionDiffusion

Facilitated Diffusion

• Transport Proteins – channels for

substances to enter or exit the cell through passive diffusion.

– No Energy Required

Active Transport

• Active Transport– Substances move from a region of low

concentration on one side of the membrane to a region of high concentration on the other side.

• Active Transport Requires Energy

Osmosis: Diffusion of Water• Osmosis is the

diffusion of water, across a semipermeable membrane.– from a region of high

concentration of water to a region of low concentration of water, until equilibrium of water on both sides of the membrane is reached.

OsmosisOsmosis

Osmoregulation: Control of H2O Balance in Cells

• Tonicity: the movement of water into and out of cells in response to the water concentration on the outside of the cell. – Water moves from where it is in high concentration to where it is in low

concentration until an equilibrium of the water concentration is reached.

Transport of Large Molecules Across the Membrane

• Endocytosis – Large substances enter the cell through phagocytosis, cell “eating” or pinocytosis, cell “drinking”.

• Exocytosis – vesicles fuse with the plasma membrane and its contents are ejected from the cell

Animal Cell

Centrioles

Nucleolus

Nucleus

Nuclearenvelope

Rough endoplasmic reticulum

Golgi apparatus

Smooth endoplasmicreticulum

Mitochondrion

CellMembrane

Ribosome(free)

Ribosome(attached)

Section 7-2

Figure 7-5 Plant and Animal Cells

Plant Cell

Nuclearenvelope

Ribosome(attached)

Ribosome(free)

Smooth endoplasmicreticulum

Nucleus

Rough endoplasmic reticulum

Nucleolus

Golgi apparatus

Mitochondrion

Cell wall

CellMembrane

Chloroplast

Vacuole

Section 7-2

Figure 7-5 Plant and Animal Cells

Prokaryotes Eukaryotes

Cell membraneContain DNA

NucleusEndoplasmic reticulum

Golgi apparatusLysosomesVacuoles

MitochondriaCytoskeleton

Animal Cells Plant Cells

Centrioles

Cell membraneRibosomes

NucleusEndoplasmic reticulum

Golgi apparatusLysosomesVacuoles

MitochondriaCytoskeleton

Cell WallChloroplasts

Section 7-2

Venn Diagrams

Animal Cell vs. Plant Cell

Http://:micro.magnet.fsu.edu/cells/html