Cell Structures: Organelles

Cell Structure• Cells vary in SHAPE and SIZE• 5-50 micrometers in diameter; Required flow of

materials in and out of the cell restricts size.• Structures common to all cells:

» Cell Membrane» Genetic material» Cytoplasm

Prokaryotic Cells

• Prokaryotic

• Pro – Before

• Karyote = Nucleus

• No Membrane-bound

organelles

• Less Complex DNA

Eukaryotic Cells

• Eukaryotic• Eu = True• Karyote =

Nucleus

Cell Membrane• Separates cells from their environment• Regulates what enters and leaves the cell.

(SEMI-PERMEABLE)• Aids in protection and support of cell.• Proteins stick out of the surface of the lipid

layer, pass through.

• Carbohydrates attach to Lipids and/or proteins on the surface of the Cell Membrane

• Carbohydrates act as “identifiers”• All cells to recognize and interact with

each other.

Fluid Mosaic Model of

Cell Membrane

Phospholipid Bilayer

Heads: hydrophilic (polar)

Tails: hydrophobic(non-polar)

Protein Channels: help move

materials in/out

[Ex: Antigens on the

cell membrane (proteins) cause

Rejection Syndrome

when tissue not closely matched.]

Structure directs function

Pinocytosis / Form of Endocytosis(Active Transport requires ATP)

• “cell drinking”• Liquid or small

particles are taken into the cell.

• Cell Membrane forms a pouch, pinches off, forming a vacuole, within the cell.

• Once inside the cell, the vacuole opens, releasing its contents.

• Requires Energy*

Phagocytosis / Form of EndocytosisActive Transport requires ATP energy

• Large particles or small Organisms are ingested by the cell.

• Cell Membrane forms a pouch, pinches off, forming a vacuole, within the cell.

• Once inside the cell, the vacuole opens, releasing its contents

• Requires Energy*

Secretions / Form of Exocytosis

Active Transport requires ATP energy

•Mucus (from Goblet epithelial cells)

•Hormones (from endocrine /ductless glands-

secrete directly into the blood &

exocrine glands- secrete via ducts

ex. sweat, digestive juices, tears)

Excretions / Form of ExocytosisActive Transport requires ATP energy

•Wastes

Cell Wall made of cellulose (fibrous material)• Plants, Algae, and

some Bacteria

• Surrounds the Cell Membrane

• Protects and supports cell

• Porous H20, O2 C02 etc. pass through.

• Made of 2 or more layers.

• Lignin ↑ rigidity in woody stems.

• Pectin (gluey) helps hold cells together

Nucleus• Control Center of

the Cell • Round, dense body,

surrounded by a double membrane

• Nuclear membrane – has pores – selective passage of materials in and out of the nucleus.

• Contents of Nucleus remain separate from rest of the cell.

Nucleolus

• Within the Nucleus• Made up of DNA,

RNA, and protein.• Site of Ribosome

production• Chromosomes –

special proteins (DNA) in nucleus of the Cell that contain genetic info passed down to new generation.

Cytoplasm (cytosol)

• Semi fluid substance between the cell membrane and the nucleus.

• Cell (Metabolism) – activities take place in the cytoplasm

• Specialized structures called “organelles” have specific duties to maintain cell homeostasis.

Endoplasmic Reticulum• Transport System • Membrane enclosed, Fluid-filled

channels.

• Components of the cell membrane assembled and proteins modified & exported.

• Smooth ER= no Ribosomes stores enzymes/chemicals involved

in synthesis of membrane lipids & detoxification of drugs (↑ in liver) S&F

• Rough ER= Ribosomes on surface (site of protein synthesis)

Ribosomes (made in nucleolus)

Found in cytoplasm & on rough ER • Smalls particles made

of RNA (ribosomal nucleic acid and protein

• The site of “Protein Synthesis” (↑ in liver) (enzymes are proteins)

S&F

• Proteins (CHON) made from chains of amino acids linked together via peptide bonds Dehydration Synthesis

Functions???

Golgi Bodies • “Packaging Plant” for

proteins – stores protein which can then leave the cell

• Proteins produced by Rough ER are moved to the Golgi Bodies.

•Enzymes in the Golgi Apparatus attach Carbohydrates and lipids to proteins.

• Seceretory Vesicles w/ hormones,

neurotransmitters, etc pinching off from Golgi CM (secretions)

Lysosomes• Suicide Sacs (small sac-

like structures) • Membrane bound organelle

responsible for breaking ↓ proteins, carbohydrates, lipids w/in cell.

• Contains strong digestive/hydrolytic enzymes to digest material no longer useful &food within cell

• Tay Sachs- lacks enzyme to digest specific fat that accumulates in brain cells

• ? Presence in plant cells?

Mitochondria• “Powerhouse” of the

Cell• Cristae – inner

membrane.• Releases energy from

food molecules to be used by the cell.

Muscle Cells have more mitochondria – because they require more energy.

• Site of Cell Respiration:

food energy to ATP

enzymes

6O2 + C6H12O6 -----> 6CO2 + 6H20 + ATP

•All of our Mitochondria come from the Ovum, or egg Cell (maternal)

•Mitochondrion each have their own DNA and are capable of duplicating themselves*

Vacuoles

• “Storage Containers”• materials food,

water, sugar, starches, salts, minerals, waste products

• Larger in Plants- filled with cell sap- occupies most of the interior of the plant cell

Smaller in AnimalsSome animals have contractile vacuoles to digest food.

Cytoskeleton • Network of protein

filaments that help maintain cell shape and aid in movement

Microfilaments: threadlike made of

protein actin flexible framework aid in

movement of cytoplasm

cyclosis/cytoplasmic streaming

Microtubules: tubelike made of tubulin proteins

centrioles, flagella, cilia

Centrioles (found in area of centrosome)

• Found in Animal Cells only (plants have microtubules in centrosome)

• Made from microtubules, found in pairs near the nucleus

• Involved in movement of Chromosomes during Cell Division

• Similar structures found in Cilia and Flagella

Cilia• Microtubules support

hair-like projections from the cell surface known as Cilia.

• Cilia aid in the movement of substances along the cell’s surface – as in the mucus lining your nasal passage.

Cilia

• Protozoa – a unicellular, eukaryotic organism belonging to the Kingdom Protista

• Cilia are short, thread-like structures that help unicellular organisms move.

Flagella

Plastids

•Internal membranes Store food & pigments in plants

•Chloroplasts- store chlorophyll pigments in green plants, site of photosynthesis

•Leucoplasts- store starch granules

•Chromoplasts- store other pigment molecules

Chloroplasts

• Double-Membrane• Have their own DNA

like Mitochondria, believed to have originated as a captured bacterium.*

• Use the energy from sunlight to make energy-rich food molecules in a process of Photosynthesis

chlorophyll/light

6CO2 + 6H20 C6H12O6 + 6O2

Compare and Contrast Mitochondria and Chloroplasts

Power Stations *change energy from 1 form to another

*2x membrane structures

*contain their own DNA

(precursor eukaryotes (endosymbiotic theory)

Mitochondria: convert chemical energy stored in food to ATP through C.R.

Chloroplast: trap light energy & convert it to chemical energy through photosynthesis

Peroxisome

• Vesicles that contain enzymes (catalase/hydrogen peroxidase) that help protect the cell vs H2O2 hydrogen peroxide built up from cell metabolism.

hydrogen peroxidase / catalase

• 2H2O2 2H20 + O2