Cell Structures and Functions

Plasma Membrane

• Structure– Phospholipid Membrane:

• Amphipathic

• Forms a Bilayer (hydrophilic heads on interior and exterior faces of cell)

• Fluid

Plasma Membrane

Function

Maintain homeostasis (allow certain things to enter/leave cell so internal processes continue)

– Phospholipid bilayer acts as selectively permeable membrane

– Proteins act as channels– Carbohydrates act as receptors– Cholesterol decreases fluidity (stabilizes)

Rough Endoplasmic Reticulum

– Structure• Lipid Bilayer Network

• Studded with Ribosomes

• In animal cells, associated with the nuclear membrane

– Function• Allows cell products (protein) to travel throughout

the cytoplasm

• Protein folding occurs here as well

Smooth Endoplasmic Reticulum

• Structure– Lipid Bilayer Network

• Function– Lipid Synthesis– Allows cell products (lipid primarily) to travel

throughout the cytoplasm

Golgi Apparatus

• Structure– Layers of Flattened lipid bilayer vesicles

• Function– Works with Cell Membrane/ER’s to

• Convert lipid/protein products to usable forms

• Transport products throughout/out of cell

Golgi Body: Lysosome

• Structure– Membrane bound vesicle (golgi body)– Contains digestive enzymes

• Function– Digest ingested foods– Break-up/Recycle used-up organelles

Golgi Body: Microbodies

• Structure– Small lipid bilayer vesicles– Example is Peroxisome

• Function– Associated with mitochondria

– Break up hydrogen peroxide (harmful byproduct of aerobic respiration)

Cytoskeletal Elements

– Structure• Protein filaments (3 types)

– Function• Allows organelles to move throughout the cell• Move the cell during cell division (or in case of

muscle cell, expands and contracts the cell)

Mitochondria

• Structure– Double membrane organelle with isolated

compartments

• Function– Compartments isolate reactions involved with

aerobic respiration– Function of aerobic respiration is to produce

ATP (usable energy molecule)

Nucleus• Structure

– Nuclear Membrane and Pores• Lipid Bilayer w/ associated protein channels

– Chromatin• DNA + protein (histones)

• Function– Nuclear membrane and Pores

• Controls access to DNA

– Chromatin• Keeps Genetic information tightly packed• Genetic information – info for building proteins

Ribosomes

• Structure– Made of RNA and Protein– Large and Small Subunits

• Function– Site of protein manufacturing

Cytosol• Structure

• Aqueous solution (mostly water and ions)

• Function• Fluid medium for chemical reactions

Cilia or Flagella

• Structure– Protein filaments in a 9+2 arrangement

embedded in the membrane

• Function– Motile Elements of the Cell– Allows cell to move or moves substances

around the cell

Vacuoles

• Structure– Membrane bound vesicles – often made from

in-pocketing of plasma membrane.– Contain various cell products for storage

• Function– Store cell products, food, waste, etc.– In plants, the Central Vacuole contains

enzymes and water. When filled, it maintains turgor pressure on the cell wall.

Cell Wall– Structure

• In plants, made of the polysaccharide cellulose as well as the proteins pectin and lignin. Actually 2 layers, depending on the cell function, the thicknesses of each vary.

– Contain openings lined with membrane called Plasmodesmata, that allow things to enter the cell.

• In fungi, made of nitrogen-rich polysaccharide chitin.

– Function• Provides protection and support in plant and fungi

cells

Chloroplast

• Structure– Membrane organelle that contains smaller

vesicles called Grana– Grana’s membrane has high concentration of

chlorophyll

• Function– Use sunlight energy to produce carbohydrates

Centrosomes

• Structure– Animal cells (small protein filament bundles

called centrioles)– Plant cells (associated cytoskeleton elements)

• Function– Organizes cytoskeleton during cell division to

equally separate chromosomes– Where all cytoskeleton growth originates