Download - Cell Form and Function
Cell Form and Function
Dr. AndersonGCIT
Cell Diversity • Connect tissues and transportation – blood, epithelia
• Body movement – muscles (smooth, striated, cardiac)
• Storage – adipose (fat cells), hepatocytes
• Immune Function – WBC’s
• Communication and information processing – nerve cells
• Reproduction – Egg and sperm cells
Cell Membrane • Keeps the cell contents separate from the
environment (extracellular fluid)
The Fluid Mosaic Model• Cell membrane is made of a phospholipid
bilayer– Self-assembling!– Extremely thin
Non-polar tails
Polar Heads
Polar Heads
Polar Heads are phospholipids and the non-polar (hydrophobic) ends are fatty acids
Outside of cell – interstitial fluid
Inside of cell – cytoplasm
Membrane ProteinsFacilitate the transport of material across the membrane
Integral (trans-membrane) protein – facilitates transport into and out of the cell
Membrane Proteins
Peripheral protein – can be attached to inside or outside layer of cell membrane
• Act as enzymes (outside and inside) or serve to move or support the cell (inside)
Glycoproteins – sugar-bound proteins
Glycoproteins – make up a sugary coat that envelops the cells called the glyco-calyx or “sugar cup”
The Glycocalyx
• The carbohydrates on the cell surface provide a way for some cells to recognize each other– Sperm and egg– WBC and bacteria or other pathogens
Membrane Junctions
• Bind cells together – glycoproteins act as adhesive
• Cell membrane structure – tongue-and-groove
• Specialized Junctions – – Tight junction– Desmosomes– Gap Junctions
Special Membrane Junctions• Tight Junctions – proteins in the cell membranes
that bind cells together– Makes sure nothing passes between cells
• Desmosomes - small points of connective proteins that anchor cells together– Found in cells subject to heavy pulling forces
• Gap Junctions – an open junction between adjacent cells– Permits chemical communication (transport) between
cells
Membrane Transport
• Interstitial Fluid – extracellular fluid largely derived from blood, but acellular– Amino acids, wastes, electrolytes, sugars, etc.
• Cells need to hold a balance of these solutes between their inside and outside environments
• How is this done?
Membrane Permeability
• Membranes only allow passage to certain molecules, or only permit movement in one direction
• Selectively Permeable – only certain molecules can pass
Active Transport
• ATP is used to drive the concentration gradient across the cell membrane 1. Primary – ATP changes the shape of membrane
proteins to shuttle specific materials across2. Secondary - uses stored potential energy from
primary transport to move substances3. Vesicular – vesicles “gulp” materials from outside
the cell by pinching off a bubble from the cell membrane
ELMO
• Review Pages 74-75 in textbook to explain prior slide in more detail
Vesicular Transport
• Endocytosis – cell ingests materials via vesicles– Receptor mediated
• Exocytosis – cell expels material into the environment via vesicles
• Phagocytosis?
Plasma Membrane – Resting Potential
• Many cells work using electrical energy which is derived from ion separation– Muscle cells, nerve cells, etc.
• How is this accomplished?
Electric Membrane Potential
- --
- --
- - ---
+ ++
K+
++
++ ++
Anions (negatively charged proteins build up)
K+
pump
Cations (postively charged ions (K, Na) build up)
Cytoplasm
• The material between the cell membrane and the nucleus
• Three major elements– Cytosol– Organelles– Inclusions
Cytosol
• Liquid part of the cytoplasm
• Consists of mostly water, but also dissolved substances such as– Salts– Sugars – proteins,– Etc.
Cytoplasmic Organelles
• Carry out cellular metabolic processes
• Specific to the kingdom of living things (e.g. chloroplasts are only found in plants)
Mitochondria
• Powerplants of the cell
• Breaks down food and uses this energy to form ATP from ADP (cellular respiration)on inner membranes (cristae)
• Have their own DNA, RNA and ribosomes– Huh?
Ribosomes• Made of two RNA-protein
subunits that work together to synthesize proteins (protein translation)
• Two types– Free ribosomes – make
soluble proteins– Membrane-bound
organelles – make proteins for packaging or export
Endoplasmic Reticulum (ER) • Membranes in the cytosol that are
continuous with the nuclear membrane
• Rough ER – lined with ribosomes that produce proteins that are secreted from cells, also make new phospholipids and intracellular membranes
• Smooth ER – Embedded with enzymes that catalyze the metabolism of proteins, fats, hormones, toxins and glycogen
Golgi Apparatus
• Stacks of membranous sacs in the cytosol
• Used to concentrate, modify and/or package proteins and lipids made by the rough ER.
• Packaged proteins are called vesicles are sent into the cytosol or outside of the cell (exocytosis)
Lysosomes
• Contain activated enzymes that may be capable of digesting all type of biological molecules
• The membrane-bound lysosomes contain these dangerous substances, preventing cell damage
Peroxisomes
• Contain extremely reactive oxygen species (ROS) that are used to detoxify certain poisons such as alcohol
• Also destroy free radicals – highly reactive waste products of metabolism that can disrupt cell processes– In which cells might these be found?
Cytoskeleton
• Consists of rods made of tubulin that run through the entire interior of the cell– Microtubules– Microfilaments– Intermediate
filaments
Cytoskeleton Components• Microtubules– Determine cell shape and influence organelle dstribution
• Microfilaments – A “web” of these filaments attach to the inner surface of
the cell membrane and give the cell strength. Also helps change cell shape during mitosis/meiosis
• Intermediate Filaments– Give the cell tensile strength by attaching to desmosomes
Centrosomes and Centrioles
• Centrosomes – serve to anchor microtubules and provide attachment points during activities such as cytokinesis, alignment of chromosomes during mitosis (mitotic spindle)
Cilia
• Relatively short extensions of tubulin that cover cells
• Enables cells to move through their environment, or move the liquid environment around themselves
Flagella
• Long extensions of tubulin protein used for propulsion
• Many microorganisms possess flagella
• Only human cells that possess flagella are sperm cells
Inclusions
• Chemical substances that may or may not be present, depending on the cell type. – Pigments– Crystals– Vacuoles– Etc.
The Nucleus
• The nucleus is a membrane-bound organelle that serves as the central control system of the cell
• All instructions for the cell’s processes are carried on genes that can be found within the DNA housed inside the nucleus
Nucleus
• Nuclear Envelope – double layered membrane that surrounds the nucleus– Outer Layer – continuous with ER– Inner Layer – lined with lamina, filaments that
hold the nuclear shape– Nuclear pores penetrate both layers, allowing
some molecules to flow into and out of the nucleus
Nucleus
• Nucleoli – dark-staining regions in the nucleus where ribosomal RNA (rRNA) is made
• Chromatin – DNA wound around protein units called histones– This form of DNA allows
efficient packing and storage of DNA (a nucleosome) during periods where the cell is not actively dividing
Nucleus - Chromosomes
• During cell division, chromatin winds up to form bar-shaped structures called chromosomes
• The arrangement of these structures allows the definition of different stages of cell division
Human Karyotype
• Chromosome sizes and number can also be used to screen for genetic diseases
DNA Replication
Helicase
DNA Polymerase
DNA Polymerase
