Lecture 4: The Cell Flashcards
Properties and Actions of cells
growth, reproduction, absorption, metabolism, excretion and secretion, excitability, conductivity, contractibility
Chemical Composition of cell
85% water 10% protein 2% lipid 1.5% inorganic matter 1.5% other substances and carbohydrates
Important organelles
golgi apparatus, endoplasmic reticulum (smooth and rough), free ribosomes, mitochondria, lysosomes, peroxisomes, microtubules and microfilaments
Endoplasmic reticulum (ER)
- mesh of interconnected membranes; used for protein synthesis and transport
- connects to the nuclear envelope/membrane through which the mRNA, the blueprints for proteins, travelto the ribosomes
mitochondria
- “power house” of cells
- have a variety of enzymes and co-enzymes
- oxidation of nutrients to CO2, ATP, and H2O
lysosomes
- small membrane-bound bags involved in digestion and detoxification
- contain 50 different digestive enzymes
- break up the material into smaller and simpler products that the cell can use
- digest worn-out cell components and pathogens engulfed by WBC’s
cytoskeleton
- organized network of three primary protein filaments: microtubles, actin filaments, and intermediate fibers
- primary importance: cell motility
- maintain cell shape and the internal movement of cell organelles
- cell locomotion and muscle fiber contraction could not take place without the cytoskeleton
microtubules
assist in transport of molecules within some cells
microfilaments
assist with cell motility
actin and intermediate fibers
assist in muscle contractions
Nucleus
- largest organelle
- surround by a double membrane: nuclear envelope
- nuc. envelope is permeated with gates called nuclear pores
- pore are routes by which genetic messages pass into the cytoplasm
- nucleus=info centre
Nucleolus
area of nucleus (looks like a dark dot) that contains chromosomes
chromosomes
contain heredity information, made of DNA and proteins
Chromatin
fragments of chromosomes, coiled together to form one
Ribosomes
- protein factories
- in the nucleus, DNA’s instructions are transcribed into a messenger molecule of ribonucleic acid called mRNA
- the code in a strand of mRNA is translated into a protein by ribosomes, in the cytoplasm
Cell Membrane
- double layer of lipid molecules interspersed with protein molecules
- maintains cell integrity
- functions as a semi-permeable barrier
- controls what goes in and out of cell
- usually semi-permeable
Types of transport across CM
diffusion, passive transport, and active transport
diffusion
- method of movement of substances to cross the membrane directly
- water, CO2, and O2 are among the few simple molecules that an cross CM by diffusion (diffusion aka osmosis)
Osmosis
- diffusion of water through a semipermeable membrane from high concentration to low
- used for filtering urine through kidneys and movement of water across intestine walls
Facilitated diffusion
does not use energy, membrane or proteins pick up molecules and coarry them across the membrane from high to low concentration
Active transport
allows molecules to move against their conc. gradient, requires energy
endocytosis
energy requiring process where cell membrane surrounds molecules, forming a pocket which becomes a vacuole in the cytoplasm
-types include phagocytosis and pinocytosis
phagocytosis
- membrane surrounds large particles, forms a pocket, then a vacuole
- this is how amoeba and WBCs feed
pinocytosis
- literally means cell drinking
- membrane surrounds a liquid, forms a pocket, then a vacuole
exocytosis
energy requiring process where a vacuole containing large molecules joins with the membrane, makes an opening, and squeezes the molecules out of the cell
vesicle-mediated transport
vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter
Tight Junctions
- the portion of the cell exposed to the lumen is called its apical surface
- the rest of the cell (sides and base) make up the basolateral surface
Gap Junctions
because ions can flow through them, gap junctions permit changes in membrane potential to pass from cell to cell
