Cell structure, Chapter 4 Flashcards
- Cells were first observed in the 17th century by?
Robert hooke
Modern cell theory is based on 3 principles
- All organisms composed of one or more cells
- Cells are smallest living things
- Cells arise only by division of a previously existing cell
Solutes move from a high concentration to low concentration
Diffusion
Rate of diffusion is affected by
- surface area available for diffusion
- temperature
- concentration gradient of diffusing substance
- distance over which diffusion must occur
Surface Area to volume ratio
As a cell’s size increases, its volume increases much more rapidly than its surface area
- small cells have an advantage over an larger cells
Light microscopes
- Use magnifying lenses with visible light
- Can view some cells, but few cellular structures
- Limit to resolution using light
Electron microscopes
- Use a beam of electrons
- Able to view cellular structures
- Transmission electrons microscopes through the material
- Scanning electron microscopes beam electrons onto the specimen surface
Cells share simple structural features
- A localized area where genetic material is stored
- The cytoplasm
- All cells have ribosomes
- A plasma membrane
Prokaryotic
- Bacteria and Archaea
- Simple cellular structure- an organization
- Lack of a membrane-bound nucleus
- Do not have an internal membrane system
- Huge diversity in prokaryotic metabolism, function and ecology
- Cytoplasm surrounded by a plasma membrane and encased by a cell wall
- Contain ribosomes for protein synthesis
- No membrane-bound organelles- operate as a single unit
Bacteria cell walls
- Composed of Peptidoglycan, a carbohydrate matrix cross-linked with shirts polypeptide units
some antibiotics function by disrupting the peptidoglycan layer of bacteria cells
killing the cells
Cell walls
Protect the cell, maintain shape and prevents excess water loss/uptake
long threadlike structures protruding from the surface of a cell, used in locomotion
Flagella
Eukaryotic cells
- Cells are broken up into compartments through the endomembrane system and organelles allowing the simultaneous and independent biochemical processes to occur
- The nucleus acts as the information center
- Largest organelle
- The nucleus contains genetic information
- Contain a single nucleus
- Nuclear envelope; bounded by 2 phospholipid bilayer membranes
- Nuclear pores; occur across the nuclear envelop- allowing ions and small molecules to diffuse freely- transport proteins that function in the nucleus
- Nuclear envelop covered with fibers that make up the nuclear lamina
- Gives the nucleus its shape and is involved in cell division
- DNA is divided into chromosomes organized into a complex structure called chromatin
- The structure of chromatin affects the function of DNA
- Nucleolus; area of concentrated RNA synthesis and ribosome assembly within the nucleus
- To make proteins cells must first make ribosomes
- Ribosomes: complex structures and are made up of 2 subunits
- Messenger RNA(mRNA): coding information from DNA and is used to direct synthesis
- Ribosomes are either free or membrane-associated
- The interior of the cell is packed with internal membranes
- divide cells into compartments
Endomembrane system
- largest internal membrane
- phospholipid bilayer embedded with proteins
- divided into 2 subdivisions
Endoplasmic reticulum (ER)
- proteins synthesized on the surface of the RER are destined to be exported from the cell, sent to lysosomes or vacuoles, or embedded in the plasma membrane
- Protein leaves the RER to be sorted to their final destination
The rough ER (RER) is a site of protein synthesis
- Membranes of the SER contain many embedded enzymes, involved in the synthesis of carbohydrates and lipids
- The majority of membrane lipids are assembled in the SER
- SER stores intracellular Ca2+, used in diverse signaling pathways
- The SER modifies foreign substances to make them less toxic
- in the liver enzymes in the SER carry out detoxification
The Smooth ER (SER) has multiple roles
The ratio of RER to SER in cells depend on
The cells function
- Sorts and packages proteins
- complex flattened stacks of membranes
- size and # of cistern varies across organism and cell types
- Abundant in cells that manufacture and secrete proteins
Golgi apparatus
- located near ER
- ## proteins arrive in transport vesicle that bud off ER
Cis face
- proteins exit and are discharged in secretory vesicles
Trans face
Add short sugar chains
- Glycoproteins or glycolipids
Glycosylation
- digestive vesicles that arise from the GA
- contain many enzymes to degrade macromolecules
- break down old organelles and recycle their molecules
- have optimal activity at an acid pH
- conditions could kill cell=keep compartmentalized
- activated by fusing with what they will breakdown
- fission activates proton pumps
- pump H+ in and lowers pH- activating digestive enzymes
Lysosomes
Tay-Sachs disease
- caused by the loss of function of a single lysosomal enzyme
- necessary to breakdown membranes glycolipid found in nerve cells
- leads to seizures and muscle rigidity
Organelles consisting of a neutral lipid core, surrounded by a single layer of phospholipid
lipid droplets
