Topic 4 Flashcards
cell surface area
The main reason that cells are small - Surface area advantage to exchange material across plasma membrane
cell volume ratio
As a cell’s size increases, its volume increases much more rapidly than its surface area.
prokaryotic cells
a cell lacking a membrane bound nucleus/organelles except ribosomes
– “Pro-” greek referring to “Before nucleus” as the DNA is concentrated in a region that is not membrane-enclosed called the nucleoid.
has a cell wall
eukaryotic cells
a cell characterized by membrane bound organelles & nucleus and one that possesses chromosomes whose DNA is associated with proteins
the three main parts of the generalized Eukaryotic cell are the Plasma membrane, Nucleus, and cytoplasm
domain
the highest taxonomic rank in the hierarchical biological classification system, above the kingdom level
there are three domains: archaea, bacteria, and eukarya
archaea and bacteria are prokaryotes while eukarya are eukaryotes
archaea
a highly diverse group of unicellular prokaryotes
cell wall made of polysaccharides and glycoconjugates
eukarya
contains the eukaryotic organisms (protists, fungi, plants, animals)
bacteria
a vast group of unicellular prokaryotes
cell wall made of Peptidoglycan
eukaryote
organisms that have cells with a distinct nucleus and other membrane-bound organelles
are larger and more complex than prokaryotic cells
nucleus
the membranous organelle that stores the chromosomal DNA and controls most of the cell’s processes & activity by controlling gene expression
Cells may be anucleate (RBCs) Mononucleate (most cells), or multinucleate (hepatocytes, and Skeletal muscles)
nucleoid
the area of a prokaryotic cell, typically near the center, that contains the genome in the form of DNA compacted with protein
cytoplasm
the Intracellular fluid, containing organelles, that perform specific cellular functions
cell junctions
ways cells can adhere to each other or the extracellular matrix
there are three types
gap junctions
a junction between adjacent animal cells that allows the passage of materials between the cells
a communicating junction between adjacent cells, which form hollow cylinders (called Connexons) that allow small molecules to pass from cell to cell.
Used to spread ions, simple sugars, and other small molecules pass through these water-filled channels.
Allows electrical signals to be passed quickly from one cell to the next cell. Are found in electrically excitable tissue, such as the heart and smooth muscle, where ion passage from cell to cell helps synchronize their electrical activity and contraction.
tight junctions
region of actual fusion of plasma membranes between two adjacent animal cells that prevents materials from leaking through the tissue
Integral proteins on adjacent cells fuse to form an impermeable junction that encircles the whole cell, similar to the seal on a “Ziploc bag.” Prevents fluids and most molecules from moving in between cells
Found in the Epidermis, and digestive tract, to keep digestive enzymes and microbes from seeping into the bloodstream
desmosomes
a type of anchoring junction that links adjacent cells by connecting they cytoskeletons with cadherin proteins
mechanical couplings scattered like rivets along the sides of adjacent cells to prevent their separation.
Linker proteins, Cadherins, are anchored to the cell through thickened “button-like” areas on inside of the plasma membrane called Plaques.
Plaques are connected intercellularly by keratin filaments for added anchoring strength.
reduce the possibility of tearing under tension by allowing “give” between cells
Neighboring cells are bound together into sheets and also contribute to a continuous internal network of strong fibers that act as “guy-wires,” that distribute tension throughout a cellular sheet.
Are found in abundance in tissues subjected to great mechanical stress, like skin and heart muscle.
plasmodesmata
in plants, and they are the cytoplasmic connection between adjacent cells, function is similar to gap junctions in animal cells
cell walls separate every cell from all others, and cell to cell junctions occur only at holes or gaps in the walls, to allow plasma membrane of adjacent cells to communicate with one another.
ribosomes
The molecular machine that carries out protein synthesis, made up of protein and ribosomal RNA (rRNA)
There are two types…
Free ribosomes – sites of synthesis of soluble proteins that function in cytosol or other organelles
Membrane-bound ribosomes – attached to membrane of endoplasmic, site of synthesis of proteins to be incorporated into membranes or lysosomes or exported from cell.
plasma membrane
Consists of membrane lipids that form a flexible lipid bilayer
membrane surrounding the cytoplasm of a cell; consists of a single phospholipid bilayer with embedded proteins
acts as a selectively permeable barrier & allows cell recognition and communication
Physical barrier separating intracellular from extracellular environment
Specialized membrane proteins float through this fluid membrane, resulting in constantly changing patterns referred to as fluid mosaic (made up of many pieces) pattern
Surface sugars form glycocalyx
Membrane structures help to hold cells together through cell junctions
Lipid bilayer is made up of:
75% phospholipids, which consists of two parts:
Phosphate head: which is polar (Charged),
and are hydrophilic (water-loving)
Fatty acid tail: are nonpolar (no charge),
and are hydrophobic (water-hating)
5% glycolipids
Lipids with sugar groups on outer membrane surface
20% Cholesterol
Increases membrane stability
flagella
long, threadlike structures protruding from the surface of a cell and assists in movement
Present in some prokaryotic cells, also in some Eukaryotic cells, but structure is different
nuclear envelope
it is the bounding structure of the eukaryotic nucleus
composed of two phospholipid bilayers (double-membraned) that encloses the jelly-like fluid, the nucleoplasm
Outer layer Is continuous with rough endoplasmic reticulum, containing ribosomes
Inner layer (nuclear lamina) - Network mesh of proteins, which help to maintain nuclear shape, and acts as scaffolding for DNA
Nuclear pores allow substances to pass into and out of the nucleus.
endoplasmic reticulum
internal membrane system that forms a netlike array of channels and interconnections within the cytoplasm of eukaryotic cells
Consists of series of parallel, interconnected cisterns – flattened membranous tubes that enclose fluid-filled interiors
IT IS CONTINUOUS WITH THE OUTER NUCLEAR MEMBRANE
divided into the rough and smooth ER
helps in protein maturation and transport
rough endoplasmic reticulum
Looks rough because of the attached Ribosomes,
Synthesis of proteins to be secreted from cell,
Synthesis of many plasma membrane proteins and phospholipids.
Protein processing – proteins made by ribosomes go into the cisterns, modified as they move through, and put into a vesicle, and sent to the Golgi apparatus.
smooth endoplasmic reticulum
looped tubules
continuous with rough ER
WIDE variety of jobs using enzymes in its plasma membrane…
- Lipid metabolism; cholesterol and steroid-based hormone synthesis; making lipids for lipoproteins
- Absorption, synthesis, and transport of fats
- Detoxification of certain chemicals (drugs, pesticides, etc.)
- Converting of glycogen to free glucose
- Storage and release of calcium
-Sarcoplasmic reticulum is specialized
smooth ER found in skeletal and cardiac
muscle cells
* The function will depend on which cell you are in
centrioles
a cytoplasmic organelle located outside the nuclear membrane, identical in structure to a basal body
found in animal cells and in the flagellated cells of other groups
divides and organizes spindle fibers during mitosis & meiosis
golgi apparatus
a collection of flattened stacks of membranous cistern sacs in the cytoplasm of eukaryotic cells
modifies, concentrates, and packages proteins and lipids received from rough Endoplasmic reticulum.
Three steps:
1. Transport vesicles from ER fuse with cis (inner) face of Golgi
2. Proteins or lipids taken inside are further modified, tagged, sorted, and packaged.
3. Golgi is “traffic director,” controlling which of three pathways final products will take as new transport vesicles pinch off trans (outer) face.
Final Transport vesicles can take one of three pathways:
- Secretory vesicles – containing proteins to be used outside of cell fuse with plasma membrane and exocytosis
- Vesicles containing lipids or transmembrane proteins, which fuse with plasma membrane or organelle membrane
- Lysosomes – containing digestive enzymes.
mitochondria
consists of an outer membrane & an elaborate inner membrane
responsible for producing ATP, the cell’s main energy-carrying molecule
lozenge-shaped
Have their own circular DNA, RNA and Ribosome, Reproduce on their own, and inherited from individual’s mother
chloroplasts
carry out photosynthesis, converting light energy into chemical energy
Contain Thylakoids (Thylakoid disk) which are membranous sacs that contain chlorophyll, a photosynthetic pigment for photosynthesis.
Also has a double layered membrane
and contain their own DNA and Ribosomes.
chromosomes
the vehicle by which hereditary information is physically transmitted from one generation to the next
in a bacterium the chromosome consists of a single naked circle of DNA
in eukaryotes each chromosome consists of a single linear DNA molecule & associated proteins
lysosomes
Spherical Membranous bags containing digestive enzymes (acid hydrolases) produced in the golgi body that isolate potentially harmful intracellular digestion from rest of cell
Digest ingested bacteria, viruses, toxins, as well as nonfunctional organelles
Also has a metabolic function in the cell, by breaking down and releasing glycogen, and Calcium from bone.
vacuoles
a membrane-bounded sac in the cytoplasm of some cells, used for storage or digestion purposes in different kinds of cells
plant cells often contain a large central vacuole that stores water, proteins, & waste materials
storage compartments that sequester waste and help maintain water balance
autolysis
occurs when lysosomes digestive enzymes are release intracellular due to the cell becoming injured.
What differences distinguish prokaryotic and eukaryotic cells from each other?
Prokaryotes - nucleoid, 70s ribosome, no organelles except ribosomes, single circular DNA genome
Eukaryotes - nucleus, 80s ribosomes, organelles, histone proteins - DNA complex compacting DNA
Cell Size: Prokaryotic cells are generally smaller, while Eukaryotic cells are larger
- Cell Structure: Prokaryotic cells are usually unicellular, while most Eukaryotic cells are multicellular.
.
What structural differences between plant and animal cells exists?
- Cell Wall: Plant cells have a cell wall in addition to a cell membrane, while animal cells only have a cell membrane
- Shape: Animal cells are mostly round and irregular in shape, while plant cells have fixed, rectangular shapes
- Chloroplasts: These are present in plant cells for photosynthesis but absent in animal cells
- Vacuoles: Animal cells have one or more small vacuoles, while plant cells have one large central vacuole
- Energy Storage: Animal cells store energy in the form of complex carbohydrates and glycogen, while plant cells store energy as starch
theory of the origin of eukaryotic cells (endosymbiosis)
It proposes the idea that the organelles found in eukaryotic cells arose from symbiotic relationship with multiple primitive prokaryotic cells. A larger cell engulfed the smaller cell(s) and kept them in its cytoplasm.
Which of the following are differences between bacteria and archaea?
The molecular architecture of their cell walls
The type of ribosomes found in each
Plasmodesmata in plants and gap junctions in animals are functionally similar in that?
They form channels between cells that allow diffusion of small molecules
Eukaryotic Cell Walls
Found in plants, fungi, and many Protists, which protect and support the cells.
The cell walls of Eukaryotes are chemically and structurally different from Prokaryotic cells walls.
Plants have a Primary and Secondary wall, with a middle lamella (glues the walls together).
Plants and Protists, are made from Cellulose
Fungi is composed of Chitin
Peroxisomes
Membranous sacs
Detoxify substances: like free radicals, toxic, highly reactive molecules that are natural by-products of cellular metabolism
Two main detoxifier enzymes: Oxidase, and Catalase
Oxidase – uses oxygen to convert toxins to hydrogen peroxide (H2O2), which is also toxic, but Peroxisomes use then catalase.
Catalase – which converts H2O2 to harmless Water H2O
