Week 2- Cells Flashcards
Describe a eukaryote cell
“True nucleus”
Has a distinct nucleus
Has a nuclear envelope
Contains chromosomes (DNA + protein)
Describe a prokaryote cell
“Before nucleus”
Contains a single strand of DNA
Does not contain a nucleus
Free-floats in gelatinous protoplasm
Why aren’t cells very big?
Relationship between cell surface area & volume. If a cell were larger, it wouldn’t be able to take in nutrients fast enough to feed itself and would die.
Describe the cell membrane.
Aka plasma membrane or plasmalemma
Separates cell from its environment
Controls what goes in & what goes out
Describe cytoplasm
Everything inside the cell membrane except the nucleus and genetic material.
Colloidal protoplasm
Composed of proteins, electrolytes, metabolites, flexible cytoskeleton and organelles.
Describe a virus
Composed of a protein covered capsule
Contains either one strand of DNA or one strand of RNA
Parasitic- lacks biochemical mechanisms to reproduce
Relies on cells for nutritional, structural and molecular assistance to multiply
Attaches to cell’s surface & injects its genetic material into the cytoplasm (interferes with cells normal metabolic processes)
Cells are reprogrammed to manufacture viruses
Cell ruptures (dies), releasing hundreds of newly formed viruses into extracellular environment
Considered to be alive ( able to reproduce, grow, develop, adapt, respond to stimuli and maintain a stable environment using energy from their environment
Describe a prion
Not considered to be alive
Believed to be proteins or proteinaceous infective particles
Lack DNA and RNA
All known prion diseases are fatal and cause a progressive neurodegenerative disorder(leaves grossly visible holes in the brain)
Condition is called spongiform encephalopathy because affected brains resemble sponges.
Humans can contract prions by ingestion or inoculation.
What does zoonotic mean?
That the disease can be transmitted between animals and humans .
Describe the lipid bilayer
The cell membrane is composed of two layers of phospholipid molecules arranged so that the hydrophilic heads are on the outside and the hydrophobic fatty acid tails are on the inside
Hydrophilic
Attracted to water
Hydrophobic
Repelled by water
Integral proteins
Contact globular proteins that occur within the lipid bilayer
Pores created by integral proteins
Channels within the protein molecule that allow substances such as water to pass through with no resistance make up approx 0.2% of the cell surface area
Cell membrane selectivity
Most lipid soluble material (such as oxygen & carbon dioxide) pass through with ease Ionized and water-soluble molecules (amino acids sugars and proteins) do not readily pass through Globular proteins (integral proteins)form channels through which other molecules can pass some form selective passageways that only permit particular substances to enter or exit. others create pores
Describe flagella
Originate from a pair of centrioles (basal bodies) located at the periphery of the cell (just under the plasmalemma) grow outwards from basal bodies and exert pressure on plasmalemma Occur singly Are significantly longer than cilia Propels the cell forwards by undulating Moves cells through fluid
Describe Cilia
Originate from a pair of centrioles (basal bodies) located at the periphery of the cell (just under the plasma membrane)
grow outward from basal bodies and exert pressure on plasma membrane
Occur in large numbers on exposed surface of some cells
Shorter than flagella 10 µm long
Move synchronously, one after the other, creating waves of motion that propel fluids, mucus and debris across cellular surface
Upper respiratory tract & oviduct
Intracellular fluid
Water found inside the cell
