Cells Flashcards
What do osteoblasts do?
Build bone
What do osteoclasts do?
Crumble bone
What do fibroblasts do?
form connective tissue, ie periodontal ligament and pulp.
What do ameloblasts do?
Form enamel
What do odontoblasts do?
Form dentine
What does HIV do to transcription?
Causes reverse transcription
What are nucleic acids made out of?
Polymerised nucleotides
What are the five nitrogenous bases?
Adenine, Cytosine, Thymine (Uracil in RNA), Guanine
What does nucleic acid make up?
chromosomes or the genome
What does interplay between genes and the environment affect?
Gene expression
How do stem cells work?
Differentiate when a gene is switched on by a highly coordinated pattern of expression regulated by proteins and nucleic acids
What are some common features of a cell?
- Cell membrane
- Cytoplasm
- Endoplasmic reticulum
- Ribosomes
- Golgi apparatus
- Mitochondria
- Lysosomes
- Centrosomes
- Proteasomes
- Peroxisomes
- Nucleus
- Nucleolus
- Cytoskeleton
What are some types of cell appendages?
- Microvilli
- Cilia
- Flagella
What is the function of microvilli?
Increase absorptive area
What is the function of cilia?
Generate fluid movement (ie gut)
What is the function of flagella?
Aid motility
Describe the cell membrane.
A phospholipid bilayer with interspaced proteins.
What is the function of the cell membrane (proteins)?
Maintaining cellular integrity, controlling entry and exit, interacting with extracellular molecules such as hormones, forming connections with other cells and structures
Explain the cytoplasm.
A water based gel-like structure which supports organelles
What does ‘membraneous’ mean?
The organelle cannot exist in the same environment as the cell.
Explain the endoplasmic reticulum.
Membraneous canals/sacs which are invlolved in cellular transport (export).
What are the two types of ER?
-Smooth: Involved in lipid synthesis
-Rough: Involved in protein synthesis
Explain ribosomes
Non membraneous organelles made up of RNA and proteins which synthesise proteins.
Where are the two locations of ribosomes?
Free or on the ER
Describe the Golgi apparatus.
A membraneous organelle composed of stacked cisternae (sacs) which packages proteins for secretion.
Where is the golgi apparatus located?
Near the Nucleus.
Describe the mitochondria.
A membraneous organelle which has two membranes and produces ATP by oxidative phosphorylation.
What does endosymbiont theory refer to?
The evolution of mitochondria in eukaryote cells. Small bacterium invades host cell and multiplies, giving the host the ability to oxidise nutrients.
Describe lysosomes.
Membraneous organelles which are derived from golgi and contribute to the cell’s immune system by carrying out enzymatic break down of foreign particles. They protect cells from bacteria.
What are important lysosomes in the human body?
White blood cells
What are proteasomes?
Non-membraneous proteinaceous drums which destroy ubiquitin tagged proteins by causing them to unfold (enzymes) and break peptide bonds.
What do proteasomes recycle?
Amino acids.
Describe peroxisomes.
Membraneous organelles which detox the cell of harmful substances. They contain catylase and peroxidase enzymes.
Describe the nucleus.
A double membraned organelle with pores which contains the entire genome, generates mRNA which specifies a protein to ribosomes.
Describe the nucleolus.
A structure inside of the nucleus composed of mostly RNA which synthesises rRNA which is exported and combines with ribosomal proteins making functional ribosomes.
Describe the cytoskeleton.
A flexible internal supporting framework which facilitates cell movement and is composed of microfilaments, intermediate filaments, and microtubules.
What are microfilaments?
Twisted actin strands
What are intermediate filaments?
Keratinaceous structures
What are microtubules?
essential in cell division (spindle fibres) and have cilia and flagella for movement.
What is a tubulin?
An ‘engine’ which moves vesicles, chromosomes, and organelles around.
What are important functions of proteins?
- Structure
- Catalysis
- Regulation (of proteins or genes)
- Transportation (channels, pumps, binding proteins)
- Defence/offence (antibodies, defensins)
How many amino acids are there?
20
How many amino acids are essential?
9, we obtain them through food.
How are amino acids used?
They are polymerised to make peptides -> proteins
How do amino acids differ from each other?
By side (R) chain. This allows diversity of both structure and function.
What are the four R chain states?
Charged, uncharged, polar (hydrophilic), or non-polar (hydrophobic)
What does a peptide bond look like?
A C=O C-N N-H network (CHON)
What is the N terminus?
The amino terminus of a molecule.
What is the C terminus?
The carboxyl terminus of a molecule.
What is primary structure?
Sequence of amino acids forming a polypeptide chain.
What is secondary structure?
Alpha helices and Beta pleated sheets which occur as a result of interaction (H bonding) between parts of the polypeptide.
What is tertiary structure?
A combination of Alpha and Beta shapes as a result of H bonding/covalent bonding with other protein.
What is quarternary structure?
A combination of alpha and beta shapes when there is more than one polypeptide chain
Describe centrosomes.
Non-membraneous organelles which control centre and microtubule activity, as well as cell division.
What must cells be attached to?
Each other or an ECM
What is cellular attachment mediated by?
membrane proteins such as integrins, selectins, cadherins, immunoglobins
What are the three types of cellular connections?
Desmosomes, gap junctions, tight junctions.
Describe desmosomes
- plasma membranes locked together like velcro
- very strong
- help epithelial cells to resist mechanical stresses.
What is ATP?
- energy currency of cells
- energy is stored in the bonds linking the phosphate molecules.
Describe gap junctions.
- Connects cytoplasms of two cells (membrane proteins-connexons) -
- Allows transport of electrical signals through tissues
Describe tight junctions.
- impermeable seal around a group of cells
- lipid portion of plasma membranes bound by interlocking membrane proteins.
What is the basement membrane?
A non-cellular structure produced by the basal surface of the epithelium and underlying connective tissue.
What does the clear layer of the basement membrane contain?
Glycoproteins, network of fine protein filaments. Produced by the adjacent layer of epithelial cells.
Describe the dense layer of the basement membrane.
Bundles of coarse protein fibres. Gives the membrane its strength and acts as a filter.
Basic unit of composition of carbohydrates
Sugars
Basic unit of composition of proteins
Amino acids
Basic unit of composition of lipids
Glycerol and fatty acids
Nucleic acids
Nitrogenous bases
What is glycogen?
An energy storage molecule, a large branched polymer of glucose
What do enzymes do in the body?
- Speed up and slow down reactions
- Require energy from substrate or ATP
What is the function of lipids?
Storing energy
Describe lipids
- Store 2x more enrgy than carbohydrates
- mainly water insoluble
What do phospholipids do?
Form a bilayer which is the major component of biological membranes
What do steroids do?
Act as structural components or hormones, differentiated by the side chain on the steroid nucleus
What identifies an unsaturated fat?
c=c double bond
What identifies a saturated fat?
c-c single bonds only, no c=c double bonds
What is formed in the endosymbiont theory?
large, complex organisms
What is the most chemically economical shape?
Helix
