Lesson 3 - Nuclear Cell Biology Flashcards
Exception to a human cell that does not contain a nucleus
Erythrocyte
What is the nucleus separated from the cytoplasm by
The nuclear envelope/membrane
What does the nuclear membrane have that allows large molecules to synthesise in the nucleus to pass into the cytoplasm?
Pores which allow large molecules (e.g. peptides that form together to create a protein) to synthesise in the nucleus and then to pass into the cytoplasm
Is the nuclear membrane phospholipid?
Yes
Where is the nucleus in leukocytes?
Central part of the cell
Where is the nucleus in tall columnar cells?
Basal (base) of the cell
Where is the nucleus in skeletal muscle cells?
Peripheral (sides)
Why does the nucleus stain intensely with basic dyes?
Because it has a combination of euchromatin and heterochromatin
What is euchromatin?
Chromatin that is the same or very similar. Euchromatin is abundant in active nuclei e.g. plasma cells
What is heterochromatin?
Chromatin that is different. It is abundant in inactive cells e.g. nuclei of small lymphocytes
Genes determine what?
Organism characteristics
What are the 4 components of DNA
Cytosine, Guanine, Adenine, Thiamine
Chromosomes are
Discrete collections of genes and nuclear proteins
What is a phenotype?
Genes that determine what people are going to look like
What is a genotype?
Genes that determine someone’s internal framework and structure
2 membranes of the nucleus
Inner and outer nuclear membrane
Outer membrane becomes … with an organelle
Continuous
What does it mean when the outer membrane becomes continuous with an organelle?
When peptides go out of the nucleus to assemble to form a protein, they go onto the RER. The lumen of the RER is directly connected to the space between the two nuclear membrane. The RER then synthesises the protein by a ribosome and then carries it in a vesicle frm the RER to cis face of golgi apparatus
Inner nuclear membrane has…
Anchors that holds chromatin in place
What is chromatin?
Is like a chip that sits inside a device
Located in the nucleus
Is a mass of genetic material that is composed of DNA and protein that condenses into chromosomes during eukaryotic cell division
Purpose of the nuclear matrix?
Ensures that chromatin is safe and provides medium that raw material can enter the nucleus to generate whatever
Difference between nucleus and nucleolus
Nucleolus is a dense mass in the centre of the nucleus.
When is the nucleolus barely visible
In the resting or active stage
When does the nucleolus become more visible
During interphase, disappearing during metaphase and reappearing during telophase
In mitosis, the number of chromosomes must remain the…
Same
What is the diploid number
46
When a cell divides by a mitotic process, a parent will give rise to 2 daughter cells with how many chromosomes?
46 chromosomes each but are smaller in size
During mitosis, what is generated
Mitotic spindle
What is mitotic spindle?
It is located at the spindle poles. It is a process where kinetochore microtubules attach to chromosomes in the middle of the cell and travel to the spindle pole.
What is the role of kinetochore microtubules
To transport the chromosomes from the middle of a cell to the spindle poles
What is the role of aster and interpolar microtubules
To hold everything in place
Where do microtubules radiate to?
Away from each spindle towards the chromosome assembled on the metaphase plate
Do the aster and interpolar microtubules attach to chromosomes?
No - only kinetochore microtubules do
How many chromosomes do the daughter cells have in meiosis
23 (haploid number)
What does meiosis produce
Haploid sex cells or gametes
Where does meiosis occur
The gonadal cells
Why do the daughter cells in meiosis have a haploid number?
Because when the sperm fertilises the egg, they will combine to form 46 chromosomes
What phases are known as interphasse?
Period between mitotic division (G1, S and G2)
What is the M phase in the cell cycle?
Where nuclear division (mitosis) is followed by cell division (cytokinesis)
What is G1 phase
Metabolic changes (all the organelles like mitochondria, golgi apparatus etc.) prepare the cell for division. It is responsible for making sure a copy of organelles go into the 2 daughter cells
What is S phase
DNA synthesis - replicates genetic material (in order for division to occur to result in 46 chromosomes each)
What is G2 phase
Metabolic changes all assemble the cytoplasmic materials (basically a double check to check for errors in the duplicated chromosome)
2 major components of the extracellular matrix
Fibres and Matrix
Most common fibers
Collagen
What is the benefit of collagen being stringy and tough?
To allow for organs to have specific shapes and structure e.g. tendons and ligaments have a lot of collagen because they need to be strong.
Why is it hard to tear a ligament but easy to tear a blood vessel?
Because ligaments have high collagen whereas blood vessels dont
What is the matrix around a cell made up of?
Proteoglycans (protein and glucose)
What does connective tissue consist of?
Cells, fibres, extracellular matrix
What is the role of connective tissue?
It covers the brain, lungs and provides attachment sites for muscles
4 basic types of connective tissue (ECMN)
- Epithelial - skin
- Connective tissue of cells - collagen fibres
- Muscular tissue
- Nervous tissue
3 types of fibres (REF):
- Reticular fibres: Have protein called reticulin. Has criss-cross protein arrangement like a band-aid
- Elastic fibres: Located where organs need to be stretched or deflated e.g. lungs
- Fibronectin: Provides strength and stability to cells. Links cells to other EC matrix components e.g. collagen
4 important functions of the basement membrane (ABSL)
- Attachment of epithelial cells
- Barrier preventing microorganisms from entering the organisms in a domain
- Selective filtration
- Loss of cell fluids from the body
Why does skin have a thicker basement membrane than other locations?
So that bacteria from the external environment doesn’t go in to the body
4 constituents of the basement membrane (LTHF)
- Laminin
- Type 4 collagen
- Heparan sulphate
- Fibronectin
2 major fluid compartments in the body:
Intracellular (2/3 of total water)
Extracellular (1/3 of total water)
What is extracellular fluid comprised of?
Interstitial fluid that is between cells and plasma that is between blood cells.
Is diffusion a non-energy consuming process or energy consuming?
Non-energy
Osmosis
Where fluid of a lower solute concentration moves from one side of a semi-permeable membrane to another of a higher solute concentration
Most membranes are permeable or semi-permeable
semi-permeable
3 factors needed for diffusion to occur?
- Bigger surface area, quicker diffusion occurs
- Concentration gradient needs to exist (difference in concentration between 2 sides of a membrane where particles from higher concentration travel to lower concentration during passive transport)
- Thickness of membrane is important too. If membrane is thin, diffusion is quick
Facilitated diffusion occurs through what proteins
Either transmembrane proteins (gated channels) or carrier proteins (in the membrane)
How does a molecule move into a cell?
Transmembrane protein is activated by a chemical messenger which then opens the channel and allows the molecule to come in.
2 types of active transport
- Primary active: involves direct expenditure of energy in the form of ATP to transport ion in and out of cell e.g. pump that pumps sodium out and potassium in
- Secondary active: The concentration gradient of one molecule provides the energy for the transport of another molecule against the latter’s concentration gradient.
3 types of molecule transport strategies
- Uniporters: Membrane proteins that recognise 1 specific molecule in or out such as fructose.
- Symporters: when 2 molecules are moving from the inside to the outside. e.g. hydrogen being pumped out and sucrose joins in. Utilises concentration gradient
- Antiporters: While 1 molecule comes in, another comes out using concentration gradient.
When does osmosis occur?
When osmotic pressure is present - allows fluid of higher concentration to area of lower concentration
Ion channels show…
high selectivity by allowing only specific ions to pass down their concentration gradient
How are ligand-gated channels opened?
Binding of a ligand (molecule or ion that binds to a central atom for cellular signalling and regulation) specific for that channel e.g. acetylcholine binding to nicotinic receptors. Primarily located on dendrites or cell body.
How are voltage gated channels opened?
In response to a change in membrane voltage. Common on nervous system membranes.
How are gap junction channels formed?
Alignment of hemichannels called connexons, connecting the cytoplasm of the cells to allow passage of ions and small molecules between them. Can be electroneutral.
What is the job of gap junction channels?
To act as troughs e.g. salivary gland - mass flux of sodium and water via these channels he
3 vesicular membrane transport mechanisms
- Exocytosis
- Endocytosis
- Transcytosis
What is exocytosis
Fusion of vesicles to the cell membrane for extrusion (where cells export large particles or organelles through its cell membrane to the outside of substances)
What is endocytosis
Process by which a substance or particle outside the cell is engulfed by the cell membrane, forming a vesicle.
2 types of endocytosis
- Phagocytosis: engulfing large particles
- Pinocytosis: engulfing fluid (cell drinking) and small particles associated with the engulfed fluid
What is transcytosis
Moving things around cells - occurs in capillary endothelial cells and intestinal epithelial cells to move material across the cell via endocytosis and exocytosis.
What does the suffix “-ASE” mean
that its an enzyme
In cell signalling, what are the 3 chains that are apart of the G-protein?
Alpha, beta, gamma
Process of cell signalling
Alpha chain from G-protein moves onto enzyme called adenylyl cyclase which helps break down ATP to cyclic AMP (cAMP) to release energy. cAMP acts as a second messenger which ends up producing certain effects - producing phosphokinase A
How do cells signal in muscle contraction?
Alpha chain from G-protein moves onto phospholipase C and then activates 2 pathways: DAG and PK-C pathway. It then activates IP3 which then acts on the membrane receptors on the RER to cause calcium to come out in order for muscle contraction occur.
What is the process of cell signalling controlled by?
GPCR (g-protein coupled receptor)
3 Steps of cell signalling
- Reception (signalling molecule attaches onto receptor)
- Transduction (3 relay molecules are transported in a signal transduction pathway into nucleus)
- Response: activation of cellular response e.g. activation of glycogen phosphorylase
Example of primary active transport
Sodium out, potassium in for ATP
Example of passive transport
Sodium channel, Potassium channel, glucose uniporter
Example of secondary active transport
Ca antiporter
What determines osmotic movement
It is not the concentration of molecules but is instead the total concentration of all dissolved substances (osmolarity)
