Cell Structure and Function - Introduction Flashcards
What is a Prokaryotic cell?
are cells that do not have a true nucleus or membrane-bound organelles
What is a Eukaryotic cell?
cells that have a nucleus enclosed within membranes (humans)
What do Eukaryotic cells and prokaryotic cells have in common?
The plasma membrane, cytosol, DNA, RNA,
protein and ribosomes
What are the main differences between eukaryotic and prokaryotic cells?
Eukaryotic cells are much larger and have a membrane bound nucleus while prokaryotic cells are much smaller and their nucleus is not membrane-bound
What is the cytoplasm?
is everything inside the plasma membrane including the organelles,
but not including the nucleus
What is cytosol?
The fluid portion of the cytoplasm
What does cytosol consist of?
water plus dissolved and suspended substances (eg. ions, ATP, proteins, lipids)
What organelles make up the endomembrane system?
Nucleus
Endoplasmic Reticulum (smooth and rough)
Golgi apparatus
Lysosomes
What is the endomembrane system?
A network of membranes inside and around a eukaryotic cell organelles
Work together to modify, package, and transport lipids and proteins (ie shared membrane space)
Order of the sizes of microvilli, cilia and flagellum
Microvilli < Cilia < Flagellum
What is the function of the plasma membrane?
is a selectively permeable barrier controlling
the passage of substances in and out of the cell (acts as a physical barrier separating the inside and outside of the cell)
What is the plasma membrane made of?
it is made of a double layer of phospholipids with embedded proteins
How does the fat portion of a phospholipid react with water?
It is hydrophobic so it repels water
How does the phosphate (head) portion of a phospholipid react with water?
It is hydrophilic so it will face the water
What does a phospholipid consist of?
a hydrophilic polar head (phosphate) and a hydrophobic lipid tails (fatty acids) which are arranged as a double layer around cytoplasm, tail to tail
What is a feature of plasma membrane proteins? (Not the 6 things they are involved in)
An often amphipathic protein that is associated with the plasma membrane.
Mediate movement of hydrophilic substances, allow cell-to-cell identification, adhesion between cells, attach to other structures and facilitate intercellular communication.
How do plasma membrane proteins react with water?
They are often amphipathic so they have both hydrophilic and hydrophobic regions. This is to allow molecules to pass through the plasma membrane
What are integral proteins
proteins that are embedded (partially or fully) into the membrane
What are transmembrane proteins?
proteins that fully span the entire membrane, contact extracellular
and cytoplasmic areas
What are Peripheral membrane proteins?
proteins that are associated with the
membrane, but not actually embedded in it
What are the functions of the plasma membrane proteins?
Transport enzymatic activity signal transduction cell-cell recognition intercellular joining attachment to the cytoskeleton and extracellular matrix (ECM)
Example of transport function of the plasma membrane
channels or transporters may be
general or selective, gated or not
Example of enzymatic activity function of the plasma membrane
Carry out a chemical reaction,
may or may not be a part of a team of enzymes
Example of signal transduction function of the plasma membrane
External signalling molecule causing transduction of information to the inside of
the cell
Example of cell-cell recognition function of the plasma membrane
Use of glycoproteins (carbohydrate
+ protein) as molecular signatures
of the extracellular side of the cell
Example of intercellular joining function of the plasma membrane
gap and tight junctions
Example of attachment to the cytoskeleton and extracellular matrix (ECM) function of the plasma membrane. hint = FIBRONECTIN
fibronectin mediates contact between cell surface integrins and ECM (eg. collagen).
can facilitate movement
What is the fluid mosaic model?
The model used to describe proteins and other structure moving freely in a fluid bilayer of phospholipids.
What is the nucleus?
The largest distinct structure inside the cell
What is the structure of the nucleus
It is enclosed by a double lipid bilayer called the nuclear envelope, continuous with rough ER and has entry and exit through nuclear pores. Has the nucleolus in the centre
What is the function of the nucleus?
- to house/protect DNA in eukaryotic cells
- Make RNA and assemble ribosomes
- pores regulate the movement of substances (eg protein and mRNA) in and out
- Molecule segregation to allow temporal and spatial control of cell function
What is the nucleolus?
Distinct structure present in the nucleus of eukaryotic cells
What is the function of the nucleolus?
rRNA production
Assembly of the small and large ribosomal subunits
What is the nuclear envelope?
Lipid bi-layer enclosing the nucleus
Continuous with the rough ER
What is the function of the nuclear pore and where are they?
Structures in the nuclear envelope
Allow passage of certain materials between the cell nucleus and cytoplasm
What is Deoxyribonucleic Acid (DNA)?
Nucleic acid that encodes our phenotype
What is histone?
Protein molecule which binds with 7 others to form a nucleosome
What is nucleosome?
Bead-like structure in chromatin
Composed of a short length of DNA wrapped twice around core of histone proteins
What is chromatin?
‘spaghetti like’ structure
strings of nucleosomes that are wound together to from fibres
What is a chromosome?
Bundles of tightly coiled DNA located within the nucleus of almost every cell in our body
What is a gene?
a DNA segment that contributes to phenotype/function
How many chromosomes are in a human cell?
Humans are diploid so have 2N chromosomes
= 46 chromosomes (23 pairs), one from each parent
22 Autosomes and 2 sex chromosomes
What is a ribosome and its function?
The organelle that is the site of protein production/synthesis
Where are ribosomes found in the cell??
Free in the cytoplasm - making proteins to be used in the cytosol (non-endomembrane destinations)
OR
Attached to the rough ER making non-cytosolic proteins/endomembrane
How are ribosomes made?
Subunits are assembled in the nucleolus
Leave through nuclear pores (large and small subunit)
What is the endoplasmic reticulum?
An extensive network of tubes and tubules
Stretch out from the nuclear membrane
What is the function of the rough ER?
Major Function is production of:
Secreted proteins
Membrane proteins
Organelle Proteins
Proteins enter lumen within the rough ER for folding
The rough ER membrane surrounds the protein to form transport vesicles which are destined for the Golgi
What is the structure of the RER?
A membrane that is continuous with the nuclear envelope
Dotted with attached ribosomes
What is the smooth ER?
An extension of the rough ER
What is the function of the SER
Is very cell/tissue type specific
Major function:
Housing unit for proteins and enzymes
Synthesise lipids (including steroids and phospholipids)
Storage of cell-specific proteins, not all cells make proteins
What is the main difference between SER and RER
Smooth ER doesn’t have ribosomes (does not make proteins)
The function of SER in liver
Houses enzymes for detoxification and glucose release
The function of SER in muscles
Stores calcium ions which are used for contraction
What is the sarcoplasmic reticulum?
SR is a form of smooth muscle ER
Found in skeletal muscle
Function is to regulate Ca2+ storage and release homeostasis during and after muscle contraction
What is the cis face of the Golgi apparatus?
The receiving side
What is the trans face of the golgi apparatus?
The shipping side
What is the Golgi apparatus made of?
3 to 20 flattened membranous sacs called cisternae
Stacked on top of one another ( like ‘pita bread’)
What is the function of the Golgi apparatus?
Modify, sort, package and transport proteins received from the rough ER using enzymes in each cisternae
Formation of:
- Secretory vesicles (proteins for exocytosis)
- Membrane vesicles (PM molecules)
- Transport vesicles (molecules to lysosome)
What are lysosomes?
Vesicles formed from the Golgi membrane
Contain powerful digestive enzymes
Have membrane proteins that pump H+ in order to maintain an acidic pH
The rest of the cell is protected by a membrane
What is the function of lysosomes?
Main function is digestion of substances that enter the cell:
- Cell components (eg organelles, autophagy)
- Entire cells (autolysis)
What is Gaucher metabolic disorder?
Occurs when a particular lipid is poorly degraded
Results in a severe phenotype in humans
(Failure of a single lysosome enzyme can cause sever disease as digestion by lysosomes is crucial)
What is the function of mitochondria?
Generate ATP through cellular respiration
What are mitochondria made of?
Outer mitochondrial membrane
Inner mitochondrial membrane (with folds called cristae)
Fluid filled interior cavity (called mitochondrial matrix)
What is cristae?
The inner mitochondrial membrane
What is the mitochondrial matrix?
The fluid filler filled interior cavity
What is the cytoskeleton?
Structural support system of the cell
Contains fibres/filaments that help maintain the size, shape and integrity of the cell
Acts as scaffolding across the cell
Involved in intracellular transportation and cell movement
What are the microfilaments in the cytoskeleton made of?
Comprised of actin molecules assemble in two long chains twisted around each other
Assembled and disassembled as required - DYNAMIC
What is the function of microfilaments?
Bear tension and weight by anchoring the cytoskeleton to the plasma membrane proteins
Promote motility if required (eg Macrophage)
Where are microfilaments found?
Found around the periphery and lining of the interior of cell
What are the intermediate filaments in the cytoskeleton made of?
Comprised of a diverse range of materials Eg Keratin
Found in cytoplasm of the cell
What is the function of the intermediate filaments of the cytoskeleton?
Bear tension and weight throughout the cell
Eg during cell anchoring
Act as a scaffold for cellular organelles
Eg the nucleus
What are the microtubules of the cytoskeleton made of?
Tubular structure
Comprise of Lublin dimers (alpha and beta) coiled to from a tube
Extends from centriole into cytoplasm/nucleus
What is the function of the microtubules of the cytoskeleton?
Support cell shape and size
Guide movement of organelles (Eg vesicles from Golgi to membrane)
Chromosome organisation - cell division
Support and movement of cilia/flagella (sperm tail)
Diameter of microfilament
7nm
Diameter of intermediate filament
8-12nm
Diameter of micro-tubule
25nm with the central lumen of 15nm diameter
