Cell Structure & 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
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 and organelles that work together to modify, package, and transport lipids and proteins
Order of the sizes of microvilli, cilia and flagellum
Microvilli < Cilia < Flagellum
What is 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 are some features of plasma membrane proteins
An often amphipathic protein that is associated with the plasma membrane. These 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 and 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
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?
is the distinct structure present in the nucleus of eukaryotic cells
What is the function of the nucleolus?
rRNA production and the assembly of small and large subunits of ribosomes
What is the nuclear envelope?
Lipid bilayer 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 that allow passage of certain materials between the cell nucleus and the cytoplasm
What is Deoxyribonucleic Acid (DNA)?
is the 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 a core of histone proteins
What is chromatin?
‘Strings’ of nucleosomes that are wound together to form fibres.
What is a chromosome?
are 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. There are 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 RER - 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, stretching 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
Rough ER membrane surrounds the protein to form transport vesicles 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 RER
What is the function of the SER
– very cell/tissue-type specific
The major function is as a housing unit for proteins and enzymes
Synthesizes lipids, including steroids and phospholipids
Storage of cell-specific proteins, not all cells make all proteins
What is the main difference between SER and RER
SER doesn’t have ribosomes (doesn’t 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?
The sarcoplasmic reticulum (SR) is a form of smooth muscle endoplasmic reticulum (ER) found in skeletal muscle that functions as a regulator of 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?
is made up 3-20 flattened
membranous sacs called cisternae, stacked
on top of one another (“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 Golgi membrane and contain powerful digestive enzymes. They have membrane proteins that pump H+
in to maintain acidic pH and the rest of the cell is protected by a membrane
What is the function of lysosomes?
Main function is digestion of:
• substances that enter a cell
• cell components e.g. organelles - autophagy
• entire cells - autolysis
What is Gaucher metabolic disorder?
a particular lipid (glucocerebroside) is poorly degraded
• results in a severe phenotype in humans
(Failure of a single lysosome enzyme can cause severe disease as digestion by lysosomes is v important)
What is the function of mitochondria?
generation of ATP through cellular respiration
What are mitochondria made of?
- Outer mitochondrial membrane
- Inner mitochondrial membrane, with folds called cristae
- Fluid filled interior cavity, called the mitochondrial matrix
What is cristae?
the inner mitochondrial membrane
What is the mitochondrial matrix?
the fluid filled interior cavity
What is the cytoskeleton?
the structural support system of the cell
Contains fibres or filaments that help to maintain the
size, shape and integrity of the cell:
•Act 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 assembled 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 plasma membrane proteins, and promote amoeboid motility if required (eg. macrophage)
Where are microfilaments found?
Found around the periphery and lining the interior of cell
What are the intermediate filaments in the cytoskeleton made of?
Comprised of a diverse range of different materials; one example: keratin
Found in the cytoplasm of the cell.
What is the function of the intermediate filaments of the cytoskeleton?
- bear tension and weight throughout cell, e.g., during cell anchoring,
- act as scaffold for cellular organelles, e.g., the nucleus.
What are the microtubules of the cytoskeleton made of?
tubular structure,
Comprised of tubulin dimers (alpha and beta), coiled, to form a tube
Extends from centriole into cytoplasm/nucleus
What is the function of the microtubules of the cytoskeleton?
Support cell shape and size
• Guide for movement of organelles,
• e.g., vesicles from Golgi to membrane
• Chromosome organization – cell division
• Support and movement of cilia /flagella
Diameter of microfilament
Diameter: 7 nm
Diameter of intermediate filament
Diameter: 8-12 nm.
Diameter of micro-tubule
Diameter: 25 nm with the central lumen of 15 nm diameter
