Introduction to cells Flashcards
What is cell theory
- All organisms are composed of one or more cells
- The cell is the basic unit of structure and organisation
- All cells arise from pre-exisiting cells
The central dogma
DNA -> RNA -> Protein
Similarities between prokaryote and eukaryotic cells
Both have:
Plasma membrane, cytosol, DNA, RNA, protein and ribosomes
Difference between prokaryote and eukaryote cells
Eukaryotic have membrane-bound organelles while prokaryote doesn’t. Eukaryote cells are also much larger.
What is the cytoplasm
Everything inside the plasma membrane including the organelles, but not including the nucleus
What is the cytosol and what does it include
The fluid portion of the cytoplasm, which includes water plus dissolved and suspended substances
What is part of the endomembrane system
Nucleus, endoplasmic reticulum (smooth and rough), Golgi apparatus, and lysosomes
What is the function of the endomembrane system
Package, label and ship molecules
What is the plasma membrane
A selectively permeable barrier controlling the passage of substance in and out of the cell
What is the structure of the plasma membrane
Double layer of phospholipids with embedded proteins.
What do phospholipids consist of
Hydrophilic polar heads (phosphate)
Hydrophilic lipid tails (fatty acids)
How are phospholipids arranged as
Arranged as a double layer around cytoplasm, tail to tail
What are two functions of plasma membrane proteins
Mediate movement of hydrophilic substances. Allow cell identification and facilitate intercellular movement
True of false, plasma membrane proteins are often amphipathic
True, they contain both hydrophilic and hydrophobic regions
Plasma membrane - Integral proteins
Embedded (partially or fully) in the membrane
What are peripheral membrane proteins of the plasma membrane
Associated with the membrane, but not actually embedded in it.
What are the six key functions of plasma membrane proteins
a) transport
b) enzymatic activity
c) signal transduction
d) cell-cell recognition
e) intercellular joining
f) attachment to the cytoskeleton and ECM
What are examples of transport of plasma membrane proteins
Channels, transporters, may be general or selective, gated or not
What is enzymatic activity (b)
Carry out chemical reactions, may or may not be a part of a team of enzymes
What is signal transduction (c)
External signalling molecule causing communication of information to the inside of the cell
What is cell-cell recognition (d)
Use of glycoproteins (carbohydrate + protein) as molecular signatures of the extracellular side of the cell
What are examples of intercellular joining as a function of PM proteins (e)
Gao junctions or tight junctions
What are examples of the attachment to the cytoskeleton and ECM as a function of PM proteins (f) and what do they do
Fibronectin mediates contact between cell surface integrins and ECM (e.g collagen)
Can facilitate movement
Are membranes static or not, and why
No, the membrane is a mosaic of molecules bobbing in a fluid bilayer of phospholipids.
Is cell specific and dynamic repertoire of membrane-bound proteins present as required
What is the structure of the nucleus
Enclosed by double lipid bilayer called the nuclear envelope continuous with rough ER
What are two functions of nuclear pores
Regulate the movement of substances as enter and exit the cell (e.g proteins and mRNA). They protect DNA, so DNA doesn’t change or get replaced
What is the the function of the nucleolus
Used for rRNA production and the assembly of small and large subunits of ribosomes
What does molecule segregation allow for in the nucleus
Temporal and spatial control of cell function
What is the structure of the nucleosome
DNA wrapped twice around a group of 8 histones, collectively known as a chromatin
The function of chromatin as preparation for cell division
Chromatin condenses to form chromatin fibres then condenses further into loops which stack as chromosomes
What form does DNA spend most of its time as
Chromatin and chromatin fibres
What is the structure of ribosomes
Two subunits; small and large, made of ribosomal RNA (rRNA) in complex with many proteins
What is the function of ribosomes
Protein production (translation)
Where are the two places in the cell where ribosomes are found
Cytoplasm and the rough ER
Where are free ribosomes found and what is their function
In the cytoplasm
Make proteins to be used in cytosol
Where are attached/bound ribosomes found and what is their function
Found in the RER - Making non-cytosolic proteins/endomembrane
What is the endoplasmic reticulum and where is it located
An extensive network of tubes and tubules, stretching from the nuclear membrane.
What is the major function of the Rough ER - three products
Production of:
Secreted proteins
Membrane proteins
Organelle proteins
Structure and location of Rough ER
Continuous with nuclear envelope dotted with attached ribosomes
The proteins enter ____ within the rough ER for folding
The lumen
The rough ER membrane surrounds the protein to form _______ destined for Golgi
Transport vesicles
What is the function of smooth ER
Functions vary greatly from cell to cell, but its major function:
A housing unit for proteins and enzymes (e.g in the liver it houses enzymes for detoxification and glucose release and in the muscle it stores calcium ions).
Synthesises lipids, including steroids and phospholipids and storage of cell-specific proteins.
Does the smooth ER make proteins?
No it doesn’t make proteins, it lacks proteins
Where is the smooth ER found
It extends from the rough ER
What is the function of the Golgi apparatus
Modify, sort, package and transports proteins received from the rough ER using enzymes in each cisternae
What is the structure of the Golgi apparatus
Made up of 3-20 flattened membranous sacs called cisternae, stacked on top of each other.
The Golgi apparatus is responsible for the formation of what?
Secretory vesicles (proteins for exocytosis)
Membrane vesicles (PM molecules)
Transport vesicles (molecules to lysosomes)
What does each sac or cisternae of the Golgi apparatus contain
Enzymes of different functions
Movement of proteins in Golgi apparatus
Proteins move cis to trans from sac to sac
Mature at exit cisternae
Travel to destination
What occurs in each sac/cisternae of the Golgi apparatus
Modifications (formation of glycoproteins, glycolipids, and lipoproteins)
What are lysosomes
Vesicles formed from the Golgi apparatus
What do lysosomes contain
Powerful digestive enzymes
What do membrane proteins do in the lysosome
Pump H+ to maintain acidic pH.
What is the main function of lysosomes
Digestion of:
- substances that enter a cell
- cell components (e.g organelles) - autophagy
- entire cells (autolysis)
What happens once the food has been digested in the lysosomes
Once digested, all building blocks (amino acids, lipids etc.) are recycled
What is the main function of the mitochondria
Generate ATP through cellular respiration
What is the mitochondria made up of
Outer mitochondrial matrix
Inner mitochondrial matrix, with folds called cristae
Fluid-filled interior cavity, called the mitochondrial matrix
When would a greater number of mitochondria need to be present
When a cell requires more energy, so the more ATP is makes and requires more mitochondria
What kind of DNA does mitochondria have
Carries a separate small (37 genes) genome encoding mitochondrial specific products
What is the cytoskeleton and what is it’s function
The structural support system of the cell. Acts as scaffolding of the cell and involved in intracellular transportation and cell movement
What does the cytoskeleton contain that helps it carry out its function
Fibres or filaments that help to maintain the size, shape and integrity of the cell
What the three types of fibres in the cytoskeleton from smallest to largest
Microfilaments
Intermediate filaments
Microtubules
What is the microfilaments comprised of (in the cytoskeleton) and where is it found
Actin molecules assembles in two long chains, twisted around each other. It’s found around the periphery and lining of the cell interior
Function of the microfilaments in the cytoskeleton
Bear tension and weight by anchoring cytoskeleton to plasma membrane proteins, and promote amoeboid motility if required.
Are microfilaments dynamic and why
Yes they are, they can assemble and disassemble as required, so not static
What is the intermediate filaments of the cytoskeleton comprised of and what is its function
Diverse range of materials, including keratin - which allows organisms to lean on and scaffold
What is the function of the intermediate filaments of the cytoskeleon
Bear tension and weight throughout cell e.g during cell anchoring
Act as scaffold for cellular organelles e.g the nucleus
Where are intermediate filaments of the cytoskeleton found
In the cytoplasm of the cell
Which one of the three fibres of the cytoskeleton is the most permanent, and why
Intermediate filaments, because they are less dynamic
What is the microtubules of the cytoskeleton comprised of
Tubulin dimers (alpha and beta), coiled, to form a tube.
Where are microtubules of the cytoskeleton found
Extended from the centriole an cytoplasm/nucleus
What is the function of the microtubules of the cytoskeleton
- Support cell shape and size
- Guide for movement of organelles
- Chromosome organisation
- Support and movement of cilia/flagella
Are microtubules dynamic, and why
Yes, they can assemble and disassemble when needed
