Structure and Function of cells Flashcards
Approx size of a cell
0.1-100 micrometers
Why cant cells be too. small?
They must fit DNA and must also fit cellular components to sustain life and reproduce
Why cant they be too big?
Needs to exchange w outside environment, the cell needs depend on. the volume
What does the exchange capacity of.a cell depend on?
SURFACE AREA
Briefly explain surface to volume ratio and square cube law
The more volume a cell has, the more nutrients it requires to get (through surface area) however, volume and surface area do not increase at the same time therefore the nutrients needs cannot be met
What are the parts of the cell theory
- a cell is the basic structural and functional unit of living organisms
- cells come from pre existing cells
- cell characteristics are passed from parent to off spring
- cells have a plasma membrane
- proteins are produces by ribosomes
What is a cell?
Membrane bound structure contained genetic material ,cytoplasm and various organelles
Name the 3 functions of a cell
1) Can store and transmit info
2) has a plasma membrane
3) can harness energy from the environment
Explain how the cell membrane is a fluid mosaic
It contains different components and it is not uniform.
the membrane contains phospholipids, steroids like cholesterol, proteins and lipid rafts to aggregate)
Why and how is the cell asymmetrical
IT is asymmetrical because the two layers (outer and inner) are different because they have different functions/jobs)
Why is the phospholipid bilayer amphipathic
it has hydrophilic heads to intereact with the water outside the cells and hydrophobic tails on the inside layer
Explain the movements of phospholipids
They can move laterally but usually do not “flip flop” because the hydrophilic heads to not want to interact with the hydrophobic tails.
What are the 2 types of proteins within the membrane
- Integral membrane proteins
- Peripheral membrane proteins
How does cholesterol help in the membrane?
Interacts with the phospholipid bilayer and maintains the fluidity of the membrane by preventing the tails to cflump/aggregate when its too cold and to prevent them from moving alot then temp is high.
Explain the integral membrane proteins
they can cross the membrane because they have both va hydrophilic region and a hydrophobic region
Explain the peripheral membrane proteins
DO NOT cross plasma membrane because the do not have a hydrophobic region. It binds to the polar heads of the lipids and also to the hydrophilic regions of intergtral proteins
What can these two protein types do?
Transport energy have enzymatic activity signal transducdtion cell-cell recognition intracellular joining attachement to tje cytoskeleton and extracellular matrix
Explain how the membrane is a selective barrier?
It regulates what goes in and what comes out (ions, macromolecules, water)
It requires various means of transport to get across the membrane
What are the two types of membrane transport
Passive and Active Transport
Explain Passive transport
It includes diffusion and facilitated diffusion
- normal high to low concentration
- no outside energy is needed
- facilitated by channel proteins and carrier proteins
What is the difference between simple diffusion and facilitated diffusion
Simple diffusion: straight across membrane, no help needed from proteins
Facilitated diffusion: either by channel mediated or carrier mediated proteins that get the outer molecules inside the cell
What is osmosis
a process by which molecules of a solvent WATER tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane.
what are the three types of solutions and explain them
Hypotonic: it is lysed therefore has less solute and more water
Isotonic: at equlibrium
Hypertonic: it is shrivelled and has more solute and less water
Why do hydrophobic molecules go straight through the membrane with no aid?
Because the membrane itself is also hydrophobic
The diffusion rate of particles is proportional to what?
Proportional to the concentration gradient and the hydrophobicity
Do ions easily pass through the membrane?
No they need aided diffusion
What will go through the membrane easier
A particle with high hydrophobicity or low hydrophobicity?
High hydrophobicity
Facilitated diffusion is aided by what
BY TRANSPORT PROTEINS (PERMEASES)
What does active transport do and how does it differ from passive transport
It moves ions/molecules across the membrane against the concentration gradient
It differs because it requires carrier proteins and outside energy
What are the 3 kinds of transport part of active transport and what do they mean
Uniporter (1 substance in 1 direction)
Antiporter (2 substances in opposite directions)
Symporter (2 substances in in same direction)
what are the two types of active transport
Primary and Secondary
explain primary transport
Uses chemical energy directly (ATP)
It breaks bonds (to release stored energy)
Explain secondary transport
Uses energy from primary
Uses an energetically favourable process to drive an unfavourable one.
explain the Primary Active Transport Pump (Na/K)
SEE DIAGRAM IN SLIDES
Transfers 3 Na+ from cytosol to extracellular space
Up concentration gradient
Transfers 2 K+ from extracellular space to cytosol
Up concentration gradient
Generates membrane potential
Outside of cell becomes more positively charged than inside
Helps maintain cell volume & is involved in signalling & neuron function
explain the Primary Active Transport Pump (H+)
SEE DIAGRAM IN NOTES
Uses ATP
Transfers H+ from cytosol to extracellular space, up concentration gradient
Makes it easier for Secondary Active Transport of some ions
Makes it easier for other ions to diffuse into cell later
Generates membrane potential
Outside of cell becomes more positively charged than inside
explain the secondary Active Transport Pump )Na/Glc)
SEE DIAGRAM IN NOTES
Transfers Na+ from extracellular space to cytosol
Down concentration gradient
Transfers Glc from extracellular space to cytosol
Up concentration gradient
What are the two different types of vesicle transport and what they do
Exocytosis is sending off of vesicles:
- Secretion of proteins
- Release of neurotransmitters
- Turnover of plasma membrane
Endocytosis is taking in larger molecules (vesicles):
- Phagocytosis (cellular ‘eating’)
- Pinocytosis (cellular ‘drinking’)
- Receptor-mediated (specific)
Why have a cell wall?
- Provides protection
- provides structural stability and support
What are the two types of cells and their characteristic?
Eukaryotic Eu = true + Karyon = nucleus Membrane-bound nucleus Membrane-bound organelles Larger: 10-20μm (avg.)
Prokaryotic Pro = before + Karyon = nucleus No nucleus Instead have a nucleoid No membrane-bound organelles Smaller: 1-2μm (avg.)
3 main components of a prokaryotic cell
- peptidoglycan cell wall
- nucleoid
- plasmids
Describe the cell wall and its functions
Surrounds the cell membrane
Protects the cell from bursting due to osmotic pressure
Protects from invasion by viruses
Permeability barrier (allows passage of fluids + small molecules)
Role in cell-cell recognition and adhesion
Structure:
Contains peptidoglycans = sugar polymers linked by short peptides
describe the nucleoid
No membrane
Contains large circular chromosome + proteins
Describe plasmids
Independent, smaller, circular extra chromosomal DNA, non-essential genes
Transferred through an arm-like pilus
What does the prokaryotic cell used flagellum and pilum for?
Motility and movement
How do prokaryotic cells reproduce?
asexually
Prokaryotic cells may or may not need O2… what are those called
Aerobes (need oxygen)
Anaerobes (do not need oxygen)
facultative anaerobes
Why are prokaryotic cells smaller?
TO help with diffusion
What protein is flagella made of
Flagellin
what are the 3 parts of flagella and their function
Basal body: Anchors the flagellum to the cell wall and acts as the motor
Hook: connects the basal body to the filament
filament: extends into environment and spins
What are the two types of pilli
Attachment pili: allow bacteria to attach to surfaces (AKA fimbriae)
Conjugation pili: used to transfer DNA during conjugation or infection by bacteriophage (virus)
Why do cells compartmentalize?
Create different “worlds” within the same cell
Can perform different functions in different areas, due to different properties
pH
Solute concentration
Lipid composition
Be able to label a eukaryotic cell and its organelles
SEE DIAGRAM IN SLIDES
What is cytoplasm
Mixture of cytosol and organelles
What are the parts of a eukaryotic cell (7)
Nucleus Ribosomes Endomembrane System -ER -Golgi apparatus -Lysosome -Vacuole Peroxisome Mitochondria Chloroplast Cytoskeleton
Explain the nucleus and what the components are
Stores genetic information (DNA) as chromosomes
-Collection of all chromosomes is called the chromatin
Surrounded by nuclear envelope
Double-bilayer connected to the endomembrane system
Trafficking through Nuclear Pore
Nucleolus is an area of RNA (rRNA) production in the Nucleus
What is the function of the nucleolus
builds ribosomes
Explain ribosomes and their function
Built in the nucleolus
End up in the cytoplasm
Composed of proteins + rRNA
Function: protein synthesis
what are the two types of ribosomes
free ribosomes and bound ribosomes
explain free ribosomes
Suspended in the cytoplasm
Make proteins that stay in cytoplasm
explain bound ribosomes
Attached to the outside of the endoplasmic reticulum (ER) + nuclear envelope
Make proteins for export or inclusion in organelles
what is the function of the endomembrand system
Connects multiple organelles (including nucleus)
What are the components of the endomembrane system
Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Vesicles
What is the interior of the ER called
Interior is referred to as “lumen”
What. are the two types of ER and what are the main differences. between the two
Rough ER has ribosomes associated to it and specializes in producing proteins (especially membrane-bound)
Smooth ER does not have ribosomes and focuses on lipid synthesis
Components of rough er
Covered by ribosomes on cytosolic side
Function: involved in protein synthesis
Secreted proteins
Integral membrane proteins
Proteins that are made in the RER go where and how
Proteins generated in the RER are modified and leave the RER in vesicles (pinched-off portions of the RER membrane). The vesicles then migrate to the Golgi apparatus
Explain the smooth ER
Lacks ribosomes Functions: -Synthesises lipids - -Steroids, phospholipids -Stores glycogen (involved in carbohydrate metabolism) -Detoxifies drugs and poisons
What is the function of the golgi apparatus and give an example
Functions: modify, store, & route products of ER
‘Sorting Centre’ of the cell (Shipping & Receiving)
e.g. alteration of phospholipids or glycoproteins for secretion
Explain the process in the golgi apparatus
Cis face (forming face) receives products from ER
Molecules are modified by enzymes in the Golgi as they migrate to the Trans face
Vesicles pinch off from the Trans face → transport molecules to other sites (e.g., plasma membrane, membrane-bound organelles)
What do lysosomes contain and what is their per purpose
Membrane-enclosed bags of hydrolytic enzymes
Acidic (pH ~5)
Lyse = destroy
what do the enzymes in lysosomes do and name the 4 types of enzymes
Digest all major classes of molecules Include: Lipases Carbohydrases Proteases Nucleases
What are the two processes lysosomes can do?
Phagocytosis and Autophagy
Explain phagocytosis
it is Intracellular digestion:
a vacuole (generated by phagocytosis) fuses with lysosomes; enzymes digest the contents of the vacuole
e.g. human macrophages targetting bacteria
explain autophagy
If a cell has an old, damaged, or dysfunctional organelle, it can fuse this with the lysosome
What is a vacuole
Membrane enclosed-sac
Larger than vesicles
what are the three types of vacuoles and their function
- Food vacuole: site of intracellular digestion in some protists
- Contractile vacuole: pumps excess water from some freshwater protists
- Central vacuole: large vacuole in plants
Explain the central vacuole
Large vacuole in plants
Often occupies most of the cell volume
30-90%
Holds food reserves, ions, waste, pigments, poisons…
What does peroxisome do?
Involved in degrading alcohol and long fatty-acids
Produces hydrogen peroxide while doing so, and is specifically designed for eliminating this toxic compound
What are the two organelles that process energy?
Mitochondria and plasmits
Explain mitochondria
-Energy producing centre
-Responsible for respiration and producing ATP from glucose in almost all eukaryotes
-has a Double-bilayer that contains many proteins and encloses a liquid area filled with enzymes
Contains some ribosomes and circular DNA
explain the function of a plasmic and name one type
Photosynthesise or store materials
Chloroplasts are one type of plastid.
explain chloroplasts
-Energy production centre
-Responsible for photosynthesis and converting CO2 into glucose
-Exist in plants and algae (protists)
Double-bilayer enclose a liquid area filled with enzymes and “thylakoids” – sacs of chlorophyll
ALSO contains some circular DNA
where did both mitochondria and chloroplasts come from?
ORIGINATED as BACTERIA become endosymbionts of larger prokaryotic cells
What is the function of the cytoskeleton
provides structural framwork for cells and movementt system
3 parts of cytoskeleton
1) microtubules
2) microfilaments
3) intermediate filaments
What are microfilaments made of
Actin
what are microfilaments involved in?
cell movement
cell contraction
vesicular transport
explain process of cell movement
1) add actin to the edge of the cell and the microfilaments elongate and push the cell membrane forward
2) at the same time, actin is removed from the back end of the end
What is the process of removing and adding actin called
DYNAMIC INSTABILITY
explain treadmilling
unidirectional
removed actin gets added to the front
What are microtubules made of
tubullin
what do microtubules use for cell movement?
cilia and flagella
Where do microtubules come from>
centrosome
What two proteins are involved in muscle movement?
actin and myosin
Explain how myosin works in muscle movement
myosin binds and unbinds from actin polymers (always move toward the positive end)
This movement results in the shortening of the muscle cell (contraction)
Where do kinesis and dynein work
within the microtubules
what direction does dynine go in
negative end (towards centrosome)
What is the function of the centrosome
it is a microtubule organizing centre
explain spindle fibres
Important during cell division
Attach to chromosomes
Made of microtubules
what is the structure of a centriole
Cylindrical structures
Ring of 9 sets of 3 microtubules
what is the form of intermediate filaments
sturdy cable like structure
functions of intermediate filaments
help maintain structure
can link multiple cells
what is the ECM
A gel-like area filled with proteins and carbohydrates
what is the purpose of the ECM
provides support and motility
what does the ECM contain and their function
Collagen: Strong, helical protein, huge quantities
Elastin: Looser chain of protein in skin, lungs, gut
Proteoglycans: mostly sugar that capture and retain water
Integrins: integral cell proteins that anchor to ECM
Fibronections: binds integrals and collegians involved in adhesion and migration
BE ABLE TO LABEL THE ECM COMPONENTS
see diagram on slides
does the cell wall exist in animals?
no
where is the cell wall?
external to the cell membrane
In plant cells, what is the cell wall made of
cellulose (part of glucose) and other polysachhcaries and proteins like lignin and pectin
In fungi ,what is the cell wall made of
chitin
what are the functions of the cell wall. (4)
Protects cell
Maintains shape
Prevents excess water uptake (can’t expand)
Allows turgescence (water pressure pushing against the wall
what are the three classes of membrane junctions
Desmosomes
Tight Junctions
Gap Junctions
What are desmosomes formed from
cadherin
describe the interaction in desmosomes junctions
Cadherin-cadherin interactions at a specific point between two cells
Localised spot-like adhesions FOCAL POINT
what is the function of desmosome junctions
Resist shearing forces
What is the function of a tight junction
Hold cells together
Block movement of integral membrane proteins
Prevent passage of molecules & ions through space between cells
are desmosomes attached to the cytoskeleton?
yes
are tight junction attached to the cytoskeleton
no
how can a substance pass a tight junction?
MUST GO THROUGH IT
Explain gap junctions
Integral protein channels Attach between two cells Allow material (molecules, ions) to flow from the cytosol of one cell to another
are viruses living, if not give a reason why
no because they cannot produce of use energy
what are viruses made of and give an example of one
- Nucleic acid (RNA or DNA)
- Protein coat (capsid): surrounds the nucleic acid
- Envelope (for some viruses): membrane derived from the host cell, + usually proteins and glycoproteins of viral origin
e. g., influenza virus
how can a virus reproduce?
To reproduce, they must infect cells (host cells)
Plants
Animals
Bacteria
explain reproduction process of a virus
Viral genome inserted into host cell
Cell replicates viral particles based on the information contained in the viral genome
what does active transport do?
- Regulation of cell volume
- cell signalling
- neuron functiom
- taking in needed resources (amino acids, carbs, minerals)
