The Cell Flashcards
Organelles
Membrane enclosed structures within eukaryotic cells.
Eukaryotic cells have
internal membranes than compartmentalize their functions
Domains of Prokaryotes & Eukaryotes
Prokaryotic - Bacteria & Archaea
Eukaryotic - Protists, fungi, animals and plants
Protists
Group of mostly unicellular eukaryotes
Basic Features in ALL cells (4)
- Plasma membrane (selective barrier)
- Cytosol
- Chromosomes (carry genes in the form of DNA)
- Ribosomes (tiny complexes that make proteins according to gene instruction)
Major Differences between Prokaryotic and Eukaryotic Cells
- Location of Nucleus -Eukaryotic: DNA is in nucleus (bounded by double membrane) -Prokaryotic: DNA in nucleoid
- Absence of membrane-bound structures in prokaryotes.
- Size - Eukaryotes larger
Nucleoid
Location of DNA in prokaryotes NOT membrane enclosed.
Cytoplasm
Interior of either type of cell
-Eukaryotic –> region between nucleus and plasma membrane where there are a variety of organelles.
-Prokaryotic → Organized into different regions
Why are there “size limits” on cells?
- Metabolic requirements impose upper limits on the size that is practical for a single cell.
Ratio of SA to volume = critical
- As cell increases in size surface area grows proportionately less than volume
- Need for surface area large enough to accommodate volume –> reason why cells are so small & why some are narrow and elongated (nerve cells)
- Larger organisms don’t have larger cells but MORE cells
High ratio of surface area to volume
- Allows for rapid diffusion
- Important in cells that exchange a lot of material with their surroundings (Intestinal cells! eg microvilli)
Mycoplasmas
- Smallest cells (bacteria)
Plasma Membrane
- Selective barrier that allows passage of enough oxygen nutrients & wastes to service the entire cell.
- Only a limited amount of a particular substance can cross per second so the ration of SA to Volume is critical.
As a cell increases in size, the SA becomes ____ than the volume.
Smaller object = ____ ratio of SA to volume.
Less; greater
Compartmentalisation occurs in ____ and allows for… (2)
- Eukaryotic cells;
1. Different environments to support specific metabolic functions.
2. Incompatible chemical processes to occur simultaneously
Metabolism
- Life-sustaining chemical transformations within cells.
- Enzyme-catalyzed reactions which allow organisms to grow, reproduce, maintain structure and respond to their environments.
What membranes participate directly in cell metabolism?
Plasma & organelle
- Many enzymes are built right into membranes
Basic Fabric of Most Biological Membranes
- Double layer of phospholipids
- Embedded proteins
- Unique composition of lipids/proteins suited to specific functions. ex) Enzymes embedded in mitochondria = cellular respiration
Where are Eukaryotic Cell’s Genetic Instructions housed and what carries them out?
- Nucleus
- Ribosomes use info from DNA to make proteins
Nucleus
Contains most genes in Eukaryotic cell Genetic info– chromatin Non dividing structure!
Nuclear Envelope (4)
- Separate the cell’s genetic material from the rest of the cell
- Maintains a distinct environment.
- Surrounds the nuclear content and is continuous with the ER membrane
- Has pore structures which mRNA goes through
Pore Complex
- Protein structure that lines pores
- Regulates entry/exit of proteins and RNAs and large molecule complexes.
Nuclear Lamina is an array of ____ that… (2)
Protein filaments;
- Maintains the shape of the nucleus
- Organises material so it functions efficiently
Nuclear Matrix
- Framework of protein fibers extending throughout the nuclear interior.
- Helps organize material so it functions efficiently
Chromosome
- Structure that carries genetic information (DNA) in discrete units.
- DNA molecule is coiled with histone proteins
Chromatin
- Complex of DNA & proteins making up chromosomes
- Visible and condensed during cell division
- DNA diffused mass when not dividing
Nucleolus
- Prominent structure within the nucleus
- Site of Ribosomal RNA synthesis
Functional connection between the nucleolus, nuclear pores, and the nuclear membrane:
- Subunits of ribosomes are assembled in the nucleolus and pass through the nuclear membrane via the nuclear pores.
How does the nucleus direct protein synthesis? (3)
- synthesises mRNA according to instructions provided by the DNA.
- mRNA is transported to the cytoplasm via nuclear pores
- Ribosomes translate the mRNA’s genetic message into polypeptide
Ribosomes are made of ____ and are considered ____ because they are ____. Function (1)
- Ribosomal RNA & protein
- “NON” organelles
- Not membrane bound
- Synthesise proteins
What do cells with high protein synthesis rates typically have?
- Lots of ribosomes
- eg. Pancreas cell –> make digestive enzymes –> millions of ribosomes Cells active in protein synthesis have prominent nucleoli
Free ribosomes
- Suspended in cytosol
Bound Ribosomes
- Attached to the outside of endoplasmic reticulum/nuclear envelope
- Make proteins that are destined for insertion into membranes for packaging within certain organelles such as lysosome or for export from the cell (secretion)
What do cells that specialize in protein secretion frequently have a high proportion of?
Bound ribosomes (Pancreas)
Endomembrane System
Different membranes of the eukaryotic cell that includes:
1. nuclear envelope
2. endoplasmic reticulum
3. Golgi apparatus
4. lysosomes
5. vesicles/vacuoles &
6. the plasma membrane
Functions of Endomembrane System (5)
- Protein synthesis
- Transport of proteins in/out of the membrane/organelles
- Metabolism
- Movement of lipids
- Poison detox.
How are the membranes of the endomembrane system related?
Through direct physical continuity or by transfer of membrane segments as tiny vesciles
Vesicles are ____ that can; (3)
- Self-contained structures consisting of fluid or gas surrounded and enclosed by an outer membrane.
1. store and transport materials
2. absorb and destroy toxic substances and pathogens
3. fuse with the membranes of other cells to carry out a specific role, such as breaking down another cell
Endoplasmic Reticulum structure (2), location (1) and role (1)
- Extensive network of membrane within the cytoplasm
- Consisted of cisternae
- Continuous with the nuclear envelope
- synthesises and processes molecules
Smooth ER and functions (4)
- Membrane complex lacking ribosomes
- Functions in diverse metabolic processes that vary with cell type (enzymes present)
1. Lipid Synthesis
2. Metabolism of carbs
3. Detox
4. Storage of Ca ions
Importance of the Smooth ER
- Crucial in metabolism
- Synthesises lipids and steroid hormones
- Detoxes drugs and toxins (liver and muscle cells)
Detox in the Smooth ER
- Adds hydroxyl groups to drug molecules
- This makes them soluble and easier to flush out of the body.
Storage of Calcium Ions in the Smooth ER
- In muscle cells the smooth ER pumps Ca ions from the cytosol to the ER lumen.
- When a muscle cell is stimulated by a nerve pulse, Ca ions rush back across the smooth ER into cytosol & trigger muscle contraction.
Rough ER
- Has ribosomes on outer surface
- Located next to nucleus allowing ribosomes and mRNA from nucleus to go into the rough ER and attach to a ribosome.
- Synthesises, modifies, folds and sorts proteins
Rough ER as Membrane Factory for Cell
- Grows in place by creating and adding membrane proteins and phospholipids to itself
- As ER membrane expands, portions are transferred as transport vesicles to other components of the endomembrane system
Differences between proteins made from ER and free floating ones
- ER –> Destined for secretion or incorporation into membranes or organelles
- Free floating –> Usually function in the cytosol or organelles
How do cells secrete proteins produced by the Rough ER? (4)
- Polypeptide chain grows from ribosome.
- Is threaded into ER
- Folds into functional form
- Secreted in transport vesicles
Glycoproteins
Proteins covalently attached to the plasma membrane with carbohydrate chains
Transport Vesicles are …
Vesicles in transit from one part of the cell to another.
Process of protein transport ER –> Golgi
1.Transport vesicles take proteins made in ER
2. Transport vesicles fuse with cis side of Golgi
3. Product goes through and is modified
4. Product bud off into vesicles on trans face of Golgi and go where needed
Golgi Apparatus Structure and Organisation (4)
- A complex of vesicles and folded membranes (cisternae) involved in secretion and intracellular transport
- Processes proteins made by ER and secretes them into the cell
- Proteins enter on the cis side facing the ER and exit on the trans side
Functions of the Golgi Apparatus
- Contains enzymes that catalyse modifications –> the addition or removal of sugars from cargo proteins (glycosylation), the addition of sulfate groups (sulfation), and the addition of phosphate groups (phosphorylation).
- Act as signals to direct the proteins to their final destinations within cells, including the lysosome and the plasma membrane
Golgi Cisternae
- Flattened, membranous sacs that differ in number, shape and organisation
- Each contains different protein modification enzymes.
The Golgi is extensive in cells specialised for..
secretion
Golgi - Cis Face –>
Receiving end near ER
- Where transport vesicles fuse with Golgi
Golgi - Trans Face –>
Shipping end.
- Where vesicles pinch off and travel to other sites.
Golgi Manufacture & Refines its products in ____ using unique teams of ____
stages; enzymes
Products of the ER modified on the journey from the ___ to ___ face
cis; trans
Cisternal maturation model →
Cisternae of Golgi progress from cis to trans face carrying & modifying their cargo as they move.
Molecular Identification Tags are groups of ___
phosphate, added to the Golgi products before budding into vesicles from the trans face
Lysosome structure and production
- Membranous sac of lipids and enzymes that can digest macromolecules.
- Made by RER and transferred to Golgi for processing –> bud off from trans face of Golgi
Function of Lysosomes (3)
- Breakdown/digest macromolecules
- Repair membranes
- Responsd to foreign substances (bacteria, viruses and antigens)
What is phagocytosis?
Intracellular digestion via engulfing smaller organisms or food particles
Process of Phagocytosis
- Cell recognises and binds to target
- Food vacuole is formed around target which fuses together
- Enzymes digest the food
Macrophages
- White blood cells that help defend the body by engulfing and destroying bacteria/pathogens
Vacuoles
- Store food or other nutrients required by a cell to survive.
- Store waste products and prevent the entire cell from contamination.
How are Food Vacuoles formed?
by phagocytosis
What do contractile vacuoles do? (2)
- Pump out excess water from cell of eukaryotes in freshwater.
- Maintains suitable concentration of ions & molecules inside the cell
Central Vacuole
- Storage of inorganic ions such as potassium and chloride in plants
- Contained by mature plant cells
- Plants cells enlarge and maintain turgor pressure as vacuoles absorb water
Mitochonrdia & choloroplasts change ____ from one form to another
Energy
Mitochondria
- Generate most of the chemical energy needed to power the cell’s biochemical reactions as ATP
- Sites of cellular respiration
- Mitochondrial DNA is maternal
Mitochondria Structure
- Phospholipid bilayer with unique embedded proteins
- Outer membrane –> Smooth
- Inner membrane –> Cristae (foldings).
Mitochondria Divides interior into two compartments:
- Intermembrane space: Proteins & ATP that function during respiration are built into the inner membrane here.
- Mitochondrial Matrix: Enclosed by the inner membrane. - Has different enzymes that catalyse steps of cellular respiration.
Mitochondria Structure relating to Function:
Highly folded surfaces allow a large surface area thus enhancing cellular respiration
Chloroplasts
- Sites of photosynthesis found implants and algae
- Type of plastid
- Double membrane
Compartmentalisation allows chloroplasts to ____ light energy to ____ energy during photosynthesis
convert; chemical
Plastids
a plant organelle group that chloroplasts are in
Amyloplast
Type of plastid
- Colourless organelle that stores starch (amylose)
Chromoplast
Type of plastid
- Has pigments that give fruits and flowers their orange/yellow hues
Endosymbiont Theory
- An early ancestor of eukaryotic cells engulfed an oxygen using non photosynthetic prokaryotic cell.
- Eventually the engulfed cell formed a relationship with the host cell becoming an endosymbiont
- Over time his & cell emerged into a eukaryotic cell.
Proof for Endosymbiont theory: Mitochondria and Chloroplasts…
- have a double membranes
- contain their own DNA
- are autonomous: Organelles that grow and reproduce within the cell
What is a Peroxisome?
Specialized metabolic compartment
Peroxisome functions (3)
- Transforms reactive oxygen species like hydrogen peroxide into safer molecules like oxygen and water.
- Oxidises fatty acids
- Synthesises plasmalogens, which are crucial membrane constituents of heart and brain tissue
Glyoxysomes
- Specialised peroxisomes found in fat storing tissues of plant seeds
- Convert fatty acids into sugar
- Seedlings use this as energy source until they can produce their own sugar by photosynthesis.
The Cytoskeleton is a …
network of fibers extending throughout the cytoplasm
Cytoskeleton functions (4)
- Organisation of structure & activities of the cell
- Cell motility
- Support and anchorage for organelles and enzymes
- Extreme resilience (animal cells lack cell wall so it needs this)
Cell motility
- Changes in cell location & movement of parts
- Requires cytoskeleton interaction with motor proteins
Motor Proteins
- Outside the cell –> allow whole cells to move along fibers
- Inside the cell –> Used as “feet” by vesicles & other organelles to “walk” along a track provided by cytoskeleton
Components of the Cytoskeleton (3)
- Microtubules
- Microfilaments
- Intermediate Filaments
Microtubules structure
- Hollow Tubes
- Protein subunit: Tubulin
Microtubule function and examples
- Maintenance of cell shape
- Organelle movements (serve as tracks that they move on)
- Centrosomes & centrioles
- Cilia & flagella
Centrosomes & Centrioles
unique to animal cells
- Centrosomes are made of centrioles.
- A centrosome is a region often located near the nucleus.
- Are compression resisters that help with structure, cell division and transport
Cilia & Flagella
- Fundamental units of motion
- Move the cell itself
- Move other molecules
What are Microfilaments?
- Two intertwined strands of actin
- Gives the outer jelly-like cytoplasmic layer
Microfilament Functions (6)
- Muscle contraction
- Cell movement
- Intracellular transport/trafficking
- Maintenance of eukaryotic cell shape
- Cytokinesis
- Cytoplasmic streaming
Intermediate Filaments
- Made of different proteins such as keratin, vimentin, desmin, and lamin.
- Found in the cytoplasm except for lamins
1. maintain the cell’s shape,
2. bear tension,
3. provide structural support to the cell
Intermediate Filament Functions (5)
- Lamina
- Anchorage of nucleus and organelles
- Bear tension
- Cell shape maintenance
- Structural support
Cell Wall Structure/composition (2)
- Rigid, semi-permeable protective layer
- Composed of cellulose (strong fibers of carbohydrate polymer)
Cell wall functions (5):
- Mechanical protection
- Chemically buffered environment
- Porous medium for the circulation and distribution small nutrient molecules,
- Rigid building blocks from which stable structures of higher order can be produced
- Storage site of regulatory molecules that sense the presence of pathogenic microbes and control the development of tissues
Cell Wall Primary and secondary layers
- Primary –> thin & flexible
- Secondary –> more support & protection
Structure of Extracellular Matrix (ECM) of Animal Cells
- Made of extremely large proteins and polysaccharides that are secreted by some cells
- Three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite.
Function of ECM (3)
- Support (structural and biochemical)
- Connective material (hold cells in a defined space)
- Cell adhesion, communication and differentiation
Collagen
- Glycoprotein in ECM
- Form strong fibers outside the cells
- Embedded in a network woven out of proteoglycans secreted by cells
Integrins
- Receptor proteins built into plasma membrane
- Transmits signals between ECM & cytoskeleton.
–> integrate changes occurring in/out of the cell
Cell Junctions
- Multi-protein complexes
- Provide contact or adhesion between neighbouring cells or between a cell and the ECM
Plasmodesmata
- Small channels in the cell wall allowing direct connection between the cytoplasm of neighbouring plant cells to each other.
- Help regulate the passage of small molecules.
- Responsible for cell-to-cell communication
Tight Junctions
- Create a watertight seal between two adjacent animal cells.
- Cells are held tightly against each other by many individual groups of proteins called claudins, which interacts with a partner group on the opposite cell membrane.
Desmosomes
- Pins adjacent epithelial cells together, ensuring that cells in organs and tissues that stretch, such as skin and cardiac muscle, remain connected in an unbroken sheet.
- Uses cadherins (specialised adhesion proteins) which extends across the membrane and anchors the junction within the cell.
Gap Junctions
- Channels between neighbouring cells that allow for the transport of ions, water, and other substances.
- Directs transfer and exchange of nutrients and signal molecules between the cells
