Holiday homework/cell/protein synthesis Flashcards
(55 cards)
What is exocytosis and its process?
- active movement of substances outside the cell in membrane-bound vesicles
- Vesicles form inside the cell from the RER, golgi apparatus, lysosomes and endosomes
- Vesicles containing newly synthesised proteins or waste products move towards the plasma membrane
- plasma membrane and vesicular membrane fuse together
- contents of vesicle expelled into extracellular fluid
What are cells?
- the basic structural and functional unit of life
Why do cells need to be small?
- maximise their surface area to volume ration to efficiently move ions, nutrients and waste
Prokaryotes vs eukaryotes: unicellular/multicellular
Prokaryotes: bacteria and archaea
- lack membrane boune nucleus
- unicellular
- no cytoskeleton
- chemicallu complex cell wall
Eukaryotes: animals, plants, chromista, fungi, protozoa,
- mostly mutlicellular (can be unicellular)
- sometimes cell wall but chemically simple
Importance of compartmentalisation in eukaryotic cells:
- efficiency
- creates specific microenvironments (e.g. pH, ion concentration) within the cell so each organelle can have the advantages it needs to perform to the best of its ability
Location of nucleolus and what it does
- within nucleus
- ribosomal subunits are synthesised
Where can ribosomes be found and what is their role?
- free in cytosol or attached to RER
- role is protein synthesis
- small subunit reads mRNA and large subunit joins amino acids which are connected via peptide bonds to form polypeptide chains
what do the endoplasmic reticulums look like?
- interconnected network of flattened membrane-enclosed channels
- continuous with outer nuclear membrane
Role of smooth ER
- synthesise lipids
- metabolism of carbohydrates
- calcium storage
- detoxification of drugs and poisons
Role of rough ER and what happens to proteins there
- processes proteins from ribosomes
- attaches carbohydrate groups to some proteins to form glycoproteins
- folds proteins into correct functional shape
- joins together several popypeptide chains to form complex proteins
Golgi apparatus appearance and function
- mutli layered structure composed of stacks of membrane-lined channels with wider ends
- modifies, sorts, packages and distributes proteins into secretory vesicles
Lysosomes
- membrane bound sac
- contain hydrolytic enzymes
- found only in animal cells
- contains digestive enzymes
- breaks down material taken into the cell and obsolete components of the cell itself
Vacuoles
- large membrane bound sacs
- found in plant cells (one, large) and some animal (smaller, multiple)
- store water
- isolate harmful materials to cells
- store waste products
- maintain internal turgor pressure (plant cells- force that pushes cell membrane against cell wall)
peroxisomes
- eukaryotic cells
- act as recycling centre of the cell, breaking down harmful substances
- involved in oxidation of molecules (e.g., amino acids, fatty acids), where electrons are lost.
- Produce hydrogen peroxide (H₂O₂) as a byproduct of oxidation.
Contain the enzyme catalase, which converts hydrogen peroxide into water and oxygen. - break down very long fatty acid chains through beta oxidation
- metabolism of other substances (e.g. lipids, amino acids)
mitochondria and role in protein synthesis and secretion
- double membrane
- inner membrane has series of folds (cristae) containing enzymes for ATP synthesis
- matrix is fluid-filled space within inner membrane
- provide energy in form of ATP for translation (e.g condensation reactions)/synthesis of protein, for packaging proteins into vesicles
Plasma membrane
- semi permeable
- controls the entry and exit of materials into and out of cells
Functions:
- is an active and selective boundary (separates cell from external environment)
- denotes cell identity (vital for immune response)
- receives external signals
- transports materials.
Factors that affect a substance’s ability to cross a membrane
Molecules that can pass easily through the cell membrane:
* small polar molecules such as water
* non-polar molecules such as carbon dioxide.
Molecules that cannot pass easily through a membrane:
* large polar molecules such as glucose (polar molecules are neutral because the uneven charges balance out)
* charged molecules (ions)
Simple diffusion
the movement of solute particles across a semi-permeable membrane from a region of high concentration to a region of low concentration to reach equilibrium
- small polar molecules
- non-polar (lipophilic/hydrophobic)
Facilitated diffusion
net passive movement of polar or charged molecules from an area of high to low concentration with the aid of proteins such as carrier or channel proteins.
- large polar and charged molecules, water (aquaporins)
Active transport
The net active movement of particles that requires energy in the form of ATP from an area of low to high concentration with the aid of transport proteins such as carrier proteins.
- hydrophyllic substances
Bulk transport
- active transport
- too large for carrier proteins
- high to low concentration??
Endocytosis:
- enter cell
- phagocytosis (solid)
- pinocytosis (liquid)
1. substance approaches plasma membrane
2. Portion of plasma membrane is invaginated
3. membrane forms vesicle that contains substance
Exocytosis:
- substance encolsed in a vesicle from the golgi apparatus
- vesicle fuses with plasma membrane and releases contents
Osmosis
a specialised process of
passive transport in which water
molecules move across a partially
permeable membrane from an area
of high water (low solute) to an area
of low water (high solute)
structure of membrane (proteins, cholesterol, temp, carbs)
- double layer of phospholipids
(hydrophilic heads on outside, hydrophobic tails face each other) - integral proteins (embedded in membrane, transmembrane proteins span entire width)
- peripheral proteins (anchored to exterior of plasma membrane
through bonding with lipids, or indirectly associated with plasma membrane through interactions with integral proteins) - cholestoral (animal cells only):
at low temps, maintains fluidity by keeping phospholipids separated and keeping it from becoming too stiff
-at high temps, stabilizes membrane by restricting movement of phosopholipids, reduces permeability to some small water-soluble molecules from becoming too fluid thus raising melting point
- carbohydrates: attached to lipids (glycolipid), attached to proteins (glycoproteins) (peripheral)
cell to cell communication, receptors and recognition
How to describe structure of plasma membrane
- fluid mosaic model
- phospholipids can move laterally (influenced by unsaturated fatty acids- kinks in the tail that make it more fluid)
- looks like a mosaic with proteins embedded
