CC- Cells, Organelles & Plasma membranes Flashcards
Define nuclear envelope
Separates genetic material from cytoplasm
What are the 4 main functions of intrinsic proteins
Act as channels
Transporters
Receptors
Enzymes
Define the smooth endoplasmic reticulum
Synthesis of lipids
Abundant (lots of them) in cells secreting lipids
What are the 4 ways in which substances may move across the membrane
Diffusion
Osmosis
Facilitated diffusion
Active transport
Define the centrioles
Consist of 2 hollow cylinders at 90° to each other
They organise microtubules during cell division
Where can hydrophilic pores be found
In channel proteins
Can hydrophilic substances diffuse through the membrane?
No
instead they cross the membrane via water-filled pores or protein channels.
What is the structure and function of cuboidal tissues
1 cell thick, box shaped cells w/ a prominent nucleus.
Involved in absorption or secretion
What are the magnifications and resolutions of the two types of electron microscopes
Scanning - medium
Transmission - high
Define the nucleolus
Synthesis of ribosomes
What does the reverse transcriptase enzyme do?
Converts RNA into DNA
Explain glycolipids in the cell surface membrane
Occur on the external surface of cell
CHO part extends into intercellular space + called the glycocalyx.
Cell-cell recognition
What does the cytoplasm of a prokaryotic cell contain?
Storage products i.e glycogen and lipids
Ribosomes
Plasmids
Define differentiation
Development of a cell into a specific type
Why is the rate of movement for simple diffusion much faster than facilitated diffusion?
Because simple diffusion happens via the membrane therefore larger SA.
Facilitated diffusion is limited by no of carrier proteins available
Explain protein production
Ribosomes are synthesised in the nucleolus.
mRNA is made by transcription in the nucleus.
Small enough to pass through nuclear pore and into cytoplasm.
Ribosomes then synthesis proteins using the mRNA
RER transports proteins and folds it.
Golgi body modifies protein to then be packaged into a secretory vesicle.
Vesicle migrates towards and fuses with the plasma membrane so that the contents of the vesicle are released by exocytosis.
Define hydrophilic channel proteins
Each protein is specific to one type of small ion.
Can close and open if necessary
Explain pinocytosis
Active process that extends cell membrane around a FLUID.
What is facilitated diffusion
Diffusion that relies on the KE of molecules to move through carrier proteins in the membrane (mol-specific)
Define osmosis
Movement of water molecules from an area of high water potential to an area of low water potential across a partially permeable membrane.
What subcellular structures are ONLY found in the mitochondria
Matrix
Cristae
What happens to an animal cell in a hypotonic situation
Water goes in via osmosis
Lysis
Haemolysis (if in RBC)
What is the structure of cholesterol
Hydrocarbon tail
Ring structure region with 4 hydrocarbon rings and a hydroxyl group
Define carrier proteins
Allow diffusion of larger polar molecules. I.e glucose
A molecule attaches to binding site, protein changes shape, releases molecule on other side of membrane.
What are the 3 types of lipids found in the cell surface membrane
Phospholipids
Glycolipids
Cholesterol
What happens to an animal cell in a hypertonic situation
Water moves out via osmosis
CRENATION
Define tissue
Groups of layers of similar cells working together to perform a specific function
What is the highest water potential
0kPa
What are the 3 most common prokaryotic cell shapes
Spheres
Rods
Spirals
What does the phospholipid bilayer allow the diffusion of
Lipid soluble
Non polar
BARRIER TO:
Polar molecules as cannot pass through hydrophobic tails unless VERY SMALL. I.e water
What is peptidoglycan made of?
Polymers of modified sugars cross-linked by short chain polypeptides.
What is the relative size of a prokaryotic cell?
1-5 micrometers
Define the nuclear pore
Allows transport of mRNA out of nucleus
Define endosymbiosis
Mutually beneficial relationship in which one organism lives inside the other.
Describes the origin of chloroplasts and mitochondria.
What type of ribosome is found in prokaryotic and eukaryotic cells
Prokaryotic - 70s
Eukaryotic - 80s
What is thought to be the site of respiration in prokaryotic cells?
Mesosomes
Define amphipathic when talking about phospholipids
Meaning they have a dual nature in that one end is hydrophilic whilst the other is hydrophobic.
What transport methods can carrier proteins do?
Diffusion
Facilitated diffusion
Active transport
Why aren’t viruses considered to be a cell?
Because of their inability to replicate by themselves and lack of nucleus.
Active transport, diffusion and osmosis are for individual molecules. What is the transport known as for larger amounts of molecules?
Bulk transport
How does the cell effectively control the amount of water entering across the plasma membrane?
By regulating the concentration of ions in the cytoplasm via the sodium/potassium pump
Where can mitochondria be found
Muscle cells for contraction
Sperm cells for flagella to move
Root hair cells for active transport
Define the Golgi body
Modifies + packages proteins into vesicles to be transported around or out of cell (exocytosis)
Production of glycoproteins, lysosomes and liposomes
Why do organisms have internal cell membranes
Provide a transport system
Compartmentalisation
Large SA for attachment of enzymes and other reactants
Define extrinsic protein on a cell membrane
Usually receptors for chemical messengers i.e hormones
Define diffusion
Net movement of molecules from a region of higher concentration to a region of lower concentration.
Name a connective tissue
Collagen and elastic fibres
Define water potential
Likelihood of water to move out of a solution
What is the function of the phospholipids in the membrane
Provide stability, fluidity and gives membrane selective permeability.
What is the DNA like in prokaryotic cells?
Naked
Free
Circular
What can the rate of diffusion be affected by?
Temp
Concentration gradient
Diffusion distance
Define ribosomes
Protein synthesis
Briefly describe the sodium and potassium ion pump
3 Na+ ions move out of cell simultaneously to 2 potassium ions moving into cell = both against their concentration gradients
What type of cells have the potential to become any cell type in the body?
Stem cells
What does the degree of fluidity of a cell surface membrane depend on?
Length of FA side chains (longer chains = less fluidity)
Proportion of FA that are saturated (higher sat fats = lower fluidity)
Steroid content (higher = lower fluidity)
Where does active transport take place in the cell membrane?
Carrier proteins
Define the cholesterol on a cell membrane
Adds strength and rigidity however too much decreases membrane flexibility to a dangerous level.
Define active transport
Use of ATP to move substances against their concentration gradients.
What are the 3 types of bulk transport?
Pinocytosis
Phagocytosis
Exocytosis
Define the rough endoplasmic reticulum
System of flattened sacs (cisternae) continuous with the nuclear membrane + may link to the Golgi apparatus
Transports proteins synthesised by the ribosomes attached
Manufactures hormones and enzymes
What rule is there about pressure potential and solute potential?
Pressure pot. = always +ive or zero
Solute potential = Always -ive
Eukaryotic cells have a nucleus, what do prokaryotic cells have?
A nucleoid.
Define electron microscopes
Uses electrons
Dead sample in a vacuum
List the 4 types of epithelial tissues
Squamous
Cuboidal
Columnar or ciliated
Glandular
What is the function of columnar or ciliated tissues and where can they be found
Absorption +Secretion
i.e Lining of small intestine
What is the structure of a squamous tissue and where can it be found
Single layer of thin + smooth cells flattened on basement membrane
i.e Alveoli and blood vessels
Permeable to allow filtration or diffusion
Who came up with the fluid mosaic model
Singer and Nicholson in 1972
What is the DNA like in eukaryotic cells
Enclosed by an envelope
Linear
Define symbiosis
Relationship in which organisms from 2 separate species depend on each other for survival.
Define optical microscopy
Uses light and can observe living samples at low magnification
List 2 types of endocytosis
Phagocytosis
Pinocytosis
What type of microscope is needed to see the internal structures of chloroplasts and mitochondria?
Electron microscope
How much of the cell is vacuole
70%
Describe the process of phagocytosis
Cell surface receptor binds to antigen on bacterium
Cell membrane invaginates + bacterium is taken into a phagosome by endocytosis.
Lysosomes fuse w/ phagosome + secret digestive enzymes onto it.
Productos of digestion are absorbed into cytoplasm.
Define organ
A collection of different types of tissues working together to perform a specific function.
Define the mitochondria
Site of aerobic respiration to release energy in the form of ATP
Define the glycolipid on a cell membrane
Branched carbohydrate attached to a phospholipid
What is FD limited by?
Number of carrier proteins
Explain the transportation of water-soluble substances in regards to the permeability of the membrane
Water soluble substances (i.e glucose, polar molecules and ions) can’t diffuse through phospholipids so MUST pass through intrinsic protein molecules.
What is the structure of the columnar or ciliated tissues
Elongated column shaped cells
Some have cilia, some have microvilli
Where can cuboidal tissues be found
In the kidney tubule
Define cotransport
Type of FD in which 2 substances are simultaneously transported across a membrane by 1 protein.
What is the structure of a phospholipids bilayer membrane known as?
Fluid mosaic model
Why is it called the fluid mosaic model
Fluid = phospholipids and proteins move around each other
Mosaic = arrangement of proteins within phospholipid bilayer
Define the glycoprotein on a cell membrane
Branched carbohydrate attached to a membrane protein
What do the different electron microscopes look at
Scanning - 3D surface
Transmission - Internal cross section
How big is the Golgi body
1 x 1 micrometers
Define viral DNA
Enclosed in a protein coat called capsid
Has enzymes attached ready to convert DNA into RNA once in host cell
Define the intrinsic protein channel of a cell membrane
Passes through both layers of the cell membrane
Maintains different concentrations of ions on either side of the membrane.
Essential for the sodium/potassium pump.
How thick is the cell surface membrane?
7.5 nm thick
Why do liver cells contain more mitochondria than fat storage cells?
Because liver cells are metabolically active due to secretion therefore require large supply of ATP
Fat storage cells are metabolically inactive so need less ATP
List 3 structural differences between phospholipid and triglyceride
PL only has 2 fatty acid chains, TG has 3.
PL has a phosphate group, TG don’t.
PL has a hydrophilic and hydrophobic region, TG is entirely hydrophobic
What is the role of the glycoproteins and glycolipids on the cell membrane?
Allow cells to recognise and attach to each other.
What are the basics to a virus structure
All have genetic material (either RNA or DNA)
Protein coat (caspid)
Some have a lipid bilayer
Define cell membrane
Protection - Separating cell contents from outside environment
Cell recognition and signalling
Receptor sites
Regulation transport of materials into or out of cells, selectively permeable
Define the nucleus
Contains DNA coding for protein synthesis
What is the function of a glandular tissue and where can it be found?
Striated + Closely packed together
Secrete hormones, saliva + enzymes
i.e Digestive system
What are the levels of organisation
Cell
Tissue
Organ
Organ system
How is the structure of a virus different to that of a bacteria?
Virus has a lipid bilayer whereas bacterium just has a cell membrane
What are the 2 major biochemical components present in ALL viruses
Proteins
DNA/RNA
Do viruses have plasmids or mitochondria?
NO
