Cell Structure & Diversity Flashcards
What must a cell do?
Manufacture cellular materials, Obtain raw materials, Remove waste, Generate the Required Energy, Control all of the above.
What does the plasma membrane at the boundary of each cell do?
Provides special conditions within the cell, acts as a semi-permeable barrier
How does the plasma membrane provide the ideal conditions and act as a semipermeable barrier?
Allows passage of oxygen, nutrients and waste. Controls movement of substances in and out of the cell. This interaction with the environment limits the maximum size of the cell.
How does the size of a cell dictate the surface area to volume ratio?
A small cell has a larger surface area to volume ratio.
What forms the plasma membrane?
A double layer of phospholipids with various embedded or attached proteins. The hydrophilic heads face outwards with the hydrophobic tails facing inwards. They move!
What affects the membrane fluidity?
The composition of fatty acids
What does saturation of the phospholipids in the membrane look like?
Packed tightly together, less fluidity. VISCOSE! (like honey, a bit slower to move)
What does unsaturatedness of phospholipids in the membrane look like?
Tails prevent tight packing, more fluidity.
How does temperature affect the fluidity of the membrane?
High temps = more fluidity (think melted, becomes liquid)
Low temps = More viscose (think colder temps, makes it harder)
What does cholesterol do in the membrane?
Stabilises the fluidity. Helps the cells work properly.
What do plasma membrane proteins do?
Determine the function of the membrane. They have multiple different functions and are found in different types of cells. The function is often specific to the cell type but cells can have multiple diff proteins.
What functions are membrane proteins involved in?
Signal transduction, Cell recognition, Intercellular joining, Linking cytoskeleton and extracellular matrix, membrane transport.
The protein function signal transduction is what?
Relay messages from the body (or outside environment) into the cell.
The protein function cell recognition is what?
The cells ability to distinguish one type of neibouring cell from another. It often involves glycoproteins (proteins with added sugars).
The protein function intercellular joining is what?
Some proteins form long lasting connections between cells
The protein function linking cytoskeleton and extracellular matrix does what?
This allows the cells to physically connect with proteins structures outside of the cell
The protein function membrane transport is what?
Allows small amounts of molecules to move across the membranes. This can be passive (no energy required) or active (energy required)
What are the defining factors for whether membrane transport or bulk transport needs to be used for things to get over the cell membrane?
Size. It depends what the molecules are, how big they are and how much of it is being moved at a time.
What is passive transport?
When the molecules move down (with) the concentration gradient, so no energy is needed to get them across.
What is active transport?
When the molecules move against the concentration gradient, so energy is required to get them across.
Diffusion: What are membranes permeable to?
Lipid soluble (hydrophobic) molecules. Eg. gasses/steroid hormones
Diffusion: What are membranes NOT permeable to?
Charged molecules such as glucose ions and water
What is facilitated diffusion used for?
For hydrophilic molecules. It requires membrane proteins called carriers and channels
How are carriers different to channels?
Carriers undergo a shape change to help guide the molecule
Facilitated diffusion for water requires what?
Aquaporins. These are channel proteins. And this is a process called osmosis.
What is osmosis?
The process of water moving from an area of high water (low solute) to an area of low water (high solute) through a semipermeable membrane.
Active transport requires what type of proteins?
Transport proteins. They require ATP (energy)
Active transport allows for a cell to have what?
An internal concentration of a substance that is different from its surroundings. For example something inside the cell could be higher than outside the cell.
Can active transport go both ways (is it bidirectional)?
Yes
Co-tansport is what?
Indirect active transport (so it requires energy). One substance is powered across the membrane and its concentration gradient is used to power the movement of a second substance against its concentration gradient.
How do different parts of the cells do different things?
Organelles
What do organelles do?
Provide special conditions for specific processes, keep incompatible processes apart, allows specific substances to be concentrated, from concentration gradients, package substances for export/transport.
What are organelles like? (way to remember how organelles work)
A house. The different rooms in a house have different functions. The organelles are the different rooms (the walls being the membrane around the organelles), they separate the function inside the cell.
List the key organelles in an animal cell
Endoplasmic reticulum, Nucleus, Mitochondrium, Golgi apparatus, Lysosome
List the key organelles in a plant cell
Endoplasmic reticulum, Nucleus, Golgi apparatus, Mitochondrium, Central Vacoule, Chloroplast.