Week 2 Bioscience Flashcards
Generalised cell
- organelles: little organs found within a cell
- each organelle has a specific function
Cytoplasm
- the watery space between plasma membrane and the nucleus
- contains the cellular organelles
- composed of cytosol or Intracellular fluid (ICF)
- contains dissolved proteins and nutrients
The nucleus
- largest organelle
- houses DNA
- DNA contains the instructions which tells the cell what to do, in particular which protein to make
ribosomes
- site of protein synthesis
- free ribosomes: floating in cytosol produce proteins for use inside cell
- membrane bound ribosomes: attached to endoplasmic reticulum proteins for export
Endoplasmic Reticulum
-interconnected tubes continuous with the nuclear envelop
-functions:
synthesis
storage
transport
detoxification
Rough Endoplasmic Reticulum (RER)
-studded with ribosomes
-proteins produced by ribosomes on RER are packaged and exported out of cell
Smooth Endoplasmic Reticulum (SER)
-no ribosomes attached
-synthesis of lipids, cholesterol and steroid based hormones
-involved in detoxification
-storage of calcium ions
Golgi apparatus (“the traffic director”)
- consists of stacks of flattened sacs
- functions:
- modify, concentrate and packages proteins and lipids
- forms vesicles and distributes them:
1. within the cell
2. move and become inserted within the plasma membrane
3. move to the plasma membrane for the content to be exported out of the cell by exocytosis
Lysosomes (“the demolition crew”)
-membrane enclosed spheres
-contains lysosomal enzymes
-functions:
* dispose of invading bacteria and cell debris
* recycle molecules that have been broken down
Mitochondria (“the power house”)
-bean‐shaped organelle
-enzymes on surface of inner membrane
-function: cellular respiration
-releases energy in the form of ATP (adenosine triphosphate)
The cytoskeleton
-skeleton of the cell but not made of bone
-network of rods running through cytoplasm
-acts as cells bones, muscles and ligaments
Cilia and Flagellum
- A flagellum is a single, long tail found on bacteria and sperm
- it whips back and forth to move the sperm along
- cilia are motile cellular extensions on the top of cells
- they sweep in a wave like manner to move materials across the surface of them
Microvilli
- minute fingerlike extensions of the plasma membrane that project from the cell surface
- they increase the surface area of the cell
Plasma membrane
- cell membrane = plasma membrane
- holds the cell together, separating the ICF from ECF
- acts like a zip‐lock bag, however the membrane selects what it lets into and out of the cell
- helps maintain homeostasis (optimal working conditions)
Phospholipid structure
- made of a phospholipid molecules
- hydrophilic (“love water”) phosphate heads point toward water
- hydrophobic (“hate water”) lipid tails point away from water
Plasma membrane structure
- is a double layer (bilayer) phospholipid molecules
- is a thin flexible membrane
- fluid membrane the consistency of olive oil
- selectively permeable: a membrane that allows some substance through and excludes others
Plasma membrane consists of:
- phospholipids
- integral proteins (channel and carrier)
- peripheral proteins
- cholesterol (membrane stability)
- sugars (“name or ID tags”)
Concentration gradients
- substances (atoms, molecules, particles, ions, solutes) are constantly moving
-random movement (Brownian motion) due to kinetic energy
-non‐directional movement that leads to collisions that ricochet the substance off in another direction
Concentration gradient and equilibrium
- concentration: measure of the amount of a substance in an area
- high concentration means there are higher numbers of the substance compared to another area
- concentration gradient: the difference in concentration of a particular substance between 2 different areas
- equilibrium: equal space between substances (state of stable conditions)
Diffusion
*the movement of a substance from an area of high concentration to an area of low concentration
*substances move in a net direction to achieve equilibrium
Factors that affect rate of movement
- concentration gradient: if a larger concentration gradient exists substances will move faster
- size of the substance: smaller substance move faster than larger substance
- temperature: warmer environments increase the rate of movement
The transport processes substances use to cross the plasma membrane
- cell needs to transport substances such as nutrients, gases and waste across the plasma membrane to maintain homeostasis
- substances are moved in and out of cells via the following mechanisms:
Diffusion: simple and facilitated diffusion
Osmosis
Active transport
Exocytosis and endocytosis
Transport process depends on the type of substance transporting
- substances are classified as lipid soluble or water soluble
- lipid soluble substance=water insoluble substance
-not repelled by the lipid part of plasma membrane - water soluble substance=lipid insoluble substance
- repelled by the lipid part of plasma membrane
Simple Diffusion
- the unassisted transport of lipid soluble or very small particles across a plasma membrane
- continues until equilibrium is reached then no net movement
- Lipid soluble substances move by simple diffusion: eg O2 CO2