Cells (Chapter 2) Flashcards
Cell theory
- All living organisms are composed of one or more cells.
- The cell is the basic unit of structure and organization in organisms.
- Cells arise from pre-existing cells
Endoplasmic reticulum
- Provide a surface on which chemical reactions can occur
- The channels between the paired membranes are used for storage and transport of materials
- Rough endoplasmic reticulum has ribosomes attached to it
- Smooth endoplasmic reticulum has no ribosomes
Ribosomes
- Site of protein synthesis
Lysosomes
- Small spheres that contain enzymes able to break down proteins, lipids, nucleic acids
- Formed from golgi body
Vesicle
membrane-bound sac that transports materials into, out of, or within the cell
Nucleus
Contains the genetic material of a cell
Mitochondria
- Where cellular respiration takes place (energy production)
- The folding of its inner membrane produces a large surface area for these chemical reactions to take place
- Called ‘powerhouses’ of cell
Golgi body
- Modifies and packages proteins for their secretion from the cell
Why do cells prefer a high surface area to volume ratio?
Becasue if the volume of a cell is too big compared to the surface area the cell can’t exchange material efficiently enough to stay alive.
Homeostasis
The maintenance of the balanced environment a cell needs to operate
Phospholipid bilayer
- The basic ‘part’ of the cell membrane
- Phospholipids contain a head and a tail
- The head contains a phosphate group and likes water (hydrophilic)
- The tail is made of lipids (fats) and dislikes water (hydrophobic)
- Contains carrier proteins which act as a tunnel for substances to move in and out at will
- Contains channel proteins which bind to a particular substance to carry them through the membrane in and out of the cell
- Contains cholesterol molecules which sit within the bilayer, acting as velcro the keep the phospolipids joined
- Also cell identity markers which are nametags for the cell, letting the immune system know that the cell is not a foreign invader
Functions of the cell membrane
- Physical barrier between cytoplasm and extracellular fluid
- Regulation of passage of materials
- Support
- Sensitivity - uses receptors to detect changes in the environment
Transport across membrane
The membrane is selectively permeable. Permeable meaning it allows liquids and gases to pass through and selectively referring to having control over what goes in and out. There are 3 basic forms of transporting material across the membrane:
Diffusion
Carrier-mediated transport
Vesicular transport
Diffusion
- The movement of small molecules such as oxygen and carbon dioxide directly across the cell membrane along a concentration gradient (from areas of high concentration to low concentration)
- The greater the differential between high and low the steeper the concentration gradient. The steeper the concentration gradient the quicker diffusion happens.
- A passive process
Osmosis
the diffusion of a water from high to low concentration through a selectively permeable membrane in order to balance the concentration of another substance.