Topic 1:1 - cell theory & membranes Flashcards
What is a cell?
the smallest structural unit of life
What are the characteristics of life
MRSGREM
movement, respiration, stimuli Response, growth, reproduction, excretion, metabolism/nutrition
Why are viruses generally considered not living?
-don’t grow or develop
-don’t obtain and use energy
-don’t respond to environment
-reproduce only within host cells
What are the 4 things that cell theory states?
- all living things are composed of one or more living cells
- the cell is the structural and functional unit of life
- cells arise from pre-existing cells
- cells contain hereditary material (DNA or RNA) passed onto daughter cells
define semi permeable membrane
allows some molecules to pass through, while others are too large or charges to pass through
Define the fluid mosaic model
The cell membrane is composed of a variable number of proteins and cholesterol embedded within or on the surface of a phospholipid bilayer
What are the two types of proteins found in the cell membrane?
- Integral or intrinsic. These span the entire membrane
- peripheral or extrinsic. These are embedded in, but don’t span the whole membrane
describe cholesterol and it’s function in the cell membrane
cholesterol is a lipid found in the bilayer that restricts movement, preventing the membrane from becoming too fluid or too solid
protein function: transport
channel proteins (without ATP) and carrier proteins (with ATP) transport hydrophilic materials across the membrane
protein function: receptors
some proteins recognise and bond to target molecules (such as hormones) causing changes to occur inside the cells
Protein function: enzymes
enzymes embedded in the membrane catalyse substrate specific reactions at the boundary or within the cell membrane
protein function: cell recognition
glycoproteins are integral and peripheral proteins with carbohydrate molecules attached. They serve as markers that are recognised by membrane proteins on the surface of other cells. They also recognise certain target molecules in the extracellular environment
describe glycolipids
lipids with a carbohydrate chain found on the surface of the cell membrane, where they extend into the intercellular space. Their role is to maintain the stability of the cell and facilitate cellular recognition
describe phospholipids
consists of phosphate and glycerol (heads) and fatty acid chains (tails). the heads are hydrophilic and the tails are hydrophobic.
