State 4 functions of plasma membranes
Options:
- recognition of other cells
- separates cell contents from the outside (barrier between cells and its environment)
- controls the passage of materials in and out
- allow cell communication
- phagocytosis
- cell to cell attachment
State 4 functions of membranes inside cells
Options:
- isolates DNA
- acts as an intracellular transport system
- compartmentalises reactions
- can be the site of chemical reactions
- ribosomes attach
- protection from lysosomes
- forms vesicles
Define compartmentalisation
The formation of separate membrane-bound areas
Why is compartmentalisation useful in cells?
- incompatible reactions occur within the cell
- isolates reactions making them more efficient
- allows reaction conditions to be maintained (e.g chemical gradients)
- protects cell components
Define partially permeable
A membrane that allows some substances to cross but not others
Define cell signalling
A complex system of intercellular communication
Define phospholipid bilayer
- arrangement of phospholipids found in cell membranes
- the hydrophilic phosphate heads form the inner and outer surface of a membrane ,
- sandwhiching the fatty acid tails to form a hydrophobic core
Why are membranes referred to as having a ‘fluid-mosaic structure’ ?
- the phospholipids are able to move freely relative to each other (fluid)
- the proteins embedded in the bilayer vary in shape, size, and position (mosaic)
Define glycoprotein
Extrinsic membrane proteins with attached carbohydrate molecules of varying lengths and shapes
Define glycolipid
Cell-surface membrane lipids with attached carbohydrate molecules of varying lengths and shapes
Define phospholipid
Modified triglycerides, where one fatty acid has been replaced with a phosphate group
What are channel proteins?
Membrane proteins that provide a hydrophilic channel through a membrane
What are receptor proteins?
Extrinstic glycopoteins that bind chemical signals, triggering a response by the cell
What are carrier proteins?
Membrane proteins that play a part in the transport of substances through a membrane
What is the approximate width of an animal cell plasma membrane?
7nm
What are the functions of cholesterol in cell surface membranes?
- regulates fluidity and adds stability to membranes
- prevents phospholipids from crystallising
What are the functions of phospholipids in cell surface membranes?
- forms basic structure
- acts as partially permeable barrier
- allows the passage of lipid soluble molecules
- prevents water soluble molecules from moving across
What are the functions of glycoproteins in cell surface membranes?
- receptors for chemical signals
- cell adhesion
- when chemical binds to the receptor, events inside the cell are set off
- binding sites for chemical e.g hormones
- Hydrogen bonds to water to stabilise membrane
What are the functions of glycolipids in cell surface membranes?
- act as antigens that can be recognised by the immune system
- form hydrogen bond with water molecules to stabilise membrane
What are the functions of carrier proteins in cell surface membranes?
- have an important role in both passive movement of polar molecules and ions down a concentration gradient
- this involves the shape of the protein changing
What are the functions of channel proteins in cell surface membranes?
-provide a hydrophillic channel that allows passive movement of polar molecules and ions down a concentration gradient
What are the functions of extrinsic proteins in cell surface membranes?
-can attach to the cytoskeleton
Define cell adhesion
The process by which cells make contacts with each other
Describe 2 ways in which cholesterol regulates membrane fluidity
- hydrophillic end of cholesterol interact with phosphate heads
- hydrophobic end of cholesterol interacts with fatty acid tails
- pulling the phospholipids together
- prevents membranes from becoming too solid and crystallising by preventing the phospholipids from getting too close together
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Unit 2: Microscopy20
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Unit 2 - Cells and Organelles20
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Unit 2 - Cells and Organelles 220
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Unit 2 - Biological Elements & Water20
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Unit 2 - Carbohydrates20
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Unit 2 - Testing for biological molecules20
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Unit 2 - Lipids33
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Unit 2 - Proteins73
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Unit 2 - Nucleic acids & DNA replication73
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Unit 2 - Enzymes35
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Unit 2 - Plasma membranes34
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Unit 2 - Diffusion/osmosis/active transport66
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Unit 2 - The cell cycle, mitosis, meiosis86
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Unit 2 - Cell organisation and stem cells29
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Unit 3 - Mammalian gas exchange and ventilation24
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Unit 3 - Gas exchange and ventilation in bony fish and insects10
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Unit 3 - Circulatory systems27
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Unit 3 - Blood and blood vessels46
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Unit 3 - Tissue fluid17
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Unit 3 - Structure and anatomy of the heart23
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Unit 3 - The cardiac cycle, heart action coordination, and ECGs38
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Unit 3 - Transport of oxygen and carbon dioxide41
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Unit 3 - Transport in plants94
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Unit 4 - Classification35
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Unit 4 - Variation and Evolution69
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Unit 4 - Biodiversity124
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Unit 4 - Communicable disease, disease prevention and the immune system161
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Unit 4 - Pathogens that cause disease in plants and animals28
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Unit 4 - Specific immune response27
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Unit 5 - Neuronal Communication62
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Unit 5 - Hormonal Communication55
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Unit 5 - Communication and Homeostasis45
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Unit 5 - Excretion, homeostasis and the liver86
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Unit 5 - Plant & Animal Responses142
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Unit 5 - Photosynthesis60
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Unit 5 - Respiration48
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Unit 6 - Genetics of living systems81
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Unit 6 - Patterns of Inheritance85
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Unit 6 - Manipulating genomes85
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Unit 6 - Cloning and biotechnology91
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Unit 6 - Ecosystems90
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Unit 6 - Population and Sustainability54
