Membrane Structure and Function Flashcards
Cholesterol
Stiffens and strengthens the membrane, therefore helping to regulate its fluidity
Plasma membrane structure
Membrane is composed of phospholipid bilayer (where proteins are embedded)
Hydrophobic tails face inwards to make up the interior of the membrane, hydrophilic heads face outwards
Carbohydrate chains are attached to the outside surface
Cytoskeleton filaments are attached to the side surface
Integral Proteins
Have specific functions inside of the membrane
Channel Protein
Allows particular molecules to cross the membrane freely
Cystic fibrosis is cause by a faulty chloride channel
Carrier Protein
Selectively interacts with specific molecule or ion to freely pass
Inability to transport (NA+-K+) can be the cause of their obesity
Selective
Cell Recognition Protein
The MHC glycoproteins are different for each person, which is why finding matching transplants are difficult
Cells with foreign MHC are attacked by white blood cells
Receptor Proteins
Shaped in such a way that specific molecules can bind to it
Some types of dwarfism are the result of faulty hormone receptors
Enzymatic Proteins
Catalyzes a specific reaction
Cholrea because releases a toxin that interferes with adenylate cyclase, which leads to severe diarrhea
Differentially permeable
Certain substances can move across the membrane while others can’t
Concentration gradient
Molecules move from an area of high concentration to an area of low concentration
Permeability of the plasma membrane
Differentially permeable
Molecules that can’t be transported freely are moved through channel proteins or vesicle formation
Vesicle formation
Another way molecules can enter (endocytosis) or exit a cell (exocytosis)
Diffusion
Movement of molecules from a higher concentration to an area of low concentration
Factors influcening the rate of diffusion
Temperature
Pressure
Electrical currents
Molecular size
Osmosis
Diffusion of water across a differentially permeable membrane
Isotonic solutions
Solute concentration and water concentration both inside and outside the cell are equal and therefore there is no net gain or loss of water
Hypotonic solution
Solutions that cause cells to swell or even burst, due to intake of water
Turgor pressure
Pressure inside of a cell
Hypertonic solution
Causes cells to shrink or shrivel due to the loss of water
Plasmolysis
Shrinking of cytoplasm due to osmosis
Facilitated Transport
The passage of some molecules across the plasma membrane even though they aren’t lipid-soluble, moving with their concentration gradient
Active transport
Small molecules and ions move against their concentration gradient
Proteins in active transport are often called pumps because proteins use energy to move a substance against its concentration gradient
Exocytosis
Vesicle fuses with the plasma membrane as secretion occurs. Substances are secreted from a cell via exocytosis
Endocytosis
Substances enter a cell through endocytosis
Receptor mediated endocytosis allows calls to take up specific kinds of molecules
Pinocytosis
Occurs when vesicles form around a liquid or around very small particles
Phagocytosis
When material is taken in by endocytosis is large, such as food particles or another cell
Three methods of endocytosis
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis
Receptor-Mediated Endocytosis
A form of pinocytosis
Uses receptor protein shaped so that a specific molecule, such as a vitamin, peptide hormone, or a lipoprotein, can bind to it
Only found at one location on the plasma membrane, called a “coated pit” bc there is a layer of protein on the cytoplasmic side of the pit
The mosaic part of the fluid-mosaic model refers to the…
Phospholipids
Accumulation in cholesterol can lead to
Heart attack
clogged arteries
high blood pressure
Two lipid molecules that are vital to an animals plasma membrane
Cholesterol
Phospholipids
Consists of:
Phospholipids and proteins
“mosaic” refers to proteins
Proteins are embedded in phospholipid bilayer
Cell cytoplasm
Site of cell metabolism
Breaking down complex molecules for energy
synthesizes new cell structures
Ribosomes
Sites of protein synthesis, where an RNA strand is translated into an amino acid sequence
Prokaryotic cells
Lack a nucleus
concentrated in the region called the cells nucleoid
Eukaryotic cells
Cytoskeleton gives cell shape and stability
Housed in nucleus
Large in size
Nucleolus
Present inside of the nucleus as distinct region
consist of ribosomal RNA, protein, ribosomes and DNA
Nucleoli are the sites of ribosomal synthesis in the cell
Endoplasmic Reticulum
Complex system of membranes present within the cytoplasm
Continuous within the nuclear envelope and the plasma membrane
internal transport system for the cell
Smooth ER
Lacks ribosomes on the surface. Involved with lipid synthesis
Rough ER
Has ribosomes on surface, involved with protein synthesis
Golgi Complex
Special set of membranes derived from the ER
Looks like a set of flattened sacs or vesicles
Recieves contents from the ER, modifies them and packages them for transport out of the cell
Lysosome
Membranous sac (or vesicle) containing digestive enzymes
Used to breakdown the complex of the cell
lysosome enzymes derived from the Rough ER
lysosomes sac derived from golgi complex
Peroxisome
Similar to lysosome
Contains enzymes
Breakdown toxic substances to hydrogen peroxide
HP is then broken down by catalase to produce water and oxygen
