Cells Flashcards
fundamental organizing principle of biology and it says the following: * The cell is the smallest unit of life * Cells make up all living things * New cells can arise only from preexisting cells
Cell theory
▪ Structurally simple
▪ Typically smaller
▪ Lack membrane-bound organelles
▪ Include bacteria and Archaea
prokaryote cell
▪ Structurally complex
▪ Typically larger
▪ Have membrane-bound organelles
▪ Found in plants, animals, fungi, protist
Eukaryote Cell
As a cell gets larger, its surface area increases far more slowly than its volume
Surface to volume ratio
(height × width × number of sides) Volume 2 216
(height × width × length) Surface-to-volume ratio 1 216
(surface area:volume) 6:1 1:1
▪ Most eukaryotic and prokaryotic cells are typically measured in micrometers (μm), which equal 10–6 meters
▪ They can be seen through either light or electron microscopes ▪ Micrographs are the photographs taken with the microscope
cell size
makes up part of the cell membrane
Phospholipid bilayer, cholesterol, carbohydrates (gives quality of fluid mosaic)
Functions of the Plasma membrane
- Maintainsn structural integrity of the cell
- Selectively permeable as it regulates movement of substances into and out of the cell
- Glycoproteins provide recognition between cells
- Receptors provide communication between cells
- Cell adhesion molecules stick cells together to form tissues and organs
Types of movement across the plasma membrane
- PASSIVE TRANSPORT
▪ Movement across the membrane that doesn’t require energy - Simple diffusion, facilitated diffusion, osmosis
- ACTIVE TRANSPORT
▪ Movement across the membrane that requires energy
Simple Diffusion
- Movement of a substance following a concentration gradient, from high concentration to low concentration
- End result is an equal distribution of the substance in the two areas
- Eliminatestheconcentrationgradient
Facilitated diffusion
- Movement of a substance from a region of higher concentration to a region of lower concentration with the aid of a membrane protein
- To cross a cell membrane, water-soluble substances need to be assisted or “facilitated” by carrier proteins
Osmosis
- Movement of water across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration
▪ The water molecules move to dilute the solution
Active Transport
- Movement from a region of lower to higher concentration with the aid of a carrier protein and energy, typically ATP
Endocytosis
- A region of the plasma membrane engulfs the substance to be ingested and then pinches off from the rest of the membrane, enclosing the substance in a vesicle, which travels through the cytoplasm
▪ Applies to large molecules, single-celled organisms, and droplets of fluid containing dissolved substances
Types of endocytosis
- Phagocytosis (cell eating): large particles or bacteria
- Pinocytosis (cell drinking): droplets of fluid
Exocytosis
- Large molecules are enclosed in membrane-bound vesicles, which travel to plasma membranes, where they are released to the outside
