Chapter 3- Cells
Why is the cell membrane called selectively permeable? What does this mean?
Determines what goes in and out of the cell membrane.
What process could be used to move many molecules at once or a large object such as a cell into a cell? What about moving the same things out of a cell?
1. Endocytosis brings things into the cell while exocytosis releases things out of the cell. They move things in the opposite direction. 2. These types of transport are useful when a cell needs to move large items (such as pieces of cells or even a whole small cell) or many molecules at once across the membrane.
Name and explain the 2 major events that are thought to have occurred in the endosymbiotic theory.
1. Folding in of the cell membrane to make organelles 2. Engulfing of cells that eventually became organelles
Which type of transport moves molecules against the concentration gradient and requires ATP?
Active Transport
What cells are likely to have a lot of mitochondria?
Active cells like muscle cells!
What is the function of Mitochondria?
Mitochondria are membrane-bound organelles where energy in the form of ATP is made. Cells that are very active will have more mitochondria.
How are phospholipids aligned in a membrane?
The lipid bilayer(head(outside)-tail(inside)-tail-head) is made up of many phospholipids that align together.
What is housed in the nucleus?
The nucleus contains the cell's DNA and directs the synthesis of ribosomes and proteins
What is the function of Smooth Endoplasmic Reticulum?
The smooth endoplasmic reticulum is where lipids are synthesized. Notice there are no ribosomes.
What are the functions of the following structures: rough endoplasmic reticulum (why is it called rough) and ribosomes?
1. Rough endoplasmic reticulum looks "rough" under the microscope because it is studded with ribosomes Ribosomes are units that read RNA into proteins therefore the RER is used for protein synthesis
Explain what the constraint on the size of the cell is (why are almost all cells microscopic)?
Cell size is limited by the constraints of the cell surface area to volume ratio. As a cell increases in size, its surface area does not increase proportionately to its increase in volume. Cells need to move nutrients into the cell and excrete waste products back out. Cells larger than 500 microns do not have enough surface area to maintain cell function. Cells tend to be very small in order to increase their surface area in relation to their volume, this helps to absorb enough nutrients from their surroundings.
Which direction do molecules move during diffusion (think concentration gradient)?
During diffusion the molecules move from a higher to lower concentration
What theory that we studied does the mitochondria support based on its structure? Why?
Endosymbiotic theory-the mitochondria look like a prokaryotic cell that may have been engulfed as suggested by endosymbiosis.
What is the function of lysosomes?
Membrane- bound structures that house digestive molecules that allow intracellular digestion. Things inside the cells or things brought into the cell can be digested. For example bacteria can be engulfed and digested or a cell that is damaged can be engulfed in parts and digested.
What is the function of Cytoskeleton?
Protein scaffolding inside of cells that helps move things around the cell, helps cells to divide and gives the cell structure.
What are the two most common molecules that make up the cell membrane?
Proteins and Phospholipids
What is the function of Golgi Apparatus?
Proteins that are made are then sent to the golgi apparatus to be tagged, sorted and shipped within the cell. You can think of the golgi apparatus acting similar to a post office. Proteins from the RER go here once they are made.
