Chapter 3: Cell Structure Flashcards
Cell Theory
- the cell is the smallest unit of life
- all living things are made of cells
- every cell comes from a pre-existing cell
Why are cells small?
-Small cells have a larger amount of surface area compared to volume.
An increase in surface area allows:
- more nutrients to enter a cell wastes to exit a cell
- There is a limit to how large a cell can be and still be efficient and metabolically active. Metabolism requires nutrients to enter the cell and wastes to exit the cell.
All Cells Contain
- plasma membrane: separates the living part of a cell from the non-living environment
- Cytoplasm
- DNA
- Ribosomes: not surrounded by a membrane
The Endosymbiont Theory
Primitive Eukaryotes engulfed bacteria which eventually lost the ability to live on their own and became organelles
Which organelles evolved in this manner?
- Mitochondria
- Chloroplasts
organelle
Small membranous structure in the cytoplasm of eukaryotic cells having a specific structure and function.
Mitchondria (heterotrophic cells)
originated from purple nonsulfur bacteria (aerobic, heterotrophic cells).
Advantage: allows cell to carry out aerobic respiration which produces much more energy than anaerobic cells
Chloroplasts
originated from cyanobacteria (autotrophic cells).
Advantage: cell can produce its own sugar/ food by photosynthesis
Plasma Membrane
Plasma Membrane
Structure:
phospholipid bilayer with proteins attached and embedded in it.
heads face the watery sides of the membrane
polar heads oriented to the outside and inside of the cell
hydrophobic tails oriented inward toward each other
aquaporins: proteins channels involved in the transport of lipids
Function:regulates entry into and out of the cell
The phospholipid bilayer contains cholesterol to give it strength.
Some proteins and lipids have sugars attached to them. A protein with a sugar attached to it is called a glycoprotein .
The plasma membrane is selectively permeable/ semipermeable. This means that: only certain substances can pass directly through the lipid bilayer by themselves
what can and cant pass through the plasma membrane
What kind of molecules can pass through the plasma membrane by themselves (without using a transport protein)?
water
small, uncharged
What kind of molecules can’t pass through the plasma membrane by themselves (they need to use a transport protein in order to cross the membrane)?
charged ions
charged molecules
large molecules
How do things move across the plasma membrane?
Diffusion/ simple diffusion osmosis facilitated transpost active transport endocytosis & exocytosis
diffusion
Direction of movement: substance moves from an area of higher concentration to an area of lower concentration.
Movement is down the concentration gradient. (like rolling downhill)
Does the cell need to spend energy to move the substance across the membrane? no
osmosis
- the diffusion of water.
Water moves from an area of higher concentration of water to an area of lower concentration of water.
Does the cell need to spend energy to move the water across the membrane?
no energy input is needed
What is the difference between osmosis and diffusion?
Diffusion is the movement of solute molecules from a higher concentration to a lower concentration.
b Osmosis is the movement of water molecules from a high concentration to a low concentration.
Diffusion across a membrane
Direction of movement: solute will move from an area of high concentration to an area of low concentration
Does the cell need to input energy to move a substance across a membrane by diffusion? no energy input needed Does movement of the solute across a membrane require the use of a transport protein? no
Facilitated Diffusion
Direction of movement: solute will move from an area of high concentration to an area of low concentration
Does the cell need to input energy to move a substance across a membrane by Facilitated Diffusion? no Does movement of the solute across a membrane require the use of a transport protein? yes
