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
Active Transport
Direction of movement: solute will move from an area of low concentration to an area of high concentration
Does the cell need to input energy to move a substance across a membrane by Facilitated Diffusion? yes, ATP Does movement of the solute across a membrane require the use of a transport protein? yes
Endocytosis
Endocytosis
a The cell transports substances into the cell .
b The substance to be moved is packed into a membrane encased sac called a vesicle .
Exocytosis
Exocytosis
a The cell transports substances out of the cell.
b The substance being moved is packed into a vesicle.
When the vesicle reaches the plasma membrane it fuses with the plasma membrane and the substance being transported is released out of the cell.
Nucleus
Nucleus
describe the structure of the nucleus (or draw a diagram in your notes)
double membrane, nuclear pore, nucleolus,
DNA in chromatin
Function: stores DNA, DNA replication, RNA synthesis
Ribosome
Ribosome
Structure: large subunit & small subunit, made of 50% rRNA and 50% protein; Ribosomes are organelles composed of proteins and rRNA.
Function: makes proteins or protein synthesis
Location: free in cytoplasm or on rough ER
Ribosomes are often attached to the endoplasmic reticulum, but they also may occur free within the cytoplasm, either singly or in groups called polyribosomes. Proteins synthesized at ribosomes attached to the endoplasmic reticulum have a different destination from that of proteins manufactured at ribosomes free in the cytoplasm
Is the ribosome surrounded by a membrane (membrane-bound)? No
What is the difference between Prokaryotic and Eukaryotic ribosomes?
Prokaryotic ribosomes: have small 60s ribosomes
Eukaryotic ribosomes: have large 80s ribosomes
The Endomembrane System
What is the Endomembrane System?
-a series of membranes in the cytoplasm of the cell
Proteins and lipids are made in some of these membranes and transported to other membranes
The endomembrane system consists of:
the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, and vesicles (tiny membranous sacs)
This system compartmentalizes the cell so that chemical reactions are restricted to specific regions. The vesicles transport molecules from one part of the system to another.
Name the 5 structures/ organelles that are part of the Endomembrane System
- Smooth Endoplasmic Reticulum = SER
- Rough Endoplasmic Reticulum = RER
- Vesicles
- Golgi
- Lysosomes
Smooth Endoplasmic Reticulum (SER)
Structure: tubular sheets of membrane continuous with RER, no ribosomes
Function: *main function: lipid and membrane synthesis Ca++ storage detoxification carbohydrate metabolism
Rough Endoplasmic Reticulum (RER)
Structure: sheets of membrane, contains ribosomes on surface. RER is continuous with nuclear membrane Protein synthesis occurs on Ribosomes on RER
Function:
insertion of proteins into membrane
After a protein is made in the RER where does it go next? golgi
How does it get there? vesicles
Golgi apparatus
Structure:
stack of membranes
Function:
proteins and lipids from the RER have sugars attached to them. This is called glycosylation .
Proteins are sorted , packed into vesicles and are then are either sent to their final location or are secreted out of the cell.
What is a vesicle?
small membrane sacs that transport substances between membranes or organelles
Lysosome
How do substances get to the lysosome?
Vesicles transport substances to be broken down
What happens to these substances once they are inside the lysosome?
Contains digestive enzymes that break down macromolecules, nutrients and cell parts so they can be used/ recycled in the cell
Lysosomes, membranous sacs produced by the Golgi apparatus, contain hydrolytic enzymes.
Lysosomes are found in all cells of the body but are particularly numerous in white blood cells that engulf disease-causing microbes. When a lysosome fuses with such an endocytic vesicle, its contents are digested by hydrolytic enzymes into simpler subunits, which then enter the cytoplasm. In a process called autodigestion, parts of a cell may be broken down by the lysosomes.
Cytoskeleton
What is the cytoskeleton?
network of molecules inside the cell
What is the cytoskeleton made of?
- actin microfilaments
- intermediate filaments
- microtubules
Function:
- gives structure to the cell and organelles
- involved in intracellular transport
- involved in cell movement
Cilia and Flagella
cilia and flagella are made of: microtubules
Function:
- to move a cell through a liquid
- to move air/ water across a surface
Structure of cilia and flagella
- microtubules
- plasma membrane
Mitochondria
Structure:
the liquid part is called the: matrix
the inner membrane is called the: cristae
Function:
cellular respiration
During respiration food molecules are broken down to make ATP. The cell uses this molecule as energy to carry out enzyme reactions and metabolism.
What is Aerobic Cellular Respiration?
Function:
production of ATP from the breakdown of sugar or other food molecules
Part 1: Glycolysis Where does this process occur in the cell? cytoplasm Does this process require O2? NO
Part 2: Citric Acid Cycle Where does this process occur in the cell? mitochondria Does this process require O2? NO
Part 3: Electron transport Chain Where does this process occur in the cell? mitochondrial membrane Does this process require O2? YES
Summary of Aerobic Respiration Does it require Oxygen? YES Where does it occur? cytoplasm & 3. mitochondria Is it an efficient way to produce energy for the cell? YES
Why?
1 glucose can be broken down to produce up to 38 ATP (large amount of energy)!
What other molecules besides glucose (a sugar) can be used for cellular respiration?
- Other Carbohydrates: sugars, starch
- Proteins
- Lipids: fats and oils
How can a cell make ATP without O2?
Name of process: Anaerobic Respiration (Fermentation)
Where does this process occur in the cell?
cytoplasm
Parts of Fermentation:
- glycolysis
- fermentation reactions
Function:
short burst of energy
Is Anaerobic Respiration an efficient way to produce energy for the cell? Why?
No, breaks down 1 glucose to make 2 ATP (small amount of energy) and lactic acid in human cells
enzymes
Type of molecule?
proteins
What does an enzyme do in the cell?
Enzymes are specific to what substrate they work on. They carry out 1 specific type of chemical reaction.
Enzymes have active sites where a substrate binds
Enzymes are not used up in a reaction but instead are recycled and reused.
Enzymes are the workhorses of the cell: they carry out the chemical reactions involved in metabolism
Degradation
a substrate is broken down to smaller parts
Synthesis
substrates are combined to produce a larger product
