Cell Structure II Textbook Flashcards
What does protoplasm refer to?
It is a collective term that references the nucleus and the cytoplasm.
It refers to all the substances within the cell.
What is the cytoplasm?
the region of the protoplasm outside of the nucleus and the location where nutrients are absorbed, transported and processed
What is the cell membrane?
the edge of the living cell.
composed of a double layer of lipid or fat molecules and embedded proteins.
It provides the cell with a connection to the external environment.
What is the function of the cell membrane?
It holds the contents of the cell in place and regulates the movement of molecules into and out of the cell.
It also contains receptor sites, which serve as docks for the entry of molecules that affect cell activity.
Why is the cell membrane selectively permeable?
Because it only lets certain things pass through.
Ex. Water & Small non-polar molecules (O2, CO2)
Prevents charged particles (H+, Na+, Cl-, amino acids, glucose) from diffusing through
What are embedded proteins in a cell membrane?
Wholly or partially embedded proteins within the phospholipid bilayer.
Form protein pores to allow small charged ions and large polar molecules to diffuse in/out of the cell
Act as pumps - actively transporting molecules (requires energy - ATP)
What are glycolipids?
Carbohydrates attached to a phospholipid
Serve in cell recognition (antigens) and receptor (docking) sites on the cell membrane
Only found on the cell membrane
What are glycoproteins?
Carbohydrates attached to an embedded protein
Serve in cell recognition (antigens) and receptor (docking) sites on the cell membrane
Only found on the cell membrane
How is cholesterol used in the cell membrane?
it helps maintain the structure and fluidity of the membrane
The cholesterol molecules disturb the close packing of the phospholipids
Reduces permeability to some solutes
What is the nucleus?
It is the control center of the cell.
Controls metabolic functioning of the cell & determines the cell’s characteristics.
It contains chromatin – DNA & proteins – of the cell
What is the nuclear envelope?
it is the membrane that encloses the nucleus
What is a nuclear pore?
An opening in the nuclear envelope to allow large molecules to pass from the nucleoplasm to the cytoplasm.
What are eukaryotic cells?
Cells that have a true nuclear membrane are referred to as eukaryotic cells.
- Plant and animal cells are eukaryotic
What are prokaryotic cells?
Cells that lack a nuclear envelope.
Bacteria and blue-green algae are prokaryotic cells They are the oldest known forms of life.
The hereditary material in prokaryotic cells is spread throughout the nucleus.
What are Chromosomes?
Threadlike structures of DNA that contain genes.
What is Chromatin?
The genetic material of a cell
Made of DNA and Proteins
During cell division, chromatin condenses to form the chromosomes.
What are genes?
units of instruction that determine the specific traits of an individual.
What is the nucleolus?
A small spherical structure located inside the nucleus.
The entire function of the nucleolus is not known but scientists believe that it is involved with the synthesis of proteins in the cytoplasm.
Specialized area of chromatin that produces rRNA which is a component of ribosomes
What are organelles?
Tiny structures within the cytoplasm of cells that carry out various functions to maintain the life process of a cell.
What are mitochondria?
One of the largest organelles within the cytoplasm.
They provide the cells with energy
Often referred to as the “power plant” of the cell.
They are the centers of cell respiration.
What are ribosomes?
One of the smallest of a cell’s organelles
They are the most numerous organelles within the cell.
Site of protein synthesis
Found attached to rough ER or free-floating in the cytoplasm.
What do attached ribosomes do?
Produce proteins for export (exocytosis) out of the cell
What do free ribosomes do?
produce proteins to be used inside the cell
What is the Endoplasmic Reticulum?
A series of canals that carry materials throughout the cytoplasm.
Composed of parallel membranes.
Rough ER - has ribosomes attached to the surface, acts as transport of polypeptides through the cell
Rough ER - Where protein folding occurs
Smooth ER - Does not have ribosomes attached - acts as a transport (like rough ER)
Smooth ER - Contains enzymes to detoxify drugs and alcohol and to synthesize lipids.
What does detoxify mean?
To inactivate potentially harmful drugs by converting them to water-soluble compounds that can be eliminated from the body in urine.
What is the Golgi Apparatus?
Looks like a stack of pancakes.
Receives transport vesicles from the ER
Protein molecules are packaged and stored inside the golgi apparatus
Eventually, the pancakes filled with proteins move toward the cell membrane
Once the golgi apparatus attaches itself to the cell membrane, small packets, called vesicles, are released
What are the functions of the Golgi Apparatus?
Sorting and repackaging center
packages proteins into secretory vesicles to protein can be secreted out of the cell through exocytosis
Modifies polypeptides (adds glycogen/sugar chains to protein)
Produces lysosomes
What are vacuoles?
fluid-filled spaces that store sugars, minerals, and proteins in the cytoplasm of the cell.
What are vesicles?
Small vacuoles that can be made at the ER, the Golgi Apparatus, or from the folding of the cell membrane as in endocytosis
What types of vesicles are there?
Transport Vesicles - Made at ER and transport polypeptides to the Golgi Apparatus
Secretory Vesicles - Made at the Golgi Apparatus and transport product to the cell membrane for secretion out of the cell by exocytosis.
What are lysosomes?
Saclike structures that break down large molecules.
They are formed by the golgi apparatus.
Chemicals from the lysosome can digest the cell that houses them - often called suicide cells
An important part of the human body’s defense mechanism.
Special type of vesicle
What is pinocytosis?
A type of endocytosis (active transport - requires ATP)
A method of endocytosis where small particles that are suspended in extracellular fluid (outside the cell) are brought inside the cell by the folding of the cell membrane resulting in a suspension of the particles in a small vesicle
Called Cell Drinking
What is phagocytosis?
A type of endocytosis (requires ATP)
where the cell engulfs a larger particle giving rise to a phagosome where enzymes then digest the contents
Called cell eating
Describe the intracellular transport of proteins
Proteins synthesized in ribosome
packaged in the rough ER for transport
Protein is transported via transport vesicle to the Golgi Apparatus
Protein is modified in the Golgi Apparatus
THEN
1) Protein is transported via secretory vesicle to the cell membrane for secretion
OR
2) Protein is exported to a lysosome where it is digested and the wasted is stored in the vacuole
What is Flagella?
A whip like tail used for motility (movement)
Found in sperm - the tail is a flagella
What is Cilia?
Tiny hairs that project from the cell membrane
Used mainly as sweepers in the human body
found in the trachea and bronchi (airways) to sweep out debris before it can reach the lungs
What is the cytoskeleton?
A cellular scaffold or skeleton contained within the cytoplasm - made out of proteins
Maintains the shape of the cell, protects the cell, enables cellular movement, and plays a role in intracellular transport
What is diffusion?
The movement of molecules from an area of high concentration to an area of low concentration until the molecules are equally distributed.
How does a cell increase its surface area?
it folds or divides once it gets too big
What is osmosis?
The diffusion of water, the movement of water molecules from an area of high concentration to an area of low concentration across a differentially permeable membrane
What factors affect diffusion?
1) Increased temperature increases kinetic molecular motion and so increases the rate of diffusion
2) Smaller molecule will diffuse more quickly
3) increasing the concentration gradient will increase the rate of diffusion.
What is osmotic pressure?
the pressure generated by osmotic flow of water.
eg. keeps plants from wilting
What is passive transport?
No Energy (ATP) is required
2 types
Diffusion (osmosis)
Facilitated Transport
What is facilitated transport?
Diffusion of large polar molecules (glucose, amino acids, and fatty acids) and ions through carrier proteins (protein pore or protein channel)
What is active transport?
Energy (ATP) is required
may move substances against a concentration gradient (low to high concentration)
What is a Na+/K+ pump?
A form of active transport - requires ATP and a carrier protein
pumps Na+ and K+ into and out of the cell
What is exocytosis?
A type of active transport (requires ATP)
it is a process where substances are secreted from the cell when the vesicle fuses with the inner side of the cell membrane
What is the problem with a small SA:Volume ratio?
If the SA:Volume ratio is too small, then transport across the membrane can’t keep up (food in / waste out)
