Cell Structure and Function: A Comprehensive Guide
Cytoplasm
A jellylike fluid inside the cell in which the organelles are suspended.
Works with the nucleus to keep the cell alive.
Found in both prokaryotes and eukaryotes.
Organelles
A membrane-enclosed structure with a specialized function within a cell.
Nucleus
A cell structure that contains nucleic acids, the chemical instructions that direct all the cell’s activities.
Has coded for making proteins and other important molecules.
How does the DNA work in prokaryotic cells?
The DNA is not enclosed in a nucleus, but the cells have DNA that codes the same kind of instructions.
Nuclear Envelope
Double-membrane layer that surrounds the nucleus of a cell.
Structure of the Nuclear Envelope
Dotted with thousands of holes that allow material to move in and out of the nucleus.
Proteins, RNA, and other molecules move through the holes in the nuclear envelope to and from the rest of the cell.
Nucleolus
Small dense spot in the nucleus where ribosomes are first put together, then the ribosomes are used to build proteins.
Active Transport
Energy-requiring process that moves material across a cell membrane against a concentration difference.
Protein Pumps
Chemical energy is used to pump ions across the cell membrane.
Endocytosis
The membrane forms a pocket around a particle outside the cell.
Exocytosis
A vesicle inside the cell carries a particle to the cell membrane.
How do protein pumps work?
Protein pumps grab ions on one side of the membrane, change shape, and let go of them on the other.
How does endocytosis work?
Pocket pinches closed on the inside of the cell, forming a vesicle. The vesicle breaks loose, bringing the particle into the cell.
How does exocytosis work?
The membrane of the vesicle sticks to and becomes part of the cell membrane. The particle is forced out of the cell.
Isotonic
The concentration is the same inside and outside the cell.
Water molecules move at the same rate in both directions.
Hypertonic
The outside solution has a higher concentration than the solution inside the cell. Movement of water molecules out causes it to shrink.
Hypotonic
The outside solution has a lower concentration than the solution inside the cell. Movement of water molecules into the cell causes it to swell.
What is one of the most important jobs of the cell membrane?
To keep up the right balance between the liquid in the cell and the liquid around the cell.
How does the cell membrane keep track of the balance between liquid in the cell and liquid around the cell?
By keeping track of the movement of molecules across the cell membranes.
Diffusion
Movement of solutes from an area of higher concentration to an area of lower concentration to reach equilibrium.
Equilibrium
A condition in which molecules are spread evenly (equally).
What would happen if there were more of one substance on one side than the other?
If the substance can cross the cell membrane, its particles will diffuse toward the area of lower concentration.
The particles would keep moving to the other side until the sides are even.
Why do particles diffuse?
So they can maintain equilibrium so particles can move from both sides at equal rates.
Does diffusion need energy?
No.
Passive Transport
Movement of substances through a cell membrane without the use of cellular energy; includes diffusion, osmosis, and facilitated diffusion.
What do proteins do for things such as sugar glucose?
They act as carriers or protein channels.
Protein Channels
Proteins in the membrane whose role it is to pass molecules that cannot go through the membrane.
Facilitated Diffusion
Another type of passive transport, used for molecules that cannot readily diffuse through cell membranes.
Osmosis
Diffusion of water through a selectively permeable membrane
aquaporins
A transport protein in the plasma membrane of a plant or animal cell that specifically facilitates the diffusion of water across the membrane
osmotic pressure
Pressure that must be applied to prevent osmotic movement across a selectively permeable membrane
isotonic solution
A solution in which the concentration of solutes is essentially equal to that of the cell which resides in the solution
hypertonic solution
A solution in which the concentration of solutes is greater than that of the cell that resides in the solution.
hypotonic solution
Higher concentration of water compared to inside of the cell
Why must osmotic pressure be applied?
Pressure that must be applied to prevent osmotic movement across a selectively permeable membrane
can cause changes in the size of the central vacuole
hloroplasts
A structure in the cells of plants and some other organisms that captures
energy from sunlight and uses it to produce food.
How do chloroplasts turn energy into food?
Take energy from sunlight and change it into energy stored in food
What process do chloroplasts use ?
photosynthesis
photosynthesis
Plants and other single-celled organisms capture the energy of sunlight directly for storage and later use
chlorophyll
A green pigment located within the chloroplasts of plants. Can participate directly in the light reactions, which convert solar energy to chemical energy.
mitochondria
changes chemical energy stored in food into compounds that are easier for the cell to use.
Surrounded by outer membrane and inner membrane
Inner and outer membrane of mitochondria
Inner membrane is much larger than the outer one The inner membrane is folded up inside the membrane
cell membrane
A cell structure that controls which substances can enter or leave the cell.
selective permeability
a process in which a membrane allows some molecules to pass through while keeping others out
cell wall
A rigid structure that surrounds the cell membrane and provides support to the cell
mitochondrion
Cell organelle that converts the chemical energy stored in food into compounds that are more convenient for the cell to use
lipid bilayer
a flexible double-layered sheet that makes up the cell membrane and forms a barrier between the cell wall and it’s surroundings
proteins
Build and repair tissues, Supply energy, when needed
Proteins role
help carry out chemical reactions and make up important parts of the cell
Ribosomes
Cytoplasmic organelles at which proteins are synthesized.
How do ribosomes make protein?
by following coded directions from DNA
Where can ribosomes be found?
Either floating freely in the cell or attached to the endoplasmic reticulum
Endoplasmic Reticulum
A system of membranes that is found in a cell’s cytoplasm and that assists in the production, processing, and transport of proteins and in the production of lipids.
Proteins & other materials are also shipped and put together on the ER
Where is a Golgi Apparatus found?
In Eukaryotic Cells
What does the Golgi Apparatus look like?
a stack of flat membrane sacs
How are proteins told where they need to go?
They have molecular tags that point out where they need to go
What does the ER do when they have read the signals of the proteins?
Bundle the proteins into tiny vesicles
How are proteins transferred to the Golgi Apparatus?
The vesicles of proteins bud from the ER snd carry the proteins to the Golgi Apparatus
What happens to some of the proteins while in the Golgi Apparatus?
Some of them are stored in the cell, while others are sent outside of the cell.
Rough ER
Covered in ribosomes and is responsible for the synthesis and transport of proteins and glycoproteins.
Where are proteins made?
On the rough ER
Why is it called the Rough ER?
because ribosomes on it’s surface make it bumpy
What is the course of proteins after they are made?
Leave the ribosomes and enter the rough ER
What do enzymes inside of the rough ER?
Make changes to some of the proteins
What do proteins made on the rough ER do?
Some leave the cell while membrane proteins and proteins go to lysosomes and other specialized locations inside the cell.
Smooth ER
Does not have ribosomes on surface, makes enzyme allowing numerous functions
Why is it called the Smooth ER?
because there are no ribosomes on it’s surface
How are specialized tasks preformed in many cells of the Smooth ER?
Groups of enzymes that do specialized tasks
What are some specialized tasks performed by The Smooth ER’s group of enzymes?
make membrane lipids and get rid of toxins such as drugs
What is the role of the liver cell?
getting rid of drugs
How does the liver cell perform it’s role?
by large amounts of smooth er
Golgi Apparatus
A system of membranes that modifies and packages proteins for export by the cell
Where is a Golgi Apparatus found?
In Eukaryotic Cells
What does the Golgi Apparatus look like?
a stack of flat membrane sacs
How are proteins told where they need to go?
They have molecular tags that point out where they need to go
What does the ER do when they have read the signals of the proteins?
Bundle the proteins into tiny vesicles
How are proteins transferred to the Golgi Apparatus?
The vesicles of proteins bud from the ER snd carry the proteins to the Golgi Apparatus
What happens to some of the proteins while in the Golgi Apparatus?
Some of them are stored in the cell, while others are sent outside of the cell.
How does the liver cell perform it’s role?
by large amounts of smooth er
Golgi Apparatus
A system of membranes that modifies and packages proteins for export by the cell
Where is a Golgi Apparatus found?
In Eukaryotic Cells
What does the Golgi Apparatus look like?
a stack of flat membrane sacs
How are proteins told where they need to go?
They have molecular tags that point out where they need to go
What does the ER do when they have read the signals of the proteins?
Bundle the proteins into tiny vesicles
How are proteins transferred to the Golgi Apparatus?
The vesicles of proteins bud from the ER snd carry the proteins to the Golgi Apparatus
What happens to some of the proteins while in the Golgi Apparatus?
Some of them are stored in the cell, while others are sent outside of the cell.
Microscope
An instrument that makes small objects look larger
cells
Basic structural and functional unit of organisms
all have organelles that carry out their own special functions
cell theory
…, idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells
Light microscope
Microscope lets light pass through an object
Has two lenses that focus light to form an image
Some of light scatters as it passes through the lenses
Drawback to scattering light
light microscopes can make clear images of objects only to a magnification of 1000 times
cell stains
most living cells are nearly transparent so using chemical stains or dyes it makes it possible to see specimens under a light microscope
electron microscopes
Uses Electron beams instead of a light source, specimen are placed in a vacuum inside the microscope so only dead specimens can be observe
can show up to 1 billionth of a meter in size
Microscope
An instrument that makes small objects look larger
cells
Basic structural and functional unit of organisms
all have organelles that carry out their own special functions
cell theory
…, idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells
Light microscope
Microscope lets light pass through an object
Has two lenses that focus light to form an image
Some of light scatters as it passes through the lenses
Drawback to scattering light
light microscopes can make clear images of objects only to a magnification of 1000 times
cell stains
most living cells are nearly transparent so using chemical stains or dyes it makes it possible to see specimens under a light microscope
electron microscopes
Uses Electron beams instead of a light source, specimen are placed in a vacuum inside the microscope so only dead specimens can be observe
can show up to 1 billionth of a meter in size
Transmission microscope
The electrons slide through a very thin sample of tissue and have to take a quick photo because the sample quickly disinegrates.
scanning microscopes
pencil like beam of electrons is scanned over the surface of the specimen. produces stunning 3-D images
nucleus
A part of the cell containing DNA and RNA and responsible for growth and reproduction
DNA
A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell’s proteins.
cells
Basic structural and functional unit of organisms
all have organelles that carry out their own special functions
cell theory
…, idea that all living things are composed of cells, cells are the basic units of structure and function in living things, and new cells are produced from existing cells
Light microscope
Microscope lets light pass through an object
Has two lenses that focus light to form an image
Some of light scatters as it passes through the lenses
Drawback to scattering light
light microscopes can make clear images of objects only to a magnification of 1000 times
cell stains
most living cells are nearly transparent so using chemical stains or dyes it makes it possible to see specimens under a light microscope
electron microscopes
Uses Electron beams instead of a light source, specimen are placed in a vacuum inside the microscope so only dead specimens can be observe
can show up to 1 billionth of a meter in size
Transmission microscope
The electrons slide through a very thin sample of tissue and have to take a quick photo because the sample quickly disinegrates.
scanning microscopes
pencil like beam of electrons is scanned over the surface of the specimen. produces stunning 3-D images
nucleus
A part of the cell containing DNA and RNA and responsible for growth and reproduction
DNA
A double-stranded, helical nucleic acid molecule capable of replicating and determining the inherited structure of a cell’s proteins.
RNA
(biochemistry) a long linear polymer of nucleotides found in the nucleus but mainly in the cytoplasm of a cell where it is associated with microsomes
Eukaryotes
Cells that contain nuclei (bacteria)
prokaryotes
organisms whose cells lack a nucleus
structure of a prokaryote
small and more simple than eukaryote
DNA floats freely in the cell
Why are prokaryotes considered living organisms?
They Grow, Reproduce, respond to the environment, and guid along surfaces / swim through liquids
What is the structure of a eukaryote?
Larger and more complex than prokaryotic cells.
Most have dozens of structures and membranes inside of them
DNA is contained in the nucleus
What is a type of single celled eukaryote?
Protist
Protist
A kingdom made up of unicellular orgainisms with complex internal cellular structures
What are the types of multicellular organisms?
plants, animals, and fungi