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2.1 Cell Structure: Subcellular Components

6 min readjanuary 2, 2023

Tejas Bhartiya

Tejas Bhartiya

Haseung Jun

Haseung Jun

Tejas Bhartiya

Tejas Bhartiya

Haseung Jun

Haseung Jun

Subcomponents

A cell has subcomponents, or organelles that perform different jobs! Even a tiny cell has a lot going on, so it needs different organelles to do different jobs. Let's take a look at these components 🧐

Plasma Membrane

Arguably the most important component! The is made up of a . This means that the membrane is made up of two lipid layers. Phospholipids also have two special properties. The head is , which means it likes water. The tail, on the other hand, is , meaning it doesn't like water. The membrane is then set up in a way so that the head is pointing towards the inside and outside of the cell (thus touching water) while the tail is nested between the sandwich of the heads.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-8MiP9EcY31nK.jpg?alt=media&token=dffa2fcc-ea7b-4ead-9e5d-b70c38415f9c

Image Courtesy of Wikimedia Commons

The membrane is also known as the , which means that the membrane is very flexible. It's also made up of different proteins along the membrane, and these proteins, which you'll learn in future units, act as transporters for things that can't go through the tail section.

Nucleus

The is the largest component of the cell. It's the "brain" of the cell and directs everything the cell does. It's also in charge of reproduction because it contains all the genetic information (DNA). The is where the are assembled within the DNA.

Ribosomes

are made of primarily ribosomal RNA (rRNA). They are the site of translation and are responsible for making all of the proteins for the cell. There are 2 kinds found in different locations.

Free are in the cytosol and make proteins that stay in the cell for various functions. Bound are attached to the rough endoplasmic reticulum and mainly make proteins for export. synthesize proteins according to mRNA sequences that they receive during the process of translation.

Endoplasmic Reticulum

The endoplasmic reticulum (ER), made up of two parts, serves to make other products that the cell needs. The smooth ER has many functions. It performs synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and stores calcium ions.

The rough ER, is called rough because it has attached to its surface, making it "rough". It secretes proteins made by bound . Proteins then are moved to the , where they are wrapped in a transport vesicle to head to the .

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-yEgJoWaBRe3N.png?alt=media&token=ea384357-e3f4-4be9-81d2-1ee5c2ac12c8

Image courtesy of WikiMedia Commons.

The Golgi Apparatus

The , shown above, modifies, stores, and sends proteins that come from the rough ER. Things like glycoproteins are modified in the Golgi. There are 2 sides on the , cis and . enter the via the and depart via the . It is in the Golgi that proteins are packaged and distributed to desired locations. These proteins are packaged in little sacs called , which is pinched off from the Golgi. The Golgi is also involved in the production of .

Mitochondria

have a double membrane, which is a . The outer membrane is smooth, while the inner has many folds, called . These folds help to increase the surface area available for the Electron Transport Chain. The inside of the inner membrane is called the , which is the site of the . The creates ATP for the cell to use via cellular respiration. Because the also have their own circular DNA, most biologists think the was its own organism until it was swallowed by eukaryotes (us!). The structure of the is important to know because it comes in handy with cellular respiration. The mitochondrial contains an outer membrane and inner membrane, making up its double membrane. The inner membrane consists of folds called , which is where most of the ATP production happens. The fold increases surface area and thus efficiency. Inside the inner membrane is the matrix.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-xKY7slBVAsSe.jpg?alt=media&token=12a4de8e-4a79-429d-bb8a-d1b8e16aa480

Image Courtesy of Molecular Expressions

Lysosomes

hydrolyze most foods, amino acids, and other molecules. The inside of lysosome is extremely acidic. can digest foods by using or engulfing nutrients to digest them. The hydrolytic enzymes inside of the lysosome work to break down anything that comes into contact with it. The lysosome is also used to recycle and digest old or damaged parts of the cell. Think of it as the trash can of the cell! It's also in charge of , which is programmed cell death. Essentially, the lysosome bursts, causing the acid to kill the cell.

Vacuoles

are large which store many different things, such as food or water. Many unicellular eukaryotes have contractile to pump water out of the cell. Also, plants generally have a large central water vacuole which stores water and ions.

Chloroplast

The chloroplast is the site of photosynthesis. These organelles have a double membrane and have green pigments called that allow for the absorption of photons. The chloroplast is made up of the , or liquid filling of the chloroplast, and the , flat sacs of membranes that allow for the absorption of light. The chloroplast is in charge of photosynthesis.

Centrioles

are small, cylindrical components of the cell and are mostly active during cell division. You'll learn more about the role of in the mitosis unit, but basically, it pulls apart chromosomes by producing microtubules.

Plant Cells vs. Animal Cells

Plant cells have something called , which is made out of . It's mostly a protective outer layer other than the membrane. Animal cells don't have this. In contrast, animal cells have , while plant cells do not.

When thinking about the differences of plant cells and animal cells, also try to think about . On the AP exam, there will be questions that can only be answered if you can correctly identify if the cell is an animal, plant, or prokaryotic cell. That's why key identifiers are important to memorize.

Prokaryote 🧫Plant Cell 🌼Animal Cell 🐄
Cell wall

Also keep in mind, a prokaryotic cell does not have any subcomponents like a lysosome or golgi body. Instead it only has a , which acts like a tail to help movement. Other than that, a prokaryotic cell is pretty much an empty capsule with DNA and .

Now quiz time! Try to identify which cell is eukaryotic and which is prokaryotic! Remember to think about key components that give you an immediate hint, and look for those when looking at cell pictures!

Quick Quiz: Can you identify which Cell is Eukaryotic and which is Prokaryotic?

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2FScreen%20Shot%202020-04-21%20at%201.58-AcHXeIbtZJEw.png?alt=media&token=1f1cfeec-6199-49d5-a1db-79bbdeccb7c3

Image courtesy of Flickr.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2FScreen%20Shot%202020-04-21%20at%201.59-M5HLYCh0UPEo.png?alt=media&token=2078912e-7453-4b72-8f66-0583f8c4cab4

Image courtesy of Wikipedia.org.

💥

💥 💥 💥 💥 💥

Answer: First picture is eukaryotic, second picture is prokaryotic.


-----

Key Terms to Review (34)

Apoptosis

: Apoptosis is a process of programmed cell death that occurs in multicellular organisms. It's a way for the body to get rid of old, unnecessary, or damaged cells.

ATP (Adenosine Triphosphate)

: ATP is a high-energy molecule that stores and provides energy for many biochemical reactions in the cell.

Cell Walls

: Cell walls are rigid layers surrounding some types of cells providing structural support and protection. They're found outside the cell membrane in plant cells, bacteria, fungi, and some protists.

Cellulose

: Cellulose is a complex carbohydrate, or polysaccharide, that is composed of glucose units and forms the main component of plant cell walls.

Centrioles

: Centrioles are cylindrical structures found in most eukaryotic cells, involved in cellular division and the formation of spindle fibers that separate chromosomes during mitosis.

Chlorophyll

: Chlorophyll is a green pigment found in plants, algae, and cyanobacteria that absorbs light energy (specifically blue and red wavelengths) to carry out photosynthesis.

Chloroplasts

: Chloroplasts are organelles found in plant cells and some algae that conduct photosynthesis, where they absorb sunlight and use it in conjunction with water and carbon dioxide gas to produce food for the plant.

Cis Face

: The cis face is the receiving side of the Golgi apparatus where transport vesicles that have budded from the endoplasmic reticulum fuse with the Golgi membrane and empty their cargo into the lumen.

Cristae

: Cristae are internal compartments formed by the inner membrane folding over itself within mitochondria. They provide an increased surface area for chemical reactions that produce ATP.

Endoplasmic Reticulum (ER)

: The endoplasmic reticulum is a network of tubules and sacs that function in protein synthesis, lipid metabolism, and detoxification processes.

Eukaryotic Cells

: These are complex cells with a nucleus and other organelles, all enclosed within membranes. They make up organisms in the Protista, Fungi, Plantae, and Animalia kingdoms.

Flagella

: Flagella are long, whip-like appendages that protrude from the cell body and help in movement. They can be found in both prokaryotic and eukaryotic cells.

Fluid-Mosaic Model

: The fluid-mosaic model describes the structure of cell membranes as a flexible layer made of lipid molecules interspersed with large protein molecules that act as channels through which other molecules enter and leave the cell.

Golgi Apparatus

: The Golgi apparatus is an organelle in eukaryotic cells that modifies, sorts, and packages proteins from the endoplasmic reticulum for storage within the cell or transport out of the cell.

Hydrophilic

: Hydrophilic substances are those that have an affinity for water, meaning they can mix with or dissolve in water.

Hydrophobic

: Hydrophobic refers to substances that repel or do not mix with water.

Krebs Cycle

: The Krebs Cycle, also known as the citric acid cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats and proteins into ATP.

Lysosomes

: Lysosomes are small organelles filled with enzymes that help break down waste materials and cellular debris inside cells.

Mitochondria

: Mitochondria are organelles within eukaryotic cells that produce most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy.

Mitochondrial Matrix

: The mitochondrial matrix is a gel-like substance inside mitochondria where certain metabolic reactions occur.

Nucleolus

: The nucleolus is a small, dense region within the nucleus of a cell where ribosomal RNA (rRNA) is produced and assembled with proteins to form ribosomes.

Nucleus

: The nucleus is an organelle found in eukaryotic cells that contains most of the cell's genetic material organized as DNA molecules along with proteins forming chromosomes.

Phagocytosis

: Phagocytosis is a type of endocytosis where a cell engulfs large particles or whole cells, either as a defense mechanism or as a way to obtain food.

Phospholipid Bilayer

: The phospholipid bilayer is a two-layered arrangement of phosphate and lipid molecules that form a cell membrane, the hydrophobic lipid ends facing inward and the hydrophilic phosphate ends face outward.

Plasma Membrane

: The plasma membrane is a thin layer that separates the inside of cells from their environment. It controls what enters or leaves the cell.

Prokaryotic Cells

: Prokaryotic cells are simple, small cells that lack a nucleus or other membrane-bound organelles. They are typically found in bacteria and archaea.

Ribosomal RNA (rRNA)

: rRNA is part of ribosomes, serving as structural components and also catalyzing peptide bond formation. It's essential for protein synthesis in all living organisms.

Ribosomes

: Ribosomes are tiny structures within cells where proteins are made (protein synthesis).

Stroma

: The stroma is the fluid-filled space surrounding the grana (stacks of thylakoids) within the chloroplast where the "dark" reactions of photosynthesis (Calvin cycle) occur.

Thylakoids

: Thylakoids are flattened sac-like membranes arranged in stacks (grana) inside the chloroplasts. They contain chlorophyll and play a crucial role in capturing light energy and converting it into chemical energy during photosynthesis.

Trans Face

: The trans face is the shipping side of the Golgi apparatus in a cell, where modified proteins and lipids are sorted and packaged into vesicles that transport them to their final destinations.

Transitional ER

: The transitional endoplasmic reticulum (ER) is a region of the ER that specializes in the final steps of protein and lipid synthesis, including packaging these molecules into transport vesicles.

Vacuoles

: Vacuoles are membrane-bound sacs within the cytoplasm of a cell that function in several different ways including isolating materials that might be harmful or storing waste products.

Vesicles

: Vesicles are small membrane-bound sacs that function in moving materials within a cell as well as interactions between cells.

2.1 Cell Structure: Subcellular Components

6 min readjanuary 2, 2023

Tejas Bhartiya

Tejas Bhartiya

Haseung Jun

Haseung Jun

Tejas Bhartiya

Tejas Bhartiya

Haseung Jun

Haseung Jun

Subcomponents

A cell has subcomponents, or organelles that perform different jobs! Even a tiny cell has a lot going on, so it needs different organelles to do different jobs. Let's take a look at these components 🧐

Plasma Membrane

Arguably the most important component! The is made up of a . This means that the membrane is made up of two lipid layers. Phospholipids also have two special properties. The head is , which means it likes water. The tail, on the other hand, is , meaning it doesn't like water. The membrane is then set up in a way so that the head is pointing towards the inside and outside of the cell (thus touching water) while the tail is nested between the sandwich of the heads.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-8MiP9EcY31nK.jpg?alt=media&token=dffa2fcc-ea7b-4ead-9e5d-b70c38415f9c

Image Courtesy of Wikimedia Commons

The membrane is also known as the , which means that the membrane is very flexible. It's also made up of different proteins along the membrane, and these proteins, which you'll learn in future units, act as transporters for things that can't go through the tail section.

Nucleus

The is the largest component of the cell. It's the "brain" of the cell and directs everything the cell does. It's also in charge of reproduction because it contains all the genetic information (DNA). The is where the are assembled within the DNA.

Ribosomes

are made of primarily ribosomal RNA (rRNA). They are the site of translation and are responsible for making all of the proteins for the cell. There are 2 kinds found in different locations.

Free are in the cytosol and make proteins that stay in the cell for various functions. Bound are attached to the rough endoplasmic reticulum and mainly make proteins for export. synthesize proteins according to mRNA sequences that they receive during the process of translation.

Endoplasmic Reticulum

The endoplasmic reticulum (ER), made up of two parts, serves to make other products that the cell needs. The smooth ER has many functions. It performs synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, and stores calcium ions.

The rough ER, is called rough because it has attached to its surface, making it "rough". It secretes proteins made by bound . Proteins then are moved to the , where they are wrapped in a transport vesicle to head to the .

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-yEgJoWaBRe3N.png?alt=media&token=ea384357-e3f4-4be9-81d2-1ee5c2ac12c8

Image courtesy of WikiMedia Commons.

The Golgi Apparatus

The , shown above, modifies, stores, and sends proteins that come from the rough ER. Things like glycoproteins are modified in the Golgi. There are 2 sides on the , cis and . enter the via the and depart via the . It is in the Golgi that proteins are packaged and distributed to desired locations. These proteins are packaged in little sacs called , which is pinched off from the Golgi. The Golgi is also involved in the production of .

Mitochondria

have a double membrane, which is a . The outer membrane is smooth, while the inner has many folds, called . These folds help to increase the surface area available for the Electron Transport Chain. The inside of the inner membrane is called the , which is the site of the . The creates ATP for the cell to use via cellular respiration. Because the also have their own circular DNA, most biologists think the was its own organism until it was swallowed by eukaryotes (us!). The structure of the is important to know because it comes in handy with cellular respiration. The mitochondrial contains an outer membrane and inner membrane, making up its double membrane. The inner membrane consists of folds called , which is where most of the ATP production happens. The fold increases surface area and thus efficiency. Inside the inner membrane is the matrix.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-xKY7slBVAsSe.jpg?alt=media&token=12a4de8e-4a79-429d-bb8a-d1b8e16aa480

Image Courtesy of Molecular Expressions

Lysosomes

hydrolyze most foods, amino acids, and other molecules. The inside of lysosome is extremely acidic. can digest foods by using or engulfing nutrients to digest them. The hydrolytic enzymes inside of the lysosome work to break down anything that comes into contact with it. The lysosome is also used to recycle and digest old or damaged parts of the cell. Think of it as the trash can of the cell! It's also in charge of , which is programmed cell death. Essentially, the lysosome bursts, causing the acid to kill the cell.

Vacuoles

are large which store many different things, such as food or water. Many unicellular eukaryotes have contractile to pump water out of the cell. Also, plants generally have a large central water vacuole which stores water and ions.

Chloroplast

The chloroplast is the site of photosynthesis. These organelles have a double membrane and have green pigments called that allow for the absorption of photons. The chloroplast is made up of the , or liquid filling of the chloroplast, and the , flat sacs of membranes that allow for the absorption of light. The chloroplast is in charge of photosynthesis.

Centrioles

are small, cylindrical components of the cell and are mostly active during cell division. You'll learn more about the role of in the mitosis unit, but basically, it pulls apart chromosomes by producing microtubules.

Plant Cells vs. Animal Cells

Plant cells have something called , which is made out of . It's mostly a protective outer layer other than the membrane. Animal cells don't have this. In contrast, animal cells have , while plant cells do not.

When thinking about the differences of plant cells and animal cells, also try to think about . On the AP exam, there will be questions that can only be answered if you can correctly identify if the cell is an animal, plant, or prokaryotic cell. That's why key identifiers are important to memorize.

Prokaryote 🧫Plant Cell 🌼Animal Cell 🐄
Cell wall

Also keep in mind, a prokaryotic cell does not have any subcomponents like a lysosome or golgi body. Instead it only has a , which acts like a tail to help movement. Other than that, a prokaryotic cell is pretty much an empty capsule with DNA and .

Now quiz time! Try to identify which cell is eukaryotic and which is prokaryotic! Remember to think about key components that give you an immediate hint, and look for those when looking at cell pictures!

Quick Quiz: Can you identify which Cell is Eukaryotic and which is Prokaryotic?

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2FScreen%20Shot%202020-04-21%20at%201.58-AcHXeIbtZJEw.png?alt=media&token=1f1cfeec-6199-49d5-a1db-79bbdeccb7c3

Image courtesy of Flickr.

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2FScreen%20Shot%202020-04-21%20at%201.59-M5HLYCh0UPEo.png?alt=media&token=2078912e-7453-4b72-8f66-0583f8c4cab4

Image courtesy of Wikipedia.org.

💥

💥 💥 💥 💥 💥

Answer: First picture is eukaryotic, second picture is prokaryotic.


-----

Key Terms to Review (34)

Apoptosis

: Apoptosis is a process of programmed cell death that occurs in multicellular organisms. It's a way for the body to get rid of old, unnecessary, or damaged cells.

ATP (Adenosine Triphosphate)

: ATP is a high-energy molecule that stores and provides energy for many biochemical reactions in the cell.

Cell Walls

: Cell walls are rigid layers surrounding some types of cells providing structural support and protection. They're found outside the cell membrane in plant cells, bacteria, fungi, and some protists.

Cellulose

: Cellulose is a complex carbohydrate, or polysaccharide, that is composed of glucose units and forms the main component of plant cell walls.

Centrioles

: Centrioles are cylindrical structures found in most eukaryotic cells, involved in cellular division and the formation of spindle fibers that separate chromosomes during mitosis.

Chlorophyll

: Chlorophyll is a green pigment found in plants, algae, and cyanobacteria that absorbs light energy (specifically blue and red wavelengths) to carry out photosynthesis.

Chloroplasts

: Chloroplasts are organelles found in plant cells and some algae that conduct photosynthesis, where they absorb sunlight and use it in conjunction with water and carbon dioxide gas to produce food for the plant.

Cis Face

: The cis face is the receiving side of the Golgi apparatus where transport vesicles that have budded from the endoplasmic reticulum fuse with the Golgi membrane and empty their cargo into the lumen.

Cristae

: Cristae are internal compartments formed by the inner membrane folding over itself within mitochondria. They provide an increased surface area for chemical reactions that produce ATP.

Endoplasmic Reticulum (ER)

: The endoplasmic reticulum is a network of tubules and sacs that function in protein synthesis, lipid metabolism, and detoxification processes.

Eukaryotic Cells

: These are complex cells with a nucleus and other organelles, all enclosed within membranes. They make up organisms in the Protista, Fungi, Plantae, and Animalia kingdoms.

Flagella

: Flagella are long, whip-like appendages that protrude from the cell body and help in movement. They can be found in both prokaryotic and eukaryotic cells.

Fluid-Mosaic Model

: The fluid-mosaic model describes the structure of cell membranes as a flexible layer made of lipid molecules interspersed with large protein molecules that act as channels through which other molecules enter and leave the cell.

Golgi Apparatus

: The Golgi apparatus is an organelle in eukaryotic cells that modifies, sorts, and packages proteins from the endoplasmic reticulum for storage within the cell or transport out of the cell.

Hydrophilic

: Hydrophilic substances are those that have an affinity for water, meaning they can mix with or dissolve in water.

Hydrophobic

: Hydrophobic refers to substances that repel or do not mix with water.

Krebs Cycle

: The Krebs Cycle, also known as the citric acid cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetyl-CoA derived from carbohydrates, fats and proteins into ATP.

Lysosomes

: Lysosomes are small organelles filled with enzymes that help break down waste materials and cellular debris inside cells.

Mitochondria

: Mitochondria are organelles within eukaryotic cells that produce most of the cell’s supply of adenosine triphosphate (ATP), used as a source of chemical energy.

Mitochondrial Matrix

: The mitochondrial matrix is a gel-like substance inside mitochondria where certain metabolic reactions occur.

Nucleolus

: The nucleolus is a small, dense region within the nucleus of a cell where ribosomal RNA (rRNA) is produced and assembled with proteins to form ribosomes.

Nucleus

: The nucleus is an organelle found in eukaryotic cells that contains most of the cell's genetic material organized as DNA molecules along with proteins forming chromosomes.

Phagocytosis

: Phagocytosis is a type of endocytosis where a cell engulfs large particles or whole cells, either as a defense mechanism or as a way to obtain food.

Phospholipid Bilayer

: The phospholipid bilayer is a two-layered arrangement of phosphate and lipid molecules that form a cell membrane, the hydrophobic lipid ends facing inward and the hydrophilic phosphate ends face outward.

Plasma Membrane

: The plasma membrane is a thin layer that separates the inside of cells from their environment. It controls what enters or leaves the cell.

Prokaryotic Cells

: Prokaryotic cells are simple, small cells that lack a nucleus or other membrane-bound organelles. They are typically found in bacteria and archaea.

Ribosomal RNA (rRNA)

: rRNA is part of ribosomes, serving as structural components and also catalyzing peptide bond formation. It's essential for protein synthesis in all living organisms.

Ribosomes

: Ribosomes are tiny structures within cells where proteins are made (protein synthesis).

Stroma

: The stroma is the fluid-filled space surrounding the grana (stacks of thylakoids) within the chloroplast where the "dark" reactions of photosynthesis (Calvin cycle) occur.

Thylakoids

: Thylakoids are flattened sac-like membranes arranged in stacks (grana) inside the chloroplasts. They contain chlorophyll and play a crucial role in capturing light energy and converting it into chemical energy during photosynthesis.

Trans Face

: The trans face is the shipping side of the Golgi apparatus in a cell, where modified proteins and lipids are sorted and packaged into vesicles that transport them to their final destinations.

Transitional ER

: The transitional endoplasmic reticulum (ER) is a region of the ER that specializes in the final steps of protein and lipid synthesis, including packaging these molecules into transport vesicles.

Vacuoles

: Vacuoles are membrane-bound sacs within the cytoplasm of a cell that function in several different ways including isolating materials that might be harmful or storing waste products.

Vesicles

: Vesicles are small membrane-bound sacs that function in moving materials within a cell as well as interactions between cells.


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AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.


© 2024 Fiveable Inc. All rights reserved.

AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.