Cell Structure and Functions

What is the structure and function of the ribosome?

Ribosomes consist of RNA and proteins and they help with synthesizing proteins. There is a large and small subunit.

How does the structure of the ribosome aid in the function?

The structure of the ribosome allows proteins to be made inside or outside the cell.

What are the three types of RNA involved in the structure or function of the ribosome?

• messenger (mRNA) is transcribed from DNA and carries the message to cytoplasm where

ribosomes translate it into a polypeptide

• transfer (tRNA): carries a specific amino acid to the correct position on the ribosome using its

anticodon to match to the codon on the mRNA.

• ribosomal (rRNA): joins with proteins to make ribosomes where translation occurs to form a

protein.

How does the ribosome demonstrate a common ancestry of all known life?

All life forms have ribosomes.

What is the structure and function of the rough ER?

The rough endoplasmic reticulum is a series of connected flattened sacs, part of a continuous

membrane organelle within the cytoplasm of eukaryotic cells, that plays a central role in the

transport of proteins made on its attached ribosomes.

How does the structure of the rough ER aid in the function?

It allows for the production, folding, quality control and dispatch of some proteins.

What is the structure and function of the smooth ER?

It is a network of membranes called cisternae. They are held together by the cytoskeleton. The function of the smooth ER is to help with synthesizing lipids, phospholipids as in the plasma membrane and steroids.

How does the structure of the smooth ER aid in the function?

Smooth ER is a network of membranes that separate the cell into compartments for metabolic processes. Smooth ER functions in the synthesis of lipids in most cells, the breakdown of toxins in liver cells, and storage and release of Ca ++ in muscle cells. Keeping the enzymes or molecules needed for a specific chemical pathway together in a specific area is more efficient.

What is the relationship between the ribosome and the rough ER?

Ribosomes attach to the rough ER and insert the proteins being made into the rough ER for

intracellular transport to Golgi for modification and export

What is the structure and function of the Golgi?

The Golgi apparatus is a central intracellular membrane-bound organelle. Its key function is to

traffic, process, and sort newly synthesized membrane and secretory proteins and lipids.

How does the structure of the Golgi aid in the function?

It packages proteins into vesicles so they can be transported in or out of the cell.

What is the structure and function of the mitochondria?

It is membrane bound organelle that consists of an outer and inner membrane that produces energy for the cell by breaking down carbohydrates and producing ATP.

How does the structure of the mitochondria aid in the function?

The inner membrane folds increase surface area which allows for a lot of ATP to be formed and

quickly.

What is the structure and function of the lysosome?

It is a small membrane bound organelle that has an acidic interior. The purpose of the lysosome is to break down excess or worn-out cell parts. They can also aid in destroying invading viruses and bacteria.

How does the structure of the lysosome aid in the function?

The membrane surrounding the lysosome keeps proteolytic enzymes separated from the rest of the cell. Proton pumps in lysosomal membranes create acidic interior for digestion.

What is the structure of the vacuole?

A membrane-bound organelle that is generally small and circular in structure.

What is the function of the food vacuole?

It is used for storage of nutrients, water or waste.

What is the function of the central vacuole?

In plants it helps to maintain water balance.

What is the function of the contractile vacuole?

To maintain the constant osmotic pressure in the fluids of an organism by the control of water

and salt concentrations in a well-balanced way so that the cell doesn't get ruptured due to

cytolysis. (Osmoregulation)

What is the structure and function of a chloroplast?

Plant cell organelle that is oval-shaped and has an outer membrane and inner membrane folded

into thylakoid sacs stacked into grana that converts light energy into chemical energy through

the process of photosynthesis.

How does the structure of the chloroplast aid in the function?

Thylakoid sacs make compartments to create the H+ gradient needed for ATP production

during the light dependent reactions.

How does the endoplasmic reticulum provide mechanical support?

it can help maintain cell shape by interacting with the cytoplasmic matrix

How does the endoplasmic reticulum aid in protein synthesis?

it has ribosomes on it to perform protein synthesis

How does the endoplasmic reticulum aid in intracellular transport?

it will transport materials through vesicles

How does the lysosome aid in intracellular digestion?

it will break down food using its enzymes

How does the lysosome aid in recycling the cell's organic materials?

it will breakdown old or broken down organelles using its hydrolytic enzymes

How does the lysosome aid in apoptosis (programmed cell death)?

lysosomes can release enzymes called proteases into the cytosol that will start the cascade of apoptosis

How does the vacuole assist in storage of macromolecules?

provides a lot of space for storage of many types of macromolecules

How does the vacuole provide turgor pressure?

the vacuole will fill up with water that pushes on the cell membrane which then pushes on the cell wall

causing turgor pressure

What is the structure of the inner membrane (cristae) of the mitochondria?

highly folded membranes

How does that contribute to the function of the inner membrane (cristae) of the mitochondria?

highly folded membranes allow for more surface area to complete the oxidative phosphorylation

of cellular respiration

How is the chloroplast organized?

many thylakoid membranes stacked to increase surface area for light reactions in photosynthesis

What is embedded in the chloroplast and how does it aid in the function of the chloroplast?

photosystems containing chlorophyll to absorb sunlight

Where do the light-dependent and light-independent reactions take place?

Photosystems and ETC for the light independent reactions are located in the thylakoid membranes.

Light independent reactions happen in the stroma.

How does the thylakoid aid in energy capturing?

Chlorophyll containing photosystems are located in thylakoid membrane and numerous thylakoid sacs

create more surface area to collect more light

How does the thylakoid aid in energy storing?

Electron transport proteins are located in thylakoid membrane and transport of H+ ions into the

thylakoid space creates the H+ gradient needed for ATP production during the light dependent

reactions.

Where does the citric acid cycle (Krebs cycle) in cellular respiration take place?

Matrix of mitochondria

Where does the electron transport chain in cellular respiration take place?

Proteins for ETC are located in cristae membranes

Where does the electron transport chain in photosynthesis take place?

Proteins for ETC are located in thylakoid membranes

Where is ATP synthesized in cellular respiration?

• 2 ATP made during glycolysis in cytoplasm

• 2 ATP during Krebs cycle in matrix of mitochondria

• 32 made by ETC/ATP synthase on matrix side of cristae

Where is ATP synthesized in photosynthesis?

Stroma of chloroplast

How does surface area to volume ratio affect the size of the cell?

The surface area of the plasma membrane must be large enough to adequately exchange materials.

As a cell increases in size its surface area/volume decreases, limiting how big it can get.

What type of surface area to volume ratio is most favorable for cells?

A higher surface area-to-volume ratio is more efficient for exchange of materials with the environment

How does an increase of surface area affect the increase in volume?

As cells increase in size volume increases faster than surface area. The relative surface area decreases and the demand for internal resources increases.

How can a cell increase surface area without increasing the volume?

folded membranes

How can an increase in surface affect heat exchange?

Higher surface area = higher heat exchange

Identify and describe two examples of specialized surfaces for exchanging materials with the surrounding environment

• Root hair extensions on roots increase absorption on nutrients and water from soil

• Microvilli extensions on cells that line the gut increase absorption of nutrients in small intestine

Numerous tiny air sacs (alveoli) increase gas exchange in lungs

Identify and describe two examples of strategies that organisms use to obtain nutrients and eliminate

wastes.

• Obtain nutrients - Autotrophs (phototroph or chemotroph) and heterotrophs

• Eliminate wastes - removal of nitrogenous wastes varies - ammonia, urea, uric acid

What are the components of the cell membrane?

phospholipids, proteins, glycoproteins, glycolipids, cholesterol

How does the phospholipid bilayer maintain the internal environment of a cell?

The cell membrane acts as a barrier between the interior and exterior cellular environment It is selectively permeable and controls and maintains a balance of molecules that are present in the cell, such as proteins and ions

Define the fluid mosaic model.

The cell membrane is a mosaic of protein molecules floating within a fluid bilayer of phospholipids.

What is the function of steroids in the plasma membrane?

Cholesterol helps to control membrane fluidity and allows the cell membrane to adapt to different

environmental conditions; at moderate temps cholesterol will reduce membrane fluidity and at low

temps it stops the phospholipids from packing too closely together

What is the function of glycoproteins in the plasma membrane?

Important in cell to cell recognition and adhesion

What is the function of glycolipids in the plasma membrane?

Maintain stability of cell membrane and serve in cellular recognition

What types of materials can easily pass through the membrane?

Small, nonpolar molecules can easily pass through the nonpolar fatty acid tail portion of the membrane

example: oxygen and carbon dioxide

What types of materials require a protein to pass through the membrane?

They are large and/or polar molecules that cannot easily pass through the nonpolar region of

the membrane

examples: glucose, ions

What types of materials require a vesicle for export or a food vacuole for import?

bulk transport or larger molecules (requires bulk transport because too many of them to efficiently cross the membrane or too large to fit through the membrane)

Where are plasma membranes found in a cell?

surrounding the cell and also around many different organelles

What types of cells have a cell wall?

Fungi, plants, prokaryotes

How does the cell wall maintain cell structure?

provides a framework for the cell through an interconnected network of cellulose fibers, structural

proteins, and other polysaccharides that help maintain the shape

How does the cell wall protect the cell from hypotonic solutions?

Cell walls prevent plant cells from bursting when placed in hypotonic solutions.

What composes the cell wall of a plant?

cellulose

What composes the cell wall of a fungi?

chitin

What composes the cell wall of a prokaryote?

peptidoglycan

What is passive transport?

Type of membrane transport that does not require energy to move substances down their concentration

gradient across cell membranes.