HESI Science Portion (Biology): The Cell

What is a cell?

the basic organizational unit of all living things.

What do all cells have in common?

The one thing that all cells have in common is a membrane, which is comparable to a semi-permeable plastic bag.

What is membrane made of?

Phospholipids

What is the purpose of Transport Holes?

Are proteins that help certain molecules and ions move in and out of the cell.

What kind of fluid is a cell filled with?

Cytoplasm or cytosol

Cells have this in order to synthesize proteins?

DNA and RNA

Each cell consist of these things in their cellular structure?

Nucleic acids, cytoplasm, and a cell membrane

What happens to a cell in a single-celled organism?

That single cell contains all components necessary for life

What happens to a cell in a multicellular organism?

Cells can become specialized

How can a single cell’s life begin?

Either through asexual or sexual reproduction

How are cells grouped together?

Tissues

How tissues grouped together?

Organs

How are organs grouped together?

In systems

What is an organism?

a complete individual

What is a Nucleus?

A small structure that contains the chromosomes and regulates the DNA of a cell.

What is the nucleus responsible for?

Its responsible for the passing on the genetic traits between generations

What does a nucleus contain?

Nuclear envelop, nucleoplasm, a nucleolus, nuclear pores, chromatin, and ribosomes

What is a Chromosome?

Are highly condensed, threadlike rods of DNA. DNA is a genetic material that stores information about the plant or animal.

What is a Chromatin?

This consists of the DNA and protein that make up chromosomes

What is a Nucleolus?

This structure contained within the nucleus consists of protein. Its a small, round, does not have a membrane, is involved in protein synthesis, and synthesizes and stores RNA

What is Nuclear Envelop?

This encloses the structures of the nucleus. It consists of inner and outer membranes made of lipids

What are Nuclear Pores?

These are involved in the exchange of material between the nucleus and the cytoplasm

What is Nucleoplasm?

This is the liquid within the nucleus, and is similar to cytoplasm.

What are Ribosomes?

Involved in synthesizing proteins from amino acids. Some cells contain thousands of ribosomes. Some are mobile and some are embedded in the rough endoplasmic reticulum.

What is an Endoplasmic Reticulum?

Its a tubular network that comprises the transport system of a cell. Its also fused to the nuclear membrane and extends through the cytoplasm to the cell.

Two types; Rough (has ribosomes on the surface) and Smooth (does not have ribosomes on the surface).

What is Golgi Complex?

Also known as Golgi apparatus; Involved in synthesizing materials such as proteins that are transported out of the cell. Located near the nucleus and consists of layers of membranes.

What are Lysosomes?

They digest proteins, lipids, and carbohydrates, and transport undigested substances to the cell membrane so they can be removed. The shape of it takes depends on the material being transported.

What are Vacuoles?

Are sacs used for storage, digestion, and waste removal. Plant cells have one large vacuole, while animal cells have small and numerous vacuoles.

What is a Mitochondria?

Cell structure that perform various functions such as generating ATP, and is also involved in cell growth and death. This cell structure can vary in terms of size and quantity.

Note: While mitochondria provides energy for animal cells, chloroplast perform the same function in plant cells.

What is a Cell Membrane?

Also known as the plasma membrane, this defines the cell by acting as a barrier.

It helps keeps cytoplasm in and substances located outside the cell out. It also determines what is allowed to enter or exit the cell.

A thin semipermeable membrane of lipids and proteins. It isolates the cell from the external environment while still enabling the cell to communicate with that outside environment.

What does a cell membrane consist of?

Phospholipid bilayer or double layer, with the hydrophilic ends of the outer layer facing the external environment, the inner layer facing the inside of the cell, and the hydrophobic ends facing each other.

What does Cholesterol do in the cell membrane?

It adds stiffness ands flexibility

How does Glycolipids help the cell?

It helps the cell to recognize other cells of the organism

What does Protein do within the cell membrane?

Helps give the cells shape. Special proteins help the cell communicate with the external environment. While other proteins transport molecules across the cell membrane.

What does the cell membrane look out for when regarding “selective permeability”?

To the size, charge, and solubility of molecules

How does charge affect an Ion on a cell’s surface?

Either it attracts or repels ions

What happens when Ions have “like” charges?

They are repelled away from the cell’s surface

What happens when ions have “opposite” charges?

They are attracted to the cell’s surface.

What is passive transport?

The movement of substances across a cell membrane without the input of energy. Random motion of particles will led to the net movement of substances down their concentration gradients in a spontaneous process that leads to an increase in entropy

What are other forms of passive transport?

diffusion, osmosis, and facilitated diffusion

What happens during diffusion?

In simple diffusion, the substances cross the membrane directly, without the aid of transport protein

What happens during osmosis?

Its the passive transport of water across the membrane. Most polar molecules cannot use simple diffusion, but water molecules are small enough to slowly squeeze between the phospholipids.

What is facilitated diffusion?

When proteins are used to transport substances down their concentration gradients

What is active transport?

Energy is used to move solutes into or out of the cell. Substances are pumped against the concentration gradients from areas of low to high concertation.

Why is active transport required?

Its required for processes such as the maintenance of a membrane potential and the uptake of glucose by intestinal cells even between meals

What happens during “primary active transport”?

The pumping of solutes by a carrier protein is directly coupled to the hydrolysis of ATP. In this process, the binding of a phosphate group causes a conformational change in the protein, allowing it to transport solutes across the membrane.

What happens during “secondary active transport”?

It relies on ATP to generate an electrochemical gradient, and it is this gradient that directly drives the active transport of a different solute.

What is a symport?

When both solutes move in the same directionm

What is a antiport?

When both solutes move in the opposite directions

What type of active transports are needed to employ vesicles to import or export substances?

Endocytosis and Exocytosis