Cell Structure, Function, and Transport: A Comprehensive Biology Review

What are cells?

The basic building blocks of all living things.

What is the function of cells?

Each type of cell is specialized to perform its given function.

Why is the cell membrane semipermeable?

It is composed of a phospholipid bilayer and transport proteins that regulate the passage of molecules to maintain homeostasis.

What factors determine how substances cross the cell membrane?

Their concentration gradient, electric potential (for charged molecules), and the phospholipid bilayer.

What is passive transport?

Movement of substances across the cell membrane without energy, occurring when the concentration is higher on one side.

What is active transport?

Movement of substances from low to high concentration using energy and specialized channels or carriers.

How many types of cells are found in the human body?

Over 200 types.

What is the function of bone cells?

Support bone and regenerate.

What is the role of blood cells?

Carry oxygen and help the immune system.

What do muscle cells do?

Move the body.

What is the function of nerve cells?

Send signals to the body and brain.

What role do skin cells play?

Protect organs.

What is the function of sex cells?

Enable reproduction.

How do cells relate to tissues?

Cells are the basic unit of tissue and work in groups to form tissues.

How do cells relate to organs?

Cells form tissues, which then form organs.

How do cells relate to the entire organism?

Cells form tissues, tissues form organs, and organs comprise systems that make up organisms.

What is the plasma membrane?

A flexible barrier that forms the outer layer of an animal cell, consisting of a lipid bilayer.

What is the phospholipid bilayer?

A structure containing phospholipid molecules with hydrophilic heads and hydrophobic tails.

What are integral proteins?

Proteins that are either attached to the periphery or extend through the membrane.

What is cytoplasm?

The inner contents of all cells, containing organelles and cytosol.

What are organelles?

Specialized structures within the cytoplasm that contribute to cell growth, maintenance, and reproduction.

What is cytosol?

The fluid portion of the cytoplasm, mostly made of water with dissolved components.

What is the cytoskeleton?

A network of protein filaments that extends throughout the cytosol in the cytoplasm of most cells.

What are microtubules and their functions?

Microtubules determine the shape of the cell, contribute to the movement of organelles, grow outward toward the periphery of a cell, are the thickest of the three types, have a long hollow shape, and are composed of the protein tubulin.

What role do microfilaments play in the cell?

Microfilaments provide strength, support, and motility for the cell and are primarily composed of the protein actin.

What is the function of intermediate filaments?

Intermediate filaments stabilize the position of the nucleus and other organelles in areas that endure mechanical stress.

What is a centrosome and what does it contain?

A centrosome is an organelle in the cytoplasm of animal cells that contains a pair of centrioles and pericentriolar material.

Describe the structure and function of centrioles.

Centrioles are cylindrical structures composed of clusters of microtubules arranged in a circular pattern. They are surrounded by pericentriolar material, which contains ring-shaped protein complexes critical for cell division and building microtubules in non-dividing cells.

What are cilia and their function?

Cilia are short slender projections that extend away from the cell surface and move in a coordinated fashion to move fluid along; not all cells have cilia.

What is the primary function of ribosomes?

Ribosomes are responsible for protein synthesis, with proteins synthesized being used by organelles, the plasma membrane, or structures outside the cell.

Where can ribosomes be found in the cell?

Ribosomes can float freely in the cytosol or be located at the outer surface of the nuclear membrane, on the surface of the rough endoplasmic reticulum (ER), and in mitochondria.

What is the structure and function of the endoplasmic reticulum (ER)?

The endoplasmic reticulum is an extensive network of membrane-enclosed sacs and tubules that makes up more than half of the membranous cells, extending from the outer nuclear membrane throughout the cytoplasm. There are two types: rough ER and smooth ER.

What distinguishes rough endoplasmic reticulum from smooth endoplasmic reticulum?

Rough endoplasmic reticulum is continuous with the outer nuclear membrane and has ribosomes attached, giving it a rough appearance, while smooth endoplasmic reticulum lacks ribosomes and forms a network of tubules.

What are the functions of smooth endoplasmic reticulum?

Smooth endoplasmic reticulum detoxifies drugs and poisons, stores ions, and produces lipids, hormones, and other cellular products, which are distributed throughout the cell by transport vesicles.

What is the Golgi apparatus and its role in the cell?

The Golgi apparatus is located in the cytoplasm of eukaryotic cells, receives proteins synthesized by ribosomes on the rough ER via transport vesicles, and processes and distributes lipids and complex carbohydrates.

What is the primary function of mitochondria?

Mitochondria generate adenosine triphosphate (ATP), the cell's main source of energy, via aerobic cellular respiration and are referred to as the 'power plants' of the cell.

What is the structure of mitochondria?

Mitochondria consist of an outer membrane and an inner membrane with a space between them called the intermembrane space.

What are lysosomes and their function?

Lysosomes consist of digestive enzymes enclosed in a single membrane, which protects the cytoplasm from low pH and hydrolytic enzymes. They digest food and pathogens, break down worn-out cell parts, and recycle cell structures.

What is autophagy in relation to lysosomes?

Autophagy is the process by which a lysosome engulfs another organelle, digests it, and deposits the digested components into the cytosol for recycling.

What are peroxisomes and their functions?

Peroxisomes, or microbodies, are smaller than lysosomes but similar in structure; they neutralize toxins, metabolize long-chain fatty acids, and contribute to energy production, containing oxidases that oxidize organic substances.

What is the role of hydrogen in the formation of hydrogen peroxide during cellular processes?

Hydrogen is removed from molecules to form hydrogen peroxide.

What enzyme is contained in peroxisomes and what is its function?

Catalase, which breaks down hydrogen peroxide, a toxic compound.

Where are peroxisomes most numerous and what is their primary function?

In the liver, where detoxification of alcohol and other substances occurs.

What is the function of transport vesicles in the cell?

They take modified proteins to the Golgi complex for further processing and sorting for transport.

What is the nucleus and what does it contain?

A large membrane organelle that contains genetic information in the form of DNA.

What is the nuclear envelope and its function?

A double membrane that surrounds the nucleus and controls the flow of substances in and out through nuclear pores.

What is nucleoplasm?

A viscous liquid that contains the contents of the nucleus, including nucleoli.

What is the function of the nucleolus?

It is the site of ribosome subunit synthesis and contains proteins, DNA, and RNA.

What are chromosomes and how many do human somatic cells have?

Structures that encode genetic information; human somatic cells have 46 chromosomes.

What is the structure of the cell membrane and why is it semipermeable?

It has a phospholipid bilayer with hydrophilic heads and hydrophobic tails, allowing selective permeability.

What are the roles of membrane proteins?

They give cells unique properties, identity, transmit chemical messages, and facilitate transport.

What are marker proteins?

Proteins that give cells their identity.

What are receptor proteins and their function?

Proteins that transmit chemical messages across the membrane, influencing reactions inside the cell.

What are transport proteins and their types?

Proteins that move materials across the membrane; includes channel proteins and carrier proteins.

What is the function of channel proteins?

They form passages allowing ions or polar particles to move through the membrane.

How do carrier proteins function?

They change shape to move materials across the membrane.

What is the sodium-potassium pump?

A transport protein that uses ATP to move sodium and potassium against their concentration gradients.

Define diffusion.

The random movement of particles from higher to lower concentration until equilibrium is reached.

Define osmosis.

The diffusion of water across a membrane, continuing until equal concentration is reached.

What occurs in a hypertonic solution?

Water moves out of the cell, causing it to shrink due to higher solute concentration outside.

What happens to a cell placed in a hypertonic solution?

Water diffuses out of the cell, causing it to shrink.

What occurs when a cell is in an isotonic solution?

Water diffuses in and out of the cell at the same rate, maintaining its shape.

What is the effect of a hypotonic solution on a cell?

Water diffuses into the cell, causing it to swell and usually burst.

How do osmosis and diffusion differ?

Diffusion is the movement of any substance from high to low concentration without a membrane, while osmosis specifically refers to the movement of water across a semipermeable membrane.

What determines the direction of water movement during osmosis?

The concentration gradient.

What is osmotic pressure?

The pressure needed to stop the flow of water across a semipermeable membrane from a lower concentration to a higher concentration.

How are osmolarity and tonicity related?

Osmolarity measures the total number of particles in a solution, while tonicity measures a solution's ability to change cell volume by affecting water content.

What is the difference between active and passive transport?

Passive transport requires no energy to move molecules down the concentration gradient, while active transport requires energy (ATP) to move substances against their gradient.

What is facilitated diffusion?

The movement of particles that require transport proteins to cross the cell membrane from high to low concentrations.

What is simple diffusion?

The movement of solutes down the concentration gradient that cross the plasma membrane freely.

What does cellular respiration produce from glucose?

It breaks down glucose to produce ATP.

What are the stages of cellular respiration?

Glycolysis, Citric Acid Cycle, and Oxidative Phosphorylation.

What occurs during glycolysis?

A 6-carbon glucose molecule is broken down into two 3-carbon pyruvic acid molecules, yielding a net gain of 2 ATP.

What happens in the citric acid cycle?

2 more ATP are produced, and carbon dioxide is released as a waste product.

What is oxidative phosphorylation?

It involves the electron transport chain and chemiosmosis in the inner mitochondrial membrane.

What is the role of high-energy electrons in cellular respiration?

They are released during glycolysis and the citric acid cycle and are used in the electron transport chain to produce ATP.

What happens to osmotic pressure if solutes cannot move?

Osmotic pressure increases as water moves to balance the concentration of solutes.

What is the role of transport proteins in facilitated diffusion?

They allow the flow of large or charged particles through the lipid bilayer.

What is the primary difference between facilitated diffusion and simple diffusion?

Facilitated diffusion requires transport proteins, while simple diffusion does not.

What is the concentration of solute in a beaker containing a hypotonic solution compared to a cell?

The beaker has a lower concentration of solute than the cell.

What is the concentration of solute in a beaker containing a hypertonic solution compared to a cell?

The beaker has a higher concentration of solute than the cell.

How many ATP molecules can be produced from one glucose molecule during cellular respiration?

Up to 38 ATP molecules.

What is the process of transcription?

The unzipping of a double-helix DNA molecule to create a messenger RNA (mRNA) molecule from the DNA template, which then exits the nucleus.

What occurs during translation?

The formation of a linear chain of amino acids (a protein) using the transcribed information from the mRNA strand within the ribosome.

What is a codon?

A 3-base sequence in the mRNA that codes for a specific amino acid in a protein.

How are new cells created?

Through mitosis and cytokinesis in the cell cycle.

What are the stages of the cell cycle?

Interphase (G1, S phase, G2), followed by mitosis and cytokinesis.

What happens during the G1 phase of the cell cycle?

It follows cell division and is a time of rapid growth; most cells spend the majority of their life in this phase.

What occurs during the S phase of the cell cycle?

DNA replicates in preparation for the next cell division, forming sister chromatids and increasing organelle numbers.

What is the role of the G2 phase in the cell cycle?

The cell continues to grow and builds structures needed for mitosis.

What happens during prophase of mitosis?

Centrioles migrate to opposite poles, microtubules form the spindle, the nuclear membrane breaks down, and chromatin condenses into chromosomes.

What occurs during metaphase of mitosis?

Centromeres of each chromosome attach to spindle fibers, and chromosomes align at the cell's midline.

What happens during anaphase of mitosis?

Sister chromatids separate and are pulled toward opposite poles; animal cells form a cleavage furrow while plant cells form a cell plate.

What is telophase in mitosis?

The reverse of prophase, where the nuclear membrane reappears, chromosomes unwind into chromatin, and the nucleolus forms.

What is cytokinesis?

The process of separating the organelles and cytoplasm, resulting in two physically separated daughter cells.

What is the G0 phase?

A phase where cells, such as neurons, do not undergo the cell cycle and remain inactive.

What are sister chromatids?

Two identical copies of a single chromosome joined together at the centromere.

What is a centrosome?

The point at which identical chromatids are joined, also known as the centromere.

What are chromosomes?

Condensed chromatin that appears during cell division, made up of two identical sister chromatids.

What are genes?

Segments of DNA that code for the production of specific molecules, usually proteins.