Unit 2 Biology Study Guide

Cells

the basic structural and functional units of every organism (all cells have a plasma membrane, cytoplasm, chromosomes, and ribosomes).

Prokaryote

a single-celled life form that does not have a distinct, membrane-bound nucleus or organelles (domain: bacteria and archaea) (smaller than eukaryote)

Eukaryote

an organism whose cells contain a true, membrane-bound nucleus and other specialized structures called organelles

Chromosomes

thread-like structures made of protein and a single molecule of DNA that store and organize genetic information inside cells

Organelles

a tiny, specialized structure inside a cell that performs a specific job, much like an organ does in the human body

Nucleolus

a dense, membrane-free spherical structure inside the nucleus of eukaryotic cells whose primary job is to make and assemble ribosomes

Ribosomes

a tiny, non-membrane-bound cellular structure made of protein and ribosomal RNA (rRNA) that acts as the factory for building proteins in all living cells

Rough ER

a network of flattened, membrane-enclosed sacs studded with ribosomes that synthesizes, folds, and processes proteins for transport

Smooth ER

a membrane-bound network of tubular sacs inside eukaryotic cells that acts as a cellular factory focused on lipid production, detoxification, and regulation

Cisternae

flattened, fluid-filled membrane sacs that form the structural core of the Golgi apparatus and the Endoplasmic Reticulum (ER), where they modify, package, and transport proteins and lipids

Autophagy

a cellular recycling and self-cleaning process where a cell breaks down its own damaged parts and reuses the components

Lyosomes

acts as the cell's primary recycling and waste-disposal system by breaking down macromolecules, old cell parts, and invading microorganisms (NOT IN PLANTS)

Peroxisomes

small, membrane-bound organelles found in the cytoplasm of eukaryotic cells that break down toxic substances and process major metabolic fats

Golgi Appartus

a membrane-bound cell organelle that modifies, sorts, and packages proteins and lipids for use inside or outside the cell

Nucleus

the command center of a eukaryotic cell that houses and protects the genetic material (DNA).

Vacuoles

a membrane-bound organelle inside plant cells that functions primarily in storage, waste disposal, and maintaining structural balance

Mitochondria

membrane-bound cell parts that make most of the chemical energy required to power a cell's biochemical reactions

Chloroplast

specialized plant and algal cell organelles that convert sunlight into chemical energy through photosynthesis

Stroma

the supportive, structural framework of an organ or the fluid-filled matrix inside a cell's chloroplast

Microfilaments

The thinnest fibers of the cytoskeleton that function primarily in cell movement, structural support, and muscle contraction

Grana

stacked, coin-like membrane structures inside the chloroplasts of plant cells and algae that drive the light-dependent reactions of photosynthesis

Thylakoids

membrane-bound, disc-like compartments inside plant and algae chloroplasts that serve as the exact site for the light-dependent reactions of photosynthesis

Intermediate Filaments

provide tough, permanent mechanical support. They bear physical tension and anchor the nucleus and other organelles in place

Microtubules

Act as transport highways for motor proteins to move items inside the cell, separate chromosomes during cell division, and form structures like cilia and flagella for swimming

Actin

a vital multifunctional protein that forms thin microfilaments, providing structural support and enabling movement inside cells

Cilia

microscopic, hair-like cellular appendages found on the surface of most eukaryotic cells that facilitate movement, fluid clearance, and sensory reception

Flagella

provide cellular locomotion, allowing single cells or organisms to swim through liquid environments

Plasma Membrane

a flexible physical barrier that separates the inside of a cell from the outside world while controlling what goes in and out

What organelles are in animals cells, but not in plant cells?

centrioles (within centrosomes) and lysosomes

What organelles are in plant cells, but not in animal cells?

Chloroplasts, Large Central Vacuole, Cell Wall, Plastids, and Plasmodesmata

How do ribosomes help carry out instructions encoded in the DNA?

translating messenger RNA (mRNA) blueprints into functional chains of amino acids that fold into proteins

If a cell has a high rate of protein synthesis, what oragnelle would you expect it to have a large number of? Why?

Ribosomes because they build proteins by reading instructions from messenger RNA (mRNA).

Differentiate between Smooth ER and Rough ER?

the Rough ER is studded with ribosomes on its outer surface to build proteins, while the Smooth ER lacks ribosomes, so it builds lipids

Identify the main differences between prokaryotic and eukaryotic cells.

Eukaryotic cells contain a membrane-bound nucleus and specialized organelles, whereas prokaryotic cells lack both and keep their genetic material free in the cytoplasm

Describe the endomembrane system.

a network of membranes and organelles in eukaryotic cells that work together to modify, package, and transport lipids and proteins

Trace the path of a protein, from production to final product.

The journey starts with transcription, where the cell copies a specific gene from the DNA to make a messenger RNA (mRNA) molecule in the nucleus. This mRNA then leaves the nucleus and moves into the cytoplasm to find a ribosome on the rough endoplasmic reticulum. During translation, the ribosome reads the mRNA code and links amino acids together to build a chain called a polypeptide. Once built, the raw protein enters the rough endoplasmic reticulum, where it folds into a basic shape and gets early changes. Tiny sacs called transport vesicles then carry the protein to the Golgi apparatus. Inside the Golgi apparatus, the protein receives its final chemical modifications and gets sorted for its specific job. Finally, new vesicles pinch off from the Golgi apparatus and deliver the mature protein to its destination—whether staying inside the cell, joining the cell membrane, or leaving the cell entirely to do its work

Plants have a cell wall, therefore they do not have a plasma membrane. True or False?

False, plant cells have both a cell wall and a cell membrane

Krebs Cycle

breaks down food molecules to release stored energy and generate chemical carriers that power cellular respiration

Electron Transport Chain

a series of protein complexes and organic molecules embedded in a cell membrane that pass electrons from one molecule to another via redox reactions to generate energy

Calvin Cycle

Utilizing the ATP and NADPH produced earlier to fix carbon dioxide into sugars like glucose. (light-independent reaction)

Light Reactions

the first stage of photosynthesis where plants, algae, and cyanobacteria convert sunlight into chemical energy

Endosymbiotic Theory

key organelles inside complex eukaryotic cells—specifically mitochondria and chloroplasts—originated as independent free-living prokaryotic bacteria

Photosynthesis

the process used by plants, algae, and certain bacteria to turn sunlight, water, and carbon dioxide into food and oxygen

Compare the Golgi Complex to a warehouse/facility. How is its funtion similar?

receives, modifies, sorts, and packages proteins and lipids for distribution

What is autophagy? What are the steps in this process?

the body's natural cellular recycling and quality-control system where cells break down and reuse their own damaged, defective, or unneeded parts

• Initiation: The cell senses stress or lack of nutrients and sends signals to start the cleanup.

• Formation: A double membrane builds around damaged cell parts to create a sac called an autophagosome.

• Fusion: This sac travels and merges with a lysosome, an organelle filled with breaking-down enzymes.

• Degradation and Recycling: The waste is broken down into basic building blocks like amino acids and reused by the cell for energy.

Plants get their energy from photosynthesis, therefore they do not have mitochondria. Do you agree or disagree with this statement and why?

I disagree with the statement because plant cells contain both chloroplasts and mitochondria. Plants use mitochondria to break down the sugars they make during photosynthesis into usable energy (ATP).

Describe the roles of both the mitochondria and the chloroplasts.

These two organelles complement each other. Chloroplasts capture solar energy and package it into sugars, while mitochondria break down those sugars to release ATP for cellular work.

Differentiate between the light dependent reactions and the Calvin cycle in the chloroplast.

The light-dependent reactions require sunlight and take place in the thylakoid membranes of the chloroplast to convert light energy into chemical energy (ATP and NADPH), while the Calvin cycle does not directly use light and occurs in the stroma to use those energy molecules to convert carbon dioxide into sugars

Differentiate between the Krebs Cycle and the Electron Transport Chain in the mitochondria.

The Krebs cycle breaks down food molecules to produce carbon dioxide and electron carriers, while the electron transport chain uses those carriers to pump protons and generate most of the cell's ATP

Identify the location where each processes occur:

Light-dependent reactions: Thylakoid membranes

Calvin Cycle: Stroma

Krebs Cycle: matrix of the mitochondria

ATP Synthesis: mitochondria

Electron Transport Chain (ETC): mitochondrial membrane

Why are pigments, like chlorophyll, important to plants?

it absorbs sunlight so plants can make their own food through photosynthesis

Describe how the surface area to colume ratio should be in order for cells to optimize the exchange of material through the plasma membrane.

high surface area-to-volume ratio

Propose problems that would occur if a single cell were to keep getting larger and larger over time.

• Inefficient exchange: As volume grows much faster than surface area, the cell membrane becomes too small to supply the massive interior.

• Starvation and suffocation: The cell cannot absorb enough oxygen and nutrients to feed its volume.

• Toxic waste buildup: Metabolic waste cannot exit fast enough through the limited membrane area, poisoning the cell from within.

How do eukaryotic and prokaryotic cells differ interm of compartmentalization?

eukaryotic cells are heavily compartmentalized using internal, membrane-bound organelles, while prokaryotic cells lack these membrane-bound structures

Describe the endosymbiotic theory in your own words.

Big cells swallowed smaller bacteria billions of years ago.

Instead of digesting these smaller cells, the big host cell and the small bacteria formed a partnership (symbiosis).

The small bacteria lived safely inside the bigger cell and gave it extra benefits.

What evidence is there that supports the endosymbiotic theory?

Mitochondria and chloroplasts contain their own circular DNA molecules, enclosed by a double membrane. The inner membrane resembles a prokaryotic cell's plasma membrane, while the outer membrane matches the host cell's engulfing vesicle, and the ribosomes inside these organelles (70S) are smaller

Why is compartmentalization important in cells?

divides a cell into smaller, enclosed areas (organelles) so that different tasks can happen efficiently and safely

For example it isolates powerful hydrolytic enzymes and an acidic environment away from the rest of the cell to prevent accidental self-destruction for lysosomes

Describe how both the mitochondria and chloroplast compartmentalize processes

Chloroplast:

The Thylakoids (Inner Disc Membranes): These stacked membrane sacs trap sunlight and run the light-dependent reactions. They pump protons inside the thylakoid space to build a gradient that makes ATP.

The Stroma (Fluid Surrounding Thylakoids): This thick fluid holds the enzymes needed for the Calvin cycle, which turns carbon dioxide into sugar using the energy made in the thylakoids.

Mitochondria:

The Matrix (Inner Compartment): This fluid-filled center holds enzymes that break down fuel molecules during the citric acid cycle (Krebs cycle).

The Intermembrane Space (Between Membranes): Hydrogen ions (protons) are pumped here by the electron transport chain. Allowing these protons to flow back into the matrix through ATP synthase powers the creation of ATP (cellular energy). The inner membrane folds into cristae to create more surface area for this process.

How does compartmentalization affect surface area?

increases the total internal membrane surface area

Why is the mitochondria highly folded? (ie what is it producing)

to dramatically increase its surface area, which allows it to produce more ATP (adenosine triphosphate), the main energy currency of the cell.

Mitochondria and Chloroplasts can still be found as free living prokaroytes. True or False?

False. Over millions of years of evolution, they lost the genes and traits needed to survive on their own. They now depend entirely on the host cell to function and replicate.

Amphipathic

a molecule that contains both a hydrophilic (water-loving) region and a hydrophobic (water-fearing) region

Fluid Mosaic Model

describes the cell membrane as a flexible, two-dimensional liquid where a diverse mix of proteins, lipids, and carbohydrates drift

Integral Proteins

a type of permanent membrane protein that is embedded within the phospholipid bilayer of a cell or organelle

Peripheral Proteins

a type of protein that temporarily attaches to the surface of a cell membrane or to an integral membrane protein

Glycolipids

membrane lipids covalently bound to one or more carbohydrate (sugar) groups, functioning primarily in cell-to-cell recognition, signaling, and structural stability

Glycoproteins

complex molecules made of a protein bonded to short, branched chains of sugar molecules that play critical roles in cell recognition, structural support, and immune defense

Hydrophilic

form hydrogen bonds or ionic interactions with water, allowing them to dissolve or interact easily in aqueous environments

Hydrophobic

the natural tendency of nonpolar molecules to aggregate in aqueous solutions to minimize contact with water

Why is the plasma membrane often referred to as a fluid mosaic model?

it is a flexible, moving layer made of many different parts pieced together like a tile picture

What is the purpose of the plasma membrane?

act as a physical barrier that separates the interior of a cell from its outside environment while selectively regulating the movement of substances in and out of the cell

What is the difference between unsaturated and saturated tails of the phospholipids?

Saturated phospholipid tails contain only single carbon-carbon bonds and form straight chains, while unsaturated tails contain one or more double bonds that create a kink or bend in the structure

What causes kinks in the tails of phospholipids?

caused by a cis-double bond between two carbon atoms in an unsaturated fatty acid chain

What molecule embeds itself within the membrane and affects fluidity? How does it affect fluidity?

Cholesterol is the molecule that embeds itself within the phospholipid bilayer of the cell membrane to regulate and buffer membrane fluidity

• At High Temperatures: Cholesterol restricts the excessive movement of phospholipid molecules, reducing fluidity and preventing the membrane from becoming too permeable or falling apart.

• At Low Temperatures: Cholesterol inserts itself between adjacent phospholipid tails to prevent them from packing too closely together and crystallizing, thereby maintaining flexibility and increasing fluidity.

Differentiate between integral and peripheral proteins.

integral proteins are permanently embedded within the cell's lipid bilayer, while peripheral proteins are only temporarily attached to the inner or outer surface of the membrane

How are human cells able to maintain membrane fluidity when they are in cold temperatures?

At low temperatures, cholesterol molecules insert themselves between neighboring phospholipid molecules. This action disrupts tight packing and prevents the fatty acid tails from freezing or solidifying into a rigid gel phase.

Selective Premeabilty

a property of cell membranes that allows certain molecules and ions to pass through while blocking others

Polar

a molecule has an uneven distribution of electrical charge, creating a slight positive charge on one end and a slight negative charge on the other

Nonpolar

a chemical structure with an even distribution of electrical charge, meaning it lacks positive or negative poles

Charged

a molecule or atom has a net electrical charge due to gaining or losing electrons

In your own words, what does it mean that the plasma membrane is selectively permeable?

it allows some substances to pass through freely while blocking or restricting others

What qualities of the plasma membrane make it selectively permeable?

phospholipid bilayer structure and embedded transport proteins

Are nonpolar molecules hydrophobic and hydrophilic? What does it mean in terms of their passage across the plasma membrane?

Because nonpolar molecules are hydrophobic, they can easily pass directly through the hydrophobic, lipid-based core of the plasma membrane via simple diffusion.

Identify the following as polar or nonpolar?

Carbon Dioxide: nonpolar

Ions: neither

Oxygen: nonpolar

Water: polar

Glucose: polar

If plant cells have a cell wall, then they cannot exchange material through their plasma membrane? True or False and Why?

False. Plant cells still have a plasma membrane that is selectively permeable and actively exchanges materials, despite having a rigid cell wall. The cell wall is not a solid, closed barrier. It acts like a porous mesh made of cellulose fibers that allows water, gases, and small molecules to pass freely through to the plasma membrane.

What are cells walls composed of?

cellulose

What kind of cells have a cell wall? What is the purpose of a cell wall?

found in plant cells, fungi, algae, and most bacteria. The purpose is to provide structural support, protection, shape maintence, osmotic balance, and porus transport.

Are polar molecules hydrophobic and hydrophilic? What does it mean in terms of their passage across the plasma membrane?

Because polar molecules are hydrophilic, they cannot easily pass through this oily, hydrophobic middle layer by simple diffusion. So, larger polar molecules (like glucose) and ions require specialized transport proteins (such as channel or carrier proteins) via facilitated diffusion to cross the membrane.

Passive Transport

the movement of substances across a cell membrane from an area of higher concentration to an area of lower concentration without using cellular energy

Active Transport

the movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration, going against the concentration gradient using cellular energy

Concentration Gradient

the difference in the amount of a substance, or solute, between two connected regions

Endocytosis

an active cellular transport process where a cell brings in extracellular fluids, macromolecules, and large particles by folding its plasma membrane inward to form a vesicle

Diiffusion

the net movement of particles from an area of higher concentration to an area of lower concentration

Exocytosis

an active transport process by which a cell expels large molecules, proteins, or waste by merging a membrane-bound vesicle with the outer plasma membrane

Pinocytosis

a cellular process where a cell engulfs extracellular fluid and dissolved solutes by folding its plasma membrane inward

What are the main differences between passive and active transport?

active transport uses cellular energy to move molecules against a concentration gradient, while passive transport moves molecules down a concentration gradient without using any energy

Imagine a room is a cell and someone brings in freshly popped popcorn (gas molecules). The smell slowly drifts through the room. What type of transport is this an example of?

passive transport

In passive transport, molecules move from ____ to _____ concentration.

high to low

How are molecules able to go through diffusion?

because they possess natural kinetic energy that causes them to move randomly and spread out from areas of high concentration to areas of low concentration

How is it possible that animal cells have a high internal concentration of potassium in comparison to their external environment?

using the sodium-potassium pump, an active transport protein that uses energy (ATP) to push three sodium ions out for every two potassium ions it brings in.