Topic 2.1: Cell Structure and Function

AP Bio Unit 2

What are the components of a ribosome

Ribosomal RNA (rRNA) and proteins, forming two subunits that assemble during protein synthesis.

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

mRNA, tRNA, and rRNA.

what life forms have ribosomes

All living organisms, including prokaryotes and eukaryotes, possess ribosomes.

what is the structure and function of the ribosome

The ribosome is a complex molecular machine made of rRNA and proteins, responsible for translating mRNA into polypeptides during protein synthesis.

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

The structure of the ribosome facilitates its function by providing distinct sites for mRNA and tRNA binding, enabling accurate translation of genetic information into proteins. Its catalytic activity, contributed by rRNA, ensures efficient peptide bond formation between amino acids.

what are the components of the endomembrane system?

The endomembrane system consists of various membranous organelles such as the endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and the nuclear envelope, which work together to modify, package, and transport lipids and proteins.

what is the function of the endomembrane system?

The endomembrane system functions to synthesize, modify, package, and transport proteins and lipids to various destinations within the cell, facilitating cellular processes and communication.

how does the function of each components of the endomembrane system lead to the function of the endomembrane system?

Each component of the endomembrane system plays a specific role in synthesizing, modifying, packaging, and transporting proteins and lipids, which collectively enhances the efficiency of cellular processes and communication.

what are the 2 kinds of endoplasmic reticulum (ER)

the rough endoplasmic reticulum and smooth endoplasmic reticulum.

what is the function of the Endoplasmic reticulum

a central manufacturing and transport hub for cells, responsible for protein synthesis and folding, lipid synthesis, and calcium storage.

how does the ER provide mechanical support?

acting as a structural framework within the cell, similar to a cytoskeleton

how does the ER play a role in intracellular transport?

the starting point for the secretory pathway, where it sorts and packages newly synthesized proteins and lipids into transport vesicles

(Rough ER) What is the structure and function of the rough ER?

a network of flattened, interconnected membrane sacs studded with ribosomes, giving it a "rough" appearance. Its main function is the synthesis, folding, modification, and transport of proteins.

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

providing a large, folded membrane surface with embedded ribosomes

what is the relationship between the ribosome and the rough ER

ribosomes attached to the rough endoplasmic reticulum (RER) synthesize proteins

what is the structure and function of the smooth ER

what is the structure and function of the smooth ER

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

through a network of interconnected tubules that provide a large surface area for enzymatic reactions and the synthesis of molecules like lipids and steroids

what are the three different names for Golgi

Golgi body, Golgi complex, and dictyosome

what is the structure and function of the golgi?

“the cell post office”, a structure of flattened, membrane-bound sacs called cisternae, which are stacked together. Its primary function is to modify, sort, and package proteins and lipids from the endoplasmic reticulum for secretion or delivery to other organelles

how does the structure of the golgi aid in its function?

allows for the sequential modification, sorting, and packaging of proteins and lipids

what is the structure and function of the mitochondria

a double-membrane structure and are responsible for cellular respiration, which generates most of a cell's supply of adenosine triphosphate (ATP), the main energy currency

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

The inner membrane is folded into cristae, which significantly increases its surface area to hold the enzymes for the electron transport chain and ATP synthase, & maximizing energy output

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

finger-like or sheet-like structures that dramatically increase the membrane's surface area

how does the structure of the cristae contribute to the mitochondria? 

dramatically increasing the surface area for essential functions

what is the structure and function of the lysosome?

spherical, membrane-bound organelles containing powerful digestive enzymes that break down waste materials and cellular debris.

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

 The membrane physically separates the potent hydrolytic enzymes from the rest of the cell, preventing self-digestion.

what is apoptosis

the death of cells which occurs as a normal and controlled part of an organism's growth or development.

what role does a lysosome have is apoptosis

initiating and carrying out programmed cell death through the release of hydrolytic enzymes

what is the structure of the vacuole

A vacuole is a membrane-bound sac found inside a cell. Its primary structure consists of two main parts, The Tonoplast: A single membrane that acts as a barrier to control what enters and leaves the vacuole., The Cell Sap: The internal fluid, mostly water, which contains various nutrients, ions, waste products, and enzymes.

which vacuoles are found in plant cells

lytic vacuoles (LV) and protein storage vacuoles (PSV)

which vacuoles are found in animal cells?

food vacuoles, lysosomes, and autophagic vacuoles.

what is the function of the food vacuole

to digest and store nutrients by engulfing food particles through a process called phagocytosis.

what is the function of the central vacuole?

to store water, nutrients, and waste, and to maintain turgor pressure, which supports the cell and keeps the plant rigid.

how does the vacuole provide tugor pressure?

Through osmosis, where water enters the vacuole, causing it to swell and push against the cell wall.

what is the function of the contractile vacuole?

to prevent the cell from bursting by collecting and expelling excess water

what organisms have chloroplasts?

plants and algae

what is the structure and function of a chloroplast?

a double-membraned organelle in plant cells where photosynthesis occurs.

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

Its double membrane and internal thylakoid membranes increase surface area for light absorption and electron transport, while the fluid-filled stroma contains enzymes for the light-independent reactions (Calvin cycle).

what is the effect of surface area to volume ratios on interactions between the cells and their environment?

As a cell's volume increases, its surface area to volume ratio decreases, making it less efficient at these exchanges.

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

A high surface area to volume ratio

what is the effect of surface area to volume ratios on interactions between organisms and the environment?

A high surface area to volume ratio increases the efficiency of an organism's interactions with its environment, making it easier to exchange nutrients, gases, and waste. 

how does an increase in surface area impact an increase in volume?

volume increasing at a greater rate than surface area.

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

altering its shape or creating folds in its membrane.

how does an increase in surface area to volume ratio affect the cell

makes a cell more efficient at exchanging materials with its environment. 

what is the relationship between organism size/mass and the rate of the heat exchange?  

Smaller organisms lose or gain heat faster because they have a higher surface area-to-volume ratio.
Larger organisms exchange heat more slowly due to a lower surface area-to-volume ratio.

describe the relationship between organism size/mass and the rate of heat exchange?

As organism size or mass increases, the rate of heat exchange decreases.
Smaller organisms have a larger surface area relative to their volume, so they gain and lose heat faster, while larger organisms have a smaller surface area-to-volume ratio, so they retain heat longer and exchange it more slowly.

what are the components of the cell membrane?

Cell membrane = phospholipid bilayer + proteins + carbohydrates + cholesterol.

How do each of these components function in the cell membrane?

Phospholipids – barrier; Proteins – transport/signaling; Carbohydrates – recognition; Cholesterol – stability/fluidity.

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

The phospholipid bilayer controls what enters and exits the cell, maintaining a stable internal environment.

what are the 6 different types of membrane proteins? 

Transport, receptor, enzymatic, recognition, adhesion, and attachment proteins.

what makes a protein hydrophobic or hydrophilic?

Hydrophobic = nonpolar amino acids (avoid water)
Hydrophilic = polar/charged amino acids (attracted to water)

How does the polarity of the membrane proteins affect its orientation in the membrane?

Hydrophobic parts face lipid tails (inside membrane); hydrophilic parts face water (inside/outside cell).

what are the components that make up the plasma membrane?

Plasma membrane = phospholipids + proteins + cholesterol + carbohydrates

what is the function of steroids in the plasma membrane?

Steroids (cholesterol) stabilize the membrane, regulate fluidity, and reduce permeability.

what is the function of glycoprotiens in the plasma membrane?

Glycoproteins = proteins with carbs that enable cell recognition, signaling, and adhesion.

what is the function of glycolipids in the plasma membrane?

Glycolipids = lipids with carbs that aid in cell recognition, signaling, and membrane stability.

what is the fluid mosaic model?

Fluid mosaic model = membrane is a flexible lipid bilayer with a mosaic of proteins, cholesterol, and carbohydrates.

what is the function of the plasma membrane?

Plasma membrane protects the cell, controls transport, enables communication, provides structure, and allows cell recognition.

what is the composition of the plasma membrane?

Plasma membrane = phospholipids + proteins + cholesterol + carbohydrates.

why is the plasma membrane a selectively permeable membrane?

Plasma membrane is selectively permeable: lets some substances pass while blocking others to maintain homeostasis.

how do Large amounts of water pass through the membrane?

through aquaporins by osmosis.

what types of materials can pass easily through the membrane?

small and nonpolar, because they can move through the hydrophobic core of the lipid bilayer without assistance.

Oxygen (O₂) – small and nonpolar, diffuses freely into cells for respiration.

Carbon dioxide (CO₂) – small and nonpolar, diffuses out of cells as a waste product

what is an embedded protein?

Embedded proteins are integral proteins in the membrane; examples: channel proteins and carrier proteins.

what materials require an embedded channel or transport protein to pass through the membrane?

Large, polar, or charged molecules (e.g., glucose, Na⁺) need transport proteins to cross the membrane.

T or F, any molecule can use any transport protein

False!

How does the polarity of molecules affect its path across the plasma membrane?

Nonpolar molecules cross directly; polar/charged molecules need transport proteins.

what is a concentration gradient?

A concentration gradient is the difference in substance concentration between two areas, driving movement from high to low (or requiring energy to go low to high).

how is a concentration gradient maintained?

Concentration gradients are maintained by selective permeability, active transport, and continuous use/production of substances.

how are concentration gradients formed across the membrane?

Concentration gradients form when selective permeability, active transport, and cellular processes create different concentrations inside vs. outside the cell.

2 examples of active transport?

Examples of active transport: Na⁺/K⁺ pump and H⁺ (proton) pump – both move ions against their gradients using ATP.

2 examples of passive transport?

simple diffusion (O₂, CO₂) and facilitated diffusion (glucose, ions)

how do membranes allow for compartmentalization?

Membranes create separate compartments in cells, isolating processes and controlling each compartment’s environment.