Unit 2: Cell Structure and Function

Honors Bio 2024-2025

cell

the smallest structural and functional unit of an organism, typically microscopic; BASIC UNIT OF LIFE

unicellular

having one cell

multicellular

having more than one cell

eukaryotic

nucleus; membrane bound organelles;10-100 µm (ex: plants, animals, fungi, protists)

prokaryotic

no nucleus (nucleoid region);structures are not membrane bound; 0.1-10 µm (ex: bacteria)

organelle

a subcellular structure that has one or more specific jobs to perform in the cell

tissue

A group or layer of cells that work together to perform a specific function (ex:connective tissue, epithelial tissue, muscle tissue, and nervous tissue)

organ

a collection of tissues that structurally form a functional unit specialized to perform a particular function (ex: heart, lungs, kidneys)

organ system

a group of organs that work together in the body to perform a complex function (ex: Integumentary System, Skeletal System, Muscular System, Nervous System, Endocrine System, Cardiovascular System, Lymphatic System, Respiratory System, Digestive System, Urinary System, and Reproductive System)

cell membrane

(plant and animal cells)

function: boundary; regulates movement of materials
structure: lipid bilayer, selectively permeable, fluid mosaic

lipid bilayer

thin bimolecular sheet of mainly phospholipid molecules that forms the structural basis for all cell membranes; the two layer of lipid molecules are packed with their hydrophobic tails pointing inward and their hydrophilic heads outward, exposed to water

selectively permeable

some substances are able to pass through the membrane, while other substances are not able to pass through

fluid mosaic model

the membrane is like a fluid, enabling phospholipids and proteins to move about

peripheral membrane proteins

do not cross the membrane, but they can be attached to either side of the membrane or other proteins in the membrane (ex: surface protein, carrier/transport protein)

integral membrane proteins

Opens up and creates channel for moving things; permanently embedded within the plasma membrane (ex: channel protein)

glycoprotein

“watch tower” cell signaling; communication between cells (Y shape on a ball)

hydrophobic

“ew water”

cytoplasm

AKA cytosol (plant and animal cells)

functions: occupies space inside (cell); suspends organelles
structure: some parts = thin like liquid, other parts = thick like gelatin; CYTOPLASMIC STREAMING

cytoplasmic streaming

constant movement of cytoplasm

ribosome

(plant and animal cells)

function: site of protein synthesis
structure: found singly (single) or in groups in cytoplasm (produce proteins for the cell); found on ER (produce proteins for use outside cell)

protein synthesis

process of making proteins that involves replication , transcription, and translation (uses DNA, RNA, and various enzymes)

endoplasmic reticulum

(plant and animal cells)

function: transports protein
structure: folded membrane with many interconnected compartments

rough ER

has ribosomes

smooth ER

no ribosomes

golgi apparatus

(plant and animal cells)

function: package/transport proteins in/out of cell
structure: stacked, flattened, membrane sacs; NOT smooth ER.

mitochondria

(plant and animal cells)

function: provides energy by breaking down food molecules w/ enzymes; high number of mitochondria increases available energy to cell + metabolic activity
structure: oblong; outer membrane surrounds folded inner membrane; own DNA; cristae

enzymes

biological catalyst; speeds up rate of a specific chemical reaction in the cell (almost always a protein)

cristae

folds on the inner membrane of the mitochondria; increases surface area → increases amount of energy produced and available to cell

lysosome

(plant and animal cells)

function: breaks down old cell parts; kills invading bacteria/viruses; digests food particles
structure: small round membrane bound structure; membrane protects rest of cell from lytic enzymes inside of lysosome

cytoskeleton

(plant and animal cells)

function: structural support for organelles; maintains cell shape
structure: composed of microtubules and microfilaments (solid protein fibers)

microtubules

hollow protein tubes

cilia

(plant and animal cells)

function: locomotion in mobile cells; moves particles along in stationary cells
structure: short hairlike projections that move in a beating motion + occur in many numbers; 9+2 arrangement of microtubules

flagella

(plant and animal cells)

function: locomotion in mobile cells; moves particles along in stationary cells
structure: long whiplike projections that lash back and forth and occur singly or paired; 9+2 arrangement of microtubules

nucleus

(plant and animal cells)

function: controls center of cell; contains DNA (genetic code for all cell functions)
structure: nuclear envelope; nucleolus; DNA is usually in the form of long tangled strands of chromatin (becomes super compacted into chromosomes during cell division

nuclear envelope

double membrane of nucleus with pores

nuclear pores

allows communication between nucleus and rest of cell

nucleolus

small dark structure that produces ribosomes

chromatin

mixture of DNA and proteins (and RNA) that form chromosomes found in cells (NOT BACTERIA THO)

chromosome

threadlike structure of nucleic acids and protein found in nucleus, carrying genetic info in the form of genes

cell wall

(plant and fungus)

functions: support for cell and entire plant
structure: surrounds cell membrane; composed of cellulose in plants/chitin in fungi

cellulose

complex carbohydrate which is a main part of the cell walls in plants (commonly a white stringy substance from vegetable matter)

chitin

fibrous substance consisting of polysaccharides; forms major part of cell walls in fungi

vacuole

(plant and animal cells)

function: temporary storage of: food, enzymes, wastes, other materials; in plant cells: filled with water + provide pressure from within
structure: large membrane bound sac

turgor pressure

keeps a plant rigid

plastid

(plant cell)

function: photosynthesis; energy
structure: double membrane surrounds stacks of grana
types: chloroplasts, leucoplasts,chromoplasts

photosynthesis

the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar

chloroplast

green pigment

leucoplast

white pigment

chromoplast

red, yellow, brown, orange pigments

centriole

(animal cell)

function: moves chromosomes during mitosis and meiosis
structure: short tubular structures that kinda look like churros

mitosis

process of cell duplication → one cell divides into two genetically identical daughter cells (think asexual reproduction)

meiosis

produces cells that are genetically unique from the parent and contain only ½ as much DNA; produces four gamete cells (pretty much sexual reproduction)

protein

chain of amino acids (POLYPEPTIDE); needed for the body to function properly/do most of the work in cells; basis of body structures

homeostasis

maintenance of a stable internal environment in a changing external environment (membrane is responsible for maintaining this) if this is not maintained, the ultimate result is cell death

phospholipid

“lipid bilayer” kinda looks like a bobby pin; composed of the circle phosphate and the fatty acid (hydrophobic) tails which are uncharged and nonpolar

phosphate

lipids/fats; hydrophilic, charged, polar

glycerol

three-carbon alcohol located in the human body

fatty acids

a molecule consisting of a long hydrocarbon chain with a carboxyl group at one end; the building blocks of the fat in our bodies and in the food we eat

lipids

aka fats; chains of carbon atoms bonded to hydrogen and oxygen. broken down to provide a source of usable energy to cells, cell structure, and hormones

carrier protein

allow large lipid insoluble molecules that cannot cross the membrane by simple diffusion to be transported into the cell; use active transport (ATP)
→ binds to molecules/ions on one side of the membrane and releases them on the other (Yknow, CARRYING them over)

channel protein

(hydrophilic pores) in the membrane alow inorganic ions to apss through the membrane
→ creates a channel (hole/pores) penetrating the membrane allowing molecules/ions to flow through with diffusion

diffusion

net movement of particles from an area of high concentration to an area of low concentration; cannot occur without a. concentration gradient

dynamic equilibrium

state in which there is still constant random motion of particles, but no overall difference in concentration; particles are evenly dispersed across a given space (like perfume or food coloring

concentration gradient

difference in concentration across a space

osmosis

diffusion of water form an area of high concentration to an area of low concentration (solute + solvent = solution) btw solutions are indicated by tonicity → refer to concentration of solutes in solution, not of the water

isotonic

concentration of particles in the solution is the same as inside the cell
→ water moves in and out of the cell equally

hypotonic

concentration of particles in the solution is lower than inside the cell; cytolysis

hypertonic

concentration of particles in the solution is higher than inside the cell; plasmolysis

contractile vacuole

organelle that helps with the regulation of water concentrations

plasmolysis

water moves out of the cell, causing it to shrivel

cytolysis

water moves in the cell, causing it to burst

passive transport

(high to low)
diffusion of materials across the membrane, along the gradient WITHOUT energy
→ diffusion, osmosis, facilitated diffusion

facilitated diffusion

uses transport and channel proteins to assist movement (proteins use ATP but materials still move along gradient)

active transport

(low to high)
diffusion of materials across the membrane, against the gradient WITH energy
→ endocytosis, phagocytosis and pinocytosis, exocytosis

endocytosis

the process by which cells take in substances from outside of the cell by engulfing them in a vesicle

exocytosis

a process for moving large molecules out of the cell to the cell exterior; the molecules originate in storage vacuoles and the vacuoles fuse with the membrane to release the molecules (literally the opposite of endocytosis)

phagocytosis

“CELL EATING”
process by which a cell engulfs/internalizes a large particle by extending its membrane around it

pinocytosis

“CELL DRINKING”
process by which the cell takes in the fluids along with dissolved small molecules
→ cell membrane folds and creates small pockets and captures the cellular fluid and dissolved substances

surface area

(length of 1 side = s; measured in mm²) 6s²

volume

s³

surface area to volume ratio

as the size of the cell increases, the surface area to volume ratio decreases
→to improve/increase this ratio, make the cells smaller/ fold the cell membrane (complicating it)
→ sa:vol (ex: 6:1)

metabolic activity

sum of all chemical biological, physical reactions in an organism