Unit 2 Cell Structure and Function

Cells

the basic structural and functional units of every organism

Prokaryotic cells

single-celled organisms without a nucleus, such as bacteria

Eukaryotic cells

cells with a nucleus and membrane-bound organelles, found in organisms like plants and animals

Organelles

membrane bound structures in eukaryotes

Compartmentalization

allows for different metabolic reactions to occur in different locations

Nucleus

the membrane-bound organelle that contains the cell's genetic material and controls cellular activities

Ribosomes

small structures composed of RNA and proteins that synthesize proteins

Rough ER

a type of endoplasmic reticulum with ribosomes on its surface, involved in protein synthesis and processing

Smooth ER

a type of endoplasmic reticulum without ribosomes, involved in lipid synthesis and detoxification

Golgi Complex

an organelle that modifies, sorts, and packages proteins and lipids for secretion or use within the cell

Lysosomes

membrane-bound organelles that contain digestive enzymes used to break down waste materials and cellular debris

Vauoles

membrane-bound structures in cells that store substances such as nutrients, waste products, or water

Endosymbiont Theory

the theory that explains the similarities mitochondria and chloroplasts have to a prokaryote

Mitochondria

organelles known as the powerhouse of the cell, responsible for producing ATP through cellular respiration

Chloroplast

organelles found in plant cells that conduct photosynthesis by converting sunlight into chemical energy

Cytoskeleton

a network of fibers that provides structural support, shape, and form to the cell, as well as aiding in intracellular transport and cell division

Thylakoids

membrane-bound structures within chloroplasts that contain chlorophyll and are the site of the light-dependent reactions of photosynthesis

Grana

stacks of thylakoids within chloroplasts where light-dependent reactions of photosynthesis occur

Stroma

the fluid-filled space within chloroplasts surrounding the thylakoids, where the light-independent reactions of photosynthesis occur

Intermembrane

space located between the inner and outer membranes of chloroplasts, playing a role in the transport of proteins and metabolites

Mitochondrial matrix

the space within the inner membrane of mitochondria, where the Krebs cycle takes place and plays a role in cellular respiration

Cristae

the folds of the inner mitochondrial membrane that increase the surface area for chemical reactions involved in ATP production

Phagocytosis

a process by which a cell engulfs large particles or even other cells, allowing for their digestion or removal

Turgor pressure

the pressure of the cell contents against the cell wall in plant cells, which helps maintain their shape and rigidity

Peroxisomes

small organelles that contain enzymes for breaking down fatty acids and detoxifying harmful substances, playing a key role in cellular metabolism

Autophagy

the process by which cells degrade and recycle their own components, including damaged organelles and proteins

Exocytosis

the process by which cells transport molecules out of the cell by enclosing them in a vesicle that fuses with the cell membrane

Cisternae

flattened membrane-bound sacs found within the endoplasmic reticulum and Golgi apparatus, involved in the processing and transport of proteins

Cis face

the side of the Golgi apparatus where molecules enter and are modified before being sent to the trans face

Trans face

the side of the Golgi apparatus where modified molecules exit and are sent to their final destinations

Microtubules

structural components of the cytoskeleton, made of tubulin protein, that help maintain cell shape, facilitate cell movement, and transport organelles

Microfilaments

thin filaments of the cytoskeleton, composed of actin, that are involved in cell shape maintenance, motility, and division

Intermediate filaments

fiber-like structures in the cytoskeleton that provide mechanical support to cells, helping to maintain their shape and integrity

Cuboidal cell formula

• Total SA= height x width x number of sides x number of boxes (or SA = 6S² if only 1 box)

• Total V= height x width x length x number of boxes (or V = S³ if only one box)

• SA to V ratio = SA/V

Spherical cell formula

• SA = 4πr²

• V =   4/3πr³ 

• SA:V ratio = SA/V

Cell size

refers to the dimensions of a cell, which can impact its function and efficiency in nutrient uptake, waste removal, and overall metabolic activity

Amphipathic

has both hydrophilic and hydrophobic components

Phospholipids

are molecules that make up the cell membrane, consisting of a hydrophilic head and hydrophobic tail, form bilayers

Selective permeability

the ability of membranes to regulate the substances that enter and exit

Fluid Mosaic Model

describes the structure of cell membranes, where lipids and proteins move freely within a fluid matrix, contributing to the dynamic nature of the membrane

Cholesterol

helps maintain fluidity at high and low temps

Integral proteins

Proteins that are embedded into the lipid bilayer

Peripheral proteins

Proteins that are not embedded into the lipid bilayer

Glycolipids

Carbohydrates bonded to lipids

Glycoproteins

Carbohydrates bonded to proteins

Cell wall

a rigid outer layer that provides structural support and protection to plant cells, fungi, and certain prokaryotes

Plasmodesmata

channels that connect plant cells, allowing for communication and transport of materials

Passive transport

transport of a molecule that does not require energy from the cell because a solute is moving with its concentration or electrochemical gradient

Diffusion

spontaneous process resulting from the constant motion of molecules, substances move from a high to low concentration

Osmosis

the diffusion of water down its concentration gradient across a selectively permeable membran

Facilitated diffusion

diffusion of molecules through the membrane via transport proteins

Channel proteins

provide a channel for molecules and ions to pass

Aquaporins

specific channel protein for water

Carrier proteins

undergo conformational changes for substances to pass

Active transport

transport of a molecule that requires energy because it moves a solute against its concentration gradient

Conformational change

change of shape

Pumps

maintain membrane potential, actively transport ions across membranes

Membrane potential

unequal concentrations of ions across the membrane results in an electrical charge (electrochemical gradient)

Electrogenic pumps

proteins that generate voltage across membranes, which can be used later as an energy source for cellular processes

Sodium potassium pump

animal cells will regulate their relative concentrations of Na⁺ and K⁺

• 3 Na⁺ get pumped out of the cell

• 2  K⁺ get pumped into the cell

Proton pump

integral membrane protein that builds up a proton gradient across the membrane

Cotransport

the coupling of a favorable movement of one substance with an unfavorable movement of another substance

Favorable movement

downhill diffusion

Unfavorable movement

uphill transport

Exocytosis

the secretion of molecules via vesicles that fuse to the plasma membrane

Endocytosis

the uptake of molecules from vesicles fused from the plasma membrane (think: opposite of exocytosis)

Phagocytosis

when a cell engulfs particles to be later digested by lysosomes

Pinocytosis

nonspecific uptake of extracellular fluid containing dissolved molecules

Receptor mediated endocytosis

specific uptake of molecules via solute binding to receptors on the plasma membrane

Tonicity

the ability of an extracellular solution to cause a cell to gain or lose water

Osmoregulation

cells must be able to regulate their solute concentrations and maintain water balance

Isotonic solution

cells have no net movement of water

Hypertonic solution

cells lose water to their extracellular surroundings, cells shrivel and die

Hypotonic solution

cells gain water, cells swell and lyse

Water potential

a physical property that predicts the direction water will flow, water will flow from areas of:

• High water potential to areas of low water potential

• Low solute to areas of high solute concentration

• High pressure to areas of low pressure

Water potential formula

𝚿 = 𝚿_s + 𝚿_p where 𝚿_s is solute potential and 𝚿_p is pressure potential

Solute potential formula

𝚿_s = -iCRT where i is the ionization constant, C is the molar concentration, R is the pressure constant, and T is the temperature in Kelvin