Untitled Flashcard Set

Fluid Mosaic Model

Describes the cell membrane structure as a flexible, mosaic of various proteins, cholesterol, and glycolipids embedded in a fluid phospholipid bilayer.

Selectively Permeable

A property of cell membranes that allows them to control what enters and exits the cell, maintaining homeostasis.

Passive Transport

The movement of substances across a cell membrane without the use of energy by the cell, including processes like diffusion and osmosis.

Active Transport

Transport that requires energy (ATP) to move molecules against their concentration gradient.

Facilitated Diffusion

The process of moving molecules across a membrane via transport proteins without energy expenditure, following their concentration gradient.

Endocytosis

The process by which cells take in substances by enveloping them in a membrane.

Exocytosis

The process of vesicles fusing with the plasma membrane to release their contents outside the cell.

Glycolysis

The first step of cellular respiration, converting glucose into pyruvate and producing small amounts of ATP and NADH.

Citric Acid Cycle

A series of reactions in cellular respiration that oxidizes acetyl-CoA to CO₂, generating ATP, NADH, and FADH₂.

Oxidative Phosphorylation

The process of producing ATP using energy from electrons transferred through the electron transport chain.

NADH

A high-energy electron carrier that transports electrons to the electron transport chain during cellular respiration.

ATP Synthesis

The process of generating ATP from ADP and inorganic phosphate, powered by energy from exergonic reactions.

Photosynthesis

The process by which plants convert light energy into chemical energy, producing oxygen and glucose from CO₂ and water.

Calvin Cycle

The series of biochemical reactions in photosynthesis that convert CO₂ into G3P using ATP and NADPH produced in the light reactions.

Apoptosis

Programmed cell death that is regulated and results in the removal of damaged or unnecessary cells.

Operon

A cluster of genes under a single promoter, transcribed together, typically found in prokaryotes.

Endocrine Signaling

Hormonal communication system where hormones are released into the bloodstream to target distant cells.

Hydrophilic Ligands

Molecules that are polar and cannot cross the cell membrane, binding to surface receptors.

Hydrophobic Ligands

Nonpolar molecules that can diffuse through the cell membrane and bind to intracellular receptors.

Second Messenger

Small molecules that relay signals received at receptors on the cell surface, such as cAMP.

Epigenetics

Heritable changes in gene expression that do not involve alterations to the underlying DNA sequence.

G-protein Coupled Receptor (GPCR)

A cell surface receptor that activates intracellular signaling pathways through G proteins upon ligand binding.

RNA Polymerase

An enzyme that synthesizes RNA from a DNA template during transcription.

Homeostasis

The maintenance of stable internal physiological conditions in an organism.

Transcription Factors

Proteins that help regulate the transcription of specific genes by binding to nearby DNA.

Fluid mosaic model

describes cell membrane as a 2-dimensional liquid, like a mosaic, where various proteins, cholesterol, and glycolipids are embedded in or attached to a fluid phospholipid bilayer

plasma membrane

A selectively-permeable phospholipid bilayer forming the boundary of the cells

selective permeability

property of membrane that controls what enters and exits cell (important for homeostasis, cell communication, structural support, cell recognition, adhesion, separating interior of cell from outside)

Why is the membrane "fluid"?

membrane flexible; phospholipids and some proteins can move sideways within the membrane, lets cell change shape or allow materials to pass

What makes the membrane a "mosaic"?

Many proteins (integral + peripheral) embedded throughout.

function and types of membrane proteins

determine most of the membrane functions; they isially are anchored and move slowly

types: transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, atttchment to cytoskeletoin and ECM)

transport membrane protein

channels or pumps that move molecules across the membrane; some use ATP (active transport)

enzymatic activity membrane protein

A protein built into the membrane may be an enzyme, carry out sequential steps of metaboilic pathways

signal transduction membrane protein

protein receptor binds to signal molecule (ex: hormone); changes shape and relays message into cell

cell-cell recognition membrane protein

glycoproteins that act as identification tags; important in immune system and embryo development

intercellular joining membrane protein

membrane proteins of adjacent cells may hook together in various kinds of junctions, such as gap junctions or tight junctions

attatchment to cytoskeleton and ECM membrane protein

helps cell maintain shape, stabilizes protein position, integrins attach to ECM to pass signals inward

what molecules can penetrate semipermeable membrane easily

non-polar molecules (O2, CO2), small uncharged polar molecules (water), hydrophobic molecules (lipids), small uncharged molecules (glycerol)

what molecules struggle to penetrate semipermeable membrane

ions, polar molecules, charged or larger molecules

ex: glucode, sodium, potassium, chloride

passive transport

the movement of substances across a cell membrane without the use of energy by the cell

- diffusion, osmosis-hypertonic, hypotonic, isotonic, facilitated transport

diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

osmosis

diffusion of water from high to low concentration

Isotonic

equal concentration of water and concentration of dissolved substances; no net water movement

hypertonic

more solute concentration; water moves across a membrane toward hypertonic solution

hypotonic

lower solute concentration; water moves across a membrane, away from hypotonic solution

facilitated transport

Diffusion using channels/carrier proteins.

channel proteins

provided by transport proteins; have a hydrophilic channel that certain molecules or ions can use as a tunnel

carrier proteins

provided by transport proteins; bind to molecules and change shape to shuttle them across the membrane

facilitated transport/diffusion

diffusion with the aid of transport proteins (channel/carrier)

energy requiring transport

requires ATP because molecules move against their concentration gradients or are too large to cross by diffusion

- active transport- Na/K pump, bulk transport- phagocytosis, pinocytosis, exocytosis

active transport

membrane proteins use ATP to move molecules from low to high concentration

What does the sodium-potassium pump move and how does ATP help?

3 Na⁺ out, 2 K⁺ in; ATP provides energy for shape change of the pump.

bulk transport

moves large particles via vesicles in ER

- exocytosis and endocytosis

exocytosis

moves materials out of cell using vesicles

- vesicles from ER > golgi > plasma membrane, fuse w/membrane to release contents

ex: neurotransmitters, hormones, cell wall components

Phagocytosis

"cell eating"; engulfs large particles into a food vaccule which is fused w/lysosomes for digestion > brings in large particles

pinocytosis

"cell drinking"; engulfs extracellular fluids and dissolves solutes > brings in fluids

what increases membrane fluidity

unsaturated fatty acid tails; they introduce kinks which prevents the fatty acid chains from packing tightly together

- this space lets membrane remain flexible

how does temperature affect membrane fluidity

Higher temperatures increase fluidity, while lower temperatures decrease it.

what acts as a buffer for membrane fluidity

cholesterol

a cell placed in hypertonic solution will

shrivel/shrink

a cell placed in a hypotonic solution will

expand/swell

saturated fatty acid tails affect on fluidity

decrease it because tails are straight so: tighter packing = less movement = more rigid membrane.

why can small nonpolar molecules cross the membrane easily, while ions cannot?

nonpolar molecules dissolve in the hydrophobic lipid tails, but ions are repelled by the nonpolar core.

what factors affect membrane fluidity most

Saturated vs. unsaturated fatty acid tails & cholesterol content

Facilitated diffusion vs. active transport

Facilitated diffusion moves substances DOWN their gradient using proteins; active transport moves them AGAINST the gradient using ATP.

Which transport method does a neuron use to release neurotransmitters into the synapse?

exocytosis

why is the ECM important

It stabilizes tissue structure and helps maintain cell shape.

Why can't glucose cross the lipid bilayer directly, and how does it enter the cell?

Too large and polar; facilitated diffusion via carrier proteins

ATP hydrolysis

breaking down ATP to ADP by adding water

- releases energy

metabolism

sum of total chemical reactions in the body; manages cells materials and energy resources

chemical reaction

process that forms or breaks the chemical bonds holding atoms together, convert reactants to products

exergonic reactions

chemical reaction that releases energy sponaneous;y

- G < 0: negative; reaction will proceed without input of additional energy

- products have lower free energy then reactants

△G

change in free energy; is a measure of the energy available to do useful work in a system, and it determines whether a reaction will be spontaneous.

endergonic reactions

chemical reactions that require an input of energy; absorb energy, nonspontaneous

- G > 0: positive, reaction will not occur unless energy is added

- products have higher free energy then reactions

catabolic reactions

breakdown of complex molecules to release energy (exergonic)

- ex: cellular respiration, glycogen breakdown

anabolic reactions

build larger molecules from smaller ones; require energy (endergonic)

- ex: photosynthesis, fatty acid synthesis

relationship between catabolism and anabolism

Catabolism provides energy for anabolism

ATP

cells main high energy currency

- adenine + ribose + 3 phosphate groups

- made during cellular respiration

ADP

low energy; created when ATP releases energy (hydrolysis)

- 2 phosphate groups

enzymes

biological catalysts that speed reactions by lowering activation energy

- are highly specific and can be reused