Molecules and Cells

Comparative animal physiology lecture 2

embedding proteins and molecules in the membrane

The process of incorporating proteins and other molecules into a cell membrane, allowing for various functions such as signaling, transport, and structural support.

what holds the structure of cell membranes

actin and myosin

actin and myosin do what

play key roles in muscle contraction and cell movement. They enable cellular movement and shape maintenance.

polar heads

of phospholipids in cell membranes that interact with water. They are charged and hydrophilic

Non-Polar tail

of phospholipids in cell membranes that are hydrophobic and repel water. (all of these bonds are single bonds so it is saturated)

what happens if there is a double bond in a membrane lipid

It creates a kink in the fatty acid tail, affecting fluidity and stability. ( making it unsaturated)

What bonds do lipid membranes have

They primarily consist of single covalent bonds, making them saturated

what happens to phospholipids at a lower temperature

They become more compact and less fluid, potentially leading to a more rigid membrane structure. (they get more double bonds making them unsaturated)

What does a higher temperature in phospholipids mean

there is more fluid

channel proteins

that facilitate the transport of ions and molecules across the cell membrane by forming passageways.

diffusion

the process of molecules moving from areas of higher concentration to areas of lower concentration (which moves the lower concentrated molecules outside of the cell)

why do cells pass through a channel instead of lipids

Channel proteins provide a selective passage for specific ions and molecules, allowing faster transport compared to passing through the lipid bilayer.

carrier proteins

proteins that bind to specific molecules and change shape to shuttle them across the cell membrane. (makes conformation open, allowing for solutes to pass through)

Positive transporters

based on concentration moving with the gradient

active transport

needs energy to pass through because it is moving against the gradient

what do receptors do

Receptors are proteins that bind to specific ligands, triggering a cellular response such as signiling pathways or changes in cell activity. (info from outside cell then transfers it across the cell membrane)

How do receptors transfer information across the cell membrane

ligands bind to receptors then goes through a conformational change in the receptor, initiating intracellular signiling pathways. (becomes second messengers)

what are the structures

they attach to other proteins and anchor the intercellular elements to the cell

cytoskeleton filaments

that provide structural support and shape to the cell, composed of microfilaments, intermediate filaments, and microtubules. (creates a junction between adjacent cells

epithelia

is a type of tissue that covers body surfaces and lines cavities, consisting of closely packed cells with minimal extracellular matrix. It serves various functions including protection, secretion, and absorption.

aplical side

on the outside with microtubules (brush border) this gives them more surface area allowing more transporters to fit

basal side

where capillary blood vessels interface with epithelial cells, playing a critical role in nutrient absorption and secretion. (this side needs more transporters)

types of junctions

• tight junction

• septate junction

• desmosome junction

• gap junction

tight junctions

they are an occluding junction (almost touching) meaning they block solute from getting in

septate junction

fully sealed junction

desmosome junction

a type of junction that provides mechanical strength by linking adjacent cells together via intermediate filaments, allowing for flexibility and stability in tissues. (they act as security to prevent things from getting through)

Gap junction

a type of intercellular junction that allows for direct communication between adjacent cells through channels that permit the passage of ions and small molecules. (connexin protein)

type of transport between junctions

• transcellular

• paracellular

transcellular transport

movement THROUGH cell that happens because it cant get passed the tight junction

Paracellular transport

BETWEEN the cells

What do enzymes do

They catalyze biochemical reactions, speeding them up by lowering activation energy.

How do enzymes break the products in two

1. The substrate enters the active site of the emzymes

2. The enzyme changes the shape slightly as the substrate binds

3. The two products split as they leave the active site of the enzyme

What is LDH

LDH, or lactate dehydrogenase, is an enzyme involved in the conversion of lactate to pyruvate and vice versa, playing a crucial role in cellular respiration.

LDH causes

more ATP production which facilitates really fast junctions

LDH is a catalyst meaning

it takes pyruvic acid making it lactid acid then NAD

hyperbolic kinetics

describes the reaction rate of enzymes that show a steep increase in velocity at low substrate concentrations, achieving saturation at higher substrate levels. (one binding site)

sigmoid kinetics

describes the reaction rate of enzymes that show a gradual increase in velocity, often characterized by an S-shaped curve, typically observed in allosteric enzymes. (2 binding sites)

enzyme kinetics uses the michaelis-menten Equation

1. V0= reaction velocity

2. [S]= conc. of substrate

3. Vmax= maximum reaction velocity

4. Km= Michaelis constant, reflecting substrate concentration at half Vmax.

high affinity

refers to the strong binding interaction between an enzyme and its substrate, resulting in a low Km value in enzyme kinetics. And reaches Vmax faster

low affinity

refers to the weak binding interaction between an enzyme and its substrate, resulting in a high Km value in enzyme kinetics, thus reaching Vmax at a slower rate.

Km is the measure of

Measure of reaction ½ and conc. of substrate

isozomes

enzymes that catalyze the same reaction but differ in structure.

interspecific enzyme homologs

enzymes from different species that perform similar functions due to shared ancestry. (different forms of the same enzyme)

single enzymes can exist in ____ forms and ____ the same reaction

multiple, catalyze

constitutive enzymes

are continuously produced by the cell and are always active, regardless of the conditions. ( kept in low concentrations & normal conditions)

constitutive enzyme

An enzyme that is produced continuously by cells, remains active under normal conditions, and maintains a consistent level regardless of external factors. (steady)

signal mechanism functions

sending signals in or out of cell

Four classes of receptors

1. ligand-gated channels

2. G protein-coupled receptors

3. Enzyme-linked receptors and intracellular receptors.

4. intracellular receptors

signal reception

The process by which cells detect and respond to signaling molecules, allowing for communication and coordination of functions within and between cells.

signal transduction

The series of biochemical processes that occur after a cell receives a signal, leading to a specific cellular response.

Ligand gated channel

A type of receptor that opens in response to the binding of a channel protein, allowing ions to flow across the membrane and triggering cellular responses. (ligand binds to receptor site causing channel to open)

G Protien-coupled receptor

ligand binding to g protein coupled receptor activates the G protein, initiating intracellular signaling pathways that lead to various physiological responses. (no channel, and no chemicals pass through the cell membrane)

enzyme-linked receptor

Receptor that acts as an anchor causing quick reactions without multiple proteins (no ions/ligands pass through the membrane)

Intracellular receptor

A type of receptor that binds to ligands that have crossed the cell membrane, typically leading to changes in gene expression. (can pass through membrane inside the cell nucleus and the ligand can move itself)