BIO 1103 Exam 2

Phospholipids are

amphipathic and they cluster together in water

Phospholipid bilayer key property is

being a barrier

Basic membrane structure

phospholipid bilayer, transmembrane proteins, interior protein network, and cell surface markers

Fluid mosaic model is

mosaic of protein bobbing in a fluid bilayer

The fluid mosaic model is not

homogeneous

The fluid mosaic model varies in

lipid and protein composition

Fluidity influences

permeability

Temperature and lipid composition affect

Fluidity

Lipid composition includes

Saturated vs unsaturated, FA length, cholesterol

Integral membrane proteins

Penetrate to the hydrophobic area of membranes

Another name for integral membrane proteins

transmembrane proteins

Peripheral proteins

loosely bound to membrane surface, not in membrane

In a membrane

proteins are not floating freely

Some proteins are bound to

cytoskeleton

Functions of membranes

receptors, enzymes, channels, identity markers, cell-adhesion molecules

Membranes are

barriers and selectively permeable

Passive transport

movement of substances across a membrane without expending energy

Passive transport uses

concentration gradient

A concentration gradient is

the difference in concentration on different sides of a membrane

Diffusion

movement of a substance from high to low

Diffusion continues until

same concentration exists

Speed of diffusion depends on

Temperature and concentration

Osmosis

movement of water from a higher to a lower concentration across a membrane

Higher solute

lower water

Osmosis causes

osmotic pressure on the cell membrane

Hypertonic

Greater amount of solute on the outside of the cell causing movement of water out of the cell leading to cell shrinkage

Isotonic

The same amount of solute inside and out

Hypotonic

Greater amount of solute inside the cell causing movement of water into the cell leading to cell swelling

Simple diffusion

Directly through the membrane

Simple diffusion moves

small hydrophobic molecules like oxygen and carbon dioxide

speed of simple diffusion depends on

concentration

The bigger the distance

the faster the diffusion

Facilitated diffusion

Uses concentration gradients but facilitated by protein channels or carriers

Channel proteins

Integral proteins that form passages for certain substances

Ions pass through

Ion channels

Gated channels require

a stimulus

Ligand bind to

binding site

Aquaporin proteins are

channel proteins

Aquaporin can transport

three billion water molecules per second; in the kidney

Carrier proteins

can help transport ions, sugars, and amino acids

Carrier proteins bind

to the molecule they transport

Uniporter

Move one molecule at a time one direction

Symporter

two types of molecules in the same direction

Antiporter

two types of molecules in opposite directions

Rate of diffusion in facilitated diffusion is

limited and can become too saturated

Active transport

goes against the concentration gradient

Active transport requires

energy and carrier proteins

Pumps

move a single type of molecule in a given direction at a time

Sodium-potassium pump

moves K inside and Na outside cell

Phosphate from ATP changes

protein shape

Sodium potassium pump steps

1. Sodium in

2. ATP phosphate attached, ADP is left

3. Change in shape, release sodium

4. Potassium in

5. Release phosphate which changes protein shape

6. Release potassium, ready for sodium again

Cotransport

using the Na-K pump, drags glucose into the cell using sodium’s concentration gradient, pulling glucose against its’ gradient

Bulk transport

two processes that get larger substances into and out of the cell; requires energy

Endocytosis

bring substances into the cell

phagocytosis

larger particles are engulfed by the membrane; “cellular eating”

pinocytosis

smaller vesicles form to bring fluids into cell; “cellular drinking”

receptor-mediated endocytosis

molecules bind to receptors before being engulfed

receptor-mediated endocytosis is good for

uptake of substances at low concentration

exocytosis

the discharge of material from vesicles at the cell surface

The material discharged through exocytosis

construct the cell wall

Exocytosis secretes

hormones and neurotransmitters

Energy

the capacity to do work

Metabolism

The sum total of all chemical reactions occurring in a biological system at a given time

Metabolic reactions involve

energy changes

Anabolic reactions

complex molecules are made from simple molecules

Catabolic reactions

complex molecules are broken down into simpler ones

Biology energy

Found in changes in composition and properties of molecules

Biology energy is found in

chemical, electrical, heat, light, and mechanical

Potential energy

state or position (stored energy)

Kinetic energy

does work or of motion

Thermodynamics

study of energy transformations

The laws of thermodynamics apply to

all matter and all energy transformations

First law of thermodynamics

Energy is neither created or destroyed

Second law of thermodynamics

When energy is converted, some becomes unavailable to do work

The loss of energy leads to

the disorder of entropy increasing

It takes energy to create

order

Living organisms are

open systems

Total energy =

usable energy + unusable energy (H=G+TS)

H

Enthalpy

G

Free energy

TS

Temp entropy

Free energy is

usable energy (G=H-TS)

H is

the energy in a molecule’s chemical bonds

Change in energy can be measured in

calories

Calories are

the amount of energy needed to heat 1g or water to 1°C

If ΔG is negative

Free energy is released

If ΔG is positive

Free energy is required

Exergonic

reactions release free energy

Exergonic reactions are

catabolic metabolism, decrease complexity, generates disorder, spontaneous

Endergonic

reactions consume free energy

Endergonic reactions are

Anabolic metabolism, increase complexity, creates order

Activation energy

Energy required to get a reaction started

Activation energy destabilizes

existing bonds

The more activation energy needed

the slower a reaction will proceed

Rate of exergonic reactions can be increased by

increasing energy of reaction molecules (heating) and lowering activation energy

Catalyst

Substances that influence chemical bonds in a way that lowers activation energy

Catalysts speed up the rate of

a reaction

Catalysts cannot make

an endergonic reaction spontaneous

Catalysts do not

alter the proportion of reactant turned into product

Catalysts do not alter

the equilibrium of product