Bio140 Exam 2: Ch. 7-10

Structure of cell membrane

The plasma membrane fluid mosaic model describes the plasma membrane as a fluid combination of phospholipids, cholesterol, and proteins. Carbohydrates attached to lipids (glycolipids) and to proteins (glycoproteins) extend from the membrane's outwardfacing surface.

Integral protiens

• may serve as enzymes, as structural attachments for cytoskeleton, or as a cell recognition site

• Embedded within the phospholipid layer(s); may or may not penetrate through both layers

glycoprotiens

protein with carbohydrate attached

glycolipids

lipid with carbohydrate attached

Peripheral proteins

• may serve as enzymes, as structural attachments for cytoskeleton, or as a cell recognition site

• on the phospholipid bilayer’s inner or outer surface; not embedded within the phospholipids

Selective permeability

Some things pass through easily, some do not

What passes easily through a membrane?

• non-polar molecules

• lipid soluble molecules

• mol’s of low molecular wt

• fat soluble vitamins DEKA

• fat soluble hormones

• compounds with no charge

• Oxygen, Carbon Dioxide

What does not pass easily through a membrane?

• polar molecules

• charged ions (Ca, Na, K, Cl)

• simple sugars

• amino acids *need special transporters

Passive diffusion

• requires no energy

• Moving down concentration gradient

active diffusion

• requires ATP

• movement into a higher concentration (against concentration gradient)

What factors affect the rate of diffusion?

• extent of concentration gradient (greater difference, greater rate)

• mass of molecules (lighter mol’s move faster)

• solvent density (greater density, slower rate)

• charge of molecules (non-polar move faster than polar)

• surface area and membrane thickness (high surface area = faster movement, higher membrane thickness = slower movement)

• Distance traveled (greater dist. = slower movement)

Facilitated diffusion

• Moves substances down their concentration gradients

• may cross the plasma membrane with the aid of channel proteins

diffusion

Movement of molecules from an area of high concentration to an area of low concentration

osmosis

Movement of water from a high to low concentration (or through diffusion)

Aquaporins

water “transporter”

Carrier/Channel proteins

• assist with movement

• often “gated” channels

• must have a trigger to open

• Carrier proteins change shape as they move molecules across the membrane

Osmolarity

describes the solutions solute concentration

tonicity

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

solute

A substance that can be dissolved by a solvent

solvent

A substance in which the solute is dissolved

crenolysis

no idea what this is

plasmolysis

the process in which cells lose water when they are placed in a hypertonic solution. It causes contraction or shrinking of the plasma membrane away from the cell wall. It is a reversible process and the cell can get back to normal when placed in a hypotonic solution.

turgor pressure

force within the cell that pushes the cell membrane against the cell wall

Hypertonic solutions

• Solution that contains less water and more of the other substance

• water moves out of the cell into the solution

• cell shrinks

hypotonic solutions

• solution that contains more water and less of the other substance

• water moves into the cell from the solution

• cell swells

isotonic solutions

solution where water and another substance have the same concentration

What does it mean if the inside of a cell has an osmolarity higher than that of the outside of the cell?

• it is hypertonic

• water moves out of the cell

• cell shrinks

How do one-celled organisms deal with tonicity issues?

contractile vacuole

Electrochemical gradients

• arise from the combined effects of concentration gradients and electrical gradients

• created by primary active transport

Sodium-potassium pump

functions in nerve cell signaling, heart conditions, and kidney functions

antiporter

Carries two different molecules or ions, but in different directions

symporter

Carries two different molecules or ions, both in the same direction

uniporter

carries one molecule or ion

primary active transport

• moves ions across a membrane, creating an electrochemical gradient

  • Directly requires ATP

secondary active transport

an electrochemical gradient can move other substances against their concentration gradients

pinocytosis

• “Cell drinking”

• the cell membrane invaginates, surrounds a small volume of fluid, and pinches it off

phagocytosis

• “cell eating”

• the cell membrane surrounds the particle and engulfs it

endocytosis

• includes pinocytosis and phagocytosis

• Taking particles that are too big to passively cross the cell membrane

exocytosis

Vesicles containing substances fuse with the plasma membrane. The contents are then released to the cell’s exterior.

Passive or Active: oxygen

passive

Passive or Active: glucose

passive

Passive or Active: molecules move from low to high concentration

active

Passive or Active: water

passive

Passive or Active: charged molecules

active

Passive or Active: fat soluble

passive

Passive or Active: facilitated transport

passive

Passive or Active: osmosis

passive

Passive or Active: endocytosis

active

Passive or Active: phagocytosis

active

Passive or Active: sodium-potassium pump

active

Bioenergetics

the flow of energy through living systems

metabolism

the chemical reactions in the body when your cells turn food to energy

anabolic reactions

• pathways that require energy to synthesize larger molecules

• small molecules assemble into larger ones

• energy is required

catabolic reactions

• pathways that generate energy by breaking down larger molecules

• large molecules break down into small ones

• energy is released

transfer of energy

relocation of energy from one place to another, typically in a different form

endergonic reactions

• process that requires energy

• nonspontaneous

exergonic reactions

• process that releases energy

• spontaneous

catalysts

speeds up a reaction

enzyme role in chemical reactions

enzymes decrease the energy required for a chemical reaction to start

ATP

• Adenosine Triphosphate

• the primary energy currency of the cell

ADP

• Adenosine Diphosphate

• when combined with a phosphate it creates ATP

AMP

• Adenosine Monophosphate

• when combined with a phosphate it creates ADP

Phosphoanhydride bonds

high energy bonds between phosphate molecules

dephosphorylation

phosphate group is removed from a molecule

phosphorylation

phosphate group is added to a molecule

Enzyme function- active site

where enzymes bind substrates

Enzyme function- substrate

a molecule an enzyme reacts and binds with

Enzyme function- allosteric competitive inhibition

• modify the active site of the enzyme so that substrate binding is reduced or prevented

• blocks an enzyme’s active site

Enzyme function- allosteric non-competitive inhibition

• modify the active site of the enzyme so that substrate binding is reduced or prevented

• binds to an enzyme somewhere other than the active site, changing its shape and preventing enzyme-substrate interaction

Enzyme function- feedback inhibition

where the end product of the pathway inhibits an upstream step

Enzyme function- allosteric activation

modify the enzyme’s active site so that the affinity for the substrate increases

role of vitamins as cofactors

critical for processes involved in proper vision, blood coagulation, hormone production, and the integrity of collagen, a protein found in bones.

role of vitamins as coenzymes

participate in numerous biochemical reactions involving energy release or catabolism, as well as the accompanying anabolic reactions

chemiosmosis

produces most of the ATP for a cell

photoautotroph

using the energy of sunlight to make organic molecules

chemoautotroph

able to synthesize their own organic molecules from the fixation of carbon dioxide

Role of NAD

• an electron carrier used to temporarily store energy during cellular respiration

• oxidized

• vitamin B derivatives

role of FAD

• another electron carrier

• can carry fewer electrons than NAD

• Vitamin derivatives

role of ATP in cell respiration

• can be broken down

• like a rechargeable battery

• main energy source

Oxidation-reduction reactions

• reactions that involve the transfer of electrons from one species to another

• Lose electrons = oxidized

• gain electrons = reduced

Steps of cell respiration (aerobic)

Step 1- Glycolysis

Step 2- pyruvic acid breakdown (oxidation of pyruvate)

Step 3- krebs cycle

Step 4- oxidative phosphorylation (electron transport chain)

Steps of cell respiration (anaerobic)

Step 1- glycolysis

Step 2- oxidation of pyruvate

Step 3- fermentation

Steps of fermentation

Step 1: glycolysis

Step 2: NAD+ regeneration

How can proteins be used for energy?

protein is broken down into ketone bodies to be used for energy

How can fats be used for energy?

fats are broken down into fatty acids and glycerol then these fatty acid chains are converted into energy

ATP synthase

• integral membrane protein

• allows protons to flow down their electrochemical gradient

electron carriers

electron shuttles moving energy from one molecule to another

carbon fixation

the conversion of atmospheric carbon dioxide into organic molecules by autotrophic organisms

NADP+ reductase

converts NADP⁺ to NADPH

How does sugar get into the cell? How is insulin involved?

The food you eat is broken down into blood sugar. Blood sugar enters your bloodstream, which signals the pancreas to release insulin. Insulin helps blood sugar enter the body's cells so it can be used for energy. Insulin also signals the liver to store blood sugar for later use.

Reactants and products for cell respiration

Reactants: Oxygen and glucose

Products: Carbon dioxide and water

reactants and products for photosynthesis

Reactants: Carbon dioxide and water

Products: Glucose and oxygen

stomata

microscopic pores where gas and water exchange occurs

stroma

dense fluid surrounded by two membranes

thylakoid

connected sacs in the chloroplast that compose a thrid membrane system

grana

stacks of thylakoids

chloroplast

the sight of photosynthesis in plants

Steps of photosynthesis (PSI, PSII, dark reaction)

Light-dependent reactions, which take place in the thylakoid membrane, use light energy to make ATP and NADPH. The Calvin cycle, which takes place in the stroma, uses energy derived from these compounds to make GA3P from CO2 .

How do plants make use of the wavelengths of light in the light spectrum?

(a) Chlorophyll a, (b) chlorophyll b, and (c) β-carotene are hydrophobic organic pigments found in the thylakoid membrane. Chlorophyll a and b, which are identical except for the part indicated in the red box, are responsible for the green color of leaves. β-carotene is responsible for the orange color in carrots. Each pigment has (d) a unique absorbance spectrum.

What is the connection between plants and animals? Why do we need each other?

Plants are producers — they take energy from the sun, nutrients from the ground, and water to grow and produce their flowers, seeds, and berries. They also release oxygen, which all animals, including humans, need to survive. Animals are consumers and they all depend on plants for survival.