Chapter 5

Phagocytosis

"cellular eating" large particles like macromolecules get packaged into food vacuoles

Enzymes

- An enzyme is a protein molecule that functions as an organic catalyst to speed a chemical reaction. - An enzyme brings together particular molecules and causes them to react.

Energy of Activation

- The energy that must be added to cause molecules to react with one another is called the energy of activation (Ea). -The addition of an enzyme lowers the energy of activation.

Sodium Potassium Pump

- The sodium-potassium pump is active in all animal cells, and moves sodium ions to the outside of the cell and potassium ions to the inside. • The sodium-potassium pump carrier protein exists in two conformations; one that moves sodium to the inside, and the other that moves potassium out of the cell.

Passive transport

- does NOT require chemical energy - Substances move DOWN their concentration gradients. - Ex. diffusion, osmosis, and facilitated transport

What are four ways substances cross the membrane?

1. Simple Diffusion: 2. Active Transport 3. Facilitated Diffusion 4. Bulk Transport

6 functions of membrane proteins

1. Stronger Framework- maintain cell shape 2. Identification Tags- important for cell-to-cell recognition 3. Link Adjacent Cells 4. Enzymes- speed up chemical reactions 5. Cell Signaling- can catch messages and relay the message between the inside and outside of the cell - signal transduction pathway 6. Transport- can move molecules into or out of a cell

Concentration Gradient

A difference in concentration of a substance across a space is called a concentration gradient. ¡ There is usually a difference in the concentration of a substance inside the cell compared to outside the cell.

active site

A substrate fits into that region of the enzyme

3 uses of ATP

Chemical Work, Mechanical Work, Transport Work

Why are enzymes specific?

Enzymes are specific because their active sites only fit specific substrate molecules.

Every reaction in a cell requires a...

Every reaction in a cell requires a specific enzyme.

Two types of bulk transport

Exocytosis and Endocytosis

Which types of transport requires carrier proteins?

Facilitated transport and active transport

What happens with higher temperatures and the rate of an enzyme

Higher temperatures increase the rate of enzyme activity because there are more collisions between substrate molecules and the enzyme...

Hypertonicity

Hypertonic solutions cause cells to lose water. - "Hyper" means more than; hypertonic solutions contain more solute.

Hypotonicity

Hypotonic solutions cause cells to swell and possibly burst. - "Hypo" means less than. • Animal cells undergo lysis (when cells swell and membrane bursts) in hypotonic solution. - Water enters cell. - Increased turgor pressure occurs in plant cells in hypotonic solutions. • Plant cells do not burst because they have a cell wall.

What does it mean when The plasma membrane is semipermeable?

Macromolecules cannot pass through because of size, and tiny charged molecules do not pass through the nonpolar interior of the membrane. - Small, uncharged molecules pass through the membrane, following their concentration gradient.

3 types of Endocytosis

Pinocytosis Receptor-mediated endocytosis Phagocytosis

Hypertonicity in plant cells

Plant cells do not burst because they have a cell wall. , increased turgor pressure. Vacuoles expand, you see the chloroplast pushed up against the cell wall

Carrier proteins

Proteins that some biologically useful molecules pass through the plasma membrane, because the carrier proteins spans the membrane (Carrier proteins are specific and carry only a certain type of molecule)

How do proteins stay in the membrane?

Since proteins are made up of polar and nonpolar amino acids, the nonpolar part of the protein is attracted to the phospholipid tails, but is repelled by the water on either side of the bilayer. ¡ The polar part of the protein is attracted to the water on the inside and outside of cells. ¡ These attractions hold the protein in place.

Why are inhibitors important?

Some antibiotics inhibit enzymes of harmful bacteria. - Some poisons are inhibitors and can be used in warefare or pesticides. - Some regulate metabolism and other bodily functions.

Cycle of an Enzyme

The active site may undergo a slight change in shape, called induced fit, in order to accommodate the substrate(s). The enzyme and substrate form an enzyme-substrate complex during the reaction. The enzyme releases the products. The enzyme is not changed by the reaction, and it is free to act again.

Osmosis

The diffusion of water across a selectively permeable membrane

osmosis

The diffusion of water across a selectively permeable membrane due to concentration differences. - Diffusion always occurs from higher to lower concentration whether it's water, gas or ions! - Water enters cells due to osmotic pressure within cells.

What is the Plasma Membrane made out of?

The plasma membrane is a phospholipid bilayer with embedded proteins.

Plasma Membrane

The plasma membrane separates the internal environment of the cell from its surroundings.

Substrates

The reactants in an enzymatic reaction for that enzyme

Synthesis

The substrates going in as different pieces but coming together as one product

Degradation

The substrates going in as one and splitting up as different products

crenation

What animal cells undergo in hypertonic solutions (They shrivel)

plasmolysis

What plant cells undergo in hypertonic solutions (the cytoplasm shrinks, and stretches away from the cell wall) (chloroplasts are seen in the middle)

Inhibitors

are chemicals that interfere with an enzyme's activity. - Some block the normal substrate from entering the active site. Others cause the enzyme to change shape so the active site no longer fits the substrate.

Pinocytosis

cell "gulps" droplets of fluid by forming vesicles, "cellular drinking"

Too high of temperatures can...

denature enzymes, which changes the shape of the proteins so they can't work.

Cells live in...

fluid environments. Water inside and outside of cell

An enzyme's shape is vital for its ...

function.

Entropy

is a measure of disorder in a system. (It takes energy to keep life organized!)

ATP

is the main energy source for cells. ATP stores energy from food and then releases it later when the energy is needed.

Diffusion

is the passive movement of molecules from a higher to a lower concentration until equilibrium is reached. - Gases move through plasma membranes by diffusion.

Feedback inhibition

is where an enzymatic reaction is blocked by one of its products.

4. Bulk Transport

large substances move across the cell membrane into the cell (endocytosis) or out of the cell (exocytosis) with the help of vesicles.

In an isotonic solution in a plant and animal cell, there is no...

net movement of water

Active transport

requires chemical energy and usually a carrier protein. - Substances move UP/AGAINST their concentration gradients. - Ex. Exocytosis and endocytosis transport macromolecules across plasma membranes using vesicle formation, which requires energy.

Isotonicity

solutions with equal solute, Cells are normally isotonic to their surroundings, and the solute concentration is the same inside and out of the cell. No net movement of water into or out of cell. - "Iso" means the same as, and "tonocity" refers to the strength of the solution.

Receptor-mediated endocytosis

specific particles

The carrier protein for glucose has...

two conformations and switches back and forth between the two, carrying glucose across the membrane.

3. Active transport

way a substance crosses the plasma membrane, 3. Active substances move against their concentration gradients, aided by transport proteins and requiring energy input

What is Simple Diffusion

way a substance crosses the plasma membrane, substances move down their concentration gradients

2. Facilitated Diffusion

way a substance crosses the plasma membrane, substances move down their concentration gradients by passing through a transport protein

Three ways of Osmosis are...

¡ Three possible directions for water movement across cell membranes. l 1. Water moves out of cell. l 2. Water moves into cell. l 3. No net water movement into or out of cell. ¡ i.e. water moving out of cell at same rate as water moving into cell

Q: Using what you know about water, do you think water can move through the plasma membrane unaided?

A: No! Since water is polar, it cannot get through the fatty acid tails of the plasma membrane, so it needs to move through with the help of a channel protein.

Mechanical work -

ATP supplies energy for cellular movements

Transport work -

ATP supplies energy needed to pump substances across the plasma membrane

Chemical work of ATP

ATP supplies energy to synthesize macromolecules, and therefore the organism

Full Name for ATP

Adenosine Triphosphate

Lysis

Animal cells undergo lysis (when cells swell and membrane bursts) in hypotonic solution.

Pumps

Carrier proteins involved in active transport are called pumps.

Active transport (detailed)

During active transport, ions or molecules are moved across the membrane against the concentration gradient - from an area of lower to higher concentration. - Energy in the form of ATP is required for the carrier protein to combine with the transported molecule.

Endocytosis

During endocytosis, cells take in substances by pinching in a portion of the plasma membrane, and forming a vesicle around the substance.

exocytosis

During exocytosis, vesicles fuse with the plasma membrane for secretion. - Molecules LEAVE the cell. - Some cells are specialized to produce and release specific molecules. • Examples include release of digestive enzymes from cells of the pancreas, or secretion of the hormone insulin in response to rising blood glucose levels.

Facilitated transport

During facilitated transport, substances pass through a carrier protein following their concentration gradients. - Facilitated transport does not require energy.

Substrate: Lipid

Enzyme: Lipase

Substrate: Maltose

Enzyme: Maltese

Substrate: Ribonucleic acid

Enzyme: Ribonuclease

Substrate: Urea

Enzyme: Urease

Phospholipid Bilayer

Two phospholipids line up tail to tail to form a bilayer.Hydrophilic (water-loving) polar heads of the phospholipid molecules lie on the outward-facing surfaces of the plasma membrane. Hydrophobic (water-fearing) nonpolar tails extend to the interior of the plasma membrane.