Living Environment Regents Exam Review - Unit 2

Unit 2 Review

the cell theory

1. all living things are made of cells (basic unit of structure)

2. all cells carry out the life processes (basic unit of function)

3. all cells come from other living cells

exceptions to the cell theory

• viruses - carry on none of the life processes; can only reproduce when inside a HOST cell)

• the first cell (doesn’t support that all cells come from other living cells…one cell had to be the first one)

• mitochondria & chloroplasts - contain their own genetic materials (may have existed on their own at one time)

cell structures (organelles)

• cell membrane

• cell wall

• nucleus

• ribosome

• mitochondria

• chloroplast

• cytoplasm

cell membrane

semi-permeable OR selectively permeable which means only certain molecules can cross the membrane

it DOES NOT protect the cell

cell wall

• found in PLANT CELLS ONLY

• provide structural support

• DOES NOT protect the cell

nucleus

• contains DNA

• controls cell metabolism and reproduction

ribosome

• where protein synthesis (building/making) occurs

mitochondria

• a cell’s powerhouse

• where energy (ATP) is made

• the site of respiration

chloroplast

• PLANT CELLS ONLY

• site of photosynthesis

• contain chlorophyll (green pigment/coloring)

cytoplasm

• transports materials throughout the cell

differences between plant and animal cells

Plant cells

• contain chloroplasts

• have a cell wall

• one large, central water vacuole

• no centrioles

Animal cells

• do NOT have chloroplasts

• do NOT have a cell wall

• many small vacuoles

• contain centrioles

transport across the cell membrane

1. cell (plasma) membrane

2. passive transport (DIFFUSION)

3. active transport

cell (plasma) membrane

• controls what materials can enter and leave the cell (selectively permeable)

• the fluid-mosaic model of cell membrane composition

• the cell membrane is composed of a LIPID BILAYER with PROTEINS embedded or attached to it

• the cell membrane maintains the cell’s HOMEOSTASIS by controlling what can enter and leave the cell

• IT DOES NOT ALWAYS PREVENT HARMFUL SUBSTANCES FROM ENTERING!

passive transport (DIFFUSION)

• requires NO ENERGY

• diffusion - movement of molecules from areas of high concentration to areas of low concentration

• osmosis - diffusion of water

active transport

• requires ENERGY or ATP (which is gotten from the mitochondria)

• movement of molecules from LOW concentration to HIGH concentration

• ex. like riding a bike uphill

levels of organization

• organelles —> cells —> tissues —> organs —> organ systems —> organism

communication between cells

• cells communicate with each other using a variety of chemical signal and receptors

cell receptors

• proteins in the cell membrane that bind to signals coming from other cells in the body

• the shape of the receptor determines its function

• receptors are very specific! they will only bind to the chemical signal that has a matching shape, much like the Lock & Key Model of Enzyme Action

• chemical signals include: neurotransmitters & hormones

• the target cell/organ is the cell/organ that has the receptor able to bind to the desired signal