Cells: The Living Units (Ch. 3)

Question 1

what is a cell?

Answer 1

most basic living structural and functional unit of the body

cells are made mostly of WATER

Question 2

extracellular fluid

Answer 2

fluid outside of cell

function: transports molecules through body

components:

water (main)

Na⁺, K⁺ , CI^- , HCO₃^-

Question 3

intracellular fluid

Answer 3

cytosol: watery fluid inside the cell

cytoplasm: cytosol + organelles

Question 4

cell membrane

Answer 4

also known as Plasma Membrane

function: act as selectively permeable membrane barrier for materials entering and exiting cell

• flexible but sturdy barrier surrounding contents of cell
• separates intracellular from extracellular

Question 5

cell membrane

Answer 5

made up of several components including:

• phospholipids
• glycolipids
• cholesterol
• proteins

Question 6

phospholipids

Answer 6

most common plasma membrane lipid

PURPOSE: creates LIPID BILAYER of Plasma Membrane

Polar Heads⇢ Hydrophilic

Non-Polar Tails⇢ Hydrophobic

makes up 75% of cell membrane

Question 7

cell junctions

Answer 7

there are 3 specialized cell junction structures that help to attach cells:

• gap junctions
• tight junctions
• desmosome (mechanical junctions)

Question 8

gap junctions

Answer 8

junction that allows communication b/w adjacent cells

plasma membranes are very close together & connected by hollow, water-filled cylinders

• allows small molecules to pass from cell to cell easily
• common in electrically excitable cells such as heart & nerves

Question 9

tight junctions

Answer 9

IMPERMEABLE junction that helps PREVENT molecules from passing through extracellular space b/w cells

plasma membranes of adjacent cells are fused together

(ex: in digestive tract organs to prevent digestive enzymes from seeping out of organ & into bloodstream)

Question 10

desmosomes

Answer 10

(Anchoring Junctions)

mechanical couplings scattered along sides of adjacent cells to prevent them from separating

found in cells that sustain a lot of mechanical stress (movement, stretching) such as skin & heart

• helps to anchor cells together by reducing tension
• fastened together by proteins & filaments

Question 11

cell membrane is…

Answer 11

selectively permeable

Question 12

types of cell membrane transportation

Answer 12

• simple diffusion
• facilitated diffusion
• osmosis
• active transport
• vesicular transport

Question 13

simple diffusion

Answer 13

passive process: requires no energy

random movement of particles from an area of HIGH concentration to LOW concentration

HIGH ⇢ LOW

Question 14

facilitated diffusion

Answer 14

passive process: requires no energy

diffusion of substance through channels or attached to protein & is carried across

Question 15

osmosis

Answer 15

passive process: requires no energy

diffusion of water through a selectively permeable membrane

Question 16

active transport

Answer 16

ENERGY IS REQUIRED

transportation of molecules across plasma membrane from area of LOW concentration to HIGH concentration

LOW ⇢ HIGH

Question 17

vesicular transport

Answer 17

vesicle ⇢ small, spherical sacs (bubble-like)

REQUIRES ATP

Question 18

types of vesicular transport

Answer 18

endocytosis⇢ moving molecules INTO a cell

phagocytosis⇢ cell EATING/ INGESTION

pinocytosis⇢ cell DRINKING

exocytosis⇢ moving molecules OUT of a cell

Question 19

tonicity

Answer 19

ability of a solution to change shape or tone of cells by changing volume of WATER within cell

3 types of solution tonicities:

isotonic

hypotonic

hypertonic

Question 20

isotonic solution

Answer 20

CELL RETAINS ITS SHAPE

concentrations of solutes & H20 are SAME inside & outside

water doesn’t have to move or moves in & out in equal amounts

Question 21

hypotonic solution

Answer 21

concentration of H₂0 OUTSIDE > INSIDE

water will move INTO cell

cell will swell & gain weight

cell will eventually burst (lyse)

Question 22

hypertonic solutions

Answer 22

concentration of H₂O INSIDE>OUTSIDE

water will move OUT of cell & cell will lose weight

cell SHRINKS (crenates)

Question 23

cilia

Answer 23

short, multiple, hair-like extensions of cell that have whip-like movement

group of “hairs” that beat in unison to generate current

ex: cells in trachea

Question 24

flagella

Answer 24

long projection from cell

humans only have ONE flagellum

moves cell through its environment

ex: sperm cell

Question 25

microvilli

Answer 25

minute, finger-like extensions of plasma membrane greatly increases surface area “little shaggy hairs”

Question 26

cell organelles

Answer 26

specialized structures inside cell cytoplasm that perform specific functions work together like an assembly line in a factory

Question 27

ribosomes

Answer 27

small granules of protein & RNA **function**: protein synthesis some are free-floating in cytosol (free) and others are attached to outside of organelles (membrane-bound)

Question 28

endoplasmic reticulum

Answer 28

network of flattened tubes & channels inside cell takes up over ½ of space inside cell 2 types of ER: Rough ER Smooth ER

Question 29

Rough ER

Answer 29

covered with ribosomes **function:** involved in protein synthesis

Question 30

Smooth ER

Answer 30

**no ribosomes** (not involved in protein synthesis) most functions involve lipids, cholesterol, steroid hormones

Question 31

golgi apparatus

Answer 31

stacked, flattened sacs modifies, concentrates, & packages materials produced by rough ER in preparation for leaving cell

Question 32

lysosomes

Answer 32

specific type of *vesicle* spherical sacs that contain digestive enzymes **function:** digest worn-out organelles, cells, or any other biological molecules

Question 33

vacuole

Answer 33

specific type of vesicle sacs filled with fluid (most often water) for use by cell more common in plant, fungus cells

Question 34

mitochondria

Answer 34

powerhouse of cell contain their own DNA, RNA, & ribosomes **function:** produce ATP

Question 35

cytoskeleton

Answer 35

cell skeleton network of rods and proteins found in cytosol **function:** stabilize and support cell structure types of rods found: microfilaments intermediate filaments microtubules

Question 36

centrosome/ centrioles

Answer 36

Centrosome ⇢ Cell Center organization center for microtubules usually found near nucleus matrix that contains 2 **CENTRIOLES** small, barrel-shaped organelles oriented at right angles to one another involved in process of mitosis

Question 37

nucleus

Answer 37

genetic control center of cell majority of cells have one nucleus **nuclear membrane (envelope):** double-layered membrane that surrounds nucleus/ encloses its contents **nuclear pores:** small holes in the membrane of the nucleus formed by proteins selectively allows substances to move in and out of nucleus

Question 37

nucleus

Answer 37

genetic control center of cell majority of cells have one nucleus **nuclear membrane (envelope):** double-layered membrane that surrounds nucleus/ encloses its contents **nuclear pores:** small holes in the membrane of the nucleus formed by proteins selectively allows substances to move in and out of nucleus

Question 38

nucleus (cont'd)

Answer 38

**nucleolus:** mass/area inside nucleus where ribosomes are produced **chromatin:** area inside nucleus where DNA/ genetic material is found

Question 39

cell cycle

Answer 39

cells will go through changes in order to grow, repair or reproduce 3 stages in cell cycle: Interphase M Phase (Mitosis) Cytokinesis

Question 40

interphase

Answer 40

phase of cell cycle that prepares cell to be split/divided into 2 daughter cells “Preparation Phase” _split into 3 phases:_ G1 ⇢ phase normal cell function & growth S Phase ⇢ DNA is replicated (synthesized) G2 Phase ⇢ Final preparations before dividing genetic material, fix mutations in DNA replicating (if possible)

Question 41

mitosis (m phase)

Answer 41

process of taking **ONE** mother cell & dividing it into **TWO IDENTICAL** daughter cells aka Nuclear Division 1 Cell ⇢ 2 Genetically identical (daughter) cells essential for growth & tissue repair, replaces old & worn out cells 4 steps in mitosis: prophase metaphase anaphase telophase

Question 42

prophase

Answer 42

chromatin condenses to form visible chromosomes nuclear envelope surrounding nucleus **disappears** mitotic spindles are formed out from centrosomes centrosomes/centrioles move away from one another

Question 43

metaphase

Answer 43

chromosomes line up in middle of cell line up along **metaphase plate**

Question 44

anaphase

Answer 44

chromosomes split & each half migrates to opposite poles of cell

Question 45

telophase

Answer 45

2 sets of chromosomes are now at opposite sides of cell & begin uncoiling back into chromatin form *nuclear envelopes reappear* mitotic spindles break down & disappear

Question 46

cytokinesis

Answer 46

process of dividing cytoplasm into 2 separate cells process actually starts during steps of late anaphase & continues through until end of telophase **cleavage furrow:** created & what was one cell officially becomes two cells cleavage created by microscopic filaments contracting & pinching cytoplasm

Question 47

protein synthesis

Answer 47

process of making proteins occurs in 2 steps: transcription & translation

Question 48

transcription

Answer 48

occurs in nucleus DNA is coded into a strand of mRNA ("half-DNA")

Question 49

translation

Answer 49

occurs in cytoplasm mRNA is decoded & used to make proteins (polypeptides/ chains of amino acids)