Chapter 3: Cells: The Living Units Flashcards Preview

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Flashcards in Chapter 3: Cells: The Living Units Deck (86):
1

Cells

Structural units of all living things

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Describe Cell Theory

1) A cell is the BASIC structural and functional UNIT OF LIVING ORGANISMS
2) The ACTIVITY of an organism depends on both the individual and combined activities of its cells
3) BIOCHEMICAL ACTIVITIES of cells are dictated by their SHAPES or forms and the relative number of the sub cellular structures they contain
4) Cells come from OTHER CELLS

3

Generalized/ Composits Cell

All cells have the same basic parts and some common functions

4

What are the 3 main parts of a cell?

1) Plasma Membrane
2) Cytoplasm
3) Nucleus

5

Extracellular materials

Substances contributing to body mass that are found outside the cells

6

What are the classes of Extracellular materials?

• Body fluids
• Cellular secretions
• Extracellular matrix

7

Body Fluids (also called extracellular fluids)

Important transport and dissolving media
• Interstitial Fluid
• Blood Plasma
• Cerebrospinal Fluid

8

Interstitial Fluid

The fluid in tissues that bathes all of our cells and has major and endless roles to play
• Rich, nutritious "soup" (ingredients: amino acids, sugars, fatty acids, regulatory substances and wastes)
• Each cell must extract from this to stay healthy

9

Cellular Secretion

Substances that aid in digestion and some act as lubricants (saliva, mucus...)

10

Extracellular Matrix

• Most abundant extracellular material
• Universal Cell "glue"- holds body cells together
1) Body cells are in contact with proteins and polysaccharides (secreted by cells)
2) Molecules self-assemble into organized mesh

11

Describe the cell membrane

• Lipid Bilayer
• Protein molecules

12

What are the lipids of the membrane?

1) Phospholipids
2) Glycolipids
3) Cholesterol

13

Describe the phospholipids

• Polar head is charged and hydrophilic
• Non Polar tail has 2 fatty acid chains and is hydrophobic

14

Describe the movement of Phospholipids

Move freely side to side

15

Glycolipids

Lipids with attached sugar groups
- 5% of total membrane lipids

16

Cholesterol

- 20% of membrane
- Polar region: Hydroxyl
- Non polar: Fused ring system
• Stabilizes membrane
• Decreases mobility of phospholipids and fluids

17

Membrane Proteins Functions

• Allows cell to communicate w/ environment
- 1/2 plasma mass
• Specialized membrane functions

18

What are the 2 distinct populations of proteins?

1) Integral
2) Peripheral

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Integral Proteins

- Firmly inserted in membrane
- Some protrude one side, Most protrude both (transmembrane proteins)
• Have Hydrophilic and Hydrophobic regions
- Can interact with Non-Polar lipid tails and water in/out of cell

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Transmembrane Proteins

• Protrude both sides of membrane
- Some transport and provide channels: Water-soluble molecules or ions pass
- Some carry: bind to substance and move through membrane
- Enzymes
- Receptors for hormones

21

Signal transduction

A process where chemical messengers relay messages to the cell interior

22

Peripheral Proteins

- Not embedded in membrane
- Attach loosely to integral proteins and can be easily removed

23

Glycocalyx

Consists of glycoproteins and glycolipids that form a fuzzy, sticky, carbohydrate-rich area at the cell surface
- enriched by glycolipids and glycoproteins secreted by the cell
**Provides highly specific biological markers by which approaching cells recognize each other; Ex: Sperm recognizes an ovum

24

What 3 factors act to bind cells together?

1) Glycoproteins in the glyocalyx act an adhesive
2) Wavy contours of the membranes of adjacent cells fit together in a tongue-and-groove fashion
3) Special cell junction form

25

What 3 junctions are important for factors in securing cells together?

1) Tight Junction
2) Desmosomes
3) Gap Junctions

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Tight Junctions

A series of integral protein molecules in the plasma membrane of adjacent cells fuse together, forming an impermeable junction that encircles the cell
- Prevents molecules from passing through the extracellular space between adjacent cells

27

Desmosomes

Anchoring junctions that bind adjacent cells together act like molecular "Velcro" and also help form an internal tension-reducing network of fibers
- Plaque: is on the face of each plasma membrane
- Cadherins: Protein filaments that hold together adjacent cells that extend from the plaques
- Keratin: the extend from the cytoplasmic side if the plaque to anchor to the plaque on the cells opposite side
Distributes tension throughout a cellular sheet and reduces the chance of tear when under pulling force
- Ex: Skin, Heart muscle

28

Gap Junctions

Communicating junctions that allow ions and small molecules to pass are particularly important for communication in heart cells and embryonic cells
- adjacent plasma membranes are close connected by hollow cylinders (connezons), which are composed of transmembrane proteins
- Present in electrically excitable tissues where ion passage from cell to cell helps synchronize their electrical activity and contraction

29

Passive Processes

Substances cross the membrane without any energy input from the cell

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Active Processes

The cell provides the metabolic energy (usually ATP) needed to move substances across the membrane

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What are the 2 main types of Passive Transport?

1) Diffusion
2) Filtration/ Facilitated

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Diffusion

The tendency of molecules or ions to move from an area where they are in higher concentration to an area where they in lower concentration (on the concentration gradient)

33

Describe the barrier of the plasma membrane?

It allows some substances to pass while excluding others
It allows nutrients to enter to cell, but keeps many undesirable substances out
- Keeps valuable cell proteins in
- Allows waste to exit

34

What molecules or ions are allowed to through the membrane?

1) Lipid soluble
2) Small enough to pass through membrane channels, or
3) Assisted by a carrier molecule

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Simple Diffusion

The unassisted diffusion of lipid-soluble or very small particles; nonpolar and lipid-soluble substances diffuse directly through the lipid bilayer
- Lipid-soluble: Oxygen, Carbon Dioxide and fat-soluble vitamins

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Osmosis

The diffusion of a solvent (usually water) through a membrane

37

Describe oxygen concentration

Higher in blood than in tissue cells so oxygen continuously diffuses from the blood into the cells

38

Describe carbon dioxide concentration

Higher in concentration within cells, so it diffuses from tissue cells into the blood

39

Facilitated Diffusion

The transported substance either (1) binds to protein carriers in the membrane and is ferried across or (2) moves through water-filled protein channels

40

Osmolarity

Measure of total concentration of solute particles

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Tonicity

Ability of a solution to change the shape or tone of cells by altering the cells internal water volume

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Isotonic

Solution has same osmolarity as inside the cell, so volume remains unchanged

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Hypertonic

Solution has higher osmolarity than inside cell, so water flows out the cell, resulting in cell shrinking

44

Hypotonic

Solution has lower osmolarity than inside cell, resulting in cell swelling

45

Carrier-mediated Facilitated Diffusion

Transmembrane Integral proteins that transport specific polar molecules that are too large for membrane channels
- Binding to molecule causes carrier to change shape, moving molecule in process

46

Channel-mediated Facilitated Diffusion

- Channels with aqueous-filled cores are formed by transmembrane proteins

Transport molecules down their concentration gradient
1) Leakage Channels (always open)
2) Gated Channels (controlled by signals)

47

What are the 2 major active membrane transport processes?

1) Active Transport
2) Vesicular Transport
- Both require ATP

48

Active Transport

• Require carrier proteins
- Anti porters
- Symporters
• Moves solutes against their concentration gradient (low-high)
- Requires ATP

49

What are the types of Active Transport?

1) Primary Active Transport
2) Secondary Active Transport

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Primary Active Transport

• Energy from hydrolysis of ATP causes change in shape of transport protein
- Shape change causes solutes (ions) bound to protein to be pumped across membrane
- Ex: Calcium, Hydrogen (proton), Na+ -K+ pumps

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Sodium-Potassium Pump

Enzyme (Na+-K+ ATPase) that pumps sodium out of cell and potassium back into cell
- Leakage channels
- Antiporter
• Maintains electrochemical gradients, which involve both concentration and electrical charge of ions

52

Secondary Active Transport

Moves a lot of molecules to one side of a membrane, they will want to diffuse back.
When they diffuse, they may drag other molecules with them
• Symporters

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Vesicular Transport

Involves transport of large particles, macromolecules, and fluids across membrane in membranous sacs called vesicles
• Requires cellular energy (usually ATP)

54

Endocytosis

- Involves formation of protein-coated vesicles
Once vesicle is pulled inside cell, it may:
1) Fuse with lysosomes or
2) Undergo transcytosis (travel through the cell)

55

Phagocytosis

Type of endocytosis that is referred to as "cell eating"
- Membrane projections called pseudopods form and flow around solid particles that are being engulfed, forming a vesicle which is pulled into cell
• Vesicle formed is called a phagosome
- used by macrophages and certain white blood cells

56

Cytoplasm

All cellular material that is located between the plasma membrane and the nucleus
* citizens/ people

57

What is cytoplasm composed of?

1) Cytosol
2) Inclusions
3) Organelles

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Cytosol

Gel-like solution made up of water and soluble molecules such as proteins, salts, sugars, etc.

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Inclusions

Insoluble molecules; vary with cell type
- Ex: Glycogen granules, pigments, lipid droplets, vacuoles, crystals

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Organelles

Metabolic machinery structures of cell; each with specialized function; either membranous or non membranous

61

What organelles are membranous?

- Cytosol
- ER
- Golgi Apparatus
- Peroxisomes
- Lysosomes

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What organelles are non membranous?

- Ribosomes
- Cytoskeleton
- Centrioles

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Mitochondria

- "Power house" of cell
- Produces cells ATP via cellular respiration
- Double layer/ many folds= cristae

64

Ribosomes

• Site of protein synthesis
- Made up of protein and ribosomal RNA (rRNA)

65

What are the 2 forms of ribosomes found in the cell?

1) Free ribosomes
2) Membrane-bound ribosomes

66

Free Ribosomes

Free floating ribosomes in cytosol

67

Membrane-bound Ribosomes

Attached to membrane of ER

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Endoplasmic Reticulum

Consists of series of parallel, interconnected cisterns- flattened membranous tubes that encloses fluid-filled interiors

69

Rough ER

Surface studded with ribosomes
• Site of synthesis of proteins that will be secreted from cell & of many plasma membrane proteins
1) Makes and modifies proteins
2) Final protein is enclosed in vesicle and sent to Golgi Apparatus for further processing

70

Smooth ER

Network of looped tubules continuous with Rough ER
- Enzymes found in its plasma membrane (integral proteins) function in:
• Lipid metabolism; cholesterol and steroid-based hormone synthesis; making lipids for lipoproteins
• Absorption, synthesis, and transport of fat

71

Golgi Apparatus

Stacked and flattened membranous cistern sacs
• Modifies, concentrates and packages proteins and lipids received from Rough ER
- Golgi is "traffic director" controlling which of 3 pathways final products will take as new transport vesicles pinch off trans (outer) face

72

Peroxisomes

Membranous sacs containing powerful detoxifying substances that neutralize toxins
- Free Radicals
1) Oxidase uses oxygen to convert toxins to hydrogen peroxide
2) Catalase converts hydrogen peroxide to harmless water
• Plays a role in breakdown and synthesis of fatty acids

73

Lysosomes

Spherical membranous bags containing digestive enzymes (acid hydrolases)
• Isolate potentially harmful intracellular digestion from rest of cell
- digest ingested bacteria, viruses and toxins
• Degrade nonfunctional organelles
• Involved in metabolism of glycogen and fatty acids

74

Free Radicals

Toxic, highly reactive molecules that are natural by-products of cellular metabolism; can cause havoc to cell if not detoxified

75

Endomembrane System

Consists of membranous organelles as well as the nuclear and plasma membranes
- Membranes and organelles work together to:
• Produce, degrade, store and export biological molecules
• Degrade potentially harmful substances

76

Cytoskeleton

Elaborate network of rods that run throughout cytosol
- Hundreds of different info of proteins link rods to other cell structures
• Also act as cells "bones, ligaments and muscles" by playing a role in movement of cell components

77

What are the 3 types of cytoskeleton?

1) Microfilaments
2) Intermediate filaments
3) Microtubules

78

Centrosome

Is a microtubule organizing center, consisting of a granular matrix and centrioles, located near the nucleus
• Some aid in cell division and some form cytoskeletal track system

79

Centrioles

A pair of barrel-shaped micro-tubular organelles that lie at right angles to each other
• Form basis of cilia and flagella

80

What are the 2 cellular extensions?

1) Cilia and flagella
2) Microvilli

81

Cilia and Flagella

Aid in movement of the cell or of materials across the surface of the cell
• Both made up of microtubules synthesized by centrioles

82

Microvilli

Minute finger like projections of plasma membrane that extends from the surface of select cells to increase surface area for absorption
- Ex: Intestinal and kidney tubule cells
• Have a core of actin microfilaments that is used for stiffening of projections

83

Cilia

Whiplike, motile extensions on surfaces of certain cells (Ex: Respiratory cells)
- Thousands work together in sweeping motion to move substances across cell surfaces in one direction (Ex: mucus)

84

Flagella

Longer extensions that propel the whole cell (Ex: tail of sperm)

85

Nucleus

Largest organelle; contains the genetic library of blueprints for synthesis of nearly all cellular proteins
• Responds to signals that dictate the kinds and amounts of proteins that needs to be synthesized

86

What are the 3 main parts of the nucleus?

1) Nuclear envelope
2) Nucleoli
3) Chrimatin