Unit 3 - CellsChapter 7

Cell Structure & Function

Brief history

• Hooke (1660’s)

• Leeuwenhoek (1670’s)

• Schleiden & Schwann(1830’s)

• Virchow (1850’s)

Cell Theory(based on 200+ years of discoveries)

• A. all living things are composed of cells

• B. cells are the basic unit of structure & function of all living things

• C. new cells are produced from existing cells

Cell Types

Prokaryotic cells = smallest, no true nucleus,

ribosomes only Ex: bacteria

• Eukaryotic cells = – large, multicellular, true nucleus,

many specialized organelles

– ex: protists, fungi, plants & animals

• 1. Nucleus = • directs cell activities• a) N. Envelope

(with pores)outer

boundary• b) Chromosomes =

(contain DNA)carry genetic code

• c) Nucleolus(contain RNA)produces ribosomes

chromatin

• 2. Endoplasmic reticulum = an interconnecting system of “pathways,” for transport

May be Rough ER(with ribosomes)or Smooth ER(without ribosomes)

• 3. Ribosomes =small bodies on ERto produce protein

4. Golgi = flattened compartments with vesiclesfor secretion (packaging & shipping)

5. Lysosomes = small filled sacs,for digestion

6. Vacuoles = large, “hollow” sacs (in plants)for storing liquids

7. Mitochondria = rod-shaped with folds,for releasing energy (ATP) by respiration

8. Chloroplasts = oval with green pigmentfor making food by photosynthesis

9. Cytoskeleton = hollow fibers• for support & shape• to move cytoplasm

10. Plasma Membrane – outer boundary of cytoplasmSemipermiable (only certain molecules enter & leave)

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

a. Phospholipid bilayer• a double layer that is an effective barrier for

most molecules• 1) Hydrophobic =

“water fearing” center tails prevent most things from entering

• 2) Hydrophilic = “water loving”

heads attract water to edges of membrane

b. Embedded Proteins• 1) Channels

“gates” to interior for transporting into & out of cytoplasm

• 2) Receptors “windows” for gathering information about cell surroundings

• 3) Markers “name tags” that identify type of cell to others

current

(Concentration gradient)

Passive or Active transport?

Passive vs Active transport:which requires energy output?

Passive Transport

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c. Types of passive transport

• 1) Diffusion• random spread of

molecules from higher to lower concentration

• Examples?

• 2) Osmosis

• Diffusion of water through a membrane

• Examples?

3) Types of osmotic solutions

• a) Hypertonic• More solutes = less water = water moves

out & cell shrinks• b) Hypotonic• Less solutes = more water = water moves

in & cell expands• c) Isotonic• Equal solutes & water, so equal movement

of water & cell is stable

Types of solutions

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Plant cells in Isotonic solution

Cells in various solutions

LYSE

TURGID

NORMAL

FLACCID

PLASMOLYZE

Plant, fungus, algae, bacteria

animal

Hypotonic Isotonic Hypertonic

Types of Active Transport

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4. Types of Active Transport

• a. Endocytosis • cell brings particles into cytoplasm

• 1) Pinocytosis • small particles

(liquids) are brought in by vesicles

• 2) Phagocytosis• large particles

(food or bacteria) are surrounded & engulfed by cell membrane

• Examples = an ameba feeding &

• a white blood cell destroying an invader

• b. Exocytosis cell deposits

particles outside of cytoplasm

• 1) Secretion = cell products given off

• 2) Excretion = wastes products given off