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Cytology

Study of cellular structure and function, part of cell biology (uses biology chemistry, and physics)

1

Two classes of cells

- sex cells (germ or reproductive cells)
- somatic cells

2

Functions of the plasma membrane

- physical isolation: separates insides from outside
- regulation of exchange with environment: only lets in and out what is needed/wanted
- sensitivity to environment: first affected by changes and has receptors/responds to signals
- structural support: connects cell to others

** not uniform or rigid some proteins only on inside or only of outside or only in one area

3

Phospholipid bilayer

Plasma membrane - phospholipid molecules in two layers (because of hydrophilic and hydrophobic ends)

4

Integral proteins

Part of the membrane structure - cannot be removed without damaging/destroying the membrane. Most span the width of the membrane one of more times = transmembrane proteins

5

Peripheral proteins

Bound to the inner/outer surface of the membrane and (like Post-it notes) are easily separated for it. # peripheral >> # integral proteins

6

Membrane protein functions

1) anchoring - attach the membrane to other structures and stabilize its position, ex. To the Cytoskeleton
2) recognition - these proteins are characteristic and allow the immune system to recognize as normal or abnormal
3) enzymes - can be integral or peripheral, catalyzing reactions inside or outside the cell
4) receptors - sensitive to the presence of specific ECM molecules called ligands (small ion or big hormone, etc). These ligand bind and can cause changes inside the cell
5) carriers - bind solutes and transport them across the membrane, some need ATP some use the concentration gradient
6) channels - proteins with a central core that form a passageway across the membrane, allowing movement of water and small solutes

7

Glycocalyx

Layer of carbohydrates that extends outside the plasma membrane. Allows for lubrication and protection (forms a viscous membrane), anchoring and locomotion (components are sticky and help anchor in place), specificity of binding (can function as receptors & alter behavior), and recognition (labels as self vs foreign)

8

Cytoplasm

General term for the material located between the plasma membrane and the membrane surrounding the nucleus

9

Cytosol

Intracellular material - cytoplasm minus the organelles, contains dissolved nutrients, ions, solvable and insoluble proteins, and waste products

- inside has more K while outside has more Na
- higher concentration of suspended proteins (many enzymes)
- small quantities of carbohydrates, and small reserves of amino acids and lipids -- but more than outside

10

Organelles

Structures suspended within the cytosol that preform specific functions for the cell.

Membranous (not completely closed off - included cilia and ribosomes) and non-membranous (surrounded by plasma membrane - includes lysosomes and mitochondria)

11

Inclusions

Masses of insoluble material found inside and outside the cell

Ex. Stored nutrients in liver or bone; or lipid droplets in fat cells; or pigment granules

12

Cytoskeleton

Functions as the cell's skeleton and provides strength and flexibility. Plays a role in metabolic organization by determining where reactions will occur. Made of:
1) micro-filaments = smallest, usually found at the periphery of the cell. Attach to the integral proteins giving additional mechanical strength and attaching the membrane to the cytoplasm. Helps determine consistency of the cytoplasm. Actin micro filaments can interact with myosin proteins to produce movement
2) intermediate filaments = strengthen the cell and help maintain its shape, stabilize the position of its organelles and the cell with respect to its surrounding cells. Insoluble and most durable.
3) thick filaments = massive bundles of myosin protein subunits. Appears only in muscle cells. Allows for powerful contractions

**microtubules = hollow tubes built from tubulin & primary component of the cytoskeleton. Gives strength and rigidity - anchors organelles. Disassembly allows shape changes. Act as a rail system for moving vesicles and organelles (requires ATP). Needed to form spindle apparatus in cellular division.

13

Microvilli

Small finger like projections of the plasma membrane on their exposed surface - which increase the surface area of the cell exposed to the environment, usually for cells that need to do a lot of absorbing of materials from the ECM, ex. Digestive tract. Many connections to cytoskeleton

14

Centrioles

Cylinder structures composed of short microtubules (9 groups of 3). Come in pairs. Allow for cell division.

** centrosome = cytoplasm + centrioles = heart if cytoskeleton

15

Cilia

Fairly long slender extensions of the plasma membrane. Structure is similar to centrioles but 9 pairs not triplets and has a central pair. Anchored on a basal body that is just below the cell surface. Moves secretions and fluids along the cell surface

16

Ribosomes

Proteins responsible for protein synthesis. Number depends on cell type & .'. Demand for new proteins. Each = 60% RNA & 40% protein. Can be free (scattered throughout cytoplasm and products -> cytosol) or fixed (attached to ER, proteins -> ER -> secretion)
- small subunit
- large subunit

17

Proteasomes

Organelles that contain an assortment of protein-digesting enzymes/proteases which remove proteins. Disassembles proteins at have been marked with ubiquitin for recycling (usually damaged or denatured proteins) -> amino acids and small peptides are released back into the cell

18

Endoplasmic Reticulum

(within cytoplasm, network) Network of intracellular membranes connected to the nuclear envelope surrounding the nucleus. SYNTHESIS of proteins, carbohydrates, and lipids. STORAGE of synthesized molecules. TRANSPORT and DETOXIFICATION via enzymes inside.

**smooth = no ribosomes are associated -> forms lipids, hormones, glycerides, glycogen, and carbohydrates. Stores and absorbs ions like Ca+2
**rough = functions as a combo shipping warehouse and workshop. New proteins are chemically modified and packaged for export. Many fixed ribosomes -> release polypeptide into cistern are (water reservoir inside ER) where they are folded. Some get carbohydrates attached some get packaged into small membranous sacs

19

Golgi apparatus

Transport vesicles containing new proteins from the ER that are destined for export goes here. Organelle modifies and packages secretions for release via exocytosis, renews or modifies the plasma membrane, packages special enzymes within vesicles for use in the cytoplasm

20

Lysosomes

Special vesicles that provide an isolated environment for potentially dangerous reactions. Contain digestive enzymes - powerful!!

**primary = inactive enzymes that become actives when in contact with damaged organelles
**secondary = active, break down lysosomal content - damaged organelles? Bacteria when the lysosomes fused with a vesicles from the outside

21

Peroxisomes

Vesicles with enzymes made from existing peroxisomes. Absorb and break down fatty acids and other organic compounds. Creates O2 and H2O from dangerous free radicals produced during the catabolism

22

Mitochondria

Organelle that is responsible for energy production. Number within a cell correlates to energy demand. Has TWO membranes. Inner is folded to create lots of surface area. Most of chemical reactions that release energy take place within this organelle. But energy is needed outside this organelle so energy must be transportable such as in ATP where the high energy bond can be broken under controlled conditions. Energy usually formed through the breakdown of carbohydrates - like glucose

23

Energy production

Glycolysis: glucose -> 2 pyruvates -> mitochondria
--CO2
Citric acid cycle: reduce the pyruvates into CO2 and H+ -> electron transport chain

24

Nucleus

Usually largest and most conspicuous structure in the cell. Serves as a control center for cellular operations. Stores all the information needed to direct the synthesis of the different proteins.

25

Peri-nuclear space

Space between the two membranes around the nucleus

26

Nuclear matrix/nucleoplasm

Fluid contents and the fine filaments that provide structural support & possibly involved in the regulation if genetic activity. Nucleoplasm contains ions, enzymes, RNA, DNA nucleotides, and small amounts of RNA and DNA

27

Nucleoli

Transient nuclear organelles that synthesize rRNA and assemble ribosomal sub units

28

Osmotic pressure

Indication of the force of its solute concentration

29

Hydrostatic pressure

Force opposing osmosis, force pressing against a fluid