Biology - Cells And Membranes

Front 1

Nucleus

Back 1

Function - contains genetic information for the cell

• Nucleolus- small and dense sphere. Produces ribosomes and RNA

• Chromatin- Chromosomes contain histone proteins and DNA

• Nucleoplasm - makes up bulk of nucleus

• Rough endoplasmic reticulum

• Nuclear envelope - double membrane with fluid in between. Contains nuclear pores and controls entry and exit of materials

• Pores - allows larger molecules to pass envelope

Front 2

Rough endoplasmic reticulum

Back 2

Function:

Provides pathway for transport of proteins. Large SA for synthesis of proteins and glycoproteins

• Ribosomes - site of protein synthesis

• Cisternae - flattened membrane bound sacs (folds)

Front 3

Mitochondria

Back 3

Function:

Site of respiration for production of adenosine triphosphate

• Ribosomes

• Outer membrane

• Inner membrane - folded into membrane bound sacs for SA (cristae)

• Matrix - central region - fluid contains ribosomes, proteins, lipids and mitochondrial DNA for protein production

Front 4

Smooth endoplasmic reticulum

Back 4

Function:

Synthesises, transports and stores carbohydrates and lipids

Front 5

Golgi apparatus

Back 5

Function:

Receives proteins and lipids from endoplasmic reticulum and modifies them by adding carbohydrates. Also labels them. Is then packaged into vesicle clipped of cisternae and transported to cell surface membrane to fuse and release contents. Also produces lysosomes.

Front 6

Lysosomes

Back 6

Function:

Contains powerful digestive enzymes

•Phospholipid bilayer

•Membrane

•Hydrolytic enzymes in centre

Front 7

Cholorplasts

Back 7

Functions:

Found in plant cells and algae. Carry out photosynthesis for production of carbs

• Stroma - fluid filled matrix - contains starch granules and enzymes

• Thylakoids - Provide large SA, folding of inner membrane (stack=granum)

• Thylakoid membrane (double)

• Lamella - has chlorophyll molecules

Front 8

Ribosomes

Back 8

Function:

Site of protein synthesis

• No membrane

• Large subunit and small subunit

• mRNA strand coming out

Front 9

Vacuole

Back 9

Function: pushes against the cell cytoplasm to make it turgid and help plant structure stability

•Tonoplast is membrane

•Contains, cell sap, sugars, amino acids, water. Etc.

•Single membrane fluid filled sac in plants

Front 10

Cell walls

Back 10

•Fungi - chitin

•Plants - cellulose

•Bacteria - peptidoglycan

Front 11

Cytoskeleton

Back 11

Network of protein fibres that provide support and shape to the cell. Moves chromosomes in cell division. Involved in changing shape of membrane in endo/exo cytosis

Front 12

Division of labour

Back 12

1. Information for protein made on gene in DNA in nucleus. Copy of gene is made on mRNA molecule by transcription

2. mRNA molecule passes out via pore

3. Binds to ribosome on rough endoplasmic reticulum. Starts translation.

4. RER packages protein into vesicle - transports to golgi apparatus

5. Fuses with golgi membrane. Golgi modifies (adds carbs) then packaged in vesicle - transports toward plasma membrane

6. Vesicle fuses with membrane and releases protein by exocytosis (is secreted)

Front 13

Binary fission

Back 13

Cell division in prokaryotes

1. Circular DNA and plasmids replicate. DNA once, plasmids multiple.

2. Cell gets bigger - DNA moves to opposite poles of cell

3. Cytoplasm divides + new cell walls formed

4. Makes 2 daughter cells - variable number of plasmids each

Front 14

Antibiotics

Back 14

• Only work on bacteria

• Prevent cell walls forming

• Penicillin inhibits enzymes for synthesis of peptide bonds in cell wall - wall bursts due to osmosis

Front 15

Eukaryotes, prokaryotes and akaryotes

Back 15

Nucleus? E

DNA? E (linear) P (circular) A (DNA/RNA)

Cell wall? E (chitin/cellulose) P (peptidoglycan)

Ribosomes? E (80s) P (70s)

Plasmids? P

Cell membrane? E, P, A (envelope - not cell)

Cytoplasm? E, P

Front 16

Fluid mosaic model

Back 16

• Phospholipids and proteins move around each other

• Arrangement of proteins and phospholipids

• Simplified description of a process to help with understanding

Front 17

Phospholipid bilayer

Back 17

1. Phospholipids:

Arranged in bilayer, barrier to polar molecules, makes membrane flexible, let's lipid-soluble, small, non-polar substances diffuse through

2. Cholesterol:

Steroid molecule, for stability and flexibility of bilayer, fits in between fatty acids tails, completes barrier, only in eukaryotes

3. Intrinsic proteins:

Span entire membrane, carrier and channel proteins, allow hydrophilic and larger molecules through bilayer

4. Extrinsic proteins:

Enzymes, cell signalling and repetition, cell adhesion and receptors, span half of membrane

5. Glycoproteins:

Cell signalling and recognition, cell adhesion, receptors

6. Glycolipids:

Cell signalling and recognition, cell adhesion

(Note: specialisation- different membranes have different amounts of proteins)

Front 18

Roles of membranes

Back 18

Within cells:

1. Compartmentalization - separates cell components from cytoplasm

2. Site of attachment

3. Controls what enters and leaves

4. Holding components of metabolic pathways

At surface of cells:

1. Separates cell contents from outside environment

2. Cell signalling and recognition

3. Regulating transport of materials in and out

4. Create/maintain concentration gradients

Front 19

Diffusion

Back 19

Movements of substances from an area of high concentration to an area of low concentration down a concentration gradient across a partially permeable membrane via phospholipid bilayer

No ATP, kinetic energy, gradient, no proteins

Factors affecting; size of molecules, temp, concentration gradient, SA, stirring motion, thickness of exchange surface

Front 20

Temperature on membrane

Back 20

• 30-50°C - more kinetic energy, more collisions, faster diffusion

• 50-60°C - denatures proteins, membrane more permeable, ions diffuse faster

• 60-70°C - increase in temperature is displaced and breaks down, ions reach equilibrium (no net movement)

Front 21

Facilitated diffusion

Back 21

Movement of substances from and area of high concentration to an area of low concentration down a concentration gradient across a phospholipid bilayer via carrier or channel proteins

Carrier:

Only allow specific large molecules to pass. When molecule binds it changes shape and transfers molecule

Channel:

Act as pores. Only allow specific ions through. Can be gated (opened/closed)

Factors affecting; number of proteins, concentration gradient

Front 22

Osmosis

Back 22

Movement of water from an area of high water potential to an area of low water potential down a water potential gradient across phospholipid bilayer via aquaporins or bilayer

Water potential (kPa) - highest is 0

• Hypotonic - solution has higher water potential

• Hypertonic - solution has lower water potential

• Isotonic - Same

Front 23

Active transport

Back 23

Movement of large/water soluble substances across a membrane via carrier proteins. Gradient not required. ATP required.

Front 24

Ways cell can be specialised

Back 24

1. Changing shape (SA)

2. Number of organelle

3. Plasma membrane (no. of protein)

Front 25

Endocytosis

Back 25

Bulk transports of substances into cell - uses ATP to move membrane go form vesicle to contain substances as it enters.

Membrane engulfs material.

Membrane fuses together.

Vesicle formed.

Front 26

Exocytosis

Back 26

Bulk transport of substances out of cell - uses ATP to move vesicle and allow it to fuse with membrane.

Vesicle fuses with membrane

Substances move out of cell.

Ex. Hormones or white blood cells