01. Cells & Microbes

Eukaryotic cell

Eukaryotic cell

• Complex

• Animal and plant cells

Prokaryotic cells

• Smaller and simpler

• Bacteria

Levels of organisation (small to large)

1. Organelles

2. Cells

3. Tissues - grp of similar cells work tgt to carry out specific function

4. Organs - grp of diff tissues work tgt to perform a function

5. Organ System - organs work tgt to form organ system

Nucleus

Contains genetic material that controls the cell’s activities

Cell membrane

• Form the outer surface of the cell

• Controls the substances that go in & out of the cell

Cell wall

Supports the cell & strengthens it

Cytoplasm

• Where the cell’s chemical reactions take place

• Contains enzymes that control these reactions.

Mitochondria

Where most reactions for aerobic respiration takes place

Ribosomes

Where proteins are made in the cell

Chloroplasts

• Site of photosynthesis

• Contains chlorophyll that converts light into energy for photosynthesis

Vacuole

• Contains cell sap [weak solution of sugars & salts]

• Plant cells : Helps support the cell + maintain water balance [bigger]

• Animal cells : Stores waste products [smaller]

Animals (3)

1. Multi-cellular

2. Have nervous coordination

3. Store carbs as glycogen

Plants (3)

1. Multi-cellular

2. Cellulose cell wall

3. Store carbs as sucrose / starch

Fungi (6)

1. Single celled

2. Body organised into a mycelium - made up of hyphae that contains many nuclei

3. Can’t photosynthesise

4. Chitin cell wall

5. Saprotrophic nutrition - excrete digestive enzymes onto food then absorbing the organic products

6. Store carbs as glycogen

Animal cell (5)

1. Cell membrane

2. Cytoplasm

3. Mitochondria

4. Ribosome

5. Nucleus

Plant cell (8)

1. Cell wall

2. Cell membrane

3. Cytoplasm

4. Chloroplast

5. Mitochondria

6. Ribosome

7. Nucleus

8. Vacuole

Bacteria parts (5)

1. Cell wall

2. Cell membrane

3. Cytoplasm

4. Plasmids

5. Circular chromosome of DNA

Protoctist (3)

1. Single celled

2. Some have chloroplast

3. Some are similar to animal cells

Bacteria (6)

1. Single celled

2. No nucleus

3. Circular chromosome of DNA

4. Plasmids

5. Some can photosynthesise

6. Feed off other organisms

Protoctist examples

• Chlorella

• Amoeba

Bacteria example

• Lactobacillus bulgaricus

• Pneumococcus

Virus (4)

1. Particles, not cells

2. Parasite [reproduce inside living cells]

3. Infect all living organisms

4. No cellular structure - protein coat around genetic material

Virus examples

• Influenza virus

• HIV

Pathogens

• Cause disease

• Include fungi, protoctists, bacteria

Protoctist : Plasmodium - cause malaria

Bacterium : Pneumococcus - cause pneumonia

Virus : Influenza virus - cause flu, HIV - cause AIDs

Cell differentiation

• Process where a cell changes to become specialised for its job

• Develop diff. organelles & turn into diff. types of cells

• Allow them to carry out specific functions

Stem cells

• Undifferentiated cells

• Divide my mitosis to produce more undifferentiated cells

• Differentiate into diff types of cell depending on instructions given

• Can differentiate into specialised cells

Where are stem cells found

1. Human embryo - can turn into any kind of cell

2. Bone marrow - can’t turn into any kind of cell, only some [e.g. blood cells]

Use of stem cells (2)

1. Grown in lab to produce clones

2. Differentiate into specialised cells for medicine / research

Against stem cell research (2)

1. Some ppl think human embryos are a potential human life

2. Think scientists should concentrate more on finding & developing other sources of stem cells

Support stem cell research (2)

1. Some ppl think curing existing patients who are suffering is more important than rights of embryos

2. Most embryos used in research are unwanted from fertility clinics which would be destroyed if not used

What are enzymes

Biological catalyst

Catalyst definition

Substances that speeds up a reaction without being changed or used up

How does temp affect enzyme activity

• Temp increase

• More KE, causing particles to vibrate more

• Increase chance for successful collisions

• More enzyme substrate complex

• Enzyme activity increase

Optimum temp of enzymes

37ºC

Enzyme activity past optimum temp

• Enzyme become denatured

• Substrate cannot fit into active site

• Enzyme activity decrease

Optimum pH of enzymes (pepsin)

1-2

Optimum pH of enzymes (trypsin)

7-8

How does too high / too low pH affect enzyme activity

• Affect the forces holding amino acid chains that make up protein

• Enzyme become denatured

• Substrate cannot fit into active site

• Enzyme activity decrease

Diffusion

• Net movement of particles from area of higher to lower conc. until equilibrium is reached

• Passive - doesn’t require energy

• Happens in liquids & gases as particles are free to move randomly

Osmosis

• Net movement of water molecules across partially permeable membrane from are of higher to lower water conc.

• Water pass both ways - water molecules move randomly

Active transport

• Movement of particles against the concentration gradient [low to higher concentration] using energy from respiration

Effect of SA:V ratio on diffusion / osmosis

• Larger SA : V ratio = Higher rate of diffusion

  • Smaller cube → larger SA:V ratio

Effect of temp on diffusion / osmosis

• Increase temp → more KE

• Particles move faster

• Substances move in & out faster

• Rate of diffusion increase

Effect of conc. gradient on diffusion / osmosis

• More particles on one side so there are more to move across

• Increase rate of diffusion