Cell Types and Requirements

Question 1

What is a cell?

Answer 1

• The basic structural unit of all forms of life on Earth.
• All living things are made up of one or more cells.

Question 2

What is a heterotroph?

Answer 2

An organism that can obtain energy by consuming organic substances (animal or plant tissue).

Question 3

What is an autotroph?

Answer 3

An organism that can use light or chemical energy to synthesise food from simple inorganic substances (photosynthesis).

Question 4

What is a chemotroph?

Answer 4

A small group of bacteria that are able to create sugars (organic molecules) from inorganic compounds without sunlight (chemosynthesis).

Question 5

What is the cell theory?

Answer 5

1.The cell is the most basic unit of life.
2. All cells arise from pre-existing cells.
3. Every living organism is made up of one or more cells.

Question 6

What are chemical reactions?

Answer 6

Cellular processes build and break down complex molecules through chemical reactions. Chemical reactions are occuring in your body at all times.

Question 7

What are the 2 types of chemical reactions?

Answer 7

• Exothermic
• Endothermic

Question 8

What are exothermic reactions?

Answer 8

Reactions that release energy.

Question 9

What are endothermic reactions?

Answer 9

Reactions that absorb energy.

Question 10

What do exothermic and endothermic reactions require?

Answer 10

The require energy to proceed.

Question 11

What is metabolism?

Answer 11

Metabolism is the sum of all of the chemical reactions occuring in a body.

Question 12

What types of energy enter/exit cells?

Answer 12

• Light from the sun
  AND/OR
• Chemical energy stored in complex molecules

Question 13

What types of matter enter/exit cells?

Answer 13

• Gases such as oxygen and carbon dioxide
• Simple nutrients, ions and water
• Wastes

Question 14

Describe prokaryotic cells.

Answer 14

• Simplest type of cell
• Small in size 1 -10μm long 0.2 - 2μm diameter
• Have difficultly in performing multiple functions at the same time
• Lack membrane bound organelles, including a nucleus
• Belong to the Domains - Bacteria and Archaea
• Exist as single cells

Question 15

Describe the cytoplasm in prokaryotic cells.

Answer 15

• Makes up the bulk of the cell and contains ribosomes, cytosol, plasmids and circular chromosomes.
• Cytosol is the semi fluid component of the cytoplasm, it contains many dissolved substances.
• Chemical reactions that enable the cell to live are carried out here.

Question 16

Describe the ribosomes in prokaryotic cells.

Answer 16

• Scattered freely throughout the cytosol.
• Only distinguishable organelles in a prokaryotic cell.
• Not bound by a membrane.
• Site of protein synthesis (joining of amino acids to form proteins).
• Proteins are required for cell growth, repair and general cell functioning.

Question 17

Describe the genetic material in prokaryotic cells.

Answer 17

• The genetic code in DNA differs between different species of bacteria.
• Most contain a single circular chromosome (not visible by light microscope) which is in direct contact with the cytoplasm.
• Chromosome contain the instructions for making different proteins.
• Numerous small rings of DNA (plasmids) may also be present. These can reproduce independently of the main chromosome.

Question 18

Describe eukaryotic cells.

Answer 18

• More complex type of cells.
• Made up of organelles/membrane bound compartments that perform specialist functions, including photosynthesis and respiration.
• Organelles allow for the synthesis of complex molecules, storage of substances for chemical reactions and for the entry and exit of substances out of the cell/
• Belong to the Kingdoms - Protist, Fungi, Plantae and Animalia.

Question 19

What cellular structures do plants and animals have?

Answer 19

Cell membrane, cytoplasm and cytosol, endoplasmic reticulum (rough and smooth), golgi apparatus, lysosomes, mitochondria, nucleus, ribosomes and centrosomes and centrioles.

Question 20

What cellular structures do only plants have?

Answer 20

Chloroplast, cell wall and large vacuole.

Question 21

What is the cell membrane and its function?

Answer 21

A flexible phospholipid bilayer that controls the entry and exit of substances and encloses the cell.
- Cell membranes can engulf large particles in liquids in its environment in a process known as endocytosis. It surrounds and encloses the material to form an endocytotic vesicle within the cell, which it then uses to store or transport the material within the cytoplasm.
- Exocytosis occurs when a small membrane bound vesicles move through the cytosol and joins with the cell membrane and then releases its contents to the exterior of the cell.

Question 22

What is the cytoplasm/cytosol and its function?

Answer 22

All of the cell’s contents (including organelles) between the nuclear membrane and the cell membrane. The cytosol is the semi-liquid (jelly-like) part of the cytoplasm and does not include the organelles. Metabolic activity occurs both in the organelles (in the cytoplasm) and the cytosol.

Question 23

What is the endoplasmic reticulum and its function?

Answer 23

• An interconnecting system of thin membrane sheets dividing the cytoplasm into compartments and channels.
• The membrane of the ER is able to pinch off small sacs called vesicles and deliver proteins to all parts.

Question 24

What is the rough endoplasmic reticulum and its function?

Answer 24

• Most of the ER is studded with ribosomes rough endoplasmic reticulum. The proteins produced by the ribosomes move directly into the ER to be moved about the cell.
• Some proteins are exported or secreted into other cells (e.g. hormones and enzymes).
• Therefore the ER is both an intercellular and intracellular transport system within the cell.

Question 25

What is the smooth endoplasmic reticulum and its function?

Answer 25

- Parts with no ribosomes attached is known as the smooth endoplasmic reticulum. The amount and function of smooth ER depends on the cell type. - Its main role is to transport proteins, synthesise lipids and to assist in the manufacture of cell membranes. In liver cells it also detoxifies drugs and in adrenal cortical cells it produces the steroid hormone. Some carbohydrates are produced on the smooth ER. It is also the place for the storage of calcium ions used in muscle contraction and some interactions between membrane proteins.

Question 26

What is the Golgi apparatus and its function?

Answer 26

- The Golgi apparatus consists of a system of membranes within the cytoplasm. Parts of the Golgi apparatus membrane are able to pinch off into small vesicles. These vesicles move to the so membrane where they joined to the membrane and discharge their contents to the outside of the cell. - Proteins produced by the ribosomes in the endoplasmic reticulum move into the Golgi apparatus were they're package and stored before being secreted from the cell to move to other parts of the body.

Question 27

What is a lysosome and its function?

Answer 27

- Recycle the raw materials that make up old organelles. - They are formed by the Golgi apparatus and contain digestive enzymes that are responsible for splitting complex chemical compounds into simpler ones. For example splitting proteins down into amino acids. These simpler substances can then be used as building blocks for new compounds and organelles. - Programmed cell death occurs when the lysosome’s membrane ruptures and releases the enzymes which digest the contents of the cell, killing it.

Question 28

What is the nucleus and its function?

Answer 28

The structure that contains most of a cell's DNA. It includes: - Nuclear membrane with nuclear pores. - A nucleolus - production of ribosomes. - Chromatin - loose form of DNA.

Question 29

What are ribosomes and their function?

Answer 29

A non-membranous structure that carries out protein synthesis.

Question 30

What are centrosomes and centrioles and their function?

Answer 30

The structures that play a major role in cell division. The centrosome is located at one end of the cell, close to the nucleus. In many cells microtubules grow out from a centrosome. In animal cells, the centrosome has a pair of centrioles.

Question 31

What is the cell wall and its function?

Answer 31

A structure made of tough cellulose fibres which protects the plant cell, maintains its shape and prevents excessive uptake of water.

Question 32

What is the large vacuole and its function?

Answer 32

A plant cell may have one or several large vacuoles that can store water, nutrients, metabolic wastes and toxins. In plant cells full vacuoles can provide rigidity of the whole organism.

Question 33

Describe the protein pathway in cells.

Answer 33

1. Protein-building instructions move from the nucleus into the cytoplasm. 2. The protein chains are manufactured on ribosomes. 3. Some protein chains have signal peptides so they enter the lumen of the ER and are chemically modified. 4. Lipids are manufactured in the membrane of the smooth ER. 5. Vesicles, which bud from the ER membrane, transport unfinished proteins and lipids to a Golgi apparatus. 6. Proteins and lipids take on final form in the space inside the golgi apparatus. 7. Vesicles budding from the golgi membrane transports finished products to the cell membrane where they are released by exocytosis.

Question 34

What are stem cells?

Answer 34

Stem cells are cells that have the potential to develop into specific kinds of cells, examples include bone marrow, cardiac muscle and neural cells.

Question 35

What are specialised cells?

Answer 35

Specialised cells are cells that are able to perform a specific function.

Question 36

What is photosynthesis?

Answer 36

- Photosynthesis is a metabolic process that converts light form the sun into stored chemical energy in the form of carbohydrates. - Carbon dioxide and water combine in the presence of light and chlorophyll to produce sugars and oxygen. - Chlorophyll absorbs light to make it available for photosynthesis.

Question 37

Where does photosynthesis occur?

Answer 37

Chloroplast

Question 38

What is the chemical equation for photosynthesis (balanced)?

Answer 38

6CO2 + 6H2O → C6H12O6 + 6O2

Question 39

Describe the structure of chloroplast.

Answer 39

- Stroma - Jelly like semi fluid interior of the chloroplast. Has the appropriate pH and enzymes required for the calvin cycle. - Thylakoids - Small flatten discs, contain chlorophyll, site for light dependent reactions. - Granum - Stacks of thylakoids that increase the surface area to volume ratio. - Lamella- Links the granum.

Question 40

What is respiration?

Answer 40

- Metabolic process that coverts stored energy (such as that in glucose) into a usable form of energy stored in ATP (adenosine triphosphate). - A series of chemical reactions that use glucose and oxygen to produce carbon dioxide and water. During certain stages of respiration, energy is released which is used to build up molecules of ATP. ATP is an energy storage molecule that is used to power cellular processes.

Question 41

Where does respiration occur?

Answer 41

First stage occurs in the cytoplasm, the second stage occurs in the mitochondria.

Question 42

What is the chemical equation for respiration (balanced)?

Answer 42

C6H12O6 + 6O2 → 6CO2 + 6H2O

Question 43

Describe the structure of a mitochondria.

Answer 43

- Outer membrane – the outer membrane contains transport proteins that enable the shuttling of pyruvate from the cytosol. - Inner membrane – contains the electron transport chain and ATP synthase (used for oxidative phosphorylation). - Cristae – the inner membrane is arranged into folds (cristae) that increase the SA:Vol ratio (more available surface). - Inter-membrane space – small space between membranes maximises hydrogen gradient upon proton accumulation. - Matrix – central cavity that contains appropriate enzymes and a suitable pH for the Krebs cycle to occur.