IB Bio unit one

Explain how the cell cycle is controlled. (4 marks)

-Cyclins control the cell cycle -Conditions inside as well as outside the cell affect regulation -Cell cycle is a sequence of stages, cell cycle is G1, S, G2 and mitosis -Levels of cyclins fluctuate during the cell cycle

Cells go through a repeating cycle of events in growth regions such as plant root tips and animal embryos. Outline the cell cycle. (4 marks)

-DNA replicates in the S phase -Cytokinesis occurs after mitosis -Consists of four phases: prophase, metaphase, anaphase, telophase -The interphase consists of the S phase, G1 and G2

Describe the process of endocytosis. (5 marks)

-Fluidity of the membrane allows endocytosis -Plasma membrane forms pit -Vesicle formed -Vesicle breaks away from plasma membrane -Plasma membrane encloses

State three processes occurring in a cell during interphase of the cell cycle but not in mitosis. (3 marks)

-Growth -Transcription -DNA replication

Cell membranes separate aqueous environments in cells. Explain how the properties of phospholipids help to maintain the structure of cell membranes. (8 marks)

-Labelled phospholipid consisting of head and two tails -Head is glycerol and phosphate -Tails are fatty acid chains -Head is hydrophilic and tails hydrophobic -Hydrophilic molecules soluble in water -Hydrophobic molecules not attracted to water but attracted to each other -Formation of a double layer in water -Fluidity allows membranes to change shape

Draw a labeled diagram to show the structure of the plasma membrane. (5 marks)

-Phospholipid bilayer - with heads and tails -Integral proteins -Protein channel -Glycoprotein with carbohydrate attached -Cholesterol

Outline the effects of putting plant tissue in a hypertonic solution. (4 marks)

-Water moves out of the cells/tissue by osmosis into the hypertonic solution -Water moves from lower solute concentration to higher solute concentration -Pressure inside the cell drops and becomes flaccid -Volume of cytoplasm drops, plasma membrane retracts from the cell wall, and cell is plasmolized

Outline four different functions of membrane proteins. (4 marks)

-cell recognition -facilitated diffusion -active transport -Cell adhesion

Describe four different types of transport of substances across a membrane. (4 marks)

-diffusion when molecules move down a concentration gradient directly through membrane -osmosis of water from area of low solute to area of high solute concentration -active transport against a concentration gradient using protein pumps -vesicles attach to plasma membrane and release materials to exterior

State the functions of the following organelles of a eukaryotic animal cell: lysosome, Golgi apparatus, free ribosomes, plasma membrane, rough endoplasmic reticulum. (5 marks)

-lysosome: break down food -Golgi apparatus: packages and releases proteins -free ribosomes: site of synthesis of proteins -plasma membrane: controls what enters/exits the cell -endoplasmic reticulum: synthesis and transport of proteins

Outline the cell theory (3 marks)

1. living things are composed of cells 2. cells are the basic unit of life 3. cells come from pre-existing cells

The electron micrograph below shows an E. coli cell. Identify the structures labelled A and B in the electron micrograph above and state one function of each. (2 marks) A: Name: Function: B: Name: Function: Compare prokaryotic and eukaryotic cells. (3 marks)

A: name: flagella/flagellum function: used for locomotion B: name: pili/pilus function: used for adhesion and transfer of genetic material prokaryotic: circular chromosomes, fission, cell wall present Eukaryotic: linear chromosomes, mitosis, cell wall only present in plants and fungi

The diagram shows some of the structures in an animal cell. Label structures I, II, III and IV. (3 marks) I. II. III. IV. State one function of structure III. Explain how materials are transported within a cell between structures X and Y. (2 marks)

I. ribosomes II. nucleus III. mitochondrion IV. plasma/cell membrane ATP production material transported by vesicles

"Molecule(s) move from..." (concentration) Energy required (Y/N) Example molecule(s) Characteristic(s) of transported molecule(s)

Simple Diffusion -High to low -No -Oxygen, carbon dioxide -Small non charged particles Osmosis -Water high to water low -No -water -Water is polar Facilitated Diffusion -High to low -No -Chloride ions -Small charged particles - ions

Identify the phases of mitosis. (3 marks)

a. Cytokinesis b. Interphase c. Metaphase d. Prophase e. Telophase f. anaphase

The diagram shows how vesicles are used to transport materials in a cell. a. State the name of organelle A. (1 mark) b. Describe how the structure of the membrane allows the formation of vesicles. (2 marks)

a. Golgi apparatus b. -kinks in the phospholipid tails prevent close packing -cholesterol affects membrane fluidity

Draw a labelled diagram of the ultrastructure of Escherichia coli as an example of a prokaryote. (4 marks)

a. cell wall b. plasma membrane c. cytoplasm d. pilus/pili e. flagellum/flagella

Reproduction in eukaryotes can be sexual or asexual. Describe the origin of eukaryotic cells according to the endosymbiotic theory. (4 marks)

a. division of chloroplast/mitochondrion b. double membrane around chloroplast/mitochondrion c. 70s ribosomes «in chloroplast/mitochondrion» d. chloroplasts and mitochondria were once independent/free-living

List two examples of how human life depends on mitosis. (2 marks) Describe the importance of stem cells in differentiation. (3 marks)

a. hair growth replacement of skin cells b. stem cells can differentiate in many ways differentiation involves expressing some genes but not others stem cells can be used to replace tissue and heal wounds

Pictured below are Louis Pasteur's original drawings of swan-necked flasks. Describe how Pasteur's experiments provided convincing evidence to falsify the concept of spontaneous generation. (3 marks)

d. no clouding and signs of bacterial growth/reproduction f. because microbes from the air contaminated the boiled broth g. curved necks allowed indirect exposure to air but prevented entry of microbes

State the process that divides one nucleus into two genetically identical nuclei. (1 mark)

mitosis

State two differences in structure between plant and animal cells. (2 marks)

plant cells: chloroplast, cell walls, no lysosomes animal cells: no chloroplast, no cell wall, lysosomes